/**
 * @fileoverview Ralph Loop - Autonomous task execution engine.
 *
 * Orchestrates autonomous Claude sessions by:
 * - Polling for available tasks from the task queue
 * - Assigning tasks to idle sessions
 * - Monitoring completion and handling failures
 * - Auto-generating follow-up tasks when min duration not reached
 *
 * Key exports:
 * - `RalphLoop` class — the loop engine, extends EventEmitter
 * - `RalphLoopEvents` interface — typed event map
 * - `RalphLoopOptions` interface — configuration options
 *
 * Lifecycle: `start()` → poll loop → `stop()` (when all tasks done + min duration met)
 *
 * @dependencies session-manager (session lifecycle), task-queue (task FIFO),
 *   state-store (persistence), session (PTY execution), task (task model)
 * @consumedby web/server (ralph routes, SSE)
 * @emits started, stopped, taskAssigned, taskCompleted, taskFailed, error
 * @persistence Ralph loop state saved to `~/.codeman/state.json` (ralphLoop key)
 *
 * @module ralph-loop
 */

import { EventEmitter } from 'node:events';
import { getSessionManager, SessionManager } from './session-manager.js';
import { getTaskQueue, TaskQueue } from './task-queue.js';
import { getStore, StateStore } from './state-store.js';
import { Session } from './session.js';
import { Task } from './task.js';
import { RalphLoopStatus, getErrorMessage } from './types.js';

/**
 * Events emitted by RalphLoop
 */
export interface RalphLoopEvents {
  started: () => void;
  stopped: () => void;
  taskAssigned: (taskId: string, sessionId: string) => void;
  taskCompleted: (taskId: string) => void;
  taskFailed: (taskId: string, error: string) => void;
  error: (error: Error) => void;
}

/**
 * Configuration options for RalphLoop
 */
export interface RalphLoopOptions {
  /** How often to check for new tasks (default from config) */
  pollIntervalMs?: number;
  /** Minimum time to run before stopping (null = no minimum) */
  minDurationMs?: number;
  /** Auto-generate follow-up tasks when queue is empty */
  autoGenerateTasks?: boolean;
}

/**
 * Autonomous task execution loop.
 *
 * @description
 * Manages the lifecycle of task execution:
 * 1. Start: Begin polling and task assignment
 * 2. Run: Assign tasks to idle sessions, monitor completion
 * 3. Stop: When all tasks done and min duration reached
 *
 * Supports time-aware loops that continue generating tasks
 * until a minimum duration is reached.
 *
 * @extends EventEmitter
 */
export class RalphLoop extends EventEmitter {
  private sessionManager: SessionManager;
  private taskQueue: TaskQueue;
  private store: StateStore;
  private pollIntervalMs: number;
  private minDurationMs: number | null;
  private autoGenerateTasks: boolean;
  private loopTimer: NodeJS.Timeout | null = null;
  private _status: RalphLoopStatus = 'stopped';
  private startedAt: number | null = null;
  private tasksCompleted: number = 0;
  private tasksGenerated: number = 0;

  /** Bound event handlers for cleanup (prevents memory leaks) */
  private sessionEventHandlers: {
    completion: (sessionId: string, phrase: string) => void;
    error: (sessionId: string, error: string) => void;
    stopped: (sessionId: string) => void;
    taskError: (sessionId: string, taskId: string, error: string) => void;
  } | null = null;

  constructor(options: RalphLoopOptions = {}) {
    super();
    this.sessionManager = getSessionManager();
    this.taskQueue = getTaskQueue();
    this.store = getStore();

    const config = this.store.getConfig();
    this.pollIntervalMs = options.pollIntervalMs ?? config.pollIntervalMs;
    this.minDurationMs = options.minDurationMs ?? null;
    this.autoGenerateTasks = options.autoGenerateTasks ?? true;

    // Load state from store
    const savedState = this.store.getRalphLoopState();
    if (savedState.status === 'running') {
      // If we crashed while running, reset to stopped
      this._status = 'stopped';
      this.store.setRalphLoopState({ status: 'stopped' });
      // Reset orphaned in_progress tasks back to pending
      for (const task of this.taskQueue.getRunningTasks()) {
        task.reset();
        this.taskQueue.updateTask(task);
      }
    }

    this.setupEventHandlers();
  }

  private setupEventHandlers(): void {
    // Store bound handlers for later cleanup
    this.sessionEventHandlers = {
      completion: (sessionId: string, phrase: string) => {
        this.handleSessionCompletion(sessionId, phrase);
      },
      error: (sessionId: string, error: string) => {
        this.handleSessionError(sessionId, error);
      },
      stopped: (sessionId: string) => {
        this.handleSessionStopped(sessionId);
      },
      taskError: (sessionId: string, taskId: string, error: string) => {
        this.handleSessionTaskError(sessionId, taskId, error);
      },
    };

    this.sessionManager.on('sessionCompletion', this.sessionEventHandlers.completion);
    this.sessionManager.on('sessionError', this.sessionEventHandlers.error);
    this.sessionManager.on('sessionStopped', this.sessionEventHandlers.stopped);
    this.sessionManager.on('sessionTaskError', this.sessionEventHandlers.taskError);
  }

  /** Remove event listeners to prevent memory leaks */
  private cleanupEventHandlers(): void {
    if (this.sessionEventHandlers) {
      this.sessionManager.off('sessionCompletion', this.sessionEventHandlers.completion);
      this.sessionManager.off('sessionError', this.sessionEventHandlers.error);
      this.sessionManager.off('sessionStopped', this.sessionEventHandlers.stopped);
      this.sessionManager.off('sessionTaskError', this.sessionEventHandlers.taskError);
      this.sessionEventHandlers = null;
    }
  }

  get status(): RalphLoopStatus {
    return this._status;
  }

  isRunning(): boolean {
    return this._status === 'running';
  }

  getElapsedMs(): number {
    if (!this.startedAt) {
      return 0;
    }
    return Date.now() - this.startedAt;
  }

  getElapsedHours(): number {
    return this.getElapsedMs() / (1000 * 60 * 60);
  }

  isMinDurationReached(): boolean {
    if (!this.minDurationMs) {
      return true;
    }
    return this.getElapsedMs() >= this.minDurationMs;
  }

  getStats() {
    const taskCounts = this.taskQueue.getCount();
    return {
      status: this._status,
      elapsedMs: this.getElapsedMs(),
      elapsedHours: this.getElapsedHours(),
      minDurationMs: this.minDurationMs,
      minDurationReached: this.isMinDurationReached(),
      tasksCompleted: this.tasksCompleted,
      tasksGenerated: this.tasksGenerated,
      ...taskCounts,
      activeSessions: this.sessionManager.getSessionCount(),
      idleSessions: this.sessionManager.getIdleSessions().length,
      busySessions: this.sessionManager.getBusySessions().length,
    };
  }

  /** Starts the task execution loop. */
  async start(): Promise<void> {
    if (this._status === 'running') {
      return;
    }

    this._status = 'running';
    this.startedAt = Date.now();
    this.tasksCompleted = 0;
    this.tasksGenerated = 0;

    // Re-setup event handlers if they were cleaned up during stop()
    if (!this.sessionEventHandlers) {
      this.setupEventHandlers();
    }

    this.store.setRalphLoopState({
      status: 'running',
      startedAt: this.startedAt,
      minDurationMs: this.minDurationMs,
      tasksCompleted: 0,
      tasksGenerated: 0,
    });

    this.emit('started');
    this.runLoop();
  }

  /** Stops the task execution loop. */
  stop(): void {
    if (this._status === 'stopped') {
      return;
    }

    this._status = 'stopped';

    if (this.loopTimer) {
      clearTimeout(this.loopTimer);
      this.loopTimer = null;
    }

    // Clean up event handlers to prevent memory leaks
    this.cleanupEventHandlers();

    this.store.setRalphLoopState({
      status: 'stopped',
      lastCheckAt: Date.now(),
    });

    this.emit('stopped');
  }

  /** Pauses the loop (can be resumed). */
  pause(): void {
    if (this._status !== 'running') {
      return;
    }

    this._status = 'paused';

    if (this.loopTimer) {
      clearTimeout(this.loopTimer);
      this.loopTimer = null;
    }

    this.store.setRalphLoopState({ status: 'paused' });
  }

  /** Resumes a paused loop. */
  resume(): void {
    if (this._status !== 'paused') {
      return;
    }

    this._status = 'running';
    this.store.setRalphLoopState({ status: 'running' });
    this.runLoop();
  }

  private runLoop(): void {
    if (this._status !== 'running') {
      return;
    }

    this.tick()
      .catch((err) => {
        // Only emit if still running (stop() may have been called during tick())
        if (this._status === 'running') {
          this.emit('error', err);
        }
      })
      .finally(() => {
        // Guard: only reschedule if still running AND no timer is pending
        // (prevents race where stop() clears timer between our check and setTimeout)
        if (this._status === 'running' && this.loopTimer === null) {
          this.loopTimer = setTimeout(() => this.runLoop(), this.pollIntervalMs);
        }
      });
  }

  private async tick(): Promise<void> {
    this.store.setRalphLoopState({ lastCheckAt: Date.now() });

    // Run sequentially: timeouts first so timed-out tasks are cleaned up
    // before assignTasks() picks new work (prevents race where both
    // mutate the same task concurrently)
    await this.checkTimeouts();
    await this.assignTasks();

    // Check if we should auto-generate tasks (depends on assignment results)
    if (this.autoGenerateTasks && this.shouldGenerateTasks()) {
      await this.generateFollowUpTasks();
    }

    // Check if we're done
    if (this.shouldStop()) {
      this.stop();
    }
  }

  private async assignTasks(): Promise<void> {
    const idleSessions = this.sessionManager.getIdleSessions();

    for (const session of idleSessions) {
      const task = this.taskQueue.next();
      if (!task) {
        break;
      }

      try {
        await this.assignTaskToSession(task, session);
      } catch (err) {
        console.error(`[RalphLoop] Failed to assign task ${task.id} to session ${session.id}:`, err);
      }
    }
  }

  private async assignTaskToSession(task: Task, session: Session): Promise<void> {
    try {
      task.assign(session.id);
      session.assignTask(task.id);
      this.taskQueue.updateTask(task);

      // Send the prompt to the session
      await session.sendInput(task.prompt);

      this.emit('taskAssigned', task.id, session.id);
    } catch (err) {
      task.fail(getErrorMessage(err));
      session.clearTask();
      this.taskQueue.updateTask(task);
      this.emit('taskFailed', task.id, getErrorMessage(err));
    }
  }

  private async checkTimeouts(): Promise<void> {
    for (const task of this.taskQueue.getRunningTasks()) {
      if (task.isTimedOut()) {
        task.fail('Task timed out');
        this.taskQueue.updateTask(task);

        const session = this.sessionManager.getSession(task.assignedSessionId!);
        if (session) {
          session.clearTask();
        }

        this.emit('taskFailed', task.id, 'Task timed out');
      }
    }
  }

  private handleSessionCompletion(sessionId: string, phrase: string): void {
    const session = this.sessionManager.getSession(sessionId);
    if (!session) {
      return;
    }

    const taskId = session.currentTaskId;
    if (!taskId) {
      return;
    }

    const task = this.taskQueue.getTask(taskId);
    if (!task) {
      return;
    }

    // Append output and check for completion
    task.appendOutput(session.getOutput());

    if (task.checkCompletion(session.getOutput()) || phrase) {
      task.complete();
      this.taskQueue.updateTask(task);
      session.clearTask();
      this.tasksCompleted++;
      this.store.setRalphLoopState({ tasksCompleted: this.tasksCompleted });
      this.emit('taskCompleted', task.id);
    }
  }

  private handleSessionError(sessionId: string, error: string): void {
    const session = this.sessionManager.getSession(sessionId);
    if (!session) {
      return;
    }

    const taskId = session.currentTaskId;
    if (!taskId) {
      return;
    }

    const task = this.taskQueue.getTask(taskId);
    if (!task) {
      return;
    }

    task.setError(error);
    // Don't fail the task immediately on stderr - some tools write to stderr normally
  }

  private handleSessionStopped(sessionId: string): void {
    const task = this.taskQueue.getRunningTaskForSession(sessionId);
    if (task) {
      task.fail('Session stopped unexpectedly');
      this.taskQueue.updateTask(task);
      this.emit('taskFailed', task.id, 'Session stopped unexpectedly');
    }
  }

  private handleSessionTaskError(_sessionId: string, taskId: string, error: string): void {
    const task = this.taskQueue.getTask(taskId);
    if (!task) {
      return;
    }

    task.fail(error);
    this.taskQueue.updateTask(task);
    this.emit('taskFailed', task.id, error);
  }

  private shouldGenerateTasks(): boolean {
    // Generate tasks if:
    // 1. No pending tasks
    // 2. Min duration not reached
    // 3. We have idle sessions
    const counts = this.taskQueue.getCount();
    return counts.pending === 0 && !this.isMinDurationReached() && this.sessionManager.getIdleSessions().length > 0;
  }

  private async generateFollowUpTasks(): Promise<void> {
    // This is a placeholder for auto-generating follow-up tasks
    // In a real implementation, this could:
    // - Analyze completed tasks to find optimization opportunities
    // - Generate tasks for code cleanup, tests, documentation
    // - Use Claude to suggest improvements

    const suggestions = [
      'Review and optimize recently changed code',
      'Add tests for uncovered code paths',
      'Update documentation for changed APIs',
      'Check for security vulnerabilities',
      'Run linting and fix any issues',
    ];

    // Only generate one task at a time
    const suggestion = suggestions[this.tasksGenerated % suggestions.length];
    const defaultDir = process.cwd();

    this.taskQueue.addTask({
      prompt: suggestion,
      workingDir: defaultDir,
      priority: -1, // Lower priority than user-added tasks
    });

    this.tasksGenerated++;
    this.store.setRalphLoopState({ tasksGenerated: this.tasksGenerated });
  }

  private shouldStop(): boolean {
    const counts = this.taskQueue.getCount();

    // Don't stop if there are pending or running tasks
    if (counts.pending > 0 || counts.running > 0) {
      return false;
    }

    // Don't stop if min duration not reached and auto-generate is on
    if (!this.isMinDurationReached() && this.autoGenerateTasks) {
      return false;
    }

    // All tasks done and conditions met
    return true;
  }

  /** Sets the minimum duration in hours before the loop can stop. */
  setMinDuration(hours: number): void {
    this.minDurationMs = hours * 60 * 60 * 1000;
    this.store.setRalphLoopState({ minDurationMs: this.minDurationMs });
  }

  /**
   * Destroys the loop and cleans up all resources.
   * Use this for complete cleanup (e.g., in tests or before creating a new instance).
   * After calling destroy(), the instance should not be reused.
   */
  destroy(): void {
    this.stop();
    this.cleanupEventHandlers();
    this.removeAllListeners();
  }
}

// Singleton instance
let loopInstance: RalphLoop | null = null;

/** Gets or creates the singleton RalphLoop instance. */
export function getRalphLoop(options?: RalphLoopOptions): RalphLoop {
  if (!loopInstance) {
    loopInstance = new RalphLoop(options);
  }
  return loopInstance;
}

/** Destroys the singleton instance. Use in tests or for cleanup. */
function destroyRalphLoop(): void {
  if (loopInstance) {
    loopInstance.destroy();
    loopInstance = null;
  }
}

// Ensure cleanup on process exit (prevents orphaned event handlers and circular references)
process.on('exit', () => {
  destroyRalphLoop();
});