import fs from "node:fs/promises";
import path from "node:path";

const ROOT = process.cwd();
const DIST_DIR = path.join(ROOT, "dist");
const DIST_INDEX_HTML = path.join(DIST_DIR, "index.html");
const SRC_CONFIG = path.join(ROOT, "src", "config.ts");

const DEFAULTS = {
  BLOG_NAME: "Hyperzine",
  BLOG_SITE_URL: "https://example.com",
  BLOG_DEFAULT_DESCRIPTION: "Hyperzine",
  MANIFEST_TX_ID: ""
};

const asObject = (value) => (typeof value === "object" && value !== null ? value : null);
const asString = (value) => (typeof value === "string" && value.trim().length > 0 ? value : "");

const htmlEscape = (value) =>
  value
    .replaceAll("&", "&")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
    .replaceAll('"', "&quot;");

const normalizeSlashPath = (input) => {
  const cleaned = input.trim().replace(/^\/+|\/+$/g, "");
  return cleaned ? `/${cleaned}` : "/";
};

const toAbsoluteUrl = (siteUrl, inputPath) => new URL(normalizeSlashPath(inputPath), siteUrl).toString();

const parseConfig = async () => {
  let source = "";
  try {
    source = await fs.readFile(SRC_CONFIG, "utf8");
  } catch {
    return DEFAULTS;
  }

  const pick = (key) => {
    const match = source.match(
      new RegExp(`export\\s+const\\s+${key}\\s*=\\s*(?:"([^"]*)"|'([^']*)')`, "m")
    );
    const value = match?.[1] || match?.[2];
    return value ?? DEFAULTS[key];
  };

  return {
    BLOG_NAME: pick("BLOG_NAME"),
    BLOG_SITE_URL: pick("BLOG_SITE_URL"),
    BLOG_DEFAULT_DESCRIPTION: pick("BLOG_DEFAULT_DESCRIPTION"),
    MANIFEST_TX_ID: pick("MANIFEST_TX_ID")
  };
};

const parseFrontmatter = (input) => {
  const obj = asObject(input);
  if (!obj) return {};
  const bannerValue = obj.banner;
  const bannerObj = asObject(bannerValue);
  const banner =
    asString(bannerValue) ||
    asString(bannerObj?.txId) ||
    asString(bannerObj?.id) ||
    asString(bannerObj?.src) ||
    asString(bannerObj?.url);

  return {
    title: asString(obj.title),
    desc: asString(obj.desc),
    description: asString(obj.description),
    excerpt: asString(obj.excerpt),
    slug: asString(obj.slug),
    banner,
    date: asString(obj.date),
    updated: asString(obj.updated)
  };
};

const parseManifest = (input) => {
  const root = asObject(input);
  const posts = Array.isArray(root?.posts) ? root.posts : [];
  return posts
    .map((entry) => {
      const post = asObject(entry);
      if (!post) return null;
      const frontmatter = parseFrontmatter(post.frontmatter);
      const bannerTxIdValue = post.bannerTxId;
      const bannerTxIdObject = asObject(bannerTxIdValue);
      const bannerTxId =
        asString(bannerTxIdValue) ||
        asString(bannerTxIdObject?.txId) ||
        asString(bannerTxIdObject?.id) ||
        asString(bannerTxIdObject?.src) ||
        asString(bannerTxIdObject?.url);
      const slug = asString(post.slug) || frontmatter.slug;
      const postTxId = asString(post.postTxId);
      if (!slug || !postTxId) return null;
      return {
        slug,
        title: asString(post.title) || frontmatter.title || "Untitled",
        description:
          asString(post.description) || frontmatter.desc || frontmatter.description || "",
        excerpt: asString(post.excerpt) || frontmatter.excerpt || "",
        bannerTxId: bannerTxId || frontmatter.banner || "",
        publishedAt: asString(post.publishedAt) || frontmatter.date || "",
        updated: asString(post.updated) || frontmatter.updated || ""
      };
    })
    .filter(Boolean)
    .sort((a, b) => {
      const aDate = a.publishedAt || "";
      const bDate = b.publishedAt || "";
      return aDate < bDate ? 1 : -1;
    });
};

const fetchManifestPosts = async (manifestTxId) => {
  if (!manifestTxId) return [];
  const url = `https://arweave.net/${manifestTxId}`;
  const response = await fetch(url, { cache: "no-store" });
  if (!response.ok) throw new Error(`Manifest fetch failed (${response.status})`);
  const payload = await response.json();
  return parseManifest(payload);
};

const buildMetaTags = ({
  title,
  description,
  canonicalUrl,
  siteName,
  imageUrl,
  type = "website",
  publishedTime,
  modifiedTime
}) => {
  const tags = [
    `<title>${htmlEscape(title)}</title>`,
    `<link rel="canonical" href="${htmlEscape(canonicalUrl)}">`,
    `<meta name="description" content="${htmlEscape(description)}">`,
    `<meta property="og:title" content="${htmlEscape(title)}">`,
    `<meta property="og:description" content="${htmlEscape(description)}">`,
    `<meta property="og:type" content="${htmlEscape(type)}">`,
    `<meta property="og:url" content="${htmlEscape(canonicalUrl)}">`,
    `<meta property="og:site_name" content="${htmlEscape(siteName)}">`,
    `<meta name="twitter:title" content="${htmlEscape(title)}">`,
    `<meta name="twitter:description" content="${htmlEscape(description)}">`,
    `<meta name="twitter:card" content="${imageUrl ? "summary_large_image" : "summary"}">`
  ];

  if (imageUrl) {
    tags.push(`<meta property="og:image" content="${htmlEscape(imageUrl)}">`);
    tags.push(`<meta name="twitter:image" content="${htmlEscape(imageUrl)}">`);
  }

  if (type === "article" && publishedTime) {
    tags.push(`<meta property="article:published_time" content="${htmlEscape(publishedTime)}">`);
  }

  if (type === "article" && modifiedTime) {
    tags.push(`<meta property="article:modified_time" content="${htmlEscape(modifiedTime)}">`);
  }

  return tags.join("\n    ");
};

const injectMeta = (html, metaBlock) => {
  const marker = "<!-- PRERENDER_META -->";
  if (html.includes(marker)) {
    return html.replace(marker, `${marker}\n    ${metaBlock}`);
  }

  const stripped = html
    .replace(/<title>[\s\S]*?<\/title>/gi, "")
    .replace(/<link[^>]+rel=["']canonical["'][^>]*>/gi, "")
    .replace(/<meta[^>]+(?:name|property)=["'](?:description|og:[^"']+|twitter:[^"']+|article:[^"']+)["'][^>]*>/gi, "");

  return stripped.replace("</head>", `    ${metaBlock}\n  </head>`);
};

const normalizeAssetPaths = (html) => html.replaceAll('src="./assets/', 'src="/assets/').replaceAll('href="./assets/', 'href="/assets/');

const writeRouteHtml = async (baseHtml, routePath, metaBlock) => {
  const routeDir = routePath === "/" ? DIST_DIR : path.join(DIST_DIR, routePath.slice(1));
  const routeHtmlPath = path.join(routeDir, "index.html");
  await fs.mkdir(routeDir, { recursive: true });

  let html = injectMeta(baseHtml, metaBlock);
  if (routePath !== "/") html = normalizeAssetPaths(html);
  await fs.writeFile(routeHtmlPath, html, "utf8");
};

const main = async () => {
  const config = await parseConfig();
  const baseHtml = await fs.readFile(DIST_INDEX_HTML, "utf8");

  let posts = [];
  try {
    posts = await fetchManifestPosts(config.MANIFEST_TX_ID);
  } catch (error) {
    console.warn(
      `[prerender-meta] Could not fetch manifest; generating root metadata only: ${error.message}`
    );
  }

  const featured = posts[0];
  const rootTitle = config.BLOG_NAME;
  const rootDescription =
    config.BLOG_DEFAULT_DESCRIPTION ||
    featured?.description ||
    featured?.excerpt ||
    `Posts from ${config.BLOG_NAME}.`;
  const rootImage = featured?.bannerTxId
    ? `https://arweave.net/${featured.bannerTxId}`
    : "";
  const rootCanonical = toAbsoluteUrl(config.BLOG_SITE_URL, "/");

  const rootMeta = buildMetaTags({
    title: rootTitle,
    description: rootDescription,
    canonicalUrl: rootCanonical,
    siteName: config.BLOG_NAME,
    imageUrl: rootImage,
    type: "website"
  });

  await writeRouteHtml(baseHtml, "/", rootMeta);

  for (const post of posts) {
    const postPath = normalizeSlashPath(post.slug);
    const postTitle = `${post.title} | ${config.BLOG_NAME}`;
    const postDescription =
      post.description || post.excerpt || config.BLOG_DEFAULT_DESCRIPTION || `Post on ${config.BLOG_NAME}`;
    const postImage = post.bannerTxId ? `https://arweave.net/${post.bannerTxId}` : "";
    const canonicalUrl = toAbsoluteUrl(config.BLOG_SITE_URL, postPath);

    const postMeta = buildMetaTags({
      title: postTitle,
      description: postDescription,
      canonicalUrl,
      siteName: config.BLOG_NAME,
      imageUrl: postImage,
      type: "article",
      publishedTime: post.publishedAt,
      modifiedTime: post.updated
    });

    await writeRouteHtml(baseHtml, postPath, postMeta);
  }

  console.log(`[prerender-meta] Generated metadata pages: ${posts.length + 1}`);
};

void main();