import { readFileSync } from 'fs';
import { join } from 'path';
import chokidar from 'chokidar';
import { EventEmitter } from 'events';

export interface Repository {
  owner: string;
  name: string;
  token?: string;
}

export interface Config {
  github: {
    token: string;
    repositories: Repository[];
  };
  server: {
    port: number;
    host: string;
  };
  cache?: {
    timeoutSeconds?: number;
  };
}

const defaultConfig: Config = {
  github: {
    token: process.env.GITHUB_TOKEN || '',
    repositories: []
  },
  server: {
    port: parseInt(process.env.PORT || '3001'),
    host: process.env.HOST || '0.0.0.0'
  },
  cache: {
    timeoutSeconds: 300
  }
};

export function loadConfig(): Config {
  const configPath = join(process.cwd(), 'config.json');
  
  try {
    const configFile = readFileSync(configPath, 'utf8');
    const fileConfig = JSON.parse(configFile);
    
    return {
      github: {
        token: fileConfig.github?.token || process.env.GITHUB_TOKEN || '',
        repositories: fileConfig.github?.repositories || []
      },
      server: {
        port: fileConfig.server?.port || parseInt(process.env.PORT || '3001'),
        host: fileConfig.server?.host || process.env.HOST || '0.0.0.0'
      },
      cache: {
        timeoutSeconds: fileConfig.cache?.timeoutSeconds || 300
      }
    };
  } catch (error) {
    console.log('Config file not found, using environment variables and defaults');
    return defaultConfig;
  }
}

// Legacy function for backward compatibility
export function createConfigWatcher(): ConfigWatcher {
  return new ConfigWatcher();
}

export function validateConfig(config: Config): void {
  if (!config.github.token) {
    throw new Error('GitHub token is required. Set GITHUB_TOKEN environment variable or add it to config.json');
  }
  
  if (!config.github.repositories.length) {
    throw new Error('At least one repository is required in config.json');
  }
  
  for (const repo of config.github.repositories) {
    if (!repo.owner || !repo.name) {
      throw new Error(`Invalid repository configuration: ${JSON.stringify(repo)}`);
    }
  }
}

export class ConfigWatcher extends EventEmitter {
  private config: Config;
  private configPath: string;
  private watcher?: chokidar.FSWatcher;

  constructor() {
    super();
    this.configPath = join(process.cwd(), 'config.json');
    this.config = this.loadConfigSync();
    this.startWatching();
  }

  private loadConfigSync(): Config {
    try {
      const configFile = readFileSync(this.configPath, 'utf8');
      const fileConfig = JSON.parse(configFile);
      
      const config = {
        github: {
          token: fileConfig.github?.token || process.env.GITHUB_TOKEN || '',
          repositories: fileConfig.github?.repositories || []
        },
        server: {
          port: fileConfig.server?.port || parseInt(process.env.PORT || '3001'),
          host: fileConfig.server?.host || process.env.HOST || '0.0.0.0'
        },
        cache: {
          timeoutSeconds: fileConfig.cache?.timeoutSeconds || 300
        }
      };
      
      validateConfig(config);
      return config;
    } catch (error) {
      console.log('Config file not found or invalid, using environment variables and defaults');
      const config = {
        github: {
          token: process.env.GITHUB_TOKEN || '',
          repositories: []
        },
        server: {
          port: parseInt(process.env.PORT || '3001'),
          host: process.env.HOST || '0.0.0.0'
        },
        cache: {
          timeoutSeconds: 300
        }
      };
      return config;
    }
  }

  private startWatching(): void {
    this.watcher = chokidar.watch(this.configPath, {
      ignored: /(^|[/\\])\../, // ignore dotfiles
      persistent: true
    });

    this.watcher.on('change', () => {
      console.log('📁 Config file changed, reloading...');
      try {
        const newConfig = this.loadConfigSync();
        this.config = newConfig;
        this.emit('configChanged', newConfig);
        console.log('✅ Config reloaded successfully');
        console.log(`📊 Now monitoring ${newConfig.github.repositories.length} repositories`);
      } catch (error) {
        console.error('❌ Failed to reload config:', error);
        this.emit('configError', error);
      }
    });

    this.watcher.on('error', (error) => {
      console.error('❌ Config watcher error:', error);
    });
  }

  public getConfig(): Config {
    return this.config;
  }

  public close(): void {
    if (this.watcher) {
      this.watcher.close();
    }
  }
}