import { resolveSessionAccess } from './session-broker.mjs';

function defaultSendData(res, _req, data) {
  return res.json({ data });
}

function defaultRouteError(res, _req, error) {
  return res.status(500).json({ message: error?.message || 'MindSpace 服务异常' });
}

function resolveRegistry(input) {
  return typeof input === 'function' ? input() : input;
}

function resolveActiveSessionAccess({ sessionAccess, getSessionAccess, userAuth, getUserAuth }) {
  const explicit = resolveRegistry(getSessionAccess ?? sessionAccess);
  if (explicit) return explicit;
  const activeUserAuth = resolveRegistry(getUserAuth ?? userAuth);
  if (!activeUserAuth) return null;
  return resolveSessionAccess({ userAuth: activeUserAuth, enabled: false });
}

async function assertConversationPackageSessionOwned(req, res, options) {
  const sessionId = String(req.params?.sessionId ?? '').trim();
  if (!sessionId) {
    res.status(400).json({ message: '缺少 sessionId' });
    return null;
  }
  const access = resolveActiveSessionAccess(options);
  if (!access) {
    res.status(503).json({ message: 'MindSpace 对话包未启用' });
    return null;
  }
  if (!(await access.validateOwnership(req.currentUser.id, sessionId))) {
    res.status(403).json({ message: '无权访问该会话' });
    return null;
  }
  return sessionId;
}

function encodeDownloadFilename(filename) {
  const safe = String(filename ?? '').trim() || 'mindspace-artifact';
  return `attachment; filename="${encodeURIComponent(safe)}"; filename*=UTF-8''${encodeURIComponent(safe)}`;
}

function sanitizeDownloadFilenameBase(value, fallback = 'mindspace-conversation-package') {
  const normalized = String(value ?? '')
    .replace(/[\\/:*?"<>|]+/g, ' ')
    .replace(/\s+/g, ' ')
    .trim();
  return normalized || fallback;
}

export function createGetConversationPackageHandler({
  registry,
  getRegistry,
  userAuth,
  getUserAuth,
  sessionAccess,
  getSessionAccess,
  ensureMindSpaceEnabled = () => true,
  sendData = defaultSendData,
  mindSpaceError = defaultRouteError,
  beforeReadManifest,
} = {}) {
  return async function getConversationPackage(req, res) {
    const activeRegistry = resolveRegistry(getRegistry ?? registry);
    if (!activeRegistry || !ensureMindSpaceEnabled(res, req)) {
      if (res.headersSent) return undefined;
      return res.status(503).json({ message: 'MindSpace 对话包未启用' });
    }
    const sessionId = await assertConversationPackageSessionOwned(req, res, {
      sessionAccess,
      getSessionAccess,
      userAuth,
      getUserAuth,
    });
    if (!sessionId) return undefined;

    try {
      if (typeof beforeReadManifest === 'function') {
        await beforeReadManifest({ req, userId: req.currentUser.id, sessionId });
      }
      const manifest = await activeRegistry.readManifestForSession({
        userId: req.currentUser.id,
        sessionId,
      });
      if (!manifest) return res.status(404).json({ message: '对话包不存在' });
      return sendData(res, req, manifest);
    } catch (error) {
      return mindSpaceError(res, req, error);
    }
  };
}

export function createDownloadConversationPackageManifestHandler({
  registry,
  getRegistry,
  userAuth,
  getUserAuth,
  sessionAccess,
  getSessionAccess,
  ensureMindSpaceEnabled = () => true,
  mindSpaceError = defaultRouteError,
  beforeReadManifest,
} = {}) {
  return async function downloadConversationPackageManifest(req, res) {
    const activeRegistry = resolveRegistry(getRegistry ?? registry);
    if (!activeRegistry || !ensureMindSpaceEnabled(res, req)) {
      if (res.headersSent) return undefined;
      return res.status(503).json({ message: 'MindSpace 对话包未启用' });
    }
    const sessionId = await assertConversationPackageSessionOwned(req, res, {
      sessionAccess,
      getSessionAccess,
      userAuth,
      getUserAuth,
    });
    if (!sessionId) return undefined;

    try {
      if (typeof beforeReadManifest === 'function') {
        await beforeReadManifest({ req, userId: req.currentUser.id, sessionId });
      }
      const manifest = await activeRegistry.readManifestForSession({
        userId: req.currentUser.id,
        sessionId,
      });
      if (!manifest) return res.status(404).json({ message: '对话包不存在' });
      const filenameBase = sanitizeDownloadFilenameBase(
        manifest.displayFolderName ?? manifest.title,
        'mindspace-conversation-package',
      );
      const filename = `${filenameBase}-manifest.json`;
      res.set('Content-Type', 'application/json; charset=utf-8');
      res.set('Content-Disposition', encodeDownloadFilename(filename));
      res.set('Cache-Control', 'private, no-store');
      if (req.requestId) res.setHeader('X-Request-Id', req.requestId);
      return res.send(`${JSON.stringify(manifest, null, 2)}\n`);
    } catch (error) {
      return mindSpaceError(res, req, error);
    }
  };
}

export function createDownloadConversationPackageArtifactHandler({
  registry,
  getRegistry,
  userAuth,
  getUserAuth,
  sessionAccess,
  getSessionAccess,
  ensureMindSpaceEnabled = () => true,
  mindSpaceError = defaultRouteError,
} = {}) {
  return async function downloadConversationPackageArtifact(req, res) {
    const activeRegistry = resolveRegistry(getRegistry ?? registry);
    if (!activeRegistry || !ensureMindSpaceEnabled(res, req)) {
      if (res.headersSent) return undefined;
      return res.status(503).json({ message: 'MindSpace 对话包未启用' });
    }
    const sessionId = await assertConversationPackageSessionOwned(req, res, {
      sessionAccess,
      getSessionAccess,
      userAuth,
      getUserAuth,
    });
    if (!sessionId) return undefined;
    const artifactId = String(req.params?.artifactId ?? '').trim();
    if (!artifactId) return res.status(400).json({ message: '缺少 artifactId' });

    try {
      const result = await activeRegistry.readArtifactObject({
        userId: req.currentUser.id,
        sessionId,
        artifactId,
      });
      if (!result) return res.status(404).json({ message: '文件不存在' });
      const filename = result.artifact.displayName || result.artifact.id;
      res.set('Content-Type', result.artifact.mimeType || 'application/octet-stream');
      res.set('Content-Disposition', encodeDownloadFilename(filename));
      res.set('Cache-Control', 'private, no-store');
      if (req.requestId) res.setHeader('X-Request-Id', req.requestId);
      return res.send(result.body);
    } catch (error) {
      return mindSpaceError(res, req, error);
    }
  };
}

export const conversationPackageRouteInternals = {
  encodeDownloadFilename,
  sanitizeDownloadFilenameBase,
};