1 files changed, 44 insertions, 1 deletions
diff --git a/astro.config.mjs b/astro.config.mjs
index 46174d3..f6dd237 100644
--- a/astro.config.mjs
+++ b/astro.config.mjs
@@ -1,3 +1,4 @@
+import { execSync } from "node:child_process";
 import { existsSync } from "node:fs";
 import { join } from "node:path";
 import { fileURLToPath } from "node:url";
@@ -45,6 +46,42 @@ function publicDirIndexPlugin() {
   };
 }
 
+// ページの最終更新日を git の履歴から引く（サイトマップの lastmod 用）。
+function buildGitDateMap() {
+  const map = new Map();
+  try {
+    const out = execSync("git log --no-merges --pretty=format:__C__%cI --name-only", {
+      encoding: "utf-8",
+      maxBuffer: 256 * 1024 * 1024,
+    });
+    let date = "";
+    for (const raw of out.split("\n")) {
+      const line = raw.trim();
+      if (line.startsWith("__C__")) {
+        date = line.slice(5);
+      } else if (line && date && !map.has(line)) {
+        map.set(line, date);
+      }
+    }
+  } catch {
+    // git が使えない環境では lastmod を付けない。
+  }
+  return map;
+}
+const gitDates = buildGitDateMap();
+
+function lastmodFor(url) {
+  const path = url.replace(/^https?:\/\/[^/]+/, "").replace(/^\/+|\/+$/g, "");
+  const bases = path ? [path, `${path}/index`] : ["index"];
+  for (const base of bases) {
+    for (const ext of [".mdx", ".md"]) {
+      const date = gitDates.get(`src/content/docs/${base}${ext}`);
+      if (date) return new Date(date);
+    }
+  }
+  return undefined;
+}
+
 export default defineConfig({
   site: "https://yasutakeyohei.com",
   base: "/",
@@ -61,7 +98,13 @@ export default defineConfig({
     plugins: [publicDirIndexPlugin()],
   },
   integrations: [
-    sitemap(),
+    sitemap({
+      serialize(item) {
+        const lastmod = lastmodFor(item.url);
+        if (lastmod) item.lastmod = lastmod;
+        return item;
+      },
+    }),
     updatesIntegration(),
     ogImagePlugin(),
     starlight({