jotdown_wasm: add output option for indented events

make events more readable, more resembling an AST

examples/jotdown_wasm/demo.html

@@ -3,6 +3,7 @@
     import init, {
         jotdown_render,
         jotdown_parse,
+        jotdown_parse_indent,
     } from './pkg/jotdown_wasm.js';
     await init();
 
@@ -17,6 +18,9 @@
         } else if (fmt.value == "events") {
             output.classList.add("verbatim")
             output.innerText = jotdown_parse(input.innerText);
+        } else if (fmt.value == "events_indent") {
+            output.classList.add("verbatim")
+            output.innerText = jotdown_parse_indent(input.innerText);
         } else if (fmt.value == "preview") {
             output.classList.remove("verbatim")
             output.innerHTML = jotdown_render(input.innerText);
@@ -36,6 +40,7 @@
       <option value="preview">preview</option>
       <option value="html">html</option>
       <option value="events">events</option>
+      <option value="events_indent">events (indented)</option>
     </select>
   </div>
   <div id="panes" style="display:flex;height:100%;gap:1rem">

examples/jotdown_wasm/src/lib.rs

@@ -1,6 +1,7 @@
 use wasm_bindgen::prelude::*;
 
 use jotdown::Render;
+use std::fmt::Write;
 
 #[must_use]
 #[wasm_bindgen]
@@ -20,3 +21,44 @@ pub fn jotdown_parse(djot: &str) -> String {
         .map(|e| format!("{:?}\n", e))
         .collect()
 }
+
+#[must_use]
+#[wasm_bindgen]
+pub fn jotdown_parse_indent(djot: &str) -> String {
+    let mut level = 0;
+    let mut out = String::new();
+    for e in jotdown::Parser::new(djot) {
+        if !matches!(e, jotdown::Event::End(..)) {
+            // use non-breaking space for indent because normal spaces gets squeezed by browser
+            let nbsp = '\u{00a0}';
+            (0..4 * level).for_each(|_| out.push(nbsp));
+        }
+        match e {
+            jotdown::Event::Start(c, attrs) => {
+                level += 1;
+                if c.is_block() {
+                    out.push('[');
+                } else {
+                    out.push('(');
+                }
+                out.write_fmt(format_args!("{:?}", c)).unwrap();
+                if c.is_block() {
+                    out.push(']');
+                } else {
+                    out.push(')');
+                }
+                if !attrs.is_empty() {
+                    out.write_fmt(format_args!(" {:?}", attrs)).unwrap();
+                }
+                out.push('\n');
+            }
+            jotdown::Event::End(..) => {
+                level -= 1;
+            }
+            e => {
+                out.write_fmt(format_args!("{:?}\n", e)).unwrap();
+            }
+        };
+    }
+    out
+}