import * as fs from 'fs';
import * as path from 'path';
import { ContextConfig } from '../types';

export class ConfigLoader {
  private static defaultConfig: ContextConfig = {
    includes: [
      '**/*.ts',
      '**/*.js',
      '**/*.py',
      '**/*.go',
      '**/*.rs',
      '**/*.java',
      '**/*.c',
      '**/*.cpp',
      '**/*.h',
      '**/*.hpp',
    ],
    excludes: [
      'node_modules/**',
      'dist/**',
      'build/**',
      '.git/**',
      '.DS_Store',
      '*.log',
    ],
    outputFormat: 'json',
    template: 'default',
    outputFile: 'ai-context.json',
    analyzeConventions: true,
    includeDevDependencies: false,
    respectGitignore: true,
  };

  static async load(
    configPath?: string
  ): Promise<ContextConfig> {
    if (!configPath) {
      const localConfig = path.join(process.cwd(), '.ai-context-config.json');
      if (await this.fileExists(localConfig)) {
        return this.loadFromFile(localConfig);
      }
      return { ...this.defaultConfig };
    }

    if (await this.fileExists(configPath)) {
      return this.loadFromFile(configPath);
    }

    throw new Error(`Config file not found: ${configPath}`);
  }

  private static async loadFromFile(
    configPath: string
  ): Promise<ContextConfig> {
    const content = await fs.promises.readFile(configPath, 'utf-8');
    const userConfig = JSON.parse(content);

    return this.mergeConfig(userConfig);
  }

  private static mergeConfig(
    userConfig: Partial<ContextConfig>
  ): ContextConfig {
    return {
      includes: userConfig.includes ?? this.defaultConfig.includes,
      excludes: userConfig.excludes ?? this.defaultConfig.excludes,
      outputFormat:
        userConfig.outputFormat ?? this.defaultConfig.outputFormat,
      template: userConfig.template ?? this.defaultConfig.template,
      outputFile:
        userConfig.outputFile ?? this.defaultConfig.outputFile,
      analyzeConventions:
        userConfig.analyzeConventions ?? this.defaultConfig.analyzeConventions,
      includeDevDependencies:
        userConfig.includeDevDependencies ??
        this.defaultConfig.includeDevDependencies,
      respectGitignore:
        userConfig.respectGitignore ?? this.defaultConfig.respectGitignore,
    };
  }

  private static async fileExists(filePath: string): Promise<boolean> {
    try {
      await fs.promises.access(filePath, fs.constants.F_OK);
      return true;
    } catch {
      return false;
    }
  }

  static save(
    config: ContextConfig,
    outputPath: string
  ): void {
    const content = JSON.stringify(config, null, 2);
    fs.writeFileSync(outputPath, content, 'utf-8');
  }
}