package router

import (
	"context"
	"encoding/json"
	"net/http"
	"reflect"
	"strconv"
	"strings"
	"sync"

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

// WebService 路由服务
type RouterService struct {
	router          *http.ServeMux
	middlewares     []func(http.Handler) http.Handler
	handlers        map[string]http.Handler // key: method + " " + path
	registeredPaths map[string]bool         // 路径是否已注册通用处理器
	mu              sync.RWMutex
}

// NewWebService 创建WebService
func NewWebService(router *http.ServeMux) *RouterService {
	ws := &RouterService{
		router:          router,
		handlers:        make(map[string]http.Handler),
		registeredPaths: make(map[string]bool),
	}

	return ws
}

// Use 添加全局中间件
func (ws *RouterService) Use(middleware func(http.Handler) http.Handler) *RouterService {
	ws.middlewares = append(ws.middlewares, middleware)
	return ws
}

// GET 注册GET请求
func (ws *RouterService) GET(path string, handler interface{}) *RouteBuilder {
	return ws.handle("GET", path, handler)
}

// POST 注册POST请求
func (ws *RouterService) POST(path string, handler interface{}) *RouteBuilder {
	return ws.handle("POST", path, handler)
}

// PUT 注册PUT请求
func (ws *RouterService) PUT(path string, handler interface{}) *RouteBuilder {
	return ws.handle("PUT", path, handler)
}

// DELETE 注册DELETE请求
func (ws *RouterService) DELETE(path string, handler interface{}) *RouteBuilder {
	return ws.handle("DELETE", path, handler)
}

// handle 统一处理方法
func (ws *RouterService) handle(method, path string, handler interface{}) *RouteBuilder {
	// 解析路径参数名
	paramNames := extractPathParams(path)

	// 获取处理器函数信息
	handlerValue := reflect.ValueOf(handler)
	handlerType := handlerValue.Type()

	// 验证处理器函数
	if handlerType.Kind() != reflect.Func {
		panic("handler must be a function")
	}

	// 验证返回值
	if handlerType.NumOut() != 2 {
		panic("handler must return exactly 2 values: (T, error)")
	}

	return &RouteBuilder{
		ws:          ws,
		method:      method,
		path:        path,
		handlerFunc: handlerValue,
		paramNames:  paramNames,
	}
}

// RouteBuilder 路由构建器
type RouteBuilder struct {
	ws          *RouterService
	method      string
	path        string
	handlerFunc reflect.Value
	paramNames  []string
	middlewares []func(http.Handler) http.Handler
	description string
}

// WrapMiddleware 通用包装函数
func WrapMiddleware[T any](middleware func(http.Handler, T) http.Handler, dep T) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return middleware(next, dep)
	}
}

// Use 添加路由级中间件
func (rb *RouteBuilder) Use(middleware ...func(http.Handler) http.Handler) *RouteBuilder {
	rb.middlewares = append(rb.middlewares, middleware...)
	return rb
}

// Desc 添加描述
func (rb *RouteBuilder) Desc(description string) *RouteBuilder {
	rb.description = description
	return rb
}

// registerPathIfNeeded 注册路径通用处理器（如果尚未注册）
func (ws *RouterService) registerPathIfNeeded(path string) {
	ws.mu.Lock()
	defer ws.mu.Unlock()

	if ws.registeredPaths[path] {
		return
	}

	// 创建通用处理器，根据方法分发
	genericHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		key := r.Method + " " + path
		ws.mu.RLock()
		handler, ok := ws.handlers[key]
		ws.mu.RUnlock()
		if !ok {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}
		handler.ServeHTTP(w, r)
	})

	ws.router.Handle(path, genericHandler)
	ws.registeredPaths[path] = true
}

// Register 注册路由
func (rb *RouteBuilder) Register() {
	// 创建适配器
	adapter := &handlerAdapter{
		ws:          rb.ws,
		method:      rb.method,
		pathPattern: rb.path,
		paramNames:  rb.paramNames,
		handlerFunc: rb.handlerFunc,
	}

	// 构建处理链：全局中间件 → 路由中间件 → 处理器
	var handler http.Handler = adapter

	// 1. 应用路由级中间件（从后往前）
	for i := len(rb.middlewares) - 1; i >= 0; i-- {
		handler = rb.middlewares[i](handler)
	}

	// 2. 应用全局中间件（从后往前）
	for i := len(rb.ws.middlewares) - 1; i >= 0; i-- {
		handler = rb.ws.middlewares[i](handler)
	}

	// 存储处理器到映射
	key := rb.method + " " + rb.path
	rb.ws.mu.Lock()
	rb.ws.handlers[key] = handler
	rb.ws.mu.Unlock()

	// 确保路径已注册通用处理器
	rb.ws.registerPathIfNeeded(rb.path)
}

// handlerAdapter 处理器适配器
type handlerAdapter struct {
	ws          *RouterService
	method      string
	pathPattern string
	paramNames  []string
	handlerFunc reflect.Value
}

func (ha *handlerAdapter) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// 只处理指定方法的请求
	if r.Method != ha.method {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	// 1. 解析路径参数
	pathParams := ha.parsePathParams(r.URL.Path)

	// 2. 构建函数参数
	args := ha.buildArgs(w, r, pathParams)
	if args == nil {
		http.Error(w, "Invalid parameters", http.StatusBadRequest)
		return
	}

	// 3. 调用处理器函数
	results := ha.handlerFunc.Call(args)

	// 4. 处理返回结果
	ha.handleResponse(w, results)
}

// parsePathParams 解析路径参数
func (ha *handlerAdapter) parsePathParams(requestPath string) map[string]string {
	params := make(map[string]string)

	pattern := strings.Trim(ha.pathPattern, "/")
	request := strings.Trim(requestPath, "/")

	patternParts := strings.Split(pattern, "/")
	requestParts := strings.Split(request, "/")

	for i, patternPart := range patternParts {
		if strings.HasPrefix(patternPart, "{") && strings.HasSuffix(patternPart, "}") {
			paramName := patternPart[1 : len(patternPart)-1]
			if i < len(requestParts) {
				params[paramName] = requestParts[i]
			}
		}
	}

	return params
}
func (ha *handlerAdapter) buildArgs(w http.ResponseWriter, r *http.Request, pathParams map[string]string) []reflect.Value {
	handlerType := ha.handlerFunc.Type()
	numIn := handlerType.NumIn()
	args := make([]reflect.Value, numIn)

	for i := 0; i < numIn; i++ {
		paramType := handlerType.In(i)
		paramName := getParamName(i, handlerType, ha.paramNames)

		// 1. 检查是否是特殊类型
		if arg := ha.bindSpecialType(paramType, w, r); arg.IsValid() {
			args[i] = arg
			continue
		}

		// 2. 检查是否是 *ctx.RequestContext 类型
		if paramType == reflect.TypeOf((*ctx.RequestContext)(nil)) {
			reqCtx := ctx.GetContext(r)
			args[i] = reflect.ValueOf(reqCtx)
			continue
		}

		// 3. 只按名称匹配路径参数
		if value, ok := pathParams[paramName]; ok {
			args[i] = convertToType(value, paramType)
			continue
		}

		// 4. 尝试从查询参数获取
		if queryValue := r.URL.Query().Get(paramName); queryValue != "" {
			args[i] = convertToType(queryValue, paramType)
			continue
		}

		// 5. 尝试从JSON body获取（POST/PUT请求）
		if (r.Method == "POST" || r.Method == "PUT" || r.Method == "PATCH") &&
			(paramType.Kind() == reflect.Struct ||
				(paramType.Kind() == reflect.Ptr && paramType.Elem().Kind() == reflect.Struct)) {
			if arg := ha.parseBody(r, paramType); arg.IsValid() {
				args[i] = arg
				continue
			}
		}

		// 6. 返回零值
		args[i] = reflect.Zero(paramType)
	}

	return args
}

// bindSpecialType 绑定特殊类型
func (ha *handlerAdapter) bindSpecialType(paramType reflect.Type, w http.ResponseWriter, r *http.Request) reflect.Value {
	switch paramType {
	case reflect.TypeOf((*http.ResponseWriter)(nil)).Elem():
		return reflect.ValueOf(w)
	case reflect.TypeOf((*http.Request)(nil)):
		return reflect.ValueOf(r)
		// 新增：支持 context.Context
	case reflect.TypeOf((*context.Context)(nil)).Elem():
		return reflect.ValueOf(r.Context())
	}

	return reflect.Value{}
}

// getParamName 获取参数名
func getParamName(index int, handlerType reflect.Type, pathParamNames []string) string {
	// 如果有路径参数名，优先使用
	if index < len(pathParamNames) {
		return pathParamNames[index]
	}

	// 使用类型名的蛇形格式
	paramType := handlerType.In(index)
	typeName := paramType.Name()
	if typeName == "" {
		return strconv.Itoa(index)
	}

	// 转换为蛇形格式：MyInterface -> my_interface
	var result []rune
	for i, r := range typeName {
		if i > 0 && 'A' <= r && r <= 'Z' {
			result = append(result, '_')
		}
		result = append(result, r)
	}
	return strings.ToLower(string(result))
}

// convertToType 字符串转换为指定类型
func convertToType(str string, targetType reflect.Type) reflect.Value {
	switch targetType.Kind() {
	case reflect.String:
		return reflect.ValueOf(str)
	case reflect.Int:
		if i, err := strconv.Atoi(str); err == nil {
			return reflect.ValueOf(i)
		}
	case reflect.Int64:
		if i, err := strconv.ParseInt(str, 10, 64); err == nil {
			return reflect.ValueOf(i)
		}
	case reflect.Bool:
		if b, err := strconv.ParseBool(str); err == nil {
			return reflect.ValueOf(b)
		}
	case reflect.Float64:
		if f, err := strconv.ParseFloat(str, 64); err == nil {
			return reflect.ValueOf(f)
		}
	}
	return reflect.Value{}
}

// parseBody 解析请求体
func (ha *handlerAdapter) parseBody(r *http.Request, paramType reflect.Type) reflect.Value {
	// 创建参数实例
	var paramValue reflect.Value
	if paramType.Kind() == reflect.Ptr {
		paramValue = reflect.New(paramType.Elem())
	} else {
		paramValue = reflect.New(paramType)
	}

	// 解析JSON
	if err := json.NewDecoder(r.Body).Decode(paramValue.Interface()); err != nil {
		return reflect.Value{}
	}
	defer r.Body.Close()

	// 如果是非指针类型，需要解引用
	if paramType.Kind() != reflect.Ptr {
		paramValue = paramValue.Elem()
	}

	return paramValue
}

// handleResponse 处理响应
func (ha *handlerAdapter) handleResponse(w http.ResponseWriter, results []reflect.Value) {
	// 第一个返回值是数据
	data := results[0].Interface()

	// 第二个返回值是error
	errVal := results[1].Interface()
	if errVal != nil {
		err := errVal.(error)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// 检查是否是 []byte 类型
	if bytes, ok := data.([]byte); ok {
		// 如果是 []byte，直接写入响应，不进行 JSON 编码
		w.Write(bytes)
		return
	}

	// 返回JSON响应
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(data)
}

// extractPathParams 从路径中提取参数名
func extractPathParams(path string) []string {
	var params []string
	parts := strings.Split(strings.Trim(path, "/"), "/")

	for _, part := range parts {
		if strings.HasPrefix(part, "{") && strings.HasSuffix(part, "}") {
			paramName := part[1 : len(part)-1]
			params = append(params, paramName)
		}
	}

	return params
}