package event

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"

	"git.x2erp.com/qdy/go-base/logger"
)

// EventDispatcher 事件分发器 - 单例模式
type EventDispatcher struct {
	mu            sync.RWMutex
	baseURL       string
	port          int
	subscriptions map[string]map[chan string]struct{} // sessionID -> set of channels
	client        *http.Client
	cancelFunc    context.CancelFunc
	running       bool
}

// NewEventDispatcher 创建新的事件分发器
func NewEventDispatcher(baseURL string, port int) *EventDispatcher {
	return &EventDispatcher{
		baseURL:       baseURL,
		port:          port,
		subscriptions: make(map[string]map[chan string]struct{}),
		client: &http.Client{
			Timeout: 0, // 无超时限制，用于长连接
		},
		running: false,
	}
}

// Start 启动事件分发器，连接到opencode全局事件流
func (ed *EventDispatcher) Start(ctx context.Context) error {
	ed.mu.Lock()
	if ed.running {
		ed.mu.Unlock()
		return fmt.Errorf("event dispatcher already running")
	}

	// 创建子上下文用于控制SSE连接
	sseCtx, cancel := context.WithCancel(ctx)
	ed.cancelFunc = cancel
	ed.running = true
	ed.mu.Unlock()

	// 启动SSE连接协程
	go ed.runSSEConnection(sseCtx)

	logger.Info(fmt.Sprintf("事件分发器已启动 baseURL=%s port=%d",
		ed.baseURL, ed.port))
	return nil
}

// Stop 停止事件分发器
func (ed *EventDispatcher) Stop() {
	ed.mu.Lock()
	if !ed.running {
		ed.mu.Unlock()
		return
	}

	if ed.cancelFunc != nil {
		ed.cancelFunc()
	}

	// 清理所有订阅通道
	for sessionID, channels := range ed.subscriptions {
		for ch := range channels {
			close(ch)
		}
		delete(ed.subscriptions, sessionID)
	}

	ed.running = false
	ed.mu.Unlock()

	logger.Info("事件分发器已停止")
}

// Subscribe 订阅指定会话的事件
func (ed *EventDispatcher) Subscribe(sessionID, userID string) (<-chan string, error) {
	ed.mu.Lock()
	defer ed.mu.Unlock()

	// 创建缓冲通道
	ch := make(chan string, 100)

	// 添加到订阅列表
	if _, exists := ed.subscriptions[sessionID]; !exists {
		ed.subscriptions[sessionID] = make(map[chan string]struct{})
	}
	ed.subscriptions[sessionID][ch] = struct{}{}

	logger.Debug(fmt.Sprintf("新订阅添加 sessionID=%s userID=%s totalSubscriptions=%d",
		sessionID, userID, len(ed.subscriptions[sessionID])))

	return ch, nil
}

// Unsubscribe 取消订阅指定会话的事件
func (ed *EventDispatcher) Unsubscribe(sessionID string, ch <-chan string) {
	ed.mu.Lock()
	defer ed.mu.Unlock()

	if channels, exists := ed.subscriptions[sessionID]; exists {
		// 遍历查找对应的通道（因为ch是只读通道，无法直接作为key）
		var foundChan chan string
		for candidate := range channels {
			// 比较通道值
			if candidate == ch {
				foundChan = candidate
				break
			}
		}

		if foundChan != nil {
			close(foundChan)
			delete(channels, foundChan)
			logger.Debug(fmt.Sprintf("订阅已移除 sessionID=%s remainingSubscriptions=%d",
				sessionID, len(channels)))
		}

		// 如果没有订阅者了，清理该会话的映射
		if len(channels) == 0 {
			delete(ed.subscriptions, sessionID)
		}
	}
}

// buildSSEURL 构建SSE URL，避免端口重复
func (ed *EventDispatcher) buildSSEURL() string {
	// 检查baseURL是否已包含端口
	base := ed.baseURL
	// 简单检查：如果baseURL已经包含端口号模式（冒号后跟数字），就不再加端口
	// 查找最后一个冒号的位置
	lastColon := -1
	for i := len(base) - 1; i >= 0; i-- {
		if base[i] == ':' {
			lastColon = i
			break
		}
	}

	if lastColon != -1 {
		// 检查冒号后是否都是数字（端口号）
		hasPort := true
		for i := lastColon + 1; i < len(base); i++ {
			if base[i] < '0' || base[i] > '9' {
				hasPort = false
				break
			}
		}
		if hasPort {
			// baseURL已有端口，直接拼接路径
			if strings.HasSuffix(base, "/") {
				return base + "global/event"
			}
			return base + "/global/event"
		}
	}

	// baseURL没有端口或端口格式不正确，添加端口
	if strings.HasSuffix(base, "/") {
		return fmt.Sprintf("%s:%d/global/event", strings.TrimSuffix(base, "/"), ed.port)
	}
	return fmt.Sprintf("%s:%d/global/event", base, ed.port)
}

// runSSEConnection 运行SSE连接，读取全局事件并分发
func (ed *EventDispatcher) runSSEConnection(ctx context.Context) {
	// 构建SSE URL，避免重复端口
	url := ed.buildSSEURL()

	for {
		select {
		case <-ctx.Done():
			logger.Info("SSE连接停止（上下文取消）")
			return
		default:
			// 建立SSE连接
			logger.Info(fmt.Sprintf("正在连接SSE流 url=%s",
				url))
			if err := ed.connectAndProcessSSE(ctx, url); err != nil {
				logger.Error(fmt.Sprintf("SSE连接失败，5秒后重试 error=%s url=%s",
					err.Error(), url))

				select {
				case <-ctx.Done():
					return
				case <-time.After(5 * time.Second):
					continue
				}
			}
		}
	}
}

// connectAndProcessSSE 连接并处理SSE流
func (ed *EventDispatcher) connectAndProcessSSE(ctx context.Context, url string) error {
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return fmt.Errorf("创建请求失败: %w", err)
	}
	req.Header.Set("Accept", "text/event-stream")

	resp, err := ed.client.Do(req)
	if err != nil {
		return fmt.Errorf("发送请求失败: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("SSE请求失败，状态码: %d, 响应: %s", resp.StatusCode, string(body))
	}

	logger.Info(fmt.Sprintf("SSE连接已建立 url=%s",
		url))

	reader := bufio.NewReader(resp.Body)
	eventCount := 0

	for {
		select {
		case <-ctx.Done():
			return nil
		default:
			line, err := reader.ReadString('\n')
			if err != nil {
				if err == io.EOF {
					logger.Info(fmt.Sprintf("SSE流正常结束 totalEvents=%d",
						eventCount))
				} else if ctx.Err() != nil {
					logger.Info("SSE流上下文取消")
				} else {
					logger.Error(fmt.Sprintf("读取SSE流错误 error=%s",
						err.Error()))
				}
				return err
			}

			line = strings.TrimSpace(line)
			if line == "" {
				continue
			}

			if strings.HasPrefix(line, "data: ") {
				data := strings.TrimPrefix(line, "data: ")
				eventCount++

				// 分发事件
				ed.dispatchEvent(data)

			}
		}
	}
}

// dispatchEvent 分发事件到相关订阅者
func (ed *EventDispatcher) dispatchEvent(data string) {
	// 解析事件数据获取sessionID
	sessionID := extractSessionIDFromEvent(data)

	if sessionID == "" {
		// 没有sessionID的事件（如全局心跳）丢弃，不广播给所有订阅者
		// 确保按sessionID严格隔离，避免多用户消息交叉
		return
	}

	// 只记录关键事件的路由日志，减少日志输出
	var eventMap map[string]interface{}
	if err := json.Unmarshal([]byte(data), &eventMap); err == nil {
		// 提取事件类型
		var eventType string
		if payload, ok := eventMap["payload"].(map[string]interface{}); ok {
			if t, ok := payload["type"].(string); ok {
				eventType = t
			}
		}
		// 只记录关键事件类型的路由信息
		switch eventType {
		case "session.status", "message.updated", "session.diff", "session.idle":
			logger.Debug(fmt.Sprintf("路由事件到会话 sessionID=%s type=%s",
				sessionID, eventType))
		}
	}

	// 只分发给订阅该会话的通道
	ed.mu.RLock()
	channels, exists := ed.subscriptions[sessionID]
	ed.mu.RUnlock()

	if !exists {
		// 没有该会话的订阅者，忽略事件
		return
	}

	// 发送事件到所有订阅该会话的通道
	ed.mu.RLock()
	for ch := range channels {
		select {
		case ch <- data:
			// 成功发送
		default:
			// 通道已满，丢弃事件并记录警告
			logger.Warn(fmt.Sprintf("事件通道已满，丢弃事件 sessionID=%s",
				sessionID))
		}
	}
	ed.mu.RUnlock()
}

// extractSessionIDFromEvent 从事件数据中提取sessionID
func extractSessionIDFromEvent(data string) string {
	// 尝试解析为JSON
	var eventMap map[string]interface{}
	if err := json.Unmarshal([]byte(data), &eventMap); err != nil {
		logger.Error("无法解析事件JSON", "error", err.Error(), "dataPreview", safeSubstring(data, 0, 200))
		return ""
	}

	// 递归查找sessionID字段
	sessionID := findSessionIDRecursive(eventMap)

	return sessionID
}

// findSessionIDRecursive 递归查找sessionID字段
func findSessionIDRecursive(data interface{}) string {
	switch v := data.(type) {
	case map[string]interface{}:
		// 检查当前层级的sessionID字段（支持多种命名变体）
		for _, key := range []string{"sessionID", "session_id", "sessionId"} {
			if val, ok := v[key]; ok {
				if str, ok := val.(string); ok && str != "" {
					return str
				}
			}
		}

		// 检查常见嵌套路径
		// 1. payload.properties.sessionID (session.status事件)
		if payload, ok := v["payload"].(map[string]interface{}); ok {
			if props, ok := payload["properties"].(map[string]interface{}); ok {
				if sessionID, ok := props["sessionID"].(string); ok && sessionID != "" {
					return sessionID
				}
			}
		}

		// 2. payload.properties.part.sessionID (message.part.updated事件)
		if payload, ok := v["payload"].(map[string]interface{}); ok {
			if props, ok := payload["properties"].(map[string]interface{}); ok {
				if part, ok := props["part"].(map[string]interface{}); ok {
					if sessionID, ok := part["sessionID"].(string); ok && sessionID != "" {
						return sessionID
					}
				}
			}
		}

		// 3. payload.properties.info.sessionID (message.updated事件)
		if payload, ok := v["payload"].(map[string]interface{}); ok {
			if props, ok := payload["properties"].(map[string]interface{}); ok {
				if info, ok := props["info"].(map[string]interface{}); ok {
					if sessionID, ok := info["sessionID"].(string); ok && sessionID != "" {
						return sessionID
					}
				}
			}
		}

		// 递归遍历所有值
		for _, value := range v {
			if result := findSessionIDRecursive(value); result != "" {
				return result
			}
		}

	case []interface{}:
		// 遍历数组
		for _, item := range v {
			if result := findSessionIDRecursive(item); result != "" {
				return result
			}
		}
	}

	return ""
}

// safeSubstring 安全的子字符串函数
func safeSubstring(s string, start, length int) string {
	if start < 0 {
		start = 0
	}
	if start >= len(s) {
		return ""
	}
	end := start + length
	if end > len(s) {
		end = len(s)
	}
	return s[start:end]
}

// GetInstance 获取单例实例（线程安全）
var (
	instance     *EventDispatcher
	instanceOnce sync.Once
)

// GetEventDispatcher 获取事件分发器单例
func GetEventDispatcher(baseURL string, port int) *EventDispatcher {
	instanceOnce.Do(func() {
		instance = NewEventDispatcher(baseURL, port)
	})
	return instance
}