/**
 * @module AgentExecutor
 * @description Interfaces and implementations for executing agent tasks
 * 
 * This module provides the interfaces and implementations for executing tasks
 * on behalf of agents in the A2A protocol. It handles task lifecycle management,
 * status updates, and event publishing.
 */

import { EventQueue } from './event-queue';
import { RequestContext } from './request-context';

/**
 * Interface for executing agent tasks
 * 
 * This interface defines the contract for executing tasks on behalf of agents.
 * Implementations are responsible for handling task execution, cancellation,
 * and lifecycle management.
 * 
 * @example
 * ```typescript
 * class CustomAgentExecutor implements AgentExecutor {
 *   async execute(context: RequestContext, eventQueue: EventQueue): Promise<void> {
 *     // Custom execution logic
 *     console.log(`Executing task ${context.task.id}`);
 *     
 *     // Publish events
 *     eventQueue.publish({
 *       type: 'task.updated',
 *       payload: { taskId: context.task.id, status: 'working' }
 *     });
 *   }
 *   
 *   async cancel(context: RequestContext, eventQueue: EventQueue): Promise<void> {
 *     // Custom cancellation logic
 *     console.log(`Canceling task ${context.task.id}`);
 *   }
 * }
 * ```
 */
export interface AgentExecutor {
  /**
   * Execute a task with the given context
   * @param context Request context including task details
   * @param eventQueue Event queue for publishing task events
   */
  execute(context: RequestContext, eventQueue: EventQueue): Promise<void>;

  /**
   * Cancel an ongoing task execution
   * @param context Request context including task details
   * @param eventQueue Event queue for publishing cancellation events
   */
  cancel(context: RequestContext, eventQueue: EventQueue): Promise<void>;
}

import { TaskManager } from '../tasks/task-manager';
import { TaskEventManager } from './task-event-manager';
import { 
  Task,
  InvalidTaskStateError,
  TaskNotFoundError,
  TaskAlreadyCompletedError,
  TaskCanceledError,
  TaskFailedError
} from '@dexwox-labs/a2a-core';

/**
 * Default implementation of the AgentExecutor interface
 * 
 * This class provides a basic implementation of the AgentExecutor interface
 * that manages task lifecycle, publishes events, and handles errors. It uses
 * a TaskManager for task persistence and a TaskEventManager for event publishing.
 * 
 * @example
 * ```typescript
 * // Create dependencies
 * const taskStore = new InMemoryTaskStore();
 * const taskManager = new TaskManager(taskStore);
 * const taskEventManager = new TaskEventManager();
 * 
 * // Create the executor
 * const executor = new DefaultAgentExecutor(taskManager, taskEventManager);
 * 
 * // Execute a task
 * await executor.execute(
 *   createRequestContext(task, 'agent-123'),
 *   new EventQueue()
 * );
 * ```
 */

export class DefaultAgentExecutor implements AgentExecutor {
  /**
   * Creates a new DefaultAgentExecutor
   * 
   * @param taskManager - The task manager for task persistence
   * @param taskEventManager - The task event manager for event publishing
   */
  constructor(
    private taskManager: TaskManager,
    private taskEventManager: TaskEventManager
  ) {}

  /**
   * Executes a task on behalf of an agent
   * 
   * This method handles the execution of a task, including updating its status,
   * publishing events, and handling errors. It transitions the task from its
   * current state to 'working' and then to 'completed' if successful.
   * 
   * @param context - The request context containing task and agent information
   * @param eventQueue - The event queue for publishing events
   * @returns Promise that resolves when execution is complete
   * @throws Various task-related errors if execution fails
   */
  async execute(context: RequestContext, eventQueue: EventQueue): Promise<void> {
    const task = await this.taskManager.getTask(context.task.id);
    
    // Update task status to working
    const workingTask = await this.taskManager.updateTaskStatus(task.id, 'working');
    
    // Publish task update event
    this.taskEventManager.taskUpdated(workingTask, task.status);

    try {
      // TODO: Implement actual agent execution logic
      // For now we'll simulate successful completion
      await new Promise(resolve => setTimeout(resolve, 1000));
      
      const completedTask = await this.taskManager.updateTaskStatus(task.id, 'completed');
      this.taskEventManager.taskCompleted(completedTask);
    } catch (error) {
      const failedTask = await this.taskManager.updateTaskStatus(task.id, 'failed');
      const normalizedError = error instanceof Error 
        ? error 
        : new Error(error instanceof Object ? JSON.stringify(error) : String(error));
      this.taskEventManager.taskFailed(failedTask, normalizedError);
      throw normalizedError;
    }
  }

  async cancel(context: RequestContext, eventQueue: EventQueue): Promise<void> {
    const task = await this.taskManager.getTask(context.task.id);
    
    if (['completed', 'failed', 'canceled'].includes(task.status)) {
      throw new InvalidTaskStateError(
        `Task ${task.id} is already in terminal state: ${task.status}`
      );
    }

    await this.taskManager.cancelTask(task.id);
    this.taskEventManager.taskCanceled(task);
  }
}