/**
 * Configuration utilities for Google Cloud MCP
 * 
 * This module provides functionality to store and retrieve configuration
 * settings for the MCP server, such as project IDs.
 */
import fs from 'fs';
import path from 'path';
import os from 'os';

/**
 * Configuration interface
 */
interface McpConfig {
  /** Default Google Cloud project ID */
  defaultProjectId?: string;
  /** List of recently used project IDs */
  recentProjectIds: string[];
  /** Maximum number of recent project IDs to store */
  maxRecentProjects: number;
}

/**
 * Default configuration
 */
const DEFAULT_CONFIG: McpConfig = {
  recentProjectIds: [],
  maxRecentProjects: 5
};

/**
 * Path to the configuration file
 */
const CONFIG_DIR = path.join(os.homedir(), '.google-cloud-mcp');
const CONFIG_FILE = path.join(CONFIG_DIR, 'config.json');

/**
 * Configuration manager for Google Cloud MCP
 */
export class ConfigManager {
  private config: McpConfig;
  private initialized = false;

  /**
   * Create a new ConfigManager instance
   */
  constructor() {
    this.config = { ...DEFAULT_CONFIG };
  }

  /**
   * Initialize the configuration manager
   */
  async initialize(): Promise<void> {
    if (this.initialized) {
      return;
    }

    try {
      // Create config directory if it doesn't exist
      if (!fs.existsSync(CONFIG_DIR)) {
        fs.mkdirSync(CONFIG_DIR, { recursive: true });
      }

      // Load config if it exists
      if (fs.existsSync(CONFIG_FILE)) {
        const configData = await fs.promises.readFile(CONFIG_FILE, 'utf-8');
        this.config = { ...DEFAULT_CONFIG, ...JSON.parse(configData) };
      } else {
        // Create default config file
        await this.saveConfig();
      }

      this.initialized = true;
    } catch (error) {
      console.error('Failed to initialize configuration:', error);
      // Continue with default config
    }
  }

  /**
   * Save the configuration to disk
   */
  private async saveConfig(): Promise<void> {
    try {
      await fs.promises.writeFile(
        CONFIG_FILE,
        JSON.stringify(this.config, null, 2),
        'utf-8'
      );
    } catch (error) {
      console.error('Failed to save configuration:', error);
    }
  }

  /**
   * Get the default project ID
   * 
   * @returns The default project ID or undefined if not set
   */
  getDefaultProjectId(): string | undefined {
    return this.config.defaultProjectId;
  }

  /**
   * Set the default project ID
   * 
   * @param projectId The project ID to set as default
   */
  async setDefaultProjectId(projectId: string): Promise<void> {
    if (!this.initialized) {
      await this.initialize();
    }

    this.config.defaultProjectId = projectId;
    
    // Add to recent projects if not already there
    this.addToRecentProjects(projectId);
    
    await this.saveConfig();
  }

  /**
   * Add a project ID to the list of recent projects
   * 
   * @param projectId The project ID to add
   */
  async addToRecentProjects(projectId: string): Promise<void> {
    if (!this.initialized) {
      await this.initialize();
    }

    // Remove if already in the list
    this.config.recentProjectIds = this.config.recentProjectIds.filter(
      id => id !== projectId
    );
    
    // Add to the beginning of the list
    this.config.recentProjectIds.unshift(projectId);
    
    // Trim to max size
    if (this.config.recentProjectIds.length > this.config.maxRecentProjects) {
      this.config.recentProjectIds = this.config.recentProjectIds.slice(
        0, this.config.maxRecentProjects
      );
    }
    
    await this.saveConfig();
  }

  /**
   * Get the list of recent project IDs
   * 
   * @returns Array of recent project IDs
   */
  getRecentProjectIds(): string[] {
    return [...this.config.recentProjectIds];
  }
}

// Export a singleton instance
export const configManager = new ConfigManager();