import {ChildProcess} from 'node:child_process';
import type {IProcessManager, ProcessManagerEvents} from '../interfaces/IProcessManager.js';
import type {IProcessSpawner} from '../interfaces/IProcessSpawner.js';
import type {ILogger} from '../interfaces/ILogger.js';
import {EventEmitter} from 'node:events';

/**
 * Manages process lifecycle
 * Single Responsibility: Process management only
 * Open/Closed: Can be extended without modification
 */
export class ProcessManager extends EventEmitter implements IProcessManager {
  private activeProcess: ChildProcess | null = null;

  constructor(
    private readonly processSpawner: IProcessSpawner,
    private readonly logger: ILogger
  ) {
    super();
  }

  start(command: string, args: string[]): void {
    if (this.isRunning()) {
      throw new Error('Process is already running');
    }

    if (!command) {
      throw new Error('Invalid command: command cannot be empty');
    }

    try {
      this.activeProcess = this.processSpawner.spawn(command, args);

      if (!this.activeProcess) {
        throw new Error('Failed to spawn process');
      }

      this.setupEventHandlers();
    } catch (error) {
      this.logger.error('Failed to start process:', error);
      this.activeProcess = null;
      throw error;
    }
  }

  stop(): void {
    if (this.activeProcess) {
      this.activeProcess.kill();
      this.activeProcess = null;
    }
  }

  isRunning(): boolean {
    return this.activeProcess !== null && !this.activeProcess.killed;
  }

  private setupEventHandlers(): void {
    if (!this.activeProcess) {
      return;
    }

    this.activeProcess.stdout?.on('data', (data: Buffer) => {
      this.logger.log(`stdout: ${data}`);
      this.emit('data', data);
    });

    this.activeProcess.stderr?.on('data', (data: Buffer) => {
      this.logger.log(`stderr: ${data}`);
      this.emit('data', data);
    });

    this.activeProcess.on('close', (code: number | null) => {
      this.logger.log(`child process exited with code ${code}`);
      this.activeProcess = null;
      this.emit('close', code);
    });

    this.activeProcess.on('error', (error: Error) => {
      this.logger.error('Process error:', error);
      this.activeProcess = null;
      this.emit('error', error);
    });
  }
}