refactor: unify markdown formatting pipeline

src/markdown/render.ts

@@ -0,0 +1,137 @@
+import type { MarkdownIR, MarkdownLinkSpan, MarkdownStyle, MarkdownStyleSpan } from "./ir.js";
+
+export type RenderStyleMarker = {
+  open: string;
+  close: string;
+};
+
+export type RenderStyleMap = Partial<Record<MarkdownStyle, RenderStyleMarker>>;
+
+export type RenderLink = {
+  start: number;
+  end: number;
+  open: string;
+  close: string;
+};
+
+export type RenderOptions = {
+  styleMarkers: RenderStyleMap;
+  escapeText: (text: string) => string;
+  buildLink?: (link: MarkdownLinkSpan, text: string) => RenderLink | null;
+};
+
+const STYLE_ORDER: MarkdownStyle[] = [
+  "code_block",
+  "code",
+  "bold",
+  "italic",
+  "strikethrough",
+  "spoiler",
+];
+
+const STYLE_RANK = new Map<MarkdownStyle, number>(
+  STYLE_ORDER.map((style, index) => [style, index]),
+);
+
+function sortStyleSpans(spans: MarkdownStyleSpan[]): MarkdownStyleSpan[] {
+  return [...spans].sort((a, b) => {
+    if (a.start !== b.start) return a.start - b.start;
+    if (a.end !== b.end) return b.end - a.end;
+    return (STYLE_RANK.get(a.style) ?? 0) - (STYLE_RANK.get(b.style) ?? 0);
+  });
+}
+
+export function renderMarkdownWithMarkers(ir: MarkdownIR, options: RenderOptions): string {
+  const text = ir.text ?? "";
+  if (!text) return "";
+
+  const styleMarkers = options.styleMarkers;
+  const styled = sortStyleSpans(
+    ir.styles.filter((span) => Boolean(styleMarkers[span.style])),
+  );
+
+  const boundaries = new Set<number>();
+  boundaries.add(0);
+  boundaries.add(text.length);
+
+  const startsAt = new Map<number, MarkdownStyleSpan[]>();
+  for (const span of styled) {
+    if (span.start === span.end) continue;
+    boundaries.add(span.start);
+    boundaries.add(span.end);
+    const bucket = startsAt.get(span.start);
+    if (bucket) bucket.push(span);
+    else startsAt.set(span.start, [span]);
+  }
+  for (const spans of startsAt.values()) {
+    spans.sort((a, b) => {
+      if (a.end !== b.end) return b.end - a.end;
+      return (STYLE_RANK.get(a.style) ?? 0) - (STYLE_RANK.get(b.style) ?? 0);
+    });
+  }
+
+  const linkStarts = new Map<number, RenderLink[]>();
+  const linkEnds = new Map<number, RenderLink[]>();
+  if (options.buildLink) {
+    for (const link of ir.links) {
+      if (link.start === link.end) continue;
+      const rendered = options.buildLink(link, text);
+      if (!rendered) continue;
+      boundaries.add(rendered.start);
+      boundaries.add(rendered.end);
+      const openBucket = linkStarts.get(rendered.start);
+      if (openBucket) openBucket.push(rendered);
+      else linkStarts.set(rendered.start, [rendered]);
+      const closeBucket = linkEnds.get(rendered.end);
+      if (closeBucket) closeBucket.push(rendered);
+      else linkEnds.set(rendered.end, [rendered]);
+    }
+  }
+
+  const points = [...boundaries].sort((a, b) => a - b);
+  const stack: MarkdownStyleSpan[] = [];
+  let out = "";
+
+  for (let i = 0; i < points.length; i += 1) {
+    const pos = points[i];
+
+    while (stack.length && stack[stack.length - 1]?.end === pos) {
+      const span = stack.pop();
+      if (!span) break;
+      const marker = styleMarkers[span.style];
+      if (marker) out += marker.close;
+    }
+
+    const closingLinks = linkEnds.get(pos);
+    if (closingLinks && closingLinks.length > 0) {
+      for (const link of closingLinks) {
+        out += link.close;
+      }
+    }
+
+    const openingLinks = linkStarts.get(pos);
+    if (openingLinks && openingLinks.length > 0) {
+      for (const link of openingLinks) {
+        out += link.open;
+      }
+    }
+
+    const openingStyles = startsAt.get(pos);
+    if (openingStyles) {
+      for (const span of openingStyles) {
+        const marker = styleMarkers[span.style];
+        if (!marker) continue;
+        stack.push(span);
+        out += marker.open;
+      }
+    }
+
+    const next = points[i + 1];
+    if (next === undefined) break;
+    if (next > pos) {
+      out += options.escapeText(text.slice(pos, next));
+    }
+  }
+
+  return out;
+}