'use strict';

/**
 * session-monitor.js — Polls sessions.json every 2s to detect new/ended sessions.
 *
 * sessions.json format (per agent):
 *   {
 *     "agent:main:mattermost:channel:abc123:thread:xyz": {
 *       "sessionId": "uuid",
 *       "spawnedBy": null | "agent:main:...",
 *       "spawnDepth": 0,
 *       "label": "proj035-planner",
 *       "channel": "mattermost"
 *     }
 *   }
 *
 * Emits:
 *   'session-added'   ({ sessionKey, transcriptFile, spawnedBy, channelId, rootPostId, agentId })
 *   'session-removed' (sessionKey)
 */

const fs = require('fs');
const path = require('path');
const { EventEmitter } = require('events');

class SessionMonitor extends EventEmitter {
  /**
   * @param {object} opts
   * @param {string} opts.transcriptDir - Base /home/node/.openclaw/agents directory
   * @param {number} [opts.pollMs] - Poll interval in ms (default 2000)
   * @param {string|null} [opts.defaultChannel] - Fallback channel ID for non-MM sessions
   * @param {object} [opts.logger] - pino logger
   */
  constructor(opts) {
    super();
    this.transcriptDir = opts.transcriptDir;
    this.pollMs = opts.pollMs || 2000;
    this.defaultChannel = opts.defaultChannel || null;
    this.logger = opts.logger || null;

    // Map<sessionKey, sessionEntry>
    this._knownSessions = new Map();
    this._pollTimer = null;
    this._running = false;
  }

  start() {
    if (this._running) return;
    this._running = true;

    // Initial scan
    this._poll();

    this._pollTimer = setInterval(() => {
      this._poll();
    }, this.pollMs);

    if (this.logger) this.logger.info({ pollMs: this.pollMs }, 'SessionMonitor started');
  }

  stop() {
    this._running = false;
    if (this._pollTimer) {
      clearInterval(this._pollTimer);
      this._pollTimer = null;
    }
    if (this.logger) this.logger.info('SessionMonitor stopped');
  }

  /**
   * Get all agent directories under transcriptDir.
   * @private
   * @returns {string[]} Agent IDs
   */
  _getAgentDirs() {
    try {
      // eslint-disable-next-line security/detect-non-literal-fs-filename
      return fs.readdirSync(this.transcriptDir).filter((name) => {
        try {
          // eslint-disable-next-line security/detect-non-literal-fs-filename
          return fs.statSync(path.join(this.transcriptDir, name)).isDirectory();
        } catch (_e) {
          return false;
        }
      });
    } catch (_e) {
      return [];
    }
  }

  /**
   * Read sessions.json for a given agent.
   * @private
   * @param {string} agentId
   * @returns {object} Sessions map
   */
  _readSessionsJson(agentId) {
    const sessionsPath = path.join(this.transcriptDir, agentId, 'sessions', 'sessions.json');
    try {
      // eslint-disable-next-line security/detect-non-literal-fs-filename
      const raw = fs.readFileSync(sessionsPath, 'utf8');
      return JSON.parse(raw);
    } catch (_e) {
      return {};
    }
  }

  /**
   * Resolve the transcript file path for a session.
   * @private
   * @param {string} agentId
   * @param {string} sessionId - UUID
   * @returns {string}
   */
  _transcriptPath(agentId, sessionId) {
    return path.join(this.transcriptDir, agentId, 'sessions', `${sessionId}.jsonl`);
  }

  /**
   * Parse channel ID from session key.
   * Session key format: "agent:main:mattermost:channel:{channelId}:thread:{threadId}"
   * or: "agent:main:mattermost:dm:{userId}"
   * @param {string} sessionKey
   * @returns {string|null}
   */
  static parseChannelId(sessionKey) {
    const parts = sessionKey.split(':');
    // agent:main:mattermost:channel:CHANNEL_ID:...
    const chanIdx = parts.indexOf('channel');
    if (chanIdx >= 0 && parts[chanIdx + 1]) {
      return parts[chanIdx + 1]; // eslint-disable-line security/detect-object-injection
    }
    // agent:main:mattermost:dm:USER_ID (use as channel)
    const dmIdx = parts.indexOf('dm');
    if (dmIdx >= 0 && parts[dmIdx + 1]) {
      return parts[dmIdx + 1]; // eslint-disable-line security/detect-object-injection
    }
    return null;
  }

  /**
   * Parse root post ID (thread ID) from session key.
   * @param {string} sessionKey
   * @returns {string|null}
   */
  static parseRootPostId(sessionKey) {
    const parts = sessionKey.split(':');
    const threadIdx = parts.indexOf('thread');
    if (threadIdx >= 0 && parts[threadIdx + 1]) {
      return parts[threadIdx + 1]; // eslint-disable-line security/detect-object-injection
    }
    return null;
  }

  /**
   * Extract agent ID from session key.
   * @param {string} sessionKey
   * @returns {string}
   */
  static parseAgentId(sessionKey) {
    const parts = sessionKey.split(':');
    if (parts[0] === 'agent' && parts[1]) return parts[1];
    return parts[0] || 'unknown';
  }

  /**
   * Determine if a session is a Mattermost session.
   * @param {string} sessionKey
   * @returns {boolean}
   */
  static isMattermostSession(sessionKey) {
    return sessionKey.includes(':mattermost:') || sessionKey.includes(':mm:');
  }

  /**
   * Poll all agents' sessions.json files for changes.
   * @private
   */
  _poll() {
    if (!this._running) return;

    const agentDirs = this._getAgentDirs();
    const currentSessions = new Map();

    for (const agentId of agentDirs) {
      const sessions = this._readSessionsJson(agentId);
      for (const [sessionKey, entry] of Object.entries(sessions)) {
        const sessionId = entry.sessionId || entry.uuid;
        if (!sessionId) continue;

        currentSessions.set(sessionKey, {
          agentId,
          sessionKey,
          sessionId,
          spawnedBy: entry.spawnedBy || null,
          spawnDepth: entry.spawnDepth || 0,
          label: entry.label || null,
          channel: entry.channel || null,
        });
      }
    }

    // Detect added sessions
    for (const [sessionKey, entry] of currentSessions) {
      if (!this._knownSessions.has(sessionKey)) {
        this._onSessionAdded(entry);
      }
    }

    // Detect removed sessions
    for (const [sessionKey] of this._knownSessions) {
      if (!currentSessions.has(sessionKey)) {
        this._onSessionRemoved(sessionKey);
      }
    }

    this._knownSessions = currentSessions;
  }

  /**
   * Handle a newly detected session.
   * @private
   */
  _onSessionAdded(entry) {
    const { agentId, sessionKey, sessionId, spawnedBy, spawnDepth, label } = entry;

    const transcriptFile = this._transcriptPath(agentId, sessionId);

    // Sub-agents always pass through — they inherit parent channel via watcher-manager
    const isSubAgent = !!spawnedBy;

    // Resolve channel ID from session key
    let channelId = SessionMonitor.parseChannelId(sessionKey);

    // Fall back to default channel for non-MM sessions
    if (!channelId && !isSubAgent && !SessionMonitor.isMattermostSession(sessionKey)) {
      channelId = this.defaultChannel;
      if (!channelId) {
        if (this.logger) {
          this.logger.debug({ sessionKey }, 'Skipping non-MM session (no channel, no default)');
        }
        return;
      }
    }

    const rootPostId = SessionMonitor.parseRootPostId(sessionKey);
    const parsedAgentId = SessionMonitor.parseAgentId(sessionKey);

    if (this.logger) {
      this.logger.info({ sessionKey, agentId, channelId, spawnedBy }, 'Session detected');
    }

    this.emit('session-added', {
      sessionKey,
      transcriptFile,
      spawnedBy,
      spawnDepth,
      channelId,
      rootPostId,
      agentId: label || parsedAgentId,
    });
  }

  /**
   * Handle a removed session.
   * @private
   */
  _onSessionRemoved(sessionKey) {
    if (this.logger) {
      this.logger.info({ sessionKey }, 'Session ended');
    }
    this.emit('session-removed', sessionKey);
  }

  /**
   * Get list of currently known sessions.
   * @returns {Map}
   */
  getKnownSessions() {
    return new Map(this._knownSessions);
  }
}

module.exports = { SessionMonitor };