feat: Added 'Table of Contents' markdown extension.

markdown/toc.odin

@@ -0,0 +1,163 @@
+package markdown
+
+import "core:strings"
+
+// generate_toc scans rendered HTML for <h1>-<h6> tags with id attributes and
+// builds a nested <ul> table of contents. Returns "" if no headings with IDs
+// are found. Must be called after inject_heading_ids.
+generate_toc :: proc(html: string, allocator := context.allocator) -> string {
+	b: strings.Builder
+	strings.builder_init(&b, allocator)
+
+	current_level := 0
+	min_level := 7
+	pos := 0
+
+	for {
+		idx, level, id, text, next_pos := next_heading(html, pos)
+		if level == 0 {
+			break
+		}
+		pos = next_pos
+
+		if level < min_level {
+			min_level = level
+		}
+
+		if current_level == 0 {
+			current_level = level
+			strings.write_string(&b, "<ul>\n")
+		} else if level > current_level {
+			for current_level < level {
+				strings.write_string(&b, "<ul>\n")
+				current_level += 1
+			}
+		} else if level < current_level {
+			strings.write_string(&b, "</li>\n")
+			for current_level > level {
+				strings.write_string(&b, "</ul>\n</li>\n")
+				current_level -= 1
+			}
+		} else {
+			strings.write_string(&b, "</li>\n")
+		}
+
+		strings.write_string(&b, `<li><a href="#`)
+		strings.write_string(&b, id)
+		strings.write_string(&b, `">`)
+		strings.write_string(&b, text)
+		strings.write_string(&b, `</a>`)
+	}
+
+	if current_level == 0 {
+		return ""
+	}
+
+	strings.write_string(&b, "</li>\n")
+	for current_level > min_level {
+		strings.write_string(&b, "</ul>\n</li>\n")
+		current_level -= 1
+	}
+	strings.write_string(&b, "</ul>\n")
+
+	return strings.to_string(b)
+}
+
+// next_heading finds the next <hN> tag with an id attribute starting from pos.
+// Returns level=0 if none found.
+next_heading :: proc(
+	html: string,
+	start: int,
+) -> (
+	idx: int,
+	level: int,
+	id: string,
+	text: string,
+	next_pos: int,
+) {
+	i := start
+	for i + 3 < len(html) {
+		if html[i] == '<' && html[i + 1] == 'h' {
+			d := html[i + 2]
+			if d >= '1' && d <= '6' {
+				level = int(d - '0')
+				idx = i
+				break
+			}
+		}
+		i += 1
+	}
+
+	if level == 0 {
+		return 0, 0, "", "", len(html)
+	}
+
+	// Find end of opening tag
+	tag_end := strings.index_byte(html[idx:], '>')
+	if tag_end < 0 {
+		return 0, 0, "", "", len(html)
+	}
+	tag_end += idx
+
+	// Find id="..." within the tag
+	tag := html[idx:tag_end + 1]
+	id_pos := strings.index(tag, `id="`)
+	if id_pos < 0 {
+		// No id — skip this heading, continue searching
+		return next_heading(html, tag_end + 1)
+	}
+
+	id_start := idx + id_pos + 4
+	id_end_rel := strings.index_byte(html[id_start:], '"')
+	if id_end_rel < 0 {
+		return 0, 0, "", "", len(html)
+	}
+	id = html[id_start:id_start + id_end_rel]
+
+	// Text between > and </hN>
+	text_start := tag_end + 1
+	close_idx := strings.index(html[text_start:], "</h")
+	if close_idx < 0 {
+		return 0, 0, "", "", len(html)
+	}
+	text_end := text_start + close_idx
+	text = strip_tags(html[text_start:text_end])
+
+	// Find end of closing tag
+	next_pos = text_end + close_tag_len(html, text_end)
+
+	return idx, level, id, text, next_pos
+}
+
+// close_tag_len returns the length of the </hN> tag at pos.
+close_tag_len :: proc(html: string, pos: int) -> int {
+	if pos + 4 > len(html) {
+		return 4
+	}
+	end := strings.index_byte(html[pos:], '>')
+	if end < 0 {
+		return 4
+	}
+	return end + 1
+}
+
+// strip_tags removes HTML tags from a string, leaving only text content.
+strip_tags :: proc(s: string) -> string {
+	b: strings.Builder
+	strings.builder_init(&b, context.temp_allocator)
+
+	i := 0
+	for i < len(s) {
+		if s[i] == '<' {
+			end := strings.index_byte(s[i:], '>')
+			if end >= 0 {
+				i += end + 1
+				continue
+			}
+		}
+		strings.write_byte(&b, s[i])
+		i += 1
+	}
+	return strings.to_string(b)
+}
+