import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

const scriptDir = path.dirname(fileURLToPath(import.meta.url));
const docsDir = path.resolve(scriptDir, "../content/docs");
const errors = [];

const files = fs
  .readdirSync(docsDir)
  .filter((file) => file.endsWith(".mdx"))
  .sort();

const pages = new Map();

for (const file of files) {
  const chinese = file.endsWith(".cn.mdx");
  const slug = file.replace(/\.cn\.mdx$|\.mdx$/, "");
  const page = pages.get(slug) ?? {};
  page[chinese ? "cn" : "en"] = file;
  pages.set(slug, page);
}

for (const [slug, page] of pages) {
  if (!page.cn || !page.en) {
    errors.push(`${slug}: missing ${page.cn ? "English" : "Chinese"} page`);
  }
}

function navigationPages(file) {
  const navigation = JSON.parse(fs.readFileSync(path.join(docsDir, file), "utf8"));
  return navigation.pages.filter((entry) => !entry.startsWith("---"));
}

const chineseNavigation = navigationPages("meta.cn.json");
const englishNavigation = navigationPages("meta.json");

for (const [name, entries] of [
  ["meta.cn.json", chineseNavigation],
  ["meta.json", englishNavigation],
]) {
  const duplicates = entries.filter((entry, index) => entries.indexOf(entry) !== index);
  for (const slug of new Set(duplicates)) errors.push(`${name}: duplicate page ${slug}`);

  for (const slug of entries) {
    if (!pages.has(slug)) errors.push(`${name}: unknown page ${slug}`);
  }

  for (const slug of pages.keys()) {
    if (!entries.includes(slug)) errors.push(`${name}: page ${slug} is not in navigation`);
  }
}

if (JSON.stringify(chineseNavigation) !== JSON.stringify(englishNavigation)) {
  errors.push("Chinese and English navigation page order differs");
}

const knownSlugs = new Set(pages.keys());

for (const file of files) {
  const fullPath = path.join(docsDir, file);
  const content = fs.readFileSync(fullPath, "utf8");
  const expectedLanguage = file.endsWith(".cn.mdx") ? "cn" : "en";
  const frontmatter = content.match(/^---\n([\s\S]*?)\n---/);

  if (!frontmatter) {
    errors.push(`${file}: missing frontmatter`);
  } else {
    if (!/^title:\s*.+$/m.test(frontmatter[1])) errors.push(`${file}: missing title`);
    if (!/^description:\s*.+$/m.test(frontmatter[1])) errors.push(`${file}: missing description`);
  }

  const headings = [...content.matchAll(/^#{2,4}\s+(.+)$/gm)].map((match) => match[1].trim());
  const headingCounts = new Map();
  for (const heading of headings) headingCounts.set(heading, (headingCounts.get(heading) ?? 0) + 1);
  for (const [heading, count] of headingCounts) {
    if (count > 1) errors.push(`${file}: duplicate heading "${heading}"`);
  }

  const links = [
    ...content.matchAll(/\]\(\/(cn|en)\/docs\/([^)#?]+)(?:#[^)]*)?\)/g),
    ...content.matchAll(/href="\/(cn|en)\/docs\/([^"#?]+)(?:#[^"]*)?"/g),
  ];

  for (const link of links) {
    const [, language, slug] = link;
    if (!knownSlugs.has(slug)) errors.push(`${file}: broken documentation link /${language}/docs/${slug}`);
    if (language !== expectedLanguage) errors.push(`${file}: cross-language documentation link /${language}/docs/${slug}`);
  }
}

if (errors.length > 0) {
  console.error("Documentation content verification failed:\n");
  for (const error of errors) console.error(`- ${error}`);
  process.exit(1);
}

console.log(`Verified ${pages.size} bilingual documentation pages.`);