const mongoose = require('mongoose');
const { agentSchema } = require('@librechat/data-schemas');
const { SystemRoles, Tools } = require('librechat-data-provider');
const { GLOBAL_PROJECT_NAME, EPHEMERAL_AGENT_ID, mcp_delimiter } =
  require('librechat-data-provider').Constants;
const { CONFIG_STORE, STARTUP_CONFIG } = require('librechat-data-provider').CacheKeys;
const {
  getProjectByName,
  addAgentIdsToProject,
  removeAgentIdsFromProject,
  removeAgentFromAllProjects,
} = require('./Project');
const getLogStores = require('~/cache/getLogStores');

// Category values - must match the frontend values in client/src/constants/agentCategories.ts
const CATEGORY_VALUES = {
  GENERAL: 'general',
  HR: 'hr',
  RD: 'rd',
  FINANCE: 'finance',
  IT: 'it',
  SALES: 'sales',
  AFTERSALES: 'aftersales',
};

const VALID_CATEGORIES = Object.values(CATEGORY_VALUES);

// Add category field to the Agent schema if it doesn't already exist
if (!agentSchema.paths.category) {
  agentSchema.add({
    category: {
      type: String,
      trim: true,
      enum: {
        values: VALID_CATEGORIES,
        message:
          '"{VALUE}" is not a supported agent category. Valid categories are: ' +
          VALID_CATEGORIES.join(', ') +
          '.',
      },
      index: true,
      default: CATEGORY_VALUES.GENERAL,
    },
  });
}

// Add support_contact field to the Agent schema if it doesn't already exist
if (!agentSchema.paths.support_contact) {
  agentSchema.add({
    support_contact: {
      type: Object,
      default: {},
      name: {
        type: String,
        minlength: [3, 'Support contact name must be at least 3 characters.'],
        trim: true,
      },
      email: {
        type: String,
        match: [
          /^\w+([.-]?\w+)*@\w+([.-]?\w+)*(\.\w{2,3})+$/,
          'Please enter a valid email address.',
        ],
        trim: true,
      },
    },
  });
}

const Agent = mongoose.model('agent', agentSchema);

/**
 * Create an agent with the provided data.
 * @param {Object} agentData - The agent data to create.
 * @returns {Promise<Agent>} The created agent document as a plain object.
 * @throws {Error} If the agent creation fails.
 */
const createAgent = async (agentData) => {
  // Ensure the agent has a category (default to 'general' if none provided)
  const dataWithCategory = {
    ...agentData,
    category: agentData.category || 'general',
  };
  return (await Agent.create(dataWithCategory)).toObject();
};

/**
 * Get an agent document based on the provided ID.
 *
 * @param {Object} searchParameter - The search parameters to find the agent to update.
 * @param {string} searchParameter.id - The ID of the agent to update.
 * @param {string} searchParameter.author - The user ID of the agent's author.
 * @returns {Promise<Agent|null>} The agent document as a plain object, or null if not found.
 */
const getAgent = async (searchParameter) => await Agent.findOne(searchParameter).lean();

/**
 * Load an agent based on the provided ID
 *
 * @param {Object} params
 * @param {ServerRequest} params.req
 * @param {string} params.agent_id
 * @param {string} params.endpoint
 * @param {import('@librechat/agents').ClientOptions} [params.model_parameters]
 * @returns {Agent|null} The agent document as a plain object, or null if not found.
 */
const loadEphemeralAgent = ({ req, agent_id, endpoint, model_parameters: _m }) => {
  const { model, ...model_parameters } = _m;
  /** @type {Record<string, FunctionTool>} */
  const availableTools = req.app.locals.availableTools;
  const mcpServers = new Set(req.body.ephemeralAgent?.mcp);
  /** @type {string[]} */
  const tools = [];
  if (req.body.ephemeralAgent?.execute_code === true) {
    tools.push(Tools.execute_code);
  }

  if (mcpServers.size > 0) {
    for (const toolName of Object.keys(availableTools)) {
      if (!toolName.includes(mcp_delimiter)) {
        continue;
      }
      const mcpServer = toolName.split(mcp_delimiter)?.[1];
      if (mcpServer && mcpServers.has(mcpServer)) {
        tools.push(toolName);
      }
    }
  }

  const instructions = req.body.promptPrefix;
  return {
    id: agent_id,
    instructions,
    provider: endpoint,
    model_parameters,
    model,
    tools,
  };
};

/**
 * Load an agent based on the provided ID
 *
 * @param {Object} params
 * @param {ServerRequest} params.req
 * @param {string} params.agent_id
 * @param {string} params.endpoint
 * @param {import('@librechat/agents').ClientOptions} [params.model_parameters]
 * @returns {Promise<Agent|null>} The agent document as a plain object, or null if not found.
 */
const loadAgent = async ({ req, agent_id, endpoint, model_parameters }) => {
  if (!agent_id) {
    return null;
  }
  if (agent_id === EPHEMERAL_AGENT_ID) {
    return loadEphemeralAgent({ req, agent_id, endpoint, model_parameters });
  }
  const agent = await getAgent({
    id: agent_id,
  });

  if (!agent) {
    return null;
  }

  if (agent.author.toString() === req.user.id) {
    return agent;
  }

  if (!agent.projectIds) {
    return null;
  }

  const cache = getLogStores(CONFIG_STORE);
  /** @type {TStartupConfig} */
  const cachedStartupConfig = await cache.get(STARTUP_CONFIG);
  let { instanceProjectId } = cachedStartupConfig ?? {};
  if (!instanceProjectId) {
    instanceProjectId = (await getProjectByName(GLOBAL_PROJECT_NAME, '_id'))._id.toString();
  }

  for (const projectObjectId of agent.projectIds) {
    const projectId = projectObjectId.toString();
    if (projectId === instanceProjectId) {
      return agent;
    }
  }
};

/**
 * Update an agent with new data without overwriting existing
 *  properties, or create a new agent if it doesn't exist.
 *
 * @param {Object} searchParameter - The search parameters to find the agent to update.
 * @param {string} searchParameter.id - The ID of the agent to update.
 * @param {string} [searchParameter.author] - The user ID of the agent's author.
 * @param {Object} updateData - An object containing the properties to update.
 * @returns {Promise<Agent>} The updated or newly created agent document as a plain object.
 */
const updateAgent = async (searchParameter, updateData) => {
  const options = { new: true, upsert: false };
  return Agent.findOneAndUpdate(searchParameter, updateData, options).lean();
};

/**
 * Modifies an agent with the resource file id.
 * @param {object} params
 * @param {ServerRequest} params.req
 * @param {string} params.agent_id
 * @param {string} params.tool_resource
 * @param {string} params.file_id
 * @returns {Promise<Agent>} The updated agent.
 */
const addAgentResourceFile = async ({ agent_id, tool_resource, file_id }) => {
  const searchParameter = { id: agent_id };
  let agent = await getAgent(searchParameter);
  if (!agent) {
    throw new Error('Agent not found for adding resource file');
  }
  const fileIdsPath = `tool_resources.${tool_resource}.file_ids`;
  await Agent.updateOne(
    {
      id: agent_id,
      [`${fileIdsPath}`]: { $exists: false },
    },
    {
      $set: {
        [`${fileIdsPath}`]: [],
      },
    },
  );

  const updateData = {
    $addToSet: {
      tools: tool_resource,
      [fileIdsPath]: file_id,
    },
  };

  const updatedAgent = await updateAgent(searchParameter, updateData);
  if (updatedAgent) {
    return updatedAgent;
  } else {
    throw new Error('Agent not found for adding resource file');
  }
};

/**
 * Removes multiple resource files from an agent using atomic operations.
 * @param {object} params
 * @param {string} params.agent_id
 * @param {Array<{tool_resource: string, file_id: string}>} params.files
 * @returns {Promise<Agent>} The updated agent.
 * @throws {Error} If the agent is not found or update fails.
 */
const removeAgentResourceFiles = async ({ agent_id, files }) => {
  const searchParameter = { id: agent_id };

  // Group files to remove by resource
  const filesByResource = files.reduce((acc, { tool_resource, file_id }) => {
    if (!acc[tool_resource]) {
      acc[tool_resource] = [];
    }
    acc[tool_resource].push(file_id);
    return acc;
  }, {});

  // Step 1: Atomically remove file IDs using $pull
  const pullOps = {};
  const resourcesToCheck = new Set();
  for (const [resource, fileIds] of Object.entries(filesByResource)) {
    const fileIdsPath = `tool_resources.${resource}.file_ids`;
    pullOps[fileIdsPath] = { $in: fileIds };
    resourcesToCheck.add(resource);
  }

  const updatePullData = { $pull: pullOps };
  const agentAfterPull = await Agent.findOneAndUpdate(searchParameter, updatePullData, {
    new: true,
  }).lean();

  if (!agentAfterPull) {
    // Agent might have been deleted concurrently, or never existed.
    // Check if it existed before trying to throw.
    const agentExists = await getAgent(searchParameter);
    if (!agentExists) {
      throw new Error('Agent not found for removing resource files');
    }
    // If it existed but findOneAndUpdate returned null, something else went wrong.
    throw new Error('Failed to update agent during file removal (pull step)');
  }

  // Return the agent state directly after the $pull operation.
  // Skipping the $unset step for now to simplify and test core $pull atomicity.
  // Empty arrays might remain, but the removal itself should be correct.
  return agentAfterPull;
};

/**
 * Deletes an agent based on the provided ID.
 *
 * @param {Object} searchParameter - The search parameters to find the agent to delete.
 * @param {string} searchParameter.id - The ID of the agent to delete.
 * @param {string} [searchParameter.author] - The user ID of the agent's author.
 * @returns {Promise<void>} Resolves when the agent has been successfully deleted.
 */
const deleteAgent = async (searchParameter) => {
  const agent = await Agent.findOneAndDelete(searchParameter);
  if (agent) {
    await removeAgentFromAllProjects(agent.id);
  }
  return agent;
};

/**
 * Get all agents.
 * @param {Object} searchParameter - The search parameters to find matching agents.
 * @param {string} searchParameter.author - The user ID of the agent's author.
 * @returns {Promise<Object>} A promise that resolves to an object containing the agents data and pagination info.
 */
const getListAgents = async (searchParameter) => {
  const { author, ...otherParams } = searchParameter;

  let query = Object.assign({ author }, otherParams);

  const globalProject = await getProjectByName(GLOBAL_PROJECT_NAME, ['agentIds']);
  if (globalProject && (globalProject.agentIds?.length ?? 0) > 0) {
    const globalQuery = { id: { $in: globalProject.agentIds }, ...otherParams };
    delete globalQuery.author;
    query = { $or: [globalQuery, query] };
  }

  const agents = (
    await Agent.find(query, {
      id: 1,
      _id: 0,
      name: 1,
      avatar: 1,
      author: 1,
      projectIds: 1,
      description: 1,
      isCollaborative: 1,
      category: 1,
    }).lean()
  ).map((agent) => {
    if (agent.author?.toString() !== author) {
      delete agent.author;
    }
    if (agent.author) {
      agent.author = agent.author.toString();
    }
    return agent;
  });

  const hasMore = agents.length > 0;
  const firstId = agents.length > 0 ? agents[0].id : null;
  const lastId = agents.length > 0 ? agents[agents.length - 1].id : null;

  return {
    data: agents,
    has_more: hasMore,
    first_id: firstId,
    last_id: lastId,
  };
};

/**
 * Updates the projects associated with an agent, adding and removing project IDs as specified.
 * This function also updates the corresponding projects to include or exclude the agent ID.
 *
 * @param {Object} params - Parameters for updating the agent's projects.
 * @param {MongoUser} params.user - Parameters for updating the agent's projects.
 * @param {string} params.agentId - The ID of the agent to update.
 * @param {string[]} [params.projectIds] - Array of project IDs to add to the agent.
 * @param {string[]} [params.removeProjectIds] - Array of project IDs to remove from the agent.
 * @returns {Promise<MongoAgent>} The updated agent document.
 * @throws {Error} If there's an error updating the agent or projects.
 */
const updateAgentProjects = async ({ user, agentId, projectIds, removeProjectIds }) => {
  const updateOps = {};

  if (removeProjectIds && removeProjectIds.length > 0) {
    for (const projectId of removeProjectIds) {
      await removeAgentIdsFromProject(projectId, [agentId]);
    }
    updateOps.$pull = { projectIds: { $in: removeProjectIds } };
  }

  if (projectIds && projectIds.length > 0) {
    for (const projectId of projectIds) {
      await addAgentIdsToProject(projectId, [agentId]);
    }
    updateOps.$addToSet = { projectIds: { $each: projectIds } };
  }

  if (Object.keys(updateOps).length === 0) {
    return await getAgent({ id: agentId });
  }

  const updateQuery = { id: agentId, author: user.id };
  if (user.role === SystemRoles.ADMIN) {
    delete updateQuery.author;
  }

  const updatedAgent = await updateAgent(updateQuery, updateOps);
  if (updatedAgent) {
    return updatedAgent;
  }
  if (updateOps.$addToSet) {
    for (const projectId of projectIds) {
      await removeAgentIdsFromProject(projectId, [agentId]);
    }
  } else if (updateOps.$pull) {
    for (const projectId of removeProjectIds) {
      await addAgentIdsToProject(projectId, [agentId]);
    }
  }

  return await getAgent({ id: agentId });
};

module.exports = {
  Agent,
  getAgent,
  loadAgent,
  createAgent,
  updateAgent,
  deleteAgent,
  getListAgents,
  updateAgentProjects,
  addAgentResourceFile,
  removeAgentResourceFiles,
};