package handler

import (
	"crypto/rand"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/yourname/cyrene-ai/tool-engine/internal/model"
	"github.com/yourname/cyrene-ai/tool-engine/internal/service"
	"github.com/yourname/cyrene-ai/tool-engine/internal/store"
)

// ToolHandler HTTP API 处理器
type ToolHandler struct {
	svc         *service.ToolService
	callLogStore *store.CallLogStore
}

// NewToolHandler 创建工具处理器
func NewToolHandler(svc *service.ToolService, callLogStore *store.CallLogStore) *ToolHandler {
	return &ToolHandler{svc: svc, callLogStore: callLogStore}
}

// RegisterRoutes 注册所有路由到 mux
func (h *ToolHandler) RegisterRoutes(mux *http.ServeMux) {
	// GET /api/v1/tools - 列出所有工具
	mux.HandleFunc("/api/v1/tools", h.handleTools)
	// GET /api/v1/tools/ - 工具详情和单个执行 (带名称)
	mux.HandleFunc("/api/v1/tools/", h.handleToolByName)
	// POST /api/v1/tools/execute - 批量执行
	mux.HandleFunc("/api/v1/tools/execute", h.handleBatchExecute)
}

// handleTools GET /api/v1/tools - 列出所有工具
func (h *ToolHandler) handleTools(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}

	tools := h.svc.ListTools()
	if tools == nil {
		tools = []model.ToolDefinition{}
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"tools": tools,
		"total": len(tools),
	})
}

// handleToolByName 处理 /api/v1/tools/{name} 和 /api/v1/tools/{name}/execute 和 /api/v1/tools/calls 和 /api/v1/tools/calls/stats
func (h *ToolHandler) handleToolByName(w http.ResponseWriter, r *http.Request) {
	// 解析路径: /api/v1/tools/{name} 或 /api/v1/tools/{name}/execute
	path := strings.TrimPrefix(r.URL.Path, "/api/v1/tools/")
	parts := strings.SplitN(path, "/", 2)

	toolName := parts[0]
	if toolName == "" {
		writeError(w, http.StatusBadRequest, "缺少工具名称")
		return
	}

	// 处理 /api/v1/tools/calls/stats
	if toolName == "calls" && len(parts) == 2 && parts[1] == "stats" {
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method not allowed")
			return
		}
		h.handleCallStats(w, r)
		return
	}

	// 处理 /api/v1/tools/calls
	if toolName == "calls" {
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method not allowed")
			return
		}
		h.handleCallLogs(w, r)
		return
	}

	// 判断是否为执行请求
	if len(parts) == 2 && parts[1] == "execute" {
		if r.Method != http.MethodPost {
			writeError(w, http.StatusMethodNotAllowed, "method not allowed, use POST")
			return
		}
		h.executeTool(w, r, toolName)
		return
	}

	// GET /api/v1/tools/{name} - 获取工具定义
	if r.Method != http.MethodGet {
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}

	def, ok := h.svc.GetTool(toolName)
	if !ok {
		writeError(w, http.StatusNotFound, "工具 "+toolName+" 不存在")
		return
	}

	writeJSON(w, http.StatusOK, def)
}

// executeTool POST /api/v1/tools/{name}/execute - 执行单个工具
func (h *ToolHandler) executeTool(w http.ResponseWriter, r *http.Request, toolName string) {
	var req model.ExecuteRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "请求体格式错误: "+err.Error())
		return
	}

	if req.Arguments == nil {
		req.Arguments = make(map[string]interface{})
	}

	startTime := time.Now()
	result, err := h.svc.Execute(r.Context(), toolName, req.Arguments)
	durationMs := int(time.Since(startTime).Milliseconds())

	if err != nil {
		log.Printf("[tool-handler] 执行工具 %s 失败: %v", toolName, err)
		h.logCall(toolName, req.Arguments, "", err.Error(), false, durationMs, r)
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}

	// 异步记录调用日志
	h.logCall(toolName, req.Arguments, result.Output, result.Error, result.Error == "" && err == nil, durationMs, r)

	writeJSON(w, http.StatusOK, result)
}

// handleBatchExecute POST /api/v1/tools/execute - 批量执行
func (h *ToolHandler) handleBatchExecute(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "method not allowed, use POST")
		return
	}

	var req model.BatchExecuteRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "请求体格式错误: "+err.Error())
		return
	}

	if len(req.Calls) == 0 {
		writeError(w, http.StatusBadRequest, "calls 不能为空")
		return
	}

	startTime := time.Now()
	response := h.svc.ExecuteBatch(r.Context(), req.Calls)
	batchDuration := int(time.Since(startTime).Milliseconds())

	// 异步记录每个调用
	for i, call := range req.Calls {
		var output, errStr string
		var success bool
		if i < len(response.Results) {
			output = response.Results[i].Output
			errStr = response.Results[i].Error
			success = errStr == ""
		}
		h.logCall(call.Name, call.Arguments, output, errStr, success, batchDuration, r)
	}

	writeJSON(w, http.StatusOK, response)
}

// newUUID generates a UUID v4 string using crypto/rand
func newUUID() string {
	b := make([]byte, 16)
	_, _ = rand.Read(b)
	b[6] = (b[6] & 0x0f) | 0x40 // Version 4
	b[8] = (b[8] & 0x3f) | 0x80 // Variant 10
	return fmt.Sprintf("%08x-%04x-%04x-%04x-%012x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:16])
}

// logCall 异步记录工具调用日志
func (h *ToolHandler) logCall(toolName string, args map[string]interface{}, output, errStr string, success bool, durationMs int, r *http.Request) {
	if h.callLogStore == nil {
		return
	}

	callID := newUUID()
	userID := r.URL.Query().Get("user_id")
	sessionID := r.URL.Query().Get("session_id")

	go func() {
		argsJSON, _ := json.Marshal(args)
		record := &store.CallLogRecord{
			CallID:     callID,
			ToolName:   toolName,
			Arguments:  argsJSON,
			Output:     output,
			Error:      errStr,
			Success:    success,
			DurationMs: durationMs,
			UserID:     userID,
			SessionID:  sessionID,
			CreatedAt:  time.Now(),
		}
		if err := h.callLogStore.Insert(record); err != nil {
			log.Printf("[tool-handler] 记录调用日志失败: %v", err)
		}
	}()
}

// handleCallLogs GET /api/v1/tools/calls - 查询调用记录
func (h *ToolHandler) handleCallLogs(w http.ResponseWriter, r *http.Request) {
	if h.callLogStore == nil {
		writeJSON(w, http.StatusOK, map[string]interface{}{
			"calls":       []interface{}{},
			"total":       0,
			"page":        1,
			"limit":       20,
			"total_pages": 0,
		})
		return
	}

	q := r.URL.Query()

	page, _ := strconv.Atoi(q.Get("page"))
	if page < 1 {
		page = 1
	}

	limit, _ := strconv.Atoi(q.Get("limit"))
	if limit < 1 || limit > 100 {
		limit = 20
	}

	query := store.CallLogQuery{
		ToolName: q.Get("tool_name"),
		Page:     page,
		Limit:    limit,
	}

	result, err := h.callLogStore.Query(query)
	if err != nil {
		log.Printf("[tool-handler] 查询调用记录失败: %v", err)
		writeError(w, http.StatusInternalServerError, "查询调用记录失败: "+err.Error())
		return
	}

	writeJSON(w, http.StatusOK, result)
}

// handleCallStats GET /api/v1/tools/calls/stats - 调用统计
func (h *ToolHandler) handleCallStats(w http.ResponseWriter, r *http.Request) {
	if h.callLogStore == nil {
		writeJSON(w, http.StatusOK, map[string]interface{}{
			"total_calls":   0,
			"success_count": 0,
			"fail_count":    0,
			"success_rate":  0,
			"avg_duration_ms": 0,
			"by_tool":       []interface{}{},
		})
		return
	}

	stats, err := h.callLogStore.Stats()
	if err != nil {
		log.Printf("[tool-handler] 查询调用统计失败: %v", err)
		writeError(w, http.StatusInternalServerError, "查询调用统计失败: "+err.Error())
		return
	}

	writeJSON(w, http.StatusOK, stats)
}

// writeJSON 写入 JSON 响应
func writeJSON(w http.ResponseWriter, status int, data interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(data); err != nil {
		log.Printf("[tool-handler] JSON 编码失败: %v", err)
	}
}

// writeError 写入错误响应
func writeError(w http.ResponseWriter, status int, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(map[string]string{
		"error": message,
	})
}