const mongoose = require('mongoose');
const { GLOBAL_PROJECT_NAME } = require('librechat-data-provider').Constants;
const {
  getProjectByName,
  addAgentIdsToProject,
  removeAgentIdsFromProject,
  removeAgentFromAllProjects,
} = require('./Project');
const agentSchema = require('./schema/agent');

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) => {
  return await Agent.create(agentData);
};

/**
 * 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();

/**
 * 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: true };
  return await Agent.findOneAndUpdate(searchParameter, updateData, options).lean();
};

/**
 * 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,
    name: 1,
    avatar: 1,
    projectIds: 1,
  }).lean();

  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 {string} agentId - The ID of the agent to update.
 * @param {string[]} [projectIds] - Array of project IDs to add to the agent.
 * @param {string[]} [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 (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 });
  }

  return await updateAgent({ id: agentId }, updateOps);
};

module.exports = {
  createAgent,
  getAgent,
  updateAgent,
  deleteAgent,
  getListAgents,
  updateAgentProjects,
};