import assert from 'node:assert/strict';
import {readFileSync, readdirSync, mkdirSync, writeFileSync} from 'node:fs';
import {join} from 'node:path';

const normalize = path => path.replace(/\/$/, '');
const read = path => JSON.parse(readFileSync(path, 'utf8'));

// Use Docusaurus's resolved IDs/routes and sidebar trees, not filename guesses.
export function auditSidebars(instances, entrySidebars) {
  const docs = new Map();
  const menus = new Map();
  for (const {plugin, version, documents, sidebars} of instances) {
    const ids = new Set();
    for (const doc of documents) {
      assert(!ids.has(doc.id), `Duplicate document ID: ${plugin}:${version}:${doc.id}`);
      ids.add(doc.id);
      const route = normalize(doc.path);
      assert(!docs.has(route), `Duplicate document route: ${route}`);
      docs.set(route, {...doc, plugin, version, menu: `${plugin}:${version}:${doc.sidebar}`});
    }
    for (const [name, items] of Object.entries(sidebars)) menus.set(`${plugin}:${version}:${name}`, items);
  }
  const links = new Map();
  for (const [menu, items] of menus) {
    const found = new Set();
    const walk = items => {
      for (const item of items) {
        assert(['category', 'link', 'html'].includes(item.type), `Unresolved sidebar type: ${item.type}`);
        assert(!item.unlisted, `Hidden sidebar item: ${item.label}`);
        if (item.href && !/^(https?:|mailto:)/.test(item.href)) {
          const route = normalize(item.href);
          if (item.docId) assert.equal(docs.get(route)?.id, item.docId, `Sidebar ID/route mismatch: ${item.docId}`);
          assert(!found.has(route), `Duplicate sidebar route in ${menu}: ${route}`);
          found.add(route);
        }
        if (item.type === 'category') walk(item.items);
      }
    };
    walk(items);
    links.set(menu, found);
  }
  const reachable = new Set(entrySidebars);
  for (const menu of reachable) {
    assert(menus.has(menu), `Unknown navigation sidebar: ${menu}`);
    for (const route of links.get(menu)) {
      const doc = docs.get(route);
      if (doc) reachable.add(doc.menu);
    }
  }
  for (const [route, doc] of docs) {
    assert(reachable.has(doc.menu), `Unreachable sidebar for ${doc.plugin}:${doc.id}`);
    assert(links.get(doc.menu)?.has(route), `Missing sidebar document: ${doc.plugin}:${doc.id}`);
  }
  return [...docs.entries()].map(([route, doc]) => ({route, id:doc.id, plugin:doc.plugin, sidebar:doc.sidebar}));
}

export async function verifySidebarCoverage() {
  const global = read('.docusaurus/globalData.json')['docusaurus-plugin-content-docs'];
  assert(global && Object.keys(global).length, 'No generated document inventory');
  const instances = [];
  for (const [plugin, data] of Object.entries(global)) {
    const folder = `.docusaurus/docusaurus-plugin-content-docs/${plugin}/p`;
    const resolved = readdirSync(folder).filter(f => f.endsWith('.json')).map(f => read(join(folder, f)).version);
    for (const version of data.versions) {
      const matches = resolved.filter(v => v.version === version.name);
      assert.equal(matches.length, 1, `Missing/duplicate resolved version: ${plugin}:${version.name}`);
      instances.push({plugin, version:version.name, documents:version.docs, sidebars:matches[0].docsSidebars});
    }
  }
  const {default:config} = await import('../.docusaurus/docusaurus.config.mjs');
  const entries = config.themeConfig.navbar.items.filter(i => i.type === 'docSidebar').map(i => `${i.docsPluginId || 'default'}:current:${i.sidebarId}`);
  const documents = auditSidebars(instances, entries);
  const routes = new Set(documents.map(d => `${d.route.replace(config.baseUrl, '')}/index.html`));
  const exclusions = [];
  const html = readdirSync('build', {recursive:true}).filter(f => f.endsWith('.html')).sort();
  for (const file of html) {
    if (routes.delete(file)) continue;
    let reason;
    if (file === 'index.html') reason = 'Dedicated React homepage, not a documentation page';
    else if (file === '404.html') reason = 'Docusaurus not-found system page';
    else if (file === 'search/index.html') reason = 'Local-search results UI, not a documentation page';
    else if (file === 'strategy/index.html') {
      assert(readFileSync(join('build',file),'utf8').includes('http-equiv="refresh"'), 'Strategy alias must remain a redirect');
      reason = 'Legacy Strategy redirect alias to Target';
    } else if (file === 'strategy/reference/measurement-contracts/index.html') {
      const body = readFileSync(join('build',file),'utf8');
      assert(body.includes('window.location.replace') && body.includes('name="robots" content="noindex"') && !body.includes('<article'), 'Metric alias must remain a non-indexed redirect');
      assert.equal(body, readFileSync(join('static',file),'utf8'));
      reason = 'Legacy measurement-contracts hash-aware redirect to canonical Measurement pages';
    } else if (file === 'presentations/less-prompting-more-shipping/index.html') {
      const body = readFileSync(join('build',file),'utf8');
      assert.equal(body, readFileSync(join('static',file),'utf8'));
      assert(body.includes('class="reveal deck"') && body.includes('class="notes"'));
      assert(readFileSync('build/index.html','utf8').includes('/presentations/less-prompting-more-shipping/?embed'));
      reason = 'Reveal presentation linked from the homepage, not a competing documentation page';
    } else if (file.startsWith('diagrams/') && readFileSync(join('build',file),'utf8').includes('<svg')) {
      assert.equal(readFileSync(join('build',file),'utf8'), readFileSync(join('static',file),'utf8'), `Viewer must match generated static asset: ${file}`);
      reason = 'Standalone diagram viewer asset, not documentation';
    }
    assert(reason, `Unclassified published HTML route: ${file}`);
    exclusions.push({file, reason});
  }
  assert.equal(routes.size, 0, `Missing published docs: ${[...routes]}`);
  // Check all local links and anchors on every document, not only selected Strategy pages.
  for (const {route} of documents) {
    const file = `build/${route.replace(config.baseUrl, '')}/index.html`;
    const body = readFileSync(file, 'utf8');
    for (const [, href] of body.matchAll(/href="([^" ]+)"/g)) {
      if (!href.startsWith(config.baseUrl) && !href.startsWith('#')) continue;
      const url = new URL(href, `https://docs.invalid${route}/`);
      let target = url.pathname.slice(config.baseUrl.length);
      if (!target || target.endsWith('/')) target += 'index.html';
      else if (!target.split('/').at(-1).includes('.')) target += '/index.html';
      const targetBody = readFileSync(join('build', decodeURIComponent(target)), 'utf8');
      if (url.hash) assert(targetBody.includes(`id="${decodeURIComponent(url.hash.slice(1))}"`), `Broken anchor: ${route} -> ${href}`);
    }
  }
  mkdirSync('.cache', {recursive:true});
  writeFileSync('.cache/sidebar-coverage.json', JSON.stringify({documents, exclusions}, null, 2));
  console.log(`PASS: ${documents.length} published docs reachable in resolved sidebars; ${exclusions.length} classified non-doc HTML routes; all doc links/anchors checked`);
  return {documents, exclusions};
}