import fs from 'node:fs';
import path from 'node:path';
import {
  buildMindSpacePublicRoutePath,
  resolveMindSpaceUserPublishDir,
} from './mindspace-runtime-config.mjs';
import { PUBLIC_ZONE_DIR, PUBLISH_KEY_UUID } from './user-publish.mjs';

const USERNAME_SLUG = /^[a-z0-9_]{2,32}$/;
const MISPLACED_PUBLIC_HTML_NAME = /^[a-z0-9][a-z0-9._-]{0,127}\.html$/i;

export async function resolveMindSpacePublishOwnerKey(segment, resolveUsernameToUserId) {
  const lower = String(segment ?? '').trim().toLowerCase();
  if (!lower) return null;
  if (PUBLISH_KEY_UUID.test(lower)) return lower;
  if (!USERNAME_SLUG.test(lower)) return null;
  const resolved = await resolveUsernameToUserId?.(lower);
  return resolved ? String(resolved).toLowerCase() : lower;
}

export function decodeMindSpaceRouteSegment(segment) {
  try {
    return decodeURIComponent(segment);
  } catch {
    return segment;
  }
}

export function resolveMindSpacePublicRouteTarget({ h5Root, ownerKey, parts = [] }) {
  const targetDir = resolveMindSpaceUserPublishDir(h5Root, { id: ownerKey });
  const resolvedRoot = path.resolve(targetDir);
  const resolvedPath = path.resolve(path.join(targetDir, ...parts));
  return {
    targetDir,
    resolvedRoot,
    resolvedPath,
    insideRoot:
      resolvedPath === resolvedRoot || resolvedPath.startsWith(`${resolvedRoot}${path.sep}`),
  };
}

export function buildMindSpaceCanonicalRedirect(ownerKey, parts = []) {
  return buildMindSpacePublicRoutePath(ownerKey, parts);
}

export function resolveMindSpaceHtmlFallbackRedirect({ ownerKey, targetDir, resolvedRoot, rest = [] }) {
  if (rest.length === 1 && String(rest[0]).toLowerCase().endsWith('.html')) {
    const publicFallback = path.resolve(targetDir, PUBLIC_ZONE_DIR, rest[0]);
    if (
      publicFallback.startsWith(`${resolvedRoot}${path.sep}`) &&
      fs.existsSync(publicFallback) &&
      fs.statSync(publicFallback).isFile()
    ) {
      return buildMindSpacePublicRoutePath(ownerKey, [PUBLIC_ZONE_DIR, rest[0]]);
    }
  }
  return null;
}

export function resolveMindSpaceSimilarHtmlRedirect({ ownerKey, relativePath }) {
  if (!relativePath) return null;
  return buildMindSpacePublicRoutePath(ownerKey, String(relativePath).split('/'));
}

export async function recoverMisplacedMindSpacePublicHtml({
  h5Root,
  targetDir,
  resolvedRoot,
  rest = [],
  ensureThumbnail,
  logger = console,
} = {}) {
  if (rest.length !== 2 || rest[0] !== PUBLIC_ZONE_DIR) return null;
  const filename = rest[1];
  if (!MISPLACED_PUBLIC_HTML_NAME.test(filename)) return null;

  const destination = path.resolve(targetDir, PUBLIC_ZONE_DIR, filename);
  if (!destination.startsWith(`${resolvedRoot}${path.sep}`)) return null;
  const candidates = [
    path.resolve(h5Root, filename),
    path.resolve(h5Root, PUBLIC_ZONE_DIR, filename),
  ];
  for (const candidate of candidates) {
    if (candidate === destination) continue;
    if (!candidate.startsWith(`${path.resolve(h5Root)}${path.sep}`)) continue;
    if (!fs.existsSync(candidate) || !fs.statSync(candidate).isFile()) continue;
    fs.mkdirSync(path.dirname(destination), { recursive: true });
    fs.copyFileSync(candidate, destination);
    await ensureThumbnail?.(targetDir, `${PUBLIC_ZONE_DIR}/${filename}`);
    logger?.warn?.(
      `[MindSpace] recovered misplaced public HTML ${path.relative(h5Root, candidate)} -> ${path.relative(h5Root, destination)}`,
    );
    return destination;
  }
  return null;
}

export async function resolveMindSpacePublicRequest({
  h5Root,
  requestPath = '',
  resolveUsernameToUserId,
  resolveClosestHtmlRelativePath,
  ensureThumbnail,
  logger = console,
} = {}) {
  const parts = String(requestPath || '')
    .split('/')
    .filter(Boolean);
  if (parts.length < 1) {
    return { action: 'not_found', reason: 'missing_path' };
  }

  const ownerKey = await resolveMindSpacePublishOwnerKey(parts[0], resolveUsernameToUserId);
  if (!ownerKey) {
    return { action: 'not_found', reason: 'missing_owner' };
  }

  if (parts[0].toLowerCase() !== ownerKey && parts[0].trim()) {
    return {
      action: 'redirect',
      status: 301,
      location: buildMindSpaceCanonicalRedirect(ownerKey, parts.slice(1)),
      ownerKey,
    };
  }

  const rest = parts.slice(1).map(decodeMindSpaceRouteSegment);
  const routeTarget = resolveMindSpacePublicRouteTarget({
    h5Root,
    ownerKey,
    parts: rest,
  });
  const { targetDir, resolvedRoot, resolvedPath } = routeTarget;

  if (!routeTarget.insideRoot) {
    return { action: 'forbidden', reason: 'outside_publish_root', ownerKey };
  }

  if (!fs.existsSync(targetDir)) {
    return { action: 'not_found', reason: 'missing_owner_dir', ownerKey };
  }

  if (!fs.existsSync(resolvedPath)) {
    const publicFallbackRedirect = resolveMindSpaceHtmlFallbackRedirect({
      ownerKey,
      targetDir,
      resolvedRoot,
      rest,
    });
    if (publicFallbackRedirect) {
      return {
        action: 'redirect',
        status: 301,
        location: publicFallbackRedirect,
        ownerKey,
      };
    }

    if (rest.length === 2 && rest[0] === PUBLIC_ZONE_DIR && rest[1].toLowerCase().endsWith('.html')) {
      const similarRelativePath = await resolveClosestHtmlRelativePath?.(
        targetDir,
        `${PUBLIC_ZONE_DIR}/${rest[1]}`,
      );
      if (similarRelativePath) {
        return {
          action: 'redirect',
          status: 301,
          location: resolveMindSpaceSimilarHtmlRedirect({
            ownerKey,
            relativePath: similarRelativePath,
          }),
          ownerKey,
        };
      }
    }

    const recoveredPublicHtml = await recoverMisplacedMindSpacePublicHtml({
      h5Root,
      targetDir,
      resolvedRoot,
      rest,
      ensureThumbnail,
      logger,
    });
    if (recoveredPublicHtml) {
      return {
        action: 'serve',
        filePath: recoveredPublicHtml,
        ownerKey,
        targetDir,
      };
    }

    // og:image points at <base>.thumbnail.png while only the SVG sidecar may exist on disk.
    // Serve resolves lazily via ensureThumbnailPng in the MindSpace public file handler.
    if (/\.thumbnail\.png$/i.test(resolvedPath)) {
      const svgSibling = resolvedPath.replace(/\.png$/i, '.svg');
      if (fs.existsSync(svgSibling)) {
        return {
          action: 'serve',
          filePath: resolvedPath,
          ownerKey,
          targetDir,
        };
      }
    }

    return { action: 'not_found', reason: 'missing_file', ownerKey };
  }

  if (fs.statSync(resolvedPath).isDirectory()) {
    const indexPath = path.join(resolvedPath, 'index.html');
    if (fs.existsSync(indexPath)) {
      return {
        action: 'serve',
        filePath: indexPath,
        ownerKey,
        targetDir,
      };
    }
    return { action: 'not_found', reason: 'missing_directory_index', ownerKey };
  }

  return {
    action: 'serve',
    filePath: resolvedPath,
    ownerKey,
    targetDir,
  };
}

export const mindspacePublicRouteInternals = {
  USERNAME_SLUG,
  MISPLACED_PUBLIC_HTML_NAME,
};