// Package inspector 提供 taskq 的统计采集功能
package inspector

import (
	"context"
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"code.tczkiot.com/wlw/taskq"
	"github.com/hibiken/asynq"
	"github.com/redis/go-redis/v9"
)

// Options 配置统计采集器的选项
type Options struct {
	// Interval 采集间隔，默认 2 秒
	Interval time.Duration

	// DBPath SQLite 数据库文件路径，默认为 "./taskq_stats.db"
	DBPath string
}

// Inspector 统计采集器，独立于 HTTP 服务运行
// 实现 taskq.Plugin 接口
type Inspector struct {
	opts Options

	rdb    redis.UniversalClient
	queues func() map[string]int

	inspector *asynq.Inspector
	db        *sql.DB
	closeCh   chan struct{}
	closeOnce sync.Once
}

// New 创建新的统计采集器
// 创建后需要通过 Servlet.Use() 注册
func New(opts Options) *Inspector {
	if opts.Interval <= 0 {
		opts.Interval = 2 * time.Second
	}

	if opts.DBPath == "" {
		opts.DBPath = "./taskq_stats.db"
	}

	return &Inspector{
		opts:    opts,
		closeCh: make(chan struct{}),
	}
}

// Name 返回插件名称
func (ins *Inspector) Name() string {
	return "inspector"
}

// Init 初始化插件，从 Context 获取 Redis 和 Queues
func (ins *Inspector) Init(ctx *taskq.Context) error {
	ins.rdb = ctx.Redis()
	ins.queues = ctx.Queues
	return nil
}

// Start 启动采集器，初始化数据库并开始后台采集
func (ins *Inspector) Start(ctx *taskq.Context) error {
	// 确保目录存在
	dir := filepath.Dir(ins.opts.DBPath)
	if dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0755); err != nil {
			return fmt.Errorf("inspector: failed to create directory: %v", err)
		}
	}

	// 打开 SQLite 数据库
	db, err := sql.Open("sqlite3", ins.opts.DBPath)
	if err != nil {
		return fmt.Errorf("inspector: failed to open database: %v", err)
	}

	// 初始化数据库表
	if err := initStatsDB(db); err != nil {
		db.Close()
		return fmt.Errorf("inspector: failed to init database: %v", err)
	}

	ins.db = db
	ins.inspector = asynq.NewInspectorFromRedisClient(ins.rdb)

	// 启动后台统计采集
	go ins.startCollector(ctx)

	return nil
}

// Stop 停止采集器，关闭数据库连接
func (ins *Inspector) Stop() error {
	ins.closeOnce.Do(func() {
		close(ins.closeCh)
	})

	if ins.db != nil {
		ins.db.Close()
	}

	if ins.inspector != nil {
		ins.inspector.Close()
	}

	return nil
}

// initStatsDB 初始化数据库
func initStatsDB(db *sql.DB) error {
	_, err := db.Exec(`
		CREATE TABLE IF NOT EXISTS metrics (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			timestamp INTEGER NOT NULL,
			queue TEXT NOT NULL,
			active INTEGER DEFAULT 0,
			pending INTEGER DEFAULT 0,
			scheduled INTEGER DEFAULT 0,
			retry INTEGER DEFAULT 0,
			archived INTEGER DEFAULT 0,
			completed INTEGER DEFAULT 0,
			succeeded INTEGER DEFAULT 0,
			failed INTEGER DEFAULT 0
		);
		CREATE INDEX IF NOT EXISTS idx_metrics_queue_time ON metrics(queue, timestamp DESC);
		CREATE INDEX IF NOT EXISTS idx_metrics_time ON metrics(timestamp DESC);
		CREATE UNIQUE INDEX IF NOT EXISTS idx_metrics_unique ON metrics(timestamp, queue);
	`)
	return err
}

// startCollector 启动后台统计采集任务
func (ins *Inspector) startCollector(ctx context.Context) {
	ticker := time.NewTicker(ins.opts.Interval)
	defer ticker.Stop()

	for {
		select {
		case <-ins.closeCh:
			return
		case <-ctx.Done():
			return
		case <-ticker.C:
			ins.collectStats()
		}
	}
}

// collectStats 采集所有队列的统计数据
func (ins *Inspector) collectStats() {
	if ins.queues == nil || ins.inspector == nil {
		return
	}

	now := time.Now().Unix()
	queueList := ins.queues()

	for queueName := range queueList {
		info, err := ins.inspector.GetQueueInfo(queueName)
		if err != nil {
			continue
		}

		stats := Stats{
			Queue:     queueName,
			Timestamp: now,
			Active:    info.Active,
			Pending:   info.Pending,
			Scheduled: info.Scheduled,
			Retry:     info.Retry,
			Archived:  info.Archived,
			Completed: info.Completed,
			Succeeded: info.Processed - info.Failed,
			Failed:    info.Failed,
		}

		ins.saveMetrics(stats)
	}
}

// saveMetrics 保存统计数据到 metrics 表
func (ins *Inspector) saveMetrics(stats Stats) error {
	if ins.db == nil {
		return nil
	}

	_, err := ins.db.Exec(`
		INSERT OR REPLACE INTO metrics (timestamp, queue, active, pending, scheduled, retry, archived, completed, succeeded, failed)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`, stats.Timestamp, stats.Queue, stats.Active, stats.Pending, stats.Scheduled, stats.Retry, stats.Archived, stats.Completed, stats.Succeeded, stats.Failed)

	return err
}

// ==================== 数据类型 ====================

// StatsQuery 统计查询参数
type StatsQuery struct {
	Queue string // 队列名称，为空则查询所有队列汇总
	Start int64  // 开始时间戳（秒），0 表示不限制
	End   int64  // 结束时间戳（秒），0 表示不限制
	Limit int    // 返回数量限制，默认 500
}

// Stats 队列统计数据点
type Stats struct {
	Timestamp int64  `json:"t"`           // Unix 时间戳（秒）
	Queue     string `json:"q,omitempty"` // 队列名称
	Active    int    `json:"a"`           // 活跃任务数
	Pending   int    `json:"p"`           // 等待任务数
	Scheduled int    `json:"s"`           // 计划任务数
	Retry     int    `json:"r"`           // 重试任务数
	Archived  int    `json:"ar"`          // 归档任务数
	Completed int    `json:"c"`           // 已完成任务数
	Succeeded int    `json:"su"`          // 成功数
	Failed    int    `json:"f"`           // 失败数
}

// QueueInfo 队列信息
type QueueInfo struct {
	Name        string        `json:"name"`
	Priority    int           `json:"priority"`
	Size        int           `json:"size"`
	Active      int           `json:"active"`
	Pending     int           `json:"pending"`
	Scheduled   int           `json:"scheduled"`
	Retry       int           `json:"retry"`
	Archived    int           `json:"archived"`
	Completed   int           `json:"completed"`
	Processed   int           `json:"processed"`
	Failed      int           `json:"failed"`
	Paused      bool          `json:"paused"`
	MemoryUsage int64         `json:"memory_usage"`
	Latency     time.Duration `json:"-"`
	LatencyMS   int64         `json:"latency"`
}

// TaskInfo 任务信息
type TaskInfo struct {
	ID            string    `json:"id"`
	Type          string    `json:"type"`
	Payload       []byte    `json:"payload"`
	Queue         string    `json:"queue"`
	Retried       int       `json:"retried"`
	LastFailedAt  time.Time `json:"last_failed_at,omitempty"`
	LastErr       string    `json:"last_error,omitempty"`
	NextProcessAt time.Time `json:"next_process_at,omitempty"`
	CompletedAt   time.Time `json:"completed_at,omitempty"`
}

// ==================== 查询方法 ====================

// QueryStats 查询统计数据
func (ins *Inspector) QueryStats(q StatsQuery) ([]Stats, error) {
	if ins.db == nil {
		return nil, nil
	}

	limit := q.Limit
	if limit <= 0 {
		limit = 500
	}

	var args []any
	var whereClause string
	var conditions []string

	if q.Queue != "" {
		conditions = append(conditions, "queue = ?")
		args = append(args, q.Queue)
	}
	if q.Start > 0 {
		conditions = append(conditions, "timestamp >= ?")
		args = append(args, q.Start)
	}
	if q.End > 0 {
		conditions = append(conditions, "timestamp <= ?")
		args = append(args, q.End)
	}

	if len(conditions) > 0 {
		whereClause = "WHERE " + strings.Join(conditions, " AND ")
	}

	var query string
	if q.Queue != "" {
		query = fmt.Sprintf(`
			SELECT timestamp, queue, active, pending, scheduled, retry, archived, completed, succeeded, failed
			FROM metrics
			%s
			ORDER BY timestamp DESC
			LIMIT ?
		`, whereClause)
	} else {
		query = fmt.Sprintf(`
			SELECT timestamp, '' as queue, SUM(active), SUM(pending), SUM(scheduled), SUM(retry), SUM(archived), SUM(completed), SUM(succeeded), SUM(failed)
			FROM metrics
			%s
			GROUP BY timestamp
			ORDER BY timestamp DESC
			LIMIT ?
		`, whereClause)
	}
	args = append(args, limit)

	rows, err := ins.db.Query(query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var statsList []Stats
	for rows.Next() {
		var s Stats
		if err := rows.Scan(&s.Timestamp, &s.Queue, &s.Active, &s.Pending, &s.Scheduled, &s.Retry, &s.Archived, &s.Completed, &s.Succeeded, &s.Failed); err != nil {
			continue
		}
		statsList = append(statsList, s)
	}

	// 反转顺序，使时间从早到晚
	for i, j := 0, len(statsList)-1; i < j; i, j = i+1, j-1 {
		statsList[i], statsList[j] = statsList[j], statsList[i]
	}

	return statsList, nil
}

// GetQueueInfo 获取队列信息
func (ins *Inspector) GetQueueInfo(queueName string) (*QueueInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	info, err := ins.inspector.GetQueueInfo(queueName)
	if err != nil {
		return nil, err
	}
	return &QueueInfo{
		Name:        info.Queue,
		Size:        info.Size,
		Active:      info.Active,
		Pending:     info.Pending,
		Scheduled:   info.Scheduled,
		Retry:       info.Retry,
		Archived:    info.Archived,
		Completed:   info.Completed,
		Processed:   info.Processed,
		Failed:      info.Failed,
		Paused:      info.Paused,
		MemoryUsage: info.MemoryUsage,
		Latency:     info.Latency,
		LatencyMS:   info.Latency.Milliseconds(),
	}, nil
}

// convertTaskInfo 将 asynq.TaskInfo 转换为 TaskInfo
func convertTaskInfo(task *asynq.TaskInfo) *TaskInfo {
	return &TaskInfo{
		ID:            task.ID,
		Type:          task.Type,
		Payload:       task.Payload,
		Queue:         task.Queue,
		Retried:       task.Retried,
		LastFailedAt:  task.LastFailedAt,
		LastErr:       task.LastErr,
		NextProcessAt: task.NextProcessAt,
		CompletedAt:   task.CompletedAt,
	}
}

// convertTaskList 批量转换任务列表
func convertTaskList(tasks []*asynq.TaskInfo) []*TaskInfo {
	result := make([]*TaskInfo, len(tasks))
	for i, t := range tasks {
		result[i] = convertTaskInfo(t)
	}
	return result
}

// ListActiveTasks 获取活跃任务列表
func (ins *Inspector) ListActiveTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListActiveTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// ListPendingTasks 获取等待任务列表
func (ins *Inspector) ListPendingTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListPendingTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// ListScheduledTasks 获取计划任务列表
func (ins *Inspector) ListScheduledTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListScheduledTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// ListRetryTasks 获取重试任务列表
func (ins *Inspector) ListRetryTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListRetryTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// ListArchivedTasks 获取归档任务列表
func (ins *Inspector) ListArchivedTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListArchivedTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// ListCompletedTasks 获取已完成任务列表
func (ins *Inspector) ListCompletedTasks(queueName string, pageSize, page int) ([]*TaskInfo, error) {
	if ins.inspector == nil {
		return nil, fmt.Errorf("inspector: not started")
	}
	tasks, err := ins.inspector.ListCompletedTasks(queueName, asynq.PageSize(pageSize), asynq.Page(page))
	if err != nil {
		return nil, err
	}
	return convertTaskList(tasks), nil
}

// RunTask 立即运行归档任务（重试失败任务）
func (ins *Inspector) RunTask(queueName, taskID string) error {
	if ins.inspector == nil {
		return fmt.Errorf("inspector: not started")
	}
	return ins.inspector.RunTask(queueName, taskID)
}

// PauseQueue 暂停队列
func (ins *Inspector) PauseQueue(queueName string) error {
	if ins.inspector == nil {
		return fmt.Errorf("inspector: not started")
	}
	return ins.inspector.PauseQueue(queueName)
}

// UnpauseQueue 恢复队列
func (ins *Inspector) UnpauseQueue(queueName string) error {
	if ins.inspector == nil {
		return fmt.Errorf("inspector: not started")
	}
	return ins.inspector.UnpauseQueue(queueName)
}