package webx

import (
	"encoding/json"
	"net/http"
	"reflect"
	"strings"
)

// WebService 路由服务
type WebService struct {
	router *http.ServeMux
}

// NewWebService 创建WebService
func NewWebService(router *http.ServeMux) *WebService {
	return &WebService{router: router}
}

// RouteBuilder 路由构建器
type RouteBuilder struct {
	method      string
	path        string
	handlerFunc reflect.Value
	paramNames  []string
	paramTypes  []reflect.Type
	middlewares []func(http.Handler) http.Handler
	router      *http.ServeMux
}

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

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

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

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

// handle 统一处理方法
func (ws *WebService) 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")
	}

	// 获取参数类型
	paramTypes := make([]reflect.Type, handlerType.NumIn())
	for i := 0; i < handlerType.NumIn(); i++ {
		paramTypes[i] = handlerType.In(i)
	}

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

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

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

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

	// 应用中间件
	var handler http.Handler = adapter
	for i := len(rb.middlewares) - 1; i >= 0; i-- {
		handler = rb.middlewares[i](handler)
	}

	// 注册到路由器
	rb.router.Handle(rb.path, handler)
}

// handlerAdapter 处理器适配器
type handlerAdapter struct {
	method      string
	pathPattern string
	paramNames  []string
	paramTypes  []reflect.Type
	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(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)

	// 简单实现：按/分割，然后匹配
	patternParts := strings.Split(ha.pathPattern, "/")
	requestParts := strings.Split(requestPath, "/")

	if len(patternParts) != len(requestParts) {
		return params
	}

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

	return params
}

// buildArgs 构建函数参数
func (ha *handlerAdapter) buildArgs(r *http.Request, pathParams map[string]string) []reflect.Value {
	args := make([]reflect.Value, len(ha.paramTypes))

	// 参数索引
	pathParamIndex := 0

	for i, paramType := range ha.paramTypes {
		// 情况1：路径参数（必须是string类型）
		if pathParamIndex < len(ha.paramNames) && paramType.Kind() == reflect.String {
			paramName := ha.paramNames[pathParamIndex]
			if value, ok := pathParams[paramName]; ok {
				args[i] = reflect.ValueOf(value)
				pathParamIndex++
				continue
			}
		}

		// 情况2：Body参数（POST/PUT等请求的结构体）
		if r.Method == "POST" || r.Method == "PUT" || r.Method == "PATCH" {
			// 检查是否是结构体类型
			if paramType.Kind() == reflect.Struct ||
				(paramType.Kind() == reflect.Ptr && paramType.Elem().Kind() == reflect.Struct) {
				bodyParam, err := ha.parseBody(r, paramType)
				if err != nil {
					return nil
				}
				args[i] = bodyParam
				continue
			}
		}

		// 无法处理的参数类型
		return nil
	}

	return args
}

// parseBody 解析请求体
func (ha *handlerAdapter) parseBody(r *http.Request, paramType reflect.Type) (reflect.Value, error) {
	// 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{}, err
	}

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

	return paramValue, nil
}

// 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
	}

	// 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(path, "/")

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

	return params
}