const multer = require('multer');
const express = require('express');
const { sleep } = require('@librechat/agents');
const {
  isEnabled,
  deleteAgentCheckpoints,
  createArchiveAllHandler,
  createSubagentActivityStreamHandler,
  createSubagentThreadViewHandler,
  resolveImportMaxFileSize,
  restoreTenantContextFromReq,
  deleteAllSharedLinksWithCleanup,
  deleteConvoSharedLinksWithCleanup,
  inspectContent,
  createContentFilter,
  isContentFilterError,
  contentFilterBlockResponse,
  extractConversationTitleContent,
  GenerationJobManager,
  isStopConfirmed,
} = require('@librechat/api');
const { logger } = require('@librechat/data-schemas');
const { CacheKeys, EModelEndpoint } = require('librechat-data-provider');
const {
  createImportLimiters,
  validateConvoAccess,
  createForkLimiters,
  configMiddleware,
} = require('~/server/middleware');
const { forkConversation, duplicateConversation } = require('~/server/utils/import/fork');
const { storage, importFileFilter } = require('~/server/routes/files/multer');
const requireJwtAuth = require('~/server/middleware/requireJwtAuth');
const { importConversations } = require('~/server/utils/import');
const subagentThreadTaskStore = require('~/server/services/Endpoints/agents/subagentThreadStore');
const getLogStores = require('~/cache/getLogStores');
const db = require('~/models');

const assistantClients = {
  [EModelEndpoint.azureAssistants]: require('~/server/services/Endpoints/azureAssistants'),
  [EModelEndpoint.assistants]: require('~/server/services/Endpoints/assistants'),
};

const router = express.Router();
const archiveAllHandler = createArchiveAllHandler({ archiveAllConvos: db.archiveAllConvos });
const subagentThreadViewHandler = createSubagentThreadViewHandler({
  getConvoOwnership: db.getConvoOwnership,
  getSubagentThreadForParent: db.getSubagentThreadForParent,
  getMessagesForSubagentThreadView: db.getMessagesForSubagentThreadView,
});
const filterConversationTitle = createContentFilter({
  getFilters: (req) => req.config?.filters,
  extract: (req) => extractConversationTitleContent(req.body),
});
const subagentActivityStreamHandler = createSubagentActivityStreamHandler(
  {
    getConvoOwnership: db.getConvoOwnership,
    getSubagentThreadForParent: db.getSubagentThreadForParent,
    getMessages: db.getMessages,
  },
  {
    subscribe: subagentThreadTaskStore.subscribeActivity.bind(subagentThreadTaskStore),
  },
);
router.use(requireJwtAuth);

const isValidProjectFilter = (projectId) =>
  !projectId || projectId === 'unassigned' || /^[a-f\d]{24}$/i.test(projectId);

router.get('/', async (req, res) => {
  const limit = parseInt(req.query.limit, 10) || 25;
  const cursor = req.query.cursor;
  const isArchived = isEnabled(req.query.isArchived);
  const pinned = isEnabled(req.query.pinned);
  const search =
    typeof req.query.search === 'string' ? req.query.search.trim() || undefined : undefined;
  const sortBy = req.query.sortBy || 'updatedAt';
  const sortDirection = req.query.sortDirection || 'desc';
  const projectId = Array.isArray(req.query.projectId)
    ? req.query.projectId[0]
    : req.query.projectId;

  if (!isValidProjectFilter(projectId)) {
    return res.status(400).json({ error: 'projectId must be a valid project id or unassigned' });
  }

  let tags;
  if (req.query.tags) {
    tags = Array.isArray(req.query.tags) ? req.query.tags : [req.query.tags];
  }

  try {
    const result = await db.getConvosByCursor(req.user.id, {
      cursor,
      limit,
      isArchived,
      pinned,
      tags,
      search,
      sortBy,
      sortDirection,
      projectId,
    });
    res.status(200).json(result);
  } catch (error) {
    logger.error('Error fetching conversations', error);
    res.status(500).json({ error: 'Error fetching conversations' });
  }
});

router.get(
  '/:parentConversationId/subagents/:threadId/tasks/:taskId/activity',
  subagentActivityStreamHandler,
);
router.get('/:parentConversationId/subagents/:threadId', subagentThreadViewHandler);

router.get('/:conversationId', async (req, res) => {
  const { conversationId } = req.params;
  const convo = await db.getConvo(req.user.id, conversationId);

  if (convo && convo.subagentThread == null) {
    res.status(200).json(convo);
  } else {
    res.status(404).end();
  }
});

router.get('/gen_title/:conversationId', async (req, res) => {
  const { conversationId } = req.params;
  const titleCache = getLogStores(CacheKeys.GEN_TITLE);
  const key = `${req.user.id}-${conversationId}`;
  let title = await titleCache.get(key);

  if (!title) {
    // Exponential backoff: 500ms, 1s, 2s, 4s, 8s (total ~15.5s max wait)
    const delays = [500, 1000, 2000, 4000, 8000];
    for (const delay of delays) {
      await sleep(delay);
      title = await titleCache.get(key);
      if (title) {
        break;
      }
    }
  }

  if (title) {
    await titleCache.delete(key);
    res.status(200).json({ title });
  } else {
    res.status(404).json({
      message: "Title not found or method not implemented for the conversation's endpoint",
    });
  }
});

const POST_DELETE_CANCEL_ATTEMPTS = 3;
const POST_DELETE_CANCEL_BACKOFF_MS = 250;
const GENERATION_PERSISTENCE_DRAIN_TIMEOUT_MS = 45_000;
const GENERATION_PERSISTENCE_DRAIN_POLL_MS = 100;
const GENERATION_LOOKUP_ATTEMPTS = 3;

async function readGenerationForDeletion(conversationId) {
  let lastError;
  for (let attempt = 1; attempt <= GENERATION_LOOKUP_ATTEMPTS; attempt += 1) {
    try {
      return await GenerationJobManager.getJob(conversationId);
    } catch (error) {
      lastError = error;
      if (attempt < GENERATION_LOOKUP_ATTEMPTS) {
        await new Promise((resolve) => setTimeout(resolve, 25 * attempt));
      }
    }
  }
  throw lastError;
}

/** Replays a cancellation plan after deletion, retrying a transiently unreachable
 * owner rather than losing the only pass that can stop a late-admitted child. */
async function retryPostDeleteCancellation(cancellationPlan, deletedConversationIds) {
  for (let attempt = 1; attempt <= POST_DELETE_CANCEL_ATTEMPTS; attempt += 1) {
    try {
      await subagentThreadTaskStore.cancelPlan(cancellationPlan, deletedConversationIds);
      return;
    } catch (error) {
      if (attempt === POST_DELETE_CANCEL_ATTEMPTS) {
        logger.warn('Post-delete subagent cancellation failed', error);
        return;
      }
      await new Promise((resolve) => setTimeout(resolve, POST_DELETE_CANCEL_BACKOFF_MS * attempt));
    }
  }
}

/** Confirms every exact generation is stopped before its conversation wave is removed. */
async function confirmAgentGenerationsDrained(userId, conversationIds, leaseTaskIds = []) {
  let foundActiveGeneration = false;
  const drainErrors = [];
  const generationIds = [...new Set([...conversationIds, ...leaseTaskIds])];
  await Promise.all(
    generationIds.map(async (conversationId) => {
      let job;
      try {
        job = await readGenerationForDeletion(conversationId);
      } catch (error) {
        logger.warn('Deleted child generation lookup failed', error);
        foundActiveGeneration = true;
        drainErrors.push(error);
        return;
      }
      if (job == null || job.metadata?.userId !== userId) {
        return;
      }
      const needsDrain =
        job.status === 'running' ||
        job.status === 'requires_action' ||
        job.metadata?.terminalPersistencePending === true;
      if (!needsDrain) return;
      foundActiveGeneration = true;
      try {
        const abortResult = await GenerationJobManager.abortJob(conversationId, {
          expectedCreatedAt: job.createdAt,
          awaitProviderDrain: true,
        });
        if (!isStopConfirmed(abortResult)) {
          throw new Error(
            `Could not confirm generation stop for ${conversationId}: ${abortResult?.failureReason ?? 'unknown'}`,
          );
        }
        const deadline = Date.now() + GENERATION_PERSISTENCE_DRAIN_TIMEOUT_MS;
        while (true) {
          const current = await GenerationJobManager.getJob(conversationId);
          if (
            current == null ||
            current.createdAt !== job.createdAt ||
            current.metadata?.terminalPersistencePending !== true
          ) {
            break;
          }
          if (Date.now() >= deadline) {
            throw new Error(`Timed out waiting for generation persistence: ${conversationId}`);
          }
          await new Promise((resolve) => setTimeout(resolve, GENERATION_PERSISTENCE_DRAIN_POLL_MS));
        }
      } catch (error) {
        logger.warn('Deleted child generation drain failed', error);
        drainErrors.push(error);
      }
    }),
  );
  if (!foundActiveGeneration) {
    return false;
  }
  if (drainErrors.length > 0) {
    throw new Error('One or more deleted child generations could not be confirmed drained.');
  }
  return true;
}

/** Stops event-bound child generations on their owning replica and then removes
 * persistence that raced the first conversation cascade. */
async function drainDeletedAgentGenerations(userId, conversationIds, leaseTaskIds = []) {
  const foundActiveGeneration = await confirmAgentGenerationsDrained(
    userId,
    conversationIds,
    leaseTaskIds,
  );
  if (!foundActiveGeneration) {
    return;
  }
  try {
    await db.deleteConvos(userId, { conversationId: { $in: conversationIds } });
  } catch {
    // Expected when no generation raced the first cascade.
  }
  await db
    .deleteMessages({ user: userId, conversationId: { $in: conversationIds } })
    .catch((error) => logger.warn('Deleted child message remnant cleanup failed', error));
}

router.delete('/', configMiddleware, async (req, res) => {
  let filter = {};
  const { conversationId, source, thread_id, endpoint } = req.body?.arg ?? {};

  // Prevent deletion of all conversations
  if (!conversationId && !source && !thread_id && !endpoint) {
    return res.status(400).json({
      error: 'no parameters provided',
    });
  }

  if (conversationId) {
    filter = { conversationId };
  } else if (source === 'button') {
    return res.status(200).send('No conversationId provided');
  }

  if (
    typeof endpoint !== 'undefined' &&
    Object.prototype.propertyIsEnumerable.call(assistantClients, endpoint)
  ) {
    /** @type {{ openai: OpenAI }} */
    const { openai } = await assistantClients[endpoint].initializeClient({ req, res });
    try {
      const response = await openai.beta.threads.delete(thread_id);
      logger.debug('Deleted OpenAI thread:', response);
    } catch (error) {
      logger.error('Error deleting OpenAI thread:', error);
    }
  }

  try {
    const tenantId =
      typeof req.user.tenantId === 'string' && req.user.tenantId !== ''
        ? req.user.tenantId
        : undefined;
    let cancellationPlan;
    let dbResponse;
    if (filter.conversationId) {
      /** Resolve the targets while the conversations still exist: the second pass
       * runs after their rows are gone and can only reach registered owners. */
      cancellationPlan = await subagentThreadTaskStore.planCancellationForConversations(
        req.user.id,
        [filter.conversationId],
        tenantId,
      );
      await subagentThreadTaskStore.cancelPlan(cancellationPlan);
      dbResponse = await db.deleteConvos(req.user.id, filter, {
        beforeDelete: (conversationIds) =>
          confirmAgentGenerationsDrained(req.user.id, conversationIds),
      });
    } else {
      /** An empty filter deletes every conversation this owner has, so it runs behind
       * the same admission fence as `DELETE /all` rather than a bare drain. */
      dbResponse = await subagentThreadTaskStore.withOwnerDeletionFence(req.user.id, tenantId, () =>
        db.deleteConvos(req.user.id, filter, {
          beforeDelete: (conversationIds) =>
            confirmAgentGenerationsDrained(req.user.id, conversationIds),
        }),
      );
    }
    const deletedConversationIds =
      dbResponse.conversationIds ?? (filter.conversationId ? [filter.conversationId] : []);
    /** Root deletion closes new child admission. Replay the plan to catch a task
     * admitted after the first pass but before that fence, extended with the cascade
     * this deletion reported. */
    if (cancellationPlan != null && deletedConversationIds.length > 0) {
      /** The conversations are gone, so this pass is the only thing that can still
       * stop a child admitted after the first one. It cannot fail the request — the
       * deletion already committed — so it retries briefly before giving up. */
      await retryPostDeleteCancellation(cancellationPlan, deletedConversationIds);
      await drainDeletedAgentGenerations(
        req.user.id,
        deletedConversationIds,
        cancellationPlan.leases
          .filter(
            (lease) =>
              deletedConversationIds.includes(lease.parentConversationId) ||
              deletedConversationIds.includes(lease.conversationId),
          )
          .map((lease) => lease.taskId),
      );
    } else if (deletedConversationIds.length > 0) {
      /** Owner-wide deletion drains lease-backed tasks before the cascade, but a
       * requires_action event actor has intentionally released its lease. Its durable
       * generation is still addressable by the deleted conversation id and must be
       * terminalized before its checkpoint is pruned. */
      await drainDeletedAgentGenerations(req.user.id, deletedConversationIds);
    }
    // HITL: prune the deleted conversations' durable checkpoints — a paused run's
    // checkpoint would otherwise persist until the Mongo TTL. Never throws.
    await deleteAgentCheckpoints(
      deletedConversationIds,
      req.config?.endpoints?.[EModelEndpoint.agents]?.checkpointer,
    );
    if (filter.conversationId) {
      await Promise.all(deletedConversationIds.map((id) => db.deleteToolCalls(req.user.id, id)));
      await Promise.all(
        deletedConversationIds.map((id) => deleteConvoSharedLinksWithCleanup(req.user.id, id)),
      );
    }
    res.status(201).json(dbResponse);
  } catch (error) {
    logger.error('Error clearing conversations', error);
    res.status(500).send('Error clearing conversations');
  }
});

router.delete('/all', configMiddleware, async (req, res) => {
  try {
    const tenantId =
      typeof req.user.tenantId === 'string' && req.user.tenantId !== ''
        ? req.user.tenantId
        : undefined;
    /** Fences new child admission for this owner, drains the live ones, and deletes
     * inside that fence: a child admitted on another replica mid-deletion would
     * otherwise keep running against conversations that no longer exist. */
    const dbResponse = await subagentThreadTaskStore.withOwnerDeletionFence(
      req.user.id,
      tenantId,
      () =>
        db.deleteConvos(
          req.user.id,
          {},
          {
            beforeDelete: (conversationIds) =>
              confirmAgentGenerationsDrained(req.user.id, conversationIds),
          },
        ),
    );
    await drainDeletedAgentGenerations(req.user.id, dbResponse.conversationIds ?? []);
    // HITL: prune ALL the deleted conversations' durable checkpoints in one bulk pass.
    await deleteAgentCheckpoints(
      dbResponse.conversationIds,
      req.config?.endpoints?.[EModelEndpoint.agents]?.checkpointer,
    );
    await db.deleteToolCalls(req.user.id);
    await deleteAllSharedLinksWithCleanup(req.user.id);
    res.status(201).json(dbResponse);
  } catch (error) {
    logger.error('Error clearing conversations', error);
    res.status(500).send('Error clearing conversations');
  }
});

/**
 * Archives or unarchives a conversation.
 * @route POST /archive
 * @param {string} req.body.arg.conversationId - The conversation ID to archive/unarchive.
 * @param {boolean} req.body.arg.isArchived - Whether to archive (true) or unarchive (false).
 * @returns {object} 200 - The updated conversation object.
 */
router.post('/archive', validateConvoAccess, async (req, res) => {
  const { conversationId, isArchived } = req.body?.arg ?? {};

  if (!conversationId) {
    return res.status(400).json({ error: 'conversationId is required' });
  }

  if (typeof isArchived !== 'boolean') {
    return res.status(400).json({ error: 'isArchived must be a boolean' });
  }

  try {
    const dbResponse = await db.saveConvo(
      {
        userId: req?.user?.id,
        isTemporary: req?.body?.isTemporary,
        interfaceConfig: req?.config?.interfaceConfig,
      },
      { conversationId, isArchived },
      {
        context: `POST /api/convos/archive ${conversationId}`,
        /** Filing a chat away is not activity: `updatedAt` stays the chat's own last
         * activity so unarchiving restores it to its real place in the date groups.
         * When it was archived is recorded separately, on `archivedAt`. */
        preserveUpdatedAt: true,
        /** Without timestamps, an upsert would insert a conversation that has none. */
        noUpsert: true,
      },
    );

    if (!dbResponse) {
      return res.status(404).json({ error: 'Conversation not found' });
    }

    res.status(200).json(dbResponse);
  } catch (error) {
    logger.error('Error archiving conversation', error);
    res.status(500).send('Error archiving conversation');
  }
});

/**
 * Archives every conversation currently visible to the user.
 * @route POST /archive/all
 * @returns {object} 200 - The number of conversations archived.
 */
router.post('/archive/all', archiveAllHandler);

router.post('/pin', validateConvoAccess, async (req, res) => {
  const { conversationId, pinned } = req.body?.arg ?? {};

  if (!conversationId) {
    return res.status(400).json({ error: 'conversationId is required' });
  }

  if (pinned === undefined) {
    return res.status(400).json({ error: 'pinned is required' });
  }

  if (typeof pinned !== 'boolean') {
    return res.status(400).json({ error: 'pinned must be a boolean' });
  }

  try {
    const dbResponse = await db.setConvoPinned(req.user.id, conversationId, pinned);

    if (!dbResponse) {
      return res.status(404).json({ error: 'Conversation not found' });
    }

    res.status(200).json(dbResponse);
  } catch (error) {
    logger.error('Error pinning conversation', error);
    res.status(500).send('Error pinning conversation');
  }
});

/** Maximum allowed length for conversation titles */
const MAX_CONVO_TITLE_LENGTH = 1024;

/**
 * Updates a conversation's title.
 * @route POST /update
 * @param {string} req.body.arg.conversationId - The conversation ID to update.
 * @param {string} req.body.arg.title - The new title for the conversation.
 * @returns {object} 201 - The updated conversation object.
 */
router.post('/update', validateConvoAccess, configMiddleware, async (req, res) => {
  const { conversationId, title } = req.body?.arg ?? {};

  if (!conversationId) {
    return res.status(400).json({ error: 'conversationId is required' });
  }

  if (title === undefined) {
    return res.status(400).json({ error: 'title is required' });
  }

  if (typeof title !== 'string') {
    return res.status(400).json({ error: 'title must be a string' });
  }

  const sanitizedTitle = title.trim().slice(0, MAX_CONVO_TITLE_LENGTH);
  if (req.config?.filters != null) {
    const finding = inspectContent(extractConversationTitleContent({ title: sanitizedTitle }), {
      filters: req.config.filters,
    });
    if (finding != null) {
      return res.status(400).json(contentFilterBlockResponse(finding));
    }
  }

  try {
    const dbResponse = await db.saveConvo(
      {
        userId: req?.user?.id,
        isTemporary: req?.body?.isTemporary,
        interfaceConfig: req?.config?.interfaceConfig,
      },
      { conversationId, title: sanitizedTitle },
      { context: `POST /api/convos/update ${conversationId}` },
    );
    res.status(201).json(dbResponse);
  } catch (error) {
    logger.error('Error updating conversation', error);
    res.status(500).send('Error updating conversation');
  }
});

const { importIpLimiter, importUserLimiter } = createImportLimiters();
/** Fork and duplicate share one rate-limit budget (same "clone" operation class) */
const { forkIpLimiter, forkUserLimiter } = createForkLimiters();
const importMaxFileSize = resolveImportMaxFileSize();
const upload = multer({
  storage,
  fileFilter: importFileFilter,
  limits: { fileSize: importMaxFileSize },
});
const uploadSingle = upload.single('file');

function handleUpload(req, res, next) {
  uploadSingle(req, res, (err) => {
    if (err && err.code === 'LIMIT_FILE_SIZE') {
      return res.status(413).json({ message: 'File exceeds the maximum allowed size' });
    }
    if (err) {
      return next(err);
    }
    next();
  });
}

/**
 * Imports a conversation from a JSON file and saves it to the database.
 * @route POST /import
 * @param {Express.Multer.File} req.file - The JSON file to import.
 * @returns {object} 201 - success response - application/json
 */
router.post(
  '/import',
  importIpLimiter,
  importUserLimiter,
  configMiddleware,
  handleUpload,
  restoreTenantContextFromReq,
  async (req, res) => {
    try {
      /* TODO: optimize to return imported conversations and add manually */
      await importConversations({
        filepath: req.file.path,
        requestUserId: req.user.id,
        userRole: req.user.role,
        interfaceConfig: req.config?.interfaceConfig,
        filters: req.config?.filters,
        ...(req.config?.messageFilter?.pii == null
          ? {}
          : { legacyPii: req.config.messageFilter.pii }),
      });
      res.status(201).json({ message: 'Conversation(s) imported successfully' });
    } catch (error) {
      if (isContentFilterError(error)) {
        return res.status(error.statusCode).json(error.body);
      }
      logger.error('Error processing file', error);
      res.status(500).send('Error processing file');
    }
  },
);

/**
 * POST /fork
 * This route handles forking a conversation based on the TForkConvoRequest and responds with TForkConvoResponse.
 * @route POST /fork
 * @param {express.Request<{}, TForkConvoResponse, TForkConvoRequest>} req - Express request object.
 * @param {express.Response<TForkConvoResponse>} res - Express response object.
 * @returns {Promise<void>} - The response after forking the conversation.
 */
router.post('/fork', forkIpLimiter, forkUserLimiter, configMiddleware, async (req, res) => {
  try {
    /** @type {TForkConvoRequest} */
    const { conversationId, messageId, option, splitAtTarget, latestMessageId } = req.body;
    const result = await forkConversation({
      requestUserId: req.user.id,
      originalConvoId: conversationId,
      targetMessageId: messageId,
      latestMessageId,
      records: true,
      splitAtTarget,
      option,
      filters: req.config?.filters,
      ...(req.config?.messageFilter?.pii == null
        ? {}
        : { legacyPii: req.config.messageFilter.pii }),
    });

    res.json(result);
  } catch (error) {
    if (isContentFilterError(error)) {
      return res.status(error.statusCode).json(error.body);
    }
    logger.error('Error forking conversation:', error);
    res.status(500).send('Error forking conversation');
  }
});

router.post(
  '/duplicate',
  forkIpLimiter,
  forkUserLimiter,
  configMiddleware,
  filterConversationTitle,
  async (req, res) => {
    const { conversationId, title } = req.body;

    try {
      const result = await duplicateConversation({
        userId: req.user.id,
        conversationId,
        title,
        filters: req.config?.filters,
        ...(req.config?.messageFilter?.pii == null
          ? {}
          : { legacyPii: req.config.messageFilter.pii }),
      });
      res.status(201).json(result);
    } catch (error) {
      if (isContentFilterError(error)) {
        return res.status(error.statusCode).json(error.body);
      }
      logger.error('Error duplicating conversation:', error);
      res.status(500).send('Error duplicating conversation');
    }
  },
);

module.exports = router;