use crate::Alignment;
use crate::OrderedListNumbering::*;
use crate::OrderedListStyle::*;
use crate::Span;

use crate::attr;
use crate::lex;
use crate::tree;

use Atom::*;
use Container::*;
use Leaf::*;
use ListType::*;

pub type Tree = tree::Tree<Node, Atom>;
pub type TreeBuilder = tree::Builder<Node, Atom>;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Node {
    Container(Container),
    Leaf(Leaf),
}

#[must_use]
pub fn parse(src: &str) -> Tree {
    TreeParser::new(src).parse()
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum Block {
    /// An atomic block, containing no children elements.
    Atom(Atom),

    /// A leaf block, containing only inline elements.
    Leaf(Leaf),

    /// A container block, containing children blocks.
    Container(Container),
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Atom {
    /// A line with no non-whitespace characters.
    Blankline,

    /// A list of attributes.
    Attributes,

    /// A thematic break.
    ThematicBreak,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Leaf {
    /// Span is empty, before first character of paragraph.
    /// Each inline is a line.
    Paragraph,

    /// Span is `#` characters.
    /// Each inline is a line.
    Heading { has_section: bool },

    /// Span is empty.
    DescriptionTerm,

    /// Span is '|'.
    /// Has zero or one inline for the cell contents.
    TableCell(Alignment),

    /// Span is '^' character.
    Caption,

    /// Span is the link tag.
    /// Inlines are lines of the URL.
    LinkDefinition,

    /// Span is language specifier.
    /// Each inline is a line.
    CodeBlock,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Container {
    /// Span is `>`.
    Blockquote,

    /// Span is class specifier, possibly empty.
    Div,

    /// Span is the list marker of the first list item in the list.
    List { ty: ListType, tight: bool },

    /// Span is the list marker.
    ListItem(ListType),

    /// Span is footnote tag.
    Footnote,

    /// Span is empty, before first '|' character.
    Table,

    /// Span is first '|' character.
    TableRow { head: bool },

    /// Span is '#' characters of heading.
    Section,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ListType {
    Unordered(u8),
    Ordered(crate::OrderedListNumbering, crate::OrderedListStyle),
    Task,
    Description,
}

#[derive(Debug)]
struct OpenList {
    /// Type of the list, used to determine whether this list should be continued or a new one
    /// should be created.
    ty: ListType,
    /// Depth in the tree where the direct list items of the list are. Needed to determine when to
    /// close the list.
    depth: u16,
    /// Index to node in tree, required to update tightness.
    node: tree::NodeIndex,
}

/// Parser for block-level tree structure of entire document.
struct TreeParser<'s> {
    src: &'s str,
    tree: TreeBuilder,

    /// The previous block element was a blank line.
    prev_blankline: bool,
    /// Stack of currently open lists.
    open_lists: Vec<OpenList>,
    /// Stack of currently open sections.
    open_sections: Vec<usize>,
    /// Alignments for each column in for the current table.
    alignments: Vec<Alignment>,
}

impl<'s> TreeParser<'s> {
    #[must_use]
    pub fn new(src: &'s str) -> Self {
        Self {
            src,
            tree: TreeBuilder::new(),
            prev_blankline: false,
            open_lists: Vec::new(),
            alignments: Vec::new(),
            open_sections: Vec::new(),
        }
    }

    #[must_use]
    pub fn parse(mut self) -> Tree {
        let mut lines = lines(self.src).collect::<Vec<_>>();
        let mut line_pos = 0;
        while line_pos < lines.len() {
            let line_count = self.parse_block(&mut lines[line_pos..], true);
            if line_count == 0 {
                break;
            }
            line_pos += line_count;
        }
        for _ in self.open_lists.drain(..) {
            self.tree.exit(); // list
        }
        for _ in self.open_sections.drain(..) {
            self.tree.exit(); // section
        }
        self.tree.finish()
    }

    /// Recursively parse a block and all of its children. Return number of lines the block uses.
    fn parse_block(&mut self, lines: &mut [Span], top_level: bool) -> usize {
        if let Some(MeteredBlock {
            kind,
            span,
            line_count,
        }) = MeteredBlock::new(lines.iter().map(|sp| sp.of(self.src)))
        {
            let lines = &mut lines[..line_count];
            let span = span.translate(lines[0].start());

            // skip part of first inline that is shared with the block span
            lines[0] = lines[0].with_start(span.end());

            // remove "]:" from footnote / link def
            if matches!(kind, Kind::Definition { .. }) {
                assert_eq!(&lines[0].of(self.src)[0..2], "]:");
                lines[0] = lines[0].skip("]:".len());
            }

            // skip opening and closing fence of code block / div
            let lines = if let Kind::Fenced {
                has_closing_fence, ..
            } = kind
            {
                let l = lines.len() - usize::from(has_closing_fence);
                &mut lines[1..l]
            } else {
                lines
            };

            // close list if a non list item or a list item of new type appeared
            if let Some(OpenList { ty, depth, .. }) = self.open_lists.last() {
                assert!(usize::from(*depth) <= self.tree.depth());
                if self.tree.depth() == (*depth).into()
                    && !matches!(kind, Kind::ListItem { ty: ty_new, .. } if *ty == ty_new)
                {
                    self.tree.exit(); // list
                    self.open_lists.pop();
                }
            }

            // set list to loose if blankline discovered
            if matches!(kind, Kind::Atom(Atom::Blankline)) {
                self.prev_blankline = true;
            } else {
                if self.prev_blankline {
                    for OpenList { node, depth, .. } in &self.open_lists {
                        if usize::from(*depth) < self.tree.depth()
                            && matches!(kind, Kind::ListItem { .. })
                        {
                            continue;
                        }
                        if let tree::Element::Container(Node::Container(Container::List {
                            tight,
                            ..
                        })) = self.tree.elem(*node)
                        {
                            *tight = false;
                        } else {
                            panic!();
                        }
                    }
                }
                self.prev_blankline = false;
            }

            match kind.block(top_level) {
                Block::Atom(a) => self.tree.atom(a, span),
                Block::Leaf(l) => self.parse_leaf(l, &kind, span, lines),
                Block::Container(Table) => self.parse_table(lines, span),
                Block::Container(c) => self.parse_container(c, &kind, span, lines),
            }

            line_count
        } else {
            0
        }
    }

    fn parse_leaf(&mut self, leaf: Leaf, k: &Kind, span: Span, lines: &mut [Span]) {
        if let Kind::Fenced { indent, .. } = k {
            for line in lines.iter_mut() {
                let indent_line = line
                    .of(self.src)
                    .chars()
                    .take_while(|c| *c != '\n' && c.is_whitespace())
                    .count();
                *line = line.skip_chars((*indent).min(indent_line), self.src);
            }
        } else {
            // trim starting whitespace of each inline
            for line in lines.iter_mut() {
                *line = line.trim_start(self.src);
            }

            // trim ending whitespace of block
            let l = lines.len();
            if l > 0 {
                let last = &mut lines[l - 1];
                *last = last.trim_end(self.src);
            }
        }

        if let Kind::Heading { level, .. } = k {
            // open and close sections
            if let Leaf::Heading {
                has_section: true, ..
            } = leaf
            {
                let first_close = self
                    .open_sections
                    .iter()
                    .rposition(|l| l < level)
                    .map_or(0, |i| i + 1);
                self.open_sections.drain(first_close..).for_each(|_| {
                    self.tree.exit(); // section
                });
                self.open_sections.push(*level);
                self.tree.enter(Node::Container(Section), span);
            }

            // trim '#' characters
            for line in lines[1..].iter_mut() {
                *line = line.trim_start_matches(self.src, |c| c == '#' || c.is_whitespace());
            }
        }

        self.tree.enter(Node::Leaf(leaf), span);
        lines
            .iter()
            .filter(|l| !matches!(k, Kind::Heading { .. }) || !l.is_empty())
            .for_each(|line| self.tree.inline(*line));
        self.tree.exit();
    }

    fn parse_container(&mut self, c: Container, k: &Kind, span: Span, lines: &mut [Span]) {
        // update spans, remove indentation / container prefix
        lines.iter_mut().skip(1).for_each(|sp| {
            let src = sp.of(self.src);
            let src_t = src.trim();
            let spaces = src.chars().take_while(|c| c.is_whitespace()).count();
            let skip = match k {
                Kind::Blockquote => {
                    if src_t == ">" {
                        spaces + 1
                    } else if src_t.starts_with('>')
                        && src_t.chars().nth(1).map_or(false, char::is_whitespace)
                    {
                        spaces + 1 + usize::from(src_t.len() > 1)
                    } else {
                        0
                    }
                }
                Kind::ListItem { indent, .. }
                | Kind::Definition { indent, .. }
                | Kind::Fenced { indent, .. } => spaces.min(*indent),
                _ => panic!("non-container {:?}", k),
            };
            let count = sp.of(self.src).chars().take_while(|c| *c != '\n').count();
            *sp = sp.skip_chars(skip.min(count), self.src);
        });

        if let ListItem(ty) = c {
            if self
                .open_lists
                .last()
                .map_or(true, |OpenList { depth, .. }| {
                    usize::from(*depth) < self.tree.depth()
                })
            {
                let tight = true;
                let node = self
                    .tree
                    .enter(Node::Container(Container::List { ty, tight }), span);
                self.open_lists.push(OpenList {
                    ty,
                    depth: self.tree.depth().try_into().unwrap(),
                    node,
                });
            }
        }

        let dt = if let ListItem(Description) = c {
            let dt = self
                .tree
                .enter(Node::Leaf(DescriptionTerm), span.empty_after());
            self.tree.exit();
            Some(dt)
        } else {
            None
        };

        let node = self.tree.enter(Node::Container(c), span);
        let mut l = 0;
        while l < lines.len() {
            l += self.parse_block(&mut lines[l..], false);
        }

        if let Some(node_dt) = dt {
            let node_child = if let Some(node_child) = self.tree.children(node).next() {
                if let tree::Element::Container(Node::Leaf(l @ Paragraph)) = node_child.elem {
                    *l = DescriptionTerm;
                    Some(node_child.index)
                } else {
                    None
                }
            } else {
                None
            };
            if let Some(node_child) = node_child {
                self.tree.swap_prev(node_child);
                self.tree.remove(node_dt);
            }
        }

        if let Some(OpenList { depth, .. }) = self.open_lists.last() {
            assert!(usize::from(*depth) <= self.tree.depth());
            if self.tree.depth() == (*depth).into() {
                self.prev_blankline = false;
                self.tree.exit(); // list
                self.open_lists.pop();
            }
        }

        self.tree.exit();
    }

    fn parse_table(&mut self, lines: &mut [Span], span: Span) {
        self.alignments.clear();
        self.tree.enter(Node::Container(Table), span);

        let caption_line = lines
            .iter()
            .position(|sp| sp.of(self.src).trim_start().starts_with('^'))
            .map_or(lines.len(), |caption_line| {
                self.tree.enter(Node::Leaf(Caption), span);
                lines[caption_line] = lines[caption_line]
                    .trim_start(self.src)
                    .skip_chars(2, self.src);
                lines[lines.len() - 1] = lines[lines.len() - 1].trim_end(self.src);
                for line in &lines[caption_line..] {
                    self.tree.inline(*line);
                }
                self.tree.exit();
                caption_line
            });

        let mut last_row_node = None;
        for row in &lines[..caption_line] {
            let row = row.trim(self.src);
            if row.is_empty() {
                break;
            }
            let row_node = self
                .tree
                .enter(Node::Container(TableRow { head: false }), row.with_len(1));
            let rem = row.skip(1); // |
            let lex = lex::Lexer::new(rem.of(self.src).chars());
            let mut pos = rem.start();
            let mut cell_start = pos;
            let mut separator_row = true;
            let mut verbatim = None;
            let mut column_index = 0;
            for lex::Token { kind, len } in lex {
                if let Some(l) = verbatim {
                    if matches!(kind, lex::Kind::Seq(lex::Sequence::Backtick)) && len == l {
                        verbatim = None;
                    }
                } else {
                    match kind {
                        lex::Kind::Sym(lex::Symbol::Pipe) => {
                            {
                                let span = Span::new(cell_start, pos).trim(self.src);
                                let cell = span.of(self.src);
                                let separator_cell = match cell.len() {
                                    0 => false,
                                    1 => cell == "-",
                                    2 => matches!(cell, ":-" | "--" | "-:"),
                                    l => {
                                        matches!(cell.as_bytes()[0], b'-' | b':')
                                            && matches!(cell.as_bytes()[l - 1], b'-' | b':')
                                            && cell.chars().skip(1).take(l - 2).all(|c| c == '-')
                                    }
                                };
                                separator_row &= separator_cell;
                                self.tree.enter(
                                    Node::Leaf(TableCell(
                                        self.alignments
                                            .get(column_index)
                                            .copied()
                                            .unwrap_or(Alignment::Unspecified),
                                    )),
                                    Span::by_len(cell_start - 1, 1),
                                );
                                self.tree.inline(span);
                                self.tree.exit(); // cell
                                cell_start = pos + len;
                                column_index += 1;
                            }
                        }
                        lex::Kind::Seq(lex::Sequence::Backtick) => {
                            verbatim = Some(len);
                        }
                        _ => {}
                    }
                }
                pos += len;
            }

            if separator_row && verbatim.is_none() {
                self.alignments.clear();
                self.alignments.extend(
                    self.tree
                        .children(row_node)
                        .filter(|n| matches!(n.elem, tree::Element::Inline))
                        .map(|n| {
                            let cell = n.span.of(self.src);
                            let l = cell.as_bytes()[0] == b':';
                            let r = cell.as_bytes()[cell.len() - 1] == b':';
                            match (l, r) {
                                (false, false) => Alignment::Unspecified,
                                (false, true) => Alignment::Right,
                                (true, false) => Alignment::Left,
                                (true, true) => Alignment::Center,
                            }
                        }),
                );
                self.tree.exit_discard(); // table row
                if let Some(head_row) = last_row_node {
                    self.tree
                        .children(head_row)
                        .filter(|n| {
                            matches!(n.elem, tree::Element::Container(Node::Leaf(TableCell(..))))
                        })
                        .zip(
                            self.alignments
                                .iter()
                                .copied()
                                .chain(std::iter::repeat(Alignment::Unspecified)),
                        )
                        .for_each(|(n, new_align)| {
                            if let tree::Element::Container(Node::Leaf(TableCell(alignment))) =
                                n.elem
                            {
                                *alignment = new_align;
                            }
                        });
                    if let tree::Element::Container(Node::Container(TableRow { head })) =
                        self.tree.elem(head_row)
                    {
                        *head = true;
                    } else {
                        panic!()
                    }
                }
            } else {
                self.tree.exit(); // table row
                last_row_node = Some(row_node);
            }
        }

        self.tree.exit(); // table
    }
}

/// Parser for a single block.
struct MeteredBlock {
    kind: Kind,
    span: Span,
    line_count: usize,
}

impl MeteredBlock {
    /// Identify and measure the line length of a single block.
    fn new<'s, I: Iterator<Item = &'s str>>(mut lines: I) -> Option<Self> {
        lines.next().map(|l| {
            let IdentifiedBlock { mut kind, span } = IdentifiedBlock::new(l);
            let line_count = 1 + lines.take_while(|l| kind.continues(l)).count();
            Self {
                kind,
                span,
                line_count,
            }
        })
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum FenceKind {
    Div,
    CodeBlock(u8),
}

#[cfg_attr(test, derive(PartialEq, Eq))]
#[derive(Debug)]
enum Kind {
    Atom(Atom),
    Paragraph,
    Heading {
        level: usize,
    },
    Fenced {
        indent: usize,
        fence_length: usize,
        kind: FenceKind,
        has_spec: bool,
        has_closing_fence: bool,
    },
    Definition {
        indent: usize,
        footnote: bool,
    },
    Blockquote,
    ListItem {
        indent: usize,
        ty: ListType,
        last_blankline: bool,
    },
    Table {
        caption: bool,
    },
}

struct IdentifiedBlock {
    kind: Kind,
    span: Span,
}

impl IdentifiedBlock {
    fn new(line: &str) -> Self {
        let mut chars = line.chars();
        let indent = chars
            .clone()
            .take_while(|c| *c != '\n' && c.is_whitespace())
            .count();
        (&mut chars).take(indent).last();
        let indent_bytes = line.len() - chars.as_str().len();
        let line = chars.as_str();
        let line_t = line.trim_end();
        let l = line.len();
        let lt = line_t.len();

        let first = if let Some(c) = chars.next() {
            c
        } else {
            return Self {
                kind: Kind::Atom(Blankline),
                span: Span::empty_at(indent_bytes),
            };
        };

        match first {
            '\n' => Some((Kind::Atom(Blankline), Span::by_len(indent_bytes, 1))),
            '#' => chars
                .find(|c| *c != '#')
                .map_or(true, char::is_whitespace)
                .then(|| {
                    let level = line.chars().take_while(|c| *c == '#').count();
                    (Kind::Heading { level }, Span::by_len(indent_bytes, level))
                }),
            '>' => {
                if chars.next().map_or(true, char::is_whitespace) {
                    Some((Kind::Blockquote, Span::by_len(indent_bytes, 1)))
                } else {
                    None
                }
            }
            '{' => (attr::valid(line.chars()).0 == lt)
                .then(|| (Kind::Atom(Attributes), Span::by_len(indent_bytes, l))),
            '|' => {
                if lt >= 2 && line_t.ends_with('|') && !line_t.ends_with("\\|") {
                    Some((Kind::Table { caption: false }, Span::empty_at(indent_bytes)))
                } else {
                    None
                }
            }
            '[' => chars.as_str().find("]:").map(|l| {
                let tag = &chars.as_str()[0..l];
                let footnote = tag.starts_with('^');
                (
                    Kind::Definition { indent, footnote },
                    Span::by_len(indent_bytes + 1, l).skip(usize::from(footnote)),
                )
            }),
            '-' | '*' if Self::is_thematic_break(chars.clone()) => {
                Some((Kind::Atom(ThematicBreak), Span::by_len(indent_bytes, lt)))
            }
            b @ ('-' | '*' | '+') => chars.next().map_or(true, |c| c == ' ').then(|| {
                let task_list = chars.next() == Some('[')
                    && matches!(chars.next(), Some('x' | 'X' | ' '))
                    && chars.next() == Some(']')
                    && chars.next().map_or(true, char::is_whitespace);
                if task_list {
                    (
                        Kind::ListItem {
                            indent,
                            ty: Task,
                            last_blankline: false,
                        },
                        Span::by_len(indent_bytes, 5),
                    )
                } else {
                    (
                        Kind::ListItem {
                            indent,
                            ty: Unordered(b as u8),
                            last_blankline: false,
                        },
                        Span::by_len(indent_bytes, 1),
                    )
                }
            }),
            ':' if chars.clone().next().map_or(true, char::is_whitespace) => Some((
                Kind::ListItem {
                    indent,
                    ty: Description,
                    last_blankline: false,
                },
                Span::by_len(indent_bytes, 1),
            )),
            f @ ('`' | ':' | '~') => {
                let fence_length = 1 + (&mut chars).take_while(|c| *c == f).count();
                let spec = &line_t[fence_length..].trim_start();
                let valid_spec = if f == ':' && !spec.starts_with('=') {
                    spec.chars().next().map_or(true, attr::is_name_start)
                        && spec.chars().skip(1).all(attr::is_name)
                } else {
                    !spec.chars().any(char::is_whitespace) && !spec.chars().any(|c| c == '`')
                };
                let skip = line_t.len() - spec.len();
                (valid_spec && fence_length >= 3).then(|| {
                    (
                        Kind::Fenced {
                            indent,
                            fence_length,
                            kind: match f {
                                ':' => FenceKind::Div,
                                _ => FenceKind::CodeBlock(f as u8),
                            },
                            has_spec: !spec.is_empty(),
                            has_closing_fence: false,
                        },
                        Span::by_len(indent_bytes + skip, spec.len()),
                    )
                })
            }
            c => Self::maybe_ordered_list_item(c, chars).map(|(num, style, len)| {
                (
                    Kind::ListItem {
                        indent,
                        ty: Ordered(num, style),
                        last_blankline: false,
                    },
                    Span::by_len(indent_bytes, len),
                )
            }),
        }
        .map(|(kind, span)| Self { kind, span })
        .unwrap_or(Self {
            kind: Kind::Paragraph,
            span: Span::empty_at(indent_bytes),
        })
    }

    fn is_thematic_break(chars: std::str::Chars) -> bool {
        let mut n = 1;
        for c in chars {
            if matches!(c, '-' | '*') {
                n += 1;
            } else if !c.is_whitespace() {
                return false;
            }
        }
        n >= 3
    }

    fn maybe_ordered_list_item(
        mut first: char,
        mut chars: std::str::Chars,
    ) -> Option<(crate::OrderedListNumbering, crate::OrderedListStyle, usize)> {
        fn is_roman_lower_digit(c: char) -> bool {
            matches!(c, 'i' | 'v' | 'x' | 'l' | 'c' | 'd' | 'm')
        }

        fn is_roman_upper_digit(c: char) -> bool {
            matches!(c, 'I' | 'V' | 'X' | 'L' | 'C' | 'D' | 'M')
        }

        let start_paren = first == '(';
        if start_paren {
            first = chars.next()?;
        }

        let numbering = if first.is_ascii_digit() {
            Decimal
        } else if first.is_ascii_lowercase() {
            AlphaLower
        } else if first.is_ascii_uppercase() {
            AlphaUpper
        } else if is_roman_lower_digit(first) {
            RomanLower
        } else if is_roman_upper_digit(first) {
            RomanUpper
        } else {
            return None;
        };

        let max_len = match numbering {
            Decimal => 19,
            AlphaLower | AlphaUpper | RomanLower | RomanUpper => 13,
        };

        let chars_num = chars.clone();
        let len_num = 1 + chars_num
            .clone()
            .take(max_len - 1)
            .take_while(|c| match numbering {
                Decimal => c.is_ascii_digit(),
                AlphaLower => c.is_ascii_lowercase(),
                AlphaUpper => c.is_ascii_uppercase(),
                RomanLower => is_roman_lower_digit(*c),
                RomanUpper => is_roman_upper_digit(*c),
            })
            .count();

        let post_num = chars.nth(len_num - 1)?;
        let style = if start_paren {
            if post_num == ')' {
                ParenParen
            } else {
                return None;
            }
        } else if post_num == ')' {
            Paren
        } else if post_num == '.' {
            Period
        } else {
            return None;
        };
        let len_style = usize::from(start_paren) + 1;

        let chars_num = std::iter::once(first).chain(chars_num.take(len_num - 1));
        let numbering = if matches!(numbering, AlphaLower)
            && chars_num.clone().all(is_roman_lower_digit)
        {
            RomanLower
        } else if matches!(numbering, AlphaUpper) && chars_num.clone().all(is_roman_upper_digit) {
            RomanUpper
        } else {
            numbering
        };

        if chars.next().map_or(true, char::is_whitespace) {
            Some((numbering, style, len_num + len_style))
        } else {
            None
        }
    }
}

impl Kind {
    /// Determine if a line continues the block.
    fn continues(&mut self, line: &str) -> bool {
        let IdentifiedBlock { kind: next, .. } = IdentifiedBlock::new(line);
        match self {
            Self::Atom(..)
            | Self::Fenced {
                has_closing_fence: true,
                ..
            } => false,
            Self::Blockquote => matches!(next, Self::Blockquote | Self::Paragraph),
            Self::Heading { level } => {
                matches!(next, Self::Paragraph)
                    || matches!(next, Self::Heading { level: l } if l == *level )
            }
            Self::Paragraph | Self::Table { caption: true } => {
                !matches!(next, Self::Atom(Blankline))
            }
            Self::ListItem {
                indent,
                last_blankline,
                ..
            } => {
                let spaces = line.chars().take_while(|c| c.is_whitespace()).count();
                let para = !*last_blankline && matches!(next, Self::Paragraph);
                let blankline = matches!(next, Self::Atom(Blankline));
                *last_blankline = blankline;
                blankline || spaces > *indent || para
            }
            Self::Definition { indent, footnote } => {
                if *footnote {
                    let spaces = line.chars().take_while(|c| c.is_whitespace()).count();
                    matches!(next, Self::Atom(Blankline)) || spaces > *indent
                } else {
                    line.starts_with(' ') && !matches!(next, Self::Atom(Blankline))
                }
            }
            Self::Fenced {
                fence_length,
                kind,
                has_closing_fence,
                ..
            } => {
                if let Kind::Fenced {
                    kind: k,
                    fence_length: l,
                    has_spec: false,
                    ..
                } = next
                {
                    *has_closing_fence = k == *kind
                        && (l == *fence_length
                            || (matches!(k, FenceKind::Div) && l > *fence_length));
                }
                true
            }
            Self::Table { caption } => {
                matches!(next, Self::Table { .. } | Self::Atom(Blankline)) || {
                    if line.trim().starts_with("^ ") {
                        *caption = true;
                        true
                    } else {
                        false
                    }
                }
            }
        }
    }

    fn block(&self, top_level: bool) -> Block {
        match self {
            Self::Atom(a) => Block::Atom(*a),
            Self::Paragraph => Block::Leaf(Paragraph),
            Self::Heading { .. } => Block::Leaf(Heading {
                has_section: top_level,
            }),
            Self::Fenced {
                kind: FenceKind::CodeBlock(..),
                ..
            } => Block::Leaf(CodeBlock),
            Self::Fenced {
                kind: FenceKind::Div,
                ..
            } => Block::Container(Div),
            Self::Definition {
                footnote: false, ..
            } => Block::Leaf(LinkDefinition),
            Self::Definition { footnote: true, .. } => Block::Container(Footnote),
            Self::Blockquote => Block::Container(Blockquote),
            Self::ListItem { ty, .. } => Block::Container(ListItem(*ty)),
            Self::Table { .. } => Block::Container(Table),
        }
    }
}

impl std::fmt::Display for Block {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Block::Atom(a) => std::fmt::Debug::fmt(a, f),
            Block::Leaf(e) => std::fmt::Debug::fmt(e, f),
            Block::Container(c) => std::fmt::Debug::fmt(c, f),
        }
    }
}

impl std::fmt::Display for Atom {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Inline")
    }
}

/// Similar to `std::str::split('\n')` but newline is included and spans are used instead of `str`.
fn lines(src: &str) -> impl Iterator<Item = Span> + '_ {
    let mut chars = src.chars();
    std::iter::from_fn(move || {
        if chars.as_str().is_empty() {
            None
        } else {
            let start = src.len() - chars.as_str().len();
            chars.find(|c| *c == '\n');
            let end = src.len() - chars.as_str().len();
            if start == end {
                None
            } else {
                Some(Span::new(start, end))
            }
        }
    })
}

#[cfg(test)]
mod test {
    use crate::tree::EventKind::*;
    use crate::Alignment;
    use crate::OrderedListNumbering::*;
    use crate::OrderedListStyle::*;

    use super::Atom::*;
    use super::Container::*;
    use super::FenceKind;
    use super::Kind;
    use super::Leaf::*;
    use super::ListType::*;
    use super::Node::*;

    macro_rules! test_parse {
        ($src:expr $(,$($event:expr),* $(,)?)?) => {
            let t = super::TreeParser::new($src).parse();
            let actual = t.map(|ev| (ev.kind, ev.span.of($src))).collect::<Vec<_>>();
            let expected = &[$($($event),*,)?];
            assert_eq!(
                actual,
                expected,
                concat!(
                    "\n",
                    "\x1b[0;1m====================== INPUT =========================\x1b[0m\n",
                    "\x1b[2m{}",
                    "\x1b[0;1m================ ACTUAL vs EXPECTED ==================\x1b[0m\n",
                    "{}",
                    "\x1b[0;1m======================================================\x1b[0m\n",
                ),
                $src,
                {
                    let a = actual.iter().map(|n| format!("{:?}", n)).collect::<Vec<_>>();
                    let b = expected.iter().map(|n| format!("{:?}", n)).collect::<Vec<_>>();
                    let max = a.len().max(b.len());
                    let a_width = a.iter().map(|a| a.len()).max().unwrap_or(0);
                    a.iter()
                        .map(AsRef::as_ref)
                        .chain(std::iter::repeat(""))
                        .zip(b.iter().map(AsRef::as_ref).chain(std::iter::repeat("")))
                        .take(max)
                        .map(|(a, b)|
                            format!(
                                "\x1b[{}m{:a_width$}\x1b[0m    {}=    \x1b[{}m{}\x1b[0m\n",
                                if a == b { "2" } else { "31" },
                                a,
                                if a == b { '=' } else { '!' },
                                if a == b { "2" } else { "32" },
                                b,
                                a_width = a_width,
                            )
                        )
                        .collect::<String>()
                },
            );
        };
    }

    #[test]
    fn parse_para_oneline() {
        test_parse!(
            "para\n",
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_para_multiline() {
        test_parse!(
            "para0\npara1\n",
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para0\n"),
            (Inline, "para1"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_heading() {
        test_parse!(
            concat!(
                "# a\n",
                "## b\n", //
            ),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "a"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Enter(Container(Section)), "##"),
            (Enter(Leaf(Heading { has_section: true })), "##"),
            (Inline, "b"),
            (Exit(Leaf(Heading { has_section: true })), "##"),
            (Exit(Container(Section)), "##"),
            (Exit(Container(Section)), "#"),
        );
    }

    #[test]
    fn parse_heading_empty_first_line() {
        test_parse!(
            concat!(
                "#\n",
                "heading\n", //
            ),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "heading"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Exit(Container(Section)), "#"),
        );
    }

    #[test]
    fn parse_heading_multi() {
        test_parse!(
            concat!(
                "# 2\n",
                "\n",
                " #   8\n",
                "  12\n",
                "15\n", //
            ),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "2"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Atom(Blankline), "\n"),
            (Exit(Container(Section)), "#"),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "8\n"),
            (Inline, "12\n"),
            (Inline, "15"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Exit(Container(Section)), "#"),
        );
    }

    #[test]
    fn parse_heading_multi_repeat() {
        test_parse!(
            concat!(
                "# a\n",
                "# b\n",
                "c\n", //
            ),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "a\n"),
            (Inline, "b\n"),
            (Inline, "c"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Exit(Container(Section)), "#"),
        );
    }

    #[test]
    fn parse_section() {
        test_parse!(
            concat!(
                "# a\n",
                "\n",
                "## aa\n",
                "\n",
                "#### aaaa\n",
                "\n",
                "## ab\n",
                "\n",
                "### aba\n",
                "\n",
                "# b\n",
            ),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "a"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Atom(Blankline), "\n"),
            (Enter(Container(Section)), "##"),
            (Enter(Leaf(Heading { has_section: true })), "##"),
            (Inline, "aa"),
            (Exit(Leaf(Heading { has_section: true })), "##"),
            (Atom(Blankline), "\n"),
            (Enter(Container(Section)), "####"),
            (Enter(Leaf(Heading { has_section: true })), "####"),
            (Inline, "aaaa"),
            (Exit(Leaf(Heading { has_section: true })), "####"),
            (Atom(Blankline), "\n"),
            (Exit(Container(Section)), "####"),
            (Exit(Container(Section)), "##"),
            (Enter(Container(Section)), "##"),
            (Enter(Leaf(Heading { has_section: true })), "##"),
            (Inline, "ab"),
            (Exit(Leaf(Heading { has_section: true })), "##"),
            (Atom(Blankline), "\n"),
            (Enter(Container(Section)), "###"),
            (Enter(Leaf(Heading { has_section: true })), "###"),
            (Inline, "aba"),
            (Exit(Leaf(Heading { has_section: true })), "###"),
            (Atom(Blankline), "\n"),
            (Exit(Container(Section)), "###"),
            (Exit(Container(Section)), "##"),
            (Exit(Container(Section)), "#"),
            (Enter(Container(Section)), "#"),
            (Enter(Leaf(Heading { has_section: true })), "#"),
            (Inline, "b"),
            (Exit(Leaf(Heading { has_section: true })), "#"),
            (Exit(Container(Section)), "#"),
        );
    }

    #[test]
    fn parse_blockquote() {
        test_parse!(
            "> a\n",
            (Enter(Container(Blockquote)), ">"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Blockquote)), ">"),
        );
        test_parse!(
            "> a\nb\nc\n",
            (Enter(Container(Blockquote)), ">"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a\n"),
            (Inline, "b\n"),
            (Inline, "c"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Blockquote)), ">"),
        );
        test_parse!(
            concat!(
                "> a\n",
                ">\n",
                "> ## hl\n",
                ">\n",
                ">  para\n", //
            ),
            (Enter(Container(Blockquote)), ">"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Enter(Leaf(Heading { has_section: false })), "##"),
            (Inline, "hl"),
            (Exit(Leaf(Heading { has_section: false })), "##"),
            (Atom(Blankline), "\n"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Blockquote)), ">"),
        );
    }

    #[test]
    fn parse_blockquote_empty() {
        test_parse!(
            "> \n",
            (Enter(Container(Blockquote)), ">"),
            (Atom(Blankline), "\n"),
            (Exit(Container(Blockquote)), ">"),
        );
        test_parse!(
            ">",
            (Enter(Container(Blockquote)), ">"),
            (Atom(Blankline), ""),
            (Exit(Container(Blockquote)), ">"),
        );
    }

    #[test]
    fn parse_code_block() {
        test_parse!(
            concat!("```\n", "l0\n"),
            (Enter(Leaf(CodeBlock)), "",),
            (Inline, "l0\n"),
            (Exit(Leaf(CodeBlock)), "",),
        );
        test_parse!(
            concat!(
                "```\n",
                "l0\n",
                "```\n",
                "\n",
                "para\n", //
            ),
            (Enter(Leaf(CodeBlock)), ""),
            (Inline, "l0\n"),
            (Exit(Leaf(CodeBlock)), ""),
            (Atom(Blankline), "\n"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
        test_parse!(
            concat!(
                "````  lang\n",
                "l0\n",
                "```\n",
                " l1\n",
                "````", //
            ),
            (Enter(Leaf(CodeBlock)), "lang"),
            (Inline, "l0\n"),
            (Inline, "```\n"),
            (Inline, " l1\n"),
            (Exit(Leaf(CodeBlock)), "lang"),
        );
        test_parse!(
            concat!(
                "```\n", //
                "a\n",   //
                "```\n", //
                "```\n", //
                "bbb\n", //
                "```\n", //
            ),
            (Enter(Leaf(CodeBlock)), ""),
            (Inline, "a\n"),
            (Exit(Leaf(CodeBlock)), ""),
            (Enter(Leaf(CodeBlock)), ""),
            (Inline, "bbb\n"),
            (Exit(Leaf(CodeBlock)), ""),
        );
        test_parse!(
            concat!(
                "~~~\n",
                "code\n",
                "  block\n",
                "~~~\n", //
            ),
            (Enter(Leaf(CodeBlock)), ""),
            (Inline, "code\n"),
            (Inline, "  block\n"),
            (Exit(Leaf(CodeBlock)), ""),
        );
    }

    #[test]
    fn parse_link_definition() {
        test_parse!(
            "[tag]: url\n",
            (Enter(Leaf(LinkDefinition)), "tag"),
            (Inline, "url"),
            (Exit(Leaf(LinkDefinition)), "tag"),
        );
    }

    #[test]
    fn parse_footnote() {
        test_parse!(
            "[^tag]: description\n",
            (Enter(Container(Footnote)), "tag"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "description"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Footnote)), "tag"),
        );
    }

    #[test]
    fn parse_footnote_post() {
        test_parse!(
            concat!(
                "[^a]\n",
                "\n",
                "[^a]: note\n",
                "\n",
                "para\n", //
            ),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "[^a]"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Enter(Container(Footnote)), "a"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "note"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Exit(Container(Footnote)), "a"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_attr() {
        test_parse!(
            "{.some_class}\npara\n",
            (Atom(Attributes), "{.some_class}\n"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_list_single_item() {
        test_parse!(
            "- abc",
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: true
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "abc"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: true
                })),
                "-"
            ),
        );
    }

    #[test]
    fn parse_list_tight() {
        test_parse!(
            concat!(
                "- a\n", //
                "- b\n", //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
        );
    }

    #[test]
    fn parse_list_loose() {
        test_parse!(
            concat!(
                "- a\n", //
                "- b\n", //
                "\n",    //
                "- c\n", //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: false,
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "c"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: false,
                })),
                "-"
            ),
        );
    }

    #[test]
    fn parse_list_tight_nest() {
        test_parse!(
            concat!(
                "- a\n",    //
                "\n",       //
                "  + aa\n", //
                "  + ab\n", //
                "\n",       //
                "- b\n",    //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (
                Enter(Container(List {
                    ty: Unordered(b'+'),
                    tight: true,
                })),
                "+",
            ),
            (Enter(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "aa"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "ab"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Exit(Container(ListItem(Unordered(b'+')))), "+"),
            (
                Exit(Container(List {
                    ty: Unordered(b'+'),
                    tight: true,
                })),
                "+",
            ),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
        );
    }

    #[test]
    fn parse_list_nest() {
        test_parse!(
            concat!(
                "- a\n",     //
                "    \n",    //
                "  + b\n",   //
                "      \n",  //
                "    * c\n", //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (
                Enter(Container(List {
                    ty: Unordered(b'+'),
                    tight: true,
                })),
                "+",
            ),
            (Enter(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (
                Enter(Container(List {
                    ty: Unordered(b'*'),
                    tight: true,
                })),
                "*",
            ),
            (Enter(Container(ListItem(Unordered(b'*')))), "*"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "c"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'*')))), "*"),
            (
                Exit(Container(List {
                    ty: Unordered(b'*'),
                    tight: true,
                })),
                "*",
            ),
            (Exit(Container(ListItem(Unordered(b'+')))), "+"),
            (
                Exit(Container(List {
                    ty: Unordered(b'+'),
                    tight: true,
                })),
                "+",
            ),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: true,
                })),
                "-"
            ),
        );
    }

    #[test]
    fn parse_list_post() {
        test_parse!(
            concat!(
                "- a\n",   //
                "\n",      //
                "  * b\n", //
                "\n",      //
                "cd\n",    //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(45),
                    tight: true
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(45)))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (
                Enter(Container(List {
                    ty: Unordered(42),
                    tight: true
                })),
                "*"
            ),
            (Enter(Container(ListItem(Unordered(42)))), "*"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Atom(Blankline), "\n"),
            (Exit(Container(ListItem(Unordered(42)))), "*"),
            (
                Exit(Container(List {
                    ty: Unordered(42),
                    tight: true
                })),
                "*"
            ),
            (Exit(Container(ListItem(Unordered(45)))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(45),
                    tight: true
                })),
                "-"
            ),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "cd"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_list_mixed() {
        test_parse!(
            concat!(
                "- a\n", //
                "+ b\n", //
                "+ c\n", //
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'-'),
                    tight: true
                })),
                "-"
            ),
            (Enter(Container(ListItem(Unordered(b'-')))), "-"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "a"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'-')))), "-"),
            (
                Exit(Container(List {
                    ty: Unordered(b'-'),
                    tight: true
                })),
                "-"
            ),
            (
                Enter(Container(List {
                    ty: Unordered(b'+'),
                    tight: true
                })),
                "+"
            ),
            (Enter(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "b"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Container(ListItem(Unordered(b'+')))), "+"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "c"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Unordered(b'+')))), "+"),
            (
                Exit(Container(List {
                    ty: Unordered(b'+'),
                    tight: true
                })),
                "+"
            ),
        );
    }

    #[test]
    fn parse_description_list() {
        test_parse!(
            concat!(
                ": term\n",         //
                "\n",               //
                "   description\n", //
            ),
            (
                Enter(Container(List {
                    ty: Description,
                    tight: false
                })),
                ":"
            ),
            (Enter(Leaf(DescriptionTerm)), ""),
            (Inline, "term"),
            (Exit(Leaf(DescriptionTerm)), ""),
            (Enter(Container(ListItem(Description))), ":"),
            (Atom(Blankline), "\n"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "description"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(ListItem(Description))), ":"),
            (
                Exit(Container(List {
                    ty: Description,
                    tight: false
                })),
                ":"
            ),
        );
    }

    #[test]
    fn parse_table() {
        test_parse!(
            concat!(
                "|a|b|c|\n", //
                "|-|-|-|\n", //
                "|1|2|3|\n", //
            ),
            (Enter(Container(Table)), ""),
            (Enter(Container(TableRow { head: true })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "a"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "b"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "c"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: true })), "|"),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "1"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "2"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "3"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), "")
        );
    }

    #[test]
    fn parse_table_escaped() {
        test_parse!(
            "|a\\|\n",
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "|a\\|"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_table_post() {
        test_parse!(
            "|a|\npara",
            (Enter(Container(Table)), ""),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "a"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), ""),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_table_align() {
        test_parse!(
            concat!(
                "|:---|:----:|----:|\n",
                "|left|center|right|\n", //
            ),
            (Enter(Container(Table)), ""),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Left))), "|"),
            (Inline, "left"),
            (Exit(Leaf(TableCell(Alignment::Left))), "|"),
            (Enter(Leaf(TableCell(Alignment::Center))), "|"),
            (Inline, "center"),
            (Exit(Leaf(TableCell(Alignment::Center))), "|"),
            (Enter(Leaf(TableCell(Alignment::Right))), "|"),
            (Inline, "right"),
            (Exit(Leaf(TableCell(Alignment::Right))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), "")
        );
    }

    #[test]
    fn parse_table_caption() {
        test_parse!(
            "|a|\n^ caption",
            (Enter(Container(Table)), ""),
            (Enter(Leaf(Caption)), ""),
            (Inline, "caption"),
            (Exit(Leaf(Caption)), ""),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "a"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), ""),
        );
    }

    #[test]
    fn parse_table_caption_multiline() {
        test_parse!(
            concat!(
                "|a|\n",       //
                "\n",          //
                "^ caption\n", //
                "continued\n", //
                "\n",          //
                "para\n",      //
            ),
            (Enter(Container(Table)), ""),
            (Enter(Leaf(Caption)), ""),
            (Inline, "caption\n"),
            (Inline, "continued"),
            (Exit(Leaf(Caption)), ""),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "a"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), ""),
            (Atom(Blankline), "\n"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "para"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_table_caption_empty() {
        test_parse!(
            "|a|\n^ ",
            (Enter(Container(Table)), ""),
            (Enter(Container(TableRow { head: false })), "|"),
            (Enter(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Inline, "a"),
            (Exit(Leaf(TableCell(Alignment::Unspecified))), "|"),
            (Exit(Container(TableRow { head: false })), "|"),
            (Exit(Container(Table)), ""),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "^"),
            (Exit(Leaf(Paragraph)), ""),
        );
    }

    #[test]
    fn parse_table_sep_row_only() {
        test_parse!(
            "|-|-|",
            (Enter(Container(Table)), ""),
            (Exit(Container(Table)), "")
        );
    }

    #[test]
    fn parse_div() {
        test_parse!(
            concat!("::: cls\n", "abc\n", ":::\n",),
            (Enter(Container(Div)), "cls"),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "abc"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Div)), "cls"),
        );
    }

    #[test]
    fn parse_div_no_class() {
        test_parse!(
            concat!(":::\n", "abc\n", ":::\n",),
            (Enter(Container(Div)), ""),
            (Enter(Leaf(Paragraph)), ""),
            (Inline, "abc"),
            (Exit(Leaf(Paragraph)), ""),
            (Exit(Container(Div)), ""),
        );
    }

    macro_rules! test_block {
        ($src:expr, $kind:expr, $str:expr, $len:expr $(,)?) => {
            let lines = super::lines($src).map(|sp| sp.of($src));
            let mb = super::MeteredBlock::new(lines).unwrap();
            assert_eq!(
                (mb.kind, mb.span.of($src), mb.line_count),
                ($kind, $str, $len),
                "\n\n{}\n\n",
                $src
            );
        };
    }

    #[test]
    fn block_blankline() {
        test_block!("\n", Kind::Atom(Blankline), "\n", 1);
        test_block!(" \n", Kind::Atom(Blankline), "\n", 1);
    }

    #[test]
    fn block_multiline() {
        test_block!(
            "# heading\n spanning two lines\n",
            Kind::Heading { level: 1 },
            "#",
            2
        );
    }

    #[test]
    fn block_blockquote() {
        test_block!(
            concat!(
                "> a\n",    //
                ">\n",      //
                "  >  b\n", //
                ">\n",      //
                "> c\n",    //
            ),
            Kind::Blockquote,
            ">",
            5,
        );
    }

    #[test]
    fn block_thematic_break() {
        test_block!("---\n", Kind::Atom(ThematicBreak), "---", 1);
        test_block!(
            concat!(
                "   -*- -*-\n",
                "\n",
                "para", //
            ),
            Kind::Atom(ThematicBreak),
            "-*- -*-",
            1
        );
    }

    #[test]
    fn block_code_block() {
        test_block!(
            concat!(
                "````  lang\n",
                "l0\n",
                "```\n",
                " l1\n",
                "````", //
            ),
            Kind::Fenced {
                indent: 0,
                kind: FenceKind::CodeBlock(b'`'),
                fence_length: 4,
                has_spec: true,
                has_closing_fence: true,
            },
            "lang",
            5,
        );
        test_block!(
            concat!(
                "```\n", //
                "a\n",   //
                "```\n", //
                "```\n", //
                "bbb\n", //
                "```\n", //
            ),
            Kind::Fenced {
                indent: 0,
                kind: FenceKind::CodeBlock(b'`'),
                fence_length: 3,
                has_spec: false,
                has_closing_fence: true,
            },
            "",
            3,
        );
        test_block!(
            concat!(
                "``` no space in lang specifier\n",
                "l0\n",
                "```\n", //
            ),
            Kind::Paragraph,
            "",
            3,
        );
    }

    #[test]
    fn block_link_definition() {
        test_block!(
            "[tag]: url\n",
            Kind::Definition {
                indent: 0,
                footnote: false
            },
            "tag",
            1
        );
    }

    #[test]
    fn block_link_definition_multiline() {
        test_block!(
            concat!(
                "[tag]: uuu\n",
                " rl\n", //
            ),
            Kind::Definition {
                indent: 0,
                footnote: false
            },
            "tag",
            2,
        );
        test_block!(
            concat!(
                "[tag]: url\n",
                "para\n", //
            ),
            Kind::Definition {
                indent: 0,
                footnote: false
            },
            "tag",
            1,
        );
    }

    #[test]
    fn block_footnote_empty() {
        test_block!(
            "[^tag]:\n",
            Kind::Definition {
                indent: 0,
                footnote: true
            },
            "tag",
            1
        );
    }

    #[test]
    fn block_footnote_single() {
        test_block!(
            "[^tag]: a\n",
            Kind::Definition {
                indent: 0,
                footnote: true
            },
            "tag",
            1
        );
    }

    #[test]
    fn block_footnote_multiline() {
        test_block!(
            concat!(
                "[^tag]: a\n",
                " b\n", //
            ),
            Kind::Definition {
                indent: 0,
                footnote: true
            },
            "tag",
            2,
        );
    }

    #[test]
    fn block_footnote_multiline_post() {
        test_block!(
            concat!(
                "[^tag]: a\n",
                " b\n",
                "\n",
                "para\n", //
            ),
            Kind::Definition {
                indent: 0,
                footnote: true
            },
            "tag",
            3,
        );
    }

    #[test]
    fn block_list_bullet() {
        test_block!(
            "- abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Unordered(b'-'),
                last_blankline: false,
            },
            "-",
            1
        );
        test_block!(
            "+ abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Unordered(b'+'),
                last_blankline: false,
            },
            "+",
            1
        );
        test_block!(
            "* abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Unordered(b'*'),
                last_blankline: false,
            },
            "*",
            1
        );
    }

    #[test]
    fn block_list_task() {
        test_block!(
            "- [ ] abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Task,
                last_blankline: false,
            },
            "- [ ]",
            1
        );
        test_block!(
            "+ [x] abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Task,
                last_blankline: false,
            },
            "+ [x]",
            1
        );
        test_block!(
            "* [X] abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Task,
                last_blankline: false,
            },
            "* [X]",
            1
        );
    }

    #[test]
    fn block_list_ordered() {
        test_block!(
            "123. abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(Decimal, Period),
                last_blankline: false,
            },
            "123.",
            1
        );
        test_block!(
            "i. abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(RomanLower, Period),
                last_blankline: false,
            },
            "i.",
            1
        );
        test_block!(
            "I. abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(RomanUpper, Period),
                last_blankline: false,
            },
            "I.",
            1
        );
        test_block!(
            "IJ. abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(AlphaUpper, Period),
                last_blankline: false,
            },
            "IJ.",
            1
        );
        test_block!(
            "(a) abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(AlphaLower, ParenParen),
                last_blankline: false,
            },
            "(a)",
            1
        );
        test_block!(
            "a) abc\n",
            Kind::ListItem {
                indent: 0,
                ty: Ordered(AlphaLower, Paren),
                last_blankline: false,
            },
            "a)",
            1
        );
    }
}