interface Session {
  sessionId: string;        // Primary session identifier
  runId: string;           // Current run_id for frames
  projectId: string;       // Associated project
  branch?: string;         // Git branch if applicable
  startedAt: number;       // Session start timestamp
  lastActiveAt: number;    // Last activity timestamp
  metadata: {
    user?: string;
    environment?: string;
    tags?: string[];
  };
  state: 'active' | 'suspended' | 'closed';
}

class SessionManager {
  // Session discovery priority:
  // 1. Explicit --session-id flag
  // 2. Environment variable STACKMEMORY_SESSION
  // 3. Current project + branch combination
  // 4. Last active session for project
  // 5. Create new session
  
  async getOrCreateSession(options?: SessionOptions): Promise<Session> {
    // Check explicit session
    if (options?.sessionId) {
      return this.loadSession(options.sessionId);
    }
    
    // Check environment
    if (process.env.STACKMEMORY_SESSION) {
      return this.loadSession(process.env.STACKMEMORY_SESSION);
    }
    
    // Check project context
    const projectHash = await this.getProjectHash();
    const branch = await this.getGitBranch();
    
    // Try project+branch session
    const branchSession = await this.findProjectBranchSession(projectHash, branch);
    if (branchSession && this.isSessionRecent(branchSession)) {
      return branchSession;
    }
    
    // Try last active for project
    const lastActive = await this.findLastActiveSession(projectHash);
    if (lastActive && this.isSessionRecent(lastActive)) {
      return lastActive;
    }
    
    // Create new session
    return this.createSession({ projectId: projectHash, branch });
  }
  
  private isSessionRecent(session: Session): boolean {
    const STALE_THRESHOLD = 24 * 60 * 60 * 1000; // 24 hours
    return Date.now() - session.lastActiveAt < STALE_THRESHOLD;
  }
}

enum FrameQueryMode {
  CURRENT_SESSION = 'current',    // Current run_id only (default)
  PROJECT_ACTIVE = 'project',     // All active in project
  ALL_ACTIVE = 'all',            // All active across projects
  HISTORICAL = 'historical'        // Include closed frames
}

class FrameManager {
  async loadFrames(mode: FrameQueryMode = FrameQueryMode.CURRENT_SESSION): Promise<Frame[]> {
    switch(mode) {
      case FrameQueryMode.CURRENT_SESSION:
        return this.queryFrames({ runId: this.currentRunId, state: 'active' });
        
      case FrameQueryMode.PROJECT_ACTIVE:
        return this.queryFrames({ projectId: this.projectId, state: 'active' });
        
      case FrameQueryMode.ALL_ACTIVE:
        return this.queryFrames({ state: 'active' });
        
      case FrameQueryMode.HISTORICAL:
        return this.queryFrames({ includeInactive: true });
    }
  }
}