/**
 * FeatureFlagService - Manages feature flags for both server and client
 * 
 * Server: Reads from process.env.FEATURE_FLAGS (comma-separated)
 * Client: Reads from session context or provides mock implementation
 */

// Server-side implementation
export class FeatureFlagService {
  private flags: Set<string>;

  constructor(flags?: string[]) {
    if (flags) {
      this.flags = new Set(flags);
    } else {
      // Parse from environment variable
      const flagsEnv = process.env.FEATURE_FLAGS;
      this.flags = flagsEnv 
        ? new Set(flagsEnv.split(',').map(f => f.trim()))
        : new Set();
    }
  }

  /**
   * Check if a feature flag is enabled
   */
  isEnabled(flag: string): boolean {
    return this.flags.has(flag);
  }

  /**
   * Get all enabled flags
   */
  getEnabledFlags(): string[] {
    return Array.from(this.flags);
  }

  /**
   * Factory method to create service with environment flags
   */
  static fromEnv(): FeatureFlagService {
    return new FeatureFlagService();
  }
}

// Client-side context interface
export interface FeatureFlagContextType {
  isEnabled: (flag: string) => boolean;
  getEnabledFlags: () => string[];
}

// Mock implementation for client-side when no context is available
export class MockFeatureFlagService implements FeatureFlagContextType {
  private flags: Set<string>;

  constructor(flags: string[] = []) {
    this.flags = new Set(flags);
  }

  isEnabled(flag: string): boolean {
    return this.flags.has(flag);
  }

  getEnabledFlags(): string[] {
    return Array.from(this.flags);
  }
}

// Default mock instance for client-side usage
export const mockFeatureFlags = new MockFeatureFlagService(['alpha_features']);