package task

import (
	"fmt"
	"log"
	"sync"
	"time"

	"gpt-plus/internal/db"

	"gorm.io/gorm"
)

// TaskManager controls the lifecycle of task execution.
// Only one task may run at a time (single-task serial constraint).
type TaskManager struct {
	mu      sync.Mutex
	current *TaskRunner
	gormDB  *gorm.DB
}

func NewTaskManager(d *gorm.DB) *TaskManager {
	return &TaskManager{gormDB: d}
}

// Init marks any leftover running/stopping tasks as interrupted on startup.
func (m *TaskManager) Init() {
	m.gormDB.Model(&db.Task{}).
		Where("status IN ?", []string{StatusRunning, StatusStopping}).
		Updates(map[string]interface{}{
			"status":     StatusInterrupted,
			"stopped_at": time.Now(),
		})
	log.Println("[task-manager] init: marked leftover tasks as interrupted")
}

func (m *TaskManager) Start(taskID string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.current != nil && m.current.IsRunning() {
		return fmt.Errorf("已有任务正在运行 (ID: %s)", m.current.taskID)
	}

	var t db.Task
	if err := m.gormDB.First(&t, "id = ?", taskID).Error; err != nil {
		return fmt.Errorf("任务不存在: %w", err)
	}
	if t.Status != StatusPending && t.Status != StatusStopped && t.Status != StatusInterrupted {
		return fmt.Errorf("任务状态不允许启动: %s", t.Status)
	}

	runner, err := NewTaskRunner(taskID, m.gormDB)
	if err != nil {
		return fmt.Errorf("创建任务运行器失败: %w", err)
	}
	m.current = runner

	go func() {
		runner.Run()
		m.mu.Lock()
		if m.current == runner {
			m.current = nil
		}
		m.mu.Unlock()
	}()

	return nil
}

func (m *TaskManager) Stop(taskID string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.current == nil || m.current.taskID != taskID {
		return fmt.Errorf("该任务未在运行")
	}
	m.current.GracefulStop()
	return nil
}

func (m *TaskManager) ForceStop(taskID string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.current == nil || m.current.taskID != taskID {
		return fmt.Errorf("该任务未在运行")
	}
	m.current.ForceStop()
	return nil
}

func (m *TaskManager) IsRunning() bool {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.current != nil && m.current.IsRunning()
}