feat: add announcements feature with dynamic routing and markdown support

lib/markdown.ts

@@ -0,0 +1,144 @@
+type ParseState = {
+  inCodeBlock: boolean;
+  codeLang: string;
+  paragraphBuffer: string[];
+  listType: "ul" | "ol" | null;
+  listBuffer: string[];
+};
+
+function escapeHtml(value: string): string {
+  return value
+    .replaceAll("&", "&")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;")
+    .replaceAll("'", "&#39;");
+}
+
+function applyInlineMarkdown(value: string): string {
+  const escaped = escapeHtml(value);
+
+  return escaped
+    .replace(/`([^`]+)`/g, "<code>$1</code>")
+    .replace(/\*\*([^*]+)\*\*/g, "<strong>$1</strong>")
+    .replace(/\*([^*]+)\*/g, "<em>$1</em>")
+    .replace(/~~([^~]+)~~/g, "<del>$1</del>")
+    .replace(/\[([^\]]+)\]\((https?:\/\/[^\s)]+)\)/g, '<a href="$2" target="_blank" rel="noopener noreferrer">$1</a>');
+}
+
+function flushParagraph(state: ParseState, html: string[]): void {
+  if (state.paragraphBuffer.length === 0) {
+    return;
+  }
+
+  html.push(`<p>${applyInlineMarkdown(state.paragraphBuffer.join(" "))}</p>`);
+  state.paragraphBuffer = [];
+}
+
+function flushList(state: ParseState, html: string[]): void {
+  if (!state.listType || state.listBuffer.length === 0) {
+    return;
+  }
+
+  html.push(`<${state.listType}>${state.listBuffer.join("")}</${state.listType}>`);
+  state.listType = null;
+  state.listBuffer = [];
+}
+
+export function markdownToHtml(markdown: string): string {
+  const lines = markdown.replace(/\r\n/g, "\n").split("\n");
+  const html: string[] = [];
+  const state: ParseState = {
+    inCodeBlock: false,
+    codeLang: "",
+    paragraphBuffer: [],
+    listType: null,
+    listBuffer: [],
+  };
+
+  for (const rawLine of lines) {
+    const line = rawLine.trimEnd();
+
+    if (line.startsWith("```")) {
+      flushParagraph(state, html);
+      flushList(state, html);
+
+      if (!state.inCodeBlock) {
+        state.inCodeBlock = true;
+        state.codeLang = line.slice(3).trim();
+        const className = state.codeLang ? ` class="language-${escapeHtml(state.codeLang)}"` : "";
+        html.push(`<pre><code${className}>`);
+      } else {
+        state.inCodeBlock = false;
+        state.codeLang = "";
+        html.push("</code></pre>");
+      }
+      continue;
+    }
+
+    if (state.inCodeBlock) {
+      html.push(`${escapeHtml(rawLine)}\n`);
+      continue;
+    }
+
+    if (line.length === 0) {
+      flushParagraph(state, html);
+      flushList(state, html);
+      continue;
+    }
+
+    const headingMatch = line.match(/^(#{1,6})\s+(.+)$/);
+    if (headingMatch) {
+      flushParagraph(state, html);
+      flushList(state, html);
+      const level = headingMatch[1].length;
+      html.push(`<h${level}>${applyInlineMarkdown(headingMatch[2])}</h${level}>`);
+      continue;
+    }
+
+    if (/^---$/.test(line)) {
+      flushParagraph(state, html);
+      flushList(state, html);
+      html.push("<hr />");
+      continue;
+    }
+
+    const blockquoteMatch = line.match(/^>\s?(.*)$/);
+    if (blockquoteMatch) {
+      flushParagraph(state, html);
+      flushList(state, html);
+      html.push(`<blockquote><p>${applyInlineMarkdown(blockquoteMatch[1])}</p></blockquote>`);
+      continue;
+    }
+
+    const ulMatch = line.match(/^[-*+]\s+(.+)$/);
+    if (ulMatch) {
+      flushParagraph(state, html);
+      if (state.listType !== "ul") {
+        flushList(state, html);
+        state.listType = "ul";
+      }
+      state.listBuffer.push(`<li>${applyInlineMarkdown(ulMatch[1])}</li>`);
+      continue;
+    }
+
+    const olMatch = line.match(/^\d+\.\s+(.+)$/);
+    if (olMatch) {
+      flushParagraph(state, html);
+      if (state.listType !== "ol") {
+        flushList(state, html);
+        state.listType = "ol";
+      }
+      state.listBuffer.push(`<li>${applyInlineMarkdown(olMatch[1])}</li>`);
+      continue;
+    }
+
+    flushList(state, html);
+    state.paragraphBuffer.push(line.trim());
+  }
+
+  flushParagraph(state, html);
+  flushList(state, html);
+
+  return html.join("\n");
+}