import fse from 'fs-extra';
import type { Element, ElementContent, Root as HastRoot, RootContent } from 'hast';
import path from 'node:path';

import { htmlToHast } from '../../pipeline/root.js';
import { removeHastComments } from '../../utils/hastComments.js';
import { hastToMdx, type RewriteLink } from '../convert.js';
import type { SdkNavGroup, SdkPage, SdkReference } from '../types.js';

type JavadocType = { pkg: string; name: string; file: string; slug: string };

const TYPE_NAME_PATTERN = /^[A-Za-z_$][\w$]*(\.[A-Za-z_$][\w$]*)*$/;
const DROPPED_CLASSES = new Set([
  'summary',
  'inherited-list',
  'sub-title',
  'header',
  'inheritance',
]);

export async function convertJavadoc(sourcePath: string): Promise<SdkReference> {
  const types = await discoverTypes(sourcePath);
  if (types.length === 0) {
    throw new Error(`No javadoc types found in ${sourcePath}`);
  }
  const slugByFile = new Map(types.map((type) => [type.file, type.slug]));

  const pages: SdkPage[] = [];
  const byPackage = new Map<string, JavadocType[]>();
  for (const type of types) {
    const html = await fse.readFile(path.join(sourcePath, type.file), 'utf8');
    pages.push(renderPage(type, html, slugByFile));
    const siblings = byPackage.get(type.pkg) ?? [];
    siblings.push(type);
    byPackage.set(type.pkg, siblings);
  }

  const groups: SdkNavGroup[] = [...byPackage.entries()]
    .sort(([left], [right]) => left.localeCompare(right))
    .map(([pkg, members]) => ({
      group: pkg,
      pages: members
        .sort((left, right) => left.name.localeCompare(right.name))
        .map((member) => member.slug),
    }));

  return { pages, groups };
}

async function discoverTypes(root: string): Promise<JavadocType[]> {
  const entries = (await typesFromSearchIndex(root)) ?? (await typesFromPackageDirs(root));
  const seen = new Set<string>();
  const types: JavadocType[] = [];
  for (const entry of entries) {
    if (seen.has(entry.file)) continue;
    seen.add(entry.file);
    if (await fse.pathExists(path.join(root, entry.file))) types.push(entry);
  }
  return types;
}

async function typesFromSearchIndex(root: string): Promise<JavadocType[] | undefined> {
  const indexPath = path.join(root, 'type-search-index.js');
  if (!(await fse.pathExists(indexPath))) return undefined;
  const raw = await fse.readFile(indexPath, 'utf8');
  const json = raw
    .slice(raw.indexOf('=') + 1)
    .trim()
    .replace(/;$/, '');
  let parsed: unknown;
  try {
    parsed = JSON.parse(json);
  } catch {
    return undefined;
  }
  if (!Array.isArray(parsed)) return undefined;
  const types: JavadocType[] = [];
  for (const item of parsed as { p?: string; l?: string }[]) {
    const pkg = item.p;
    const name = item.l?.replace(/<.*$/, '');
    if (!pkg || !name || !TYPE_NAME_PATTERN.test(pkg) || !TYPE_NAME_PATTERN.test(name)) continue;
    types.push(makeType(pkg, name));
  }
  return types.length > 0 ? types : undefined;
}

async function typesFromPackageDirs(root: string): Promise<JavadocType[]> {
  const packages = await readPackageList(root);
  const types: JavadocType[] = [];
  for (const pkg of packages) {
    if (!TYPE_NAME_PATTERN.test(pkg)) continue;
    const dir = path.join(root, ...pkg.split('.'));
    if (!(await fse.pathExists(dir))) continue;
    for (const file of await fse.readdir(dir)) {
      if (!file.endsWith('.html')) continue;
      const name = file.slice(0, -'.html'.length);
      if (name.startsWith('package-') || !TYPE_NAME_PATTERN.test(name)) continue;
      types.push(makeType(pkg, name));
    }
  }
  return types;
}

async function readPackageList(root: string): Promise<string[]> {
  for (const listFile of ['element-list', 'package-list']) {
    const listPath = path.join(root, listFile);
    if (!(await fse.pathExists(listPath))) continue;
    const raw = await fse.readFile(listPath, 'utf8');
    return raw
      .split('\n')
      .map((line) => line.trim())
      .filter((line) => line.length > 0 && !line.startsWith('module:'));
  }
  throw new Error(`No element-list or package-list found in ${root}`);
}

function makeType(pkg: string, name: string): JavadocType {
  return {
    pkg,
    name,
    file: `${pkg.split('.').join('/')}/${name}.html`,
    slug: `${pkg.replace(/\./g, '-')}/${name}`,
  };
}

function renderPage(type: JavadocType, html: string, slugByFile: Map<string, string>): SdkPage {
  const hast = htmlToHast(html);
  removeHastComments(hast);
  const main =
    findElement(hast, (el) => el.tagName === 'main') ??
    findElement(hast, (el) => el.properties?.id === 'main-content') ??
    findElement(hast, (el) => hasClass(el, 'contentContainer')) ??
    hast;

  const declaration =
    findElement(main, (el) => hasClass(el, 'class-description')) ??
    findElement(main, (el) => hasClass(el, 'description'));
  const details = findElement(main, (el) => hasClass(el, 'details'));

  const description = extractDescription(declaration);
  const tag = extractTag(main);

  const kept = [declaration, details].filter((node): node is Element => node !== undefined);
  const anchors = collectDetailAnchors(kept);
  const resolveHref = makeHrefResolver(type, slugByFile, anchors);
  const signatures: string[] = [];
  for (const node of kept) {
    pruneChrome(node);
    unwrapLists(node);
    resolveLinks(node, resolveHref);
    signatures.push(...codifySignatures(node));
  }

  const root: HastRoot = { type: 'root', children: kept as RootContent[] };
  let content = hastToMdx(root);
  for (const signature of signatures) {
    content = content
      .split(`\`\`\`\n${signature}\n\`\`\``)
      .join(`\`\`\`java\n${signature}\n\`\`\``);
  }

  return { slug: type.slug, title: type.name, description, tag, content };
}

function makeHrefResolver(
  type: JavadocType,
  slugByFile: Map<string, string>,
  anchors: Set<string>
): RewriteLink {
  const pkgDir = type.pkg.split('.').join('/');
  return (href) => {
    if (/^[a-z][a-z0-9+.-]*:/i.test(href) || href.startsWith('//')) return href;
    if (href.startsWith('#')) {
      const name = decodeFragment(href.slice(1)).split('(')[0] ?? '';
      return anchors.has(name) ? `#${name.toLowerCase()}` : undefined;
    }
    const target = href.split('#')[0] ?? '';
    if (!target.endsWith('.html')) return undefined;
    const resolved = path.posix.normalize(path.posix.join(pkgDir, target));
    const slug = slugByFile.get(resolved);
    return slug === undefined ? undefined : `/${slug}`;
  };
}

function decodeFragment(fragment: string): string {
  try {
    return decodeURIComponent(fragment);
  } catch {
    return fragment;
  }
}

function collectDetailAnchors(nodes: Element[]): Set<string> {
  const anchors = new Set<string>();
  for (const node of nodes) {
    visitElements(node, (el) => {
      if (!hasClass(el, 'detail')) return;
      const id = el.properties.id;
      if (typeof id === 'string') anchors.add(id.split('(')[0] ?? id);
    });
  }
  return anchors;
}

function resolveLinks(node: Element, resolveHref: RewriteLink): void {
  node.children = node.children.flatMap((child): ElementContent[] => {
    if (child.type !== 'element') return [child];
    resolveLinks(child, resolveHref);
    if (child.tagName !== 'a' || typeof child.properties.href !== 'string') return [child];
    const resolved = resolveHref(child.properties.href);
    if (resolved === undefined) return child.children;
    child.properties.href = resolved;
    return [child];
  });
}

function pruneChrome(node: Element): void {
  node.children = node.children.filter((child) => {
    if (child.type !== 'element') return true;
    if (child.tagName === 'hr') return false;
    return !elementClasses(child).some((name) => DROPPED_CLASSES.has(name));
  });
  for (const child of node.children) {
    if (child.type !== 'element') continue;
    if (child.tagName === 'a') delete child.properties.title;
    pruneChrome(child);
  }
}

const UNWRAPPED_LISTS = new Set(['details-list', 'member-list', 'detail-list']);

function unwrapLists(node: Element): void {
  node.children = node.children.flatMap((child): ElementContent[] => {
    if (
      child.type !== 'element' ||
      child.tagName !== 'ul' ||
      !elementClasses(child).some((name) => UNWRAPPED_LISTS.has(name))
    ) {
      return [child];
    }
    return child.children.flatMap((item) =>
      item.type === 'element' && item.tagName === 'li' ? item.children : []
    );
  });
  for (const child of node.children) {
    if (child.type === 'element') unwrapLists(child);
  }
}

function codifySignatures(node: Element): string[] {
  const signatures: string[] = [];
  visitElements(node, (el) => {
    if (!hasClass(el, 'member-signature') && !hasClass(el, 'type-signature')) return;
    const signature = textOf(el)
      .replace(/\u00a0/g, ' ')
      .trim();
    signatures.push(signature);
    el.tagName = 'pre';
    el.properties = {};
    el.children = [
      {
        type: 'element',
        tagName: 'code',
        properties: {},
        children: [{ type: 'text', value: signature }],
      },
    ];
  });
  return signatures;
}

function extractTag(scope: Element | HastRoot): string {
  const heading = findElement(scope, (el) => el.tagName === 'h1');
  const title = heading ? textOf(heading).trim() : '';
  if (title.startsWith('Annotation')) return 'ANNOTATION';
  if (title.startsWith('Enum')) return 'ENUM';
  if (title.startsWith('Interface')) return 'INTERFACE';
  return 'CLASS';
}

function extractDescription(declaration: Element | undefined): string | undefined {
  if (!declaration) return undefined;
  const block = findElement(declaration, (el) => hasClass(el, 'block'));
  if (!block) return undefined;
  const text = textOf(block).replace(/\s+/g, ' ').trim();
  if (!text) return undefined;
  const sentence = text.split(/(?<=\.)\s/)[0] ?? text;
  return sentence.length > 160 ? `${sentence.slice(0, 159)}…` : sentence;
}

function elementClasses(el: Element): string[] {
  const className = el.properties?.className;
  return Array.isArray(className) ? className.map(String) : [];
}

function hasClass(el: Element, name: string): boolean {
  return elementClasses(el).includes(name);
}

function findElement(
  scope: Element | HastRoot,
  predicate: (el: Element) => boolean
): Element | undefined {
  for (const child of scope.children as (RootContent | ElementContent)[]) {
    if (child.type !== 'element') continue;
    if (predicate(child)) return child;
    const found = findElement(child, predicate);
    if (found) return found;
  }
  return undefined;
}

function visitElements(scope: Element | HastRoot, visitor: (el: Element) => void): void {
  for (const child of scope.children as (RootContent | ElementContent)[]) {
    if (child.type !== 'element') continue;
    visitor(child);
    visitElements(child, visitor);
  }
}

function textOf(node: Element): string {
  let text = '';
  for (const child of node.children) {
    if (child.type === 'text') text += child.value;
    else if (child.type === 'element' && child.tagName !== 'script' && child.tagName !== 'style') {
      text += textOf(child);
    }
  }
  return text;
}