func (app *App) HEAD(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "head", handler)
	return app
}
HEAD is a shortcut for app.AppendReqAndResp(url, "head", handler).
package context
import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"math"
	"net"
	"net/http"
	"net/url"
	"os"
	"path"
	"strings"
	"time"
	"github.com/GoAdminGroup/go-admin/modules/constant"
)
const abortIndex int8 = math.MaxInt8 / 2
type Context struct {
	Request   *http.Request
	Response  *http.Response
	UserValue map[string]interface{}
	index     int8
	handlers  Handlers
}
type Path struct {
	URL    string
	Method string
}
type RouterMap map[string]Router
func (r RouterMap) Get(name string) Router {
	return r[name]
}
type Router struct {
	Methods []string
	Patten  string
}
func (r Router) Method() string {
	return r.Methods[0]
}
func (r Router) GetURL(value ...string) string {
	u := r.Patten
	for i := 0; i < len(value); i += 2 {
		u = strings.ReplaceAll(u, ":__"+value[i], value[i+1])
	}
	return u
}
type NodeProcessor func(...Node)
type Node struct {
	Path     string
	Method   string
	Handlers []Handler
	Value    map[string]interface{}
}
func (ctx *Context) SetUserValue(key string, value interface{}) {
	ctx.UserValue[key] = value
}
func (ctx *Context) Path() string {
	return ctx.Request.URL.Path
}
func (ctx *Context) Abort() {
	ctx.index = abortIndex
}
func (ctx *Context) Next() {
	ctx.index++
	for s := int8(len(ctx.handlers)); ctx.index < s; ctx.index++ {
		ctx.handlers[ctx.index](ctx)
	}
}
func (ctx *Context) SetHandlers(handlers Handlers) *Context {
	ctx.handlers = handlers
	return ctx
}
func (ctx *Context) Method() string {
	return ctx.Request.Method
}
func NewContext(req *http.Request) *Context {
	return &Context{
		Request:   req,
		UserValue: make(map[string]interface{}),
		Response: &http.Response{
			StatusCode: http.StatusOK,
			Header:     make(http.Header),
		},
		index: -1,
	}
}
const (
	HeaderContentType = "Content-Type"
	HeaderLastModified    = "Last-Modified"
	HeaderIfModifiedSince = "If-Modified-Since"
	HeaderCacheControl    = "Cache-Control"
	HeaderETag            = "ETag"
	HeaderContentDisposition = "Content-Disposition"
	HeaderContentLength      = "Content-Length"
	HeaderContentEncoding    = "Content-Encoding"
	GzipHeaderValue      = "gzip"
	HeaderAcceptEncoding = "Accept-Encoding"
	HeaderVary           = "Vary"
)
func (ctx *Context) BindJSON(data interface{}) error {
	if ctx.Request.Body != nil {
		b, err := ioutil.ReadAll(ctx.Request.Body)
		if err == nil {
			return json.Unmarshal(b, data)
		}
		return err
	}
	return errors.New("empty request body")
}
func (ctx *Context) MustBindJSON(data interface{}) {
	if ctx.Request.Body != nil {
		b, err := ioutil.ReadAll(ctx.Request.Body)
		if err != nil {
			panic(err)
		}
		err = json.Unmarshal(b, data)
		if err != nil {
			panic(err)
		}
	}
	panic("empty request body")
}
func (ctx *Context) Write(code int, header map[string]string, Body string) {
	ctx.Response.StatusCode = code
	for key, head := range header {
		ctx.AddHeader(key, head)
	}
	ctx.Response.Body = ioutil.NopCloser(strings.NewReader(Body))
}
func (ctx *Context) JSON(code int, Body map[string]interface{}) {
	ctx.Response.StatusCode = code
	ctx.SetContentType("application/json")
	BodyStr, err := json.Marshal(Body)
	if err != nil {
		panic(err)
	}
	ctx.Response.Body = ioutil.NopCloser(bytes.NewReader(BodyStr))
}
func (ctx *Context) DataWithHeaders(code int, header map[string]string, data []byte) {
	ctx.Response.StatusCode = code
	for key, head := range header {
		ctx.AddHeader(key, head)
	}
	ctx.Response.Body = ioutil.NopCloser(bytes.NewBuffer(data))
}
func (ctx *Context) Data(code int, contentType string, data []byte) {
	ctx.Response.StatusCode = code
	ctx.SetContentType(contentType)
	ctx.Response.Body = ioutil.NopCloser(bytes.NewBuffer(data))
}
func (ctx *Context) Redirect(path string) {
	ctx.Response.StatusCode = http.StatusFound
	ctx.SetContentType("text/html; charset=utf-8")
	ctx.AddHeader("Location", path)
}
func (ctx *Context) HTML(code int, body string) {
	ctx.SetContentType("text/html; charset=utf-8")
	ctx.SetStatusCode(code)
	ctx.WriteString(body)
}
func (ctx *Context) HTMLByte(code int, body []byte) {
	ctx.SetContentType("text/html; charset=utf-8")
	ctx.SetStatusCode(code)
	ctx.Response.Body = ioutil.NopCloser(bytes.NewBuffer(body))
}
func (ctx *Context) WriteString(body string) {
	ctx.Response.Body = ioutil.NopCloser(strings.NewReader(body))
}
func (ctx *Context) SetStatusCode(code int) {
	ctx.Response.StatusCode = code
}
func (ctx *Context) SetContentType(contentType string) {
	ctx.AddHeader(HeaderContentType, contentType)
}
func (ctx *Context) SetLastModified(modtime time.Time) {
	if !IsZeroTime(modtime) {
		ctx.AddHeader(HeaderLastModified, modtime.UTC().Format(http.TimeFormat))  
	}
}
var unixEpochTime = time.Unix(0, 0)
func IsZeroTime(t time.Time) bool {
	return t.IsZero() || t.Equal(unixEpochTime)
}
var ParseTime = func(text string) (t time.Time, err error) {
	t, err = time.Parse(http.TimeFormat, text)
	if err != nil {
		return http.ParseTime(text)
	}
	return
}
func (ctx *Context) WriteNotModified() {
	delete(ctx.Response.Header, HeaderContentType)
	delete(ctx.Response.Header, HeaderContentLength)
	if ctx.Headers(HeaderETag) != "" {
		delete(ctx.Response.Header, HeaderLastModified)
	}
	ctx.SetStatusCode(http.StatusNotModified)
}
func (ctx *Context) CheckIfModifiedSince(modtime time.Time) (bool, error) {
	if method := ctx.Method(); method != http.MethodGet && method != http.MethodHead {
		return false, errors.New("skip: method")
	}
	ims := ctx.Headers(HeaderIfModifiedSince)
	if ims == "" || IsZeroTime(modtime) {
		return false, errors.New("skip: zero time")
	}
	t, err := ParseTime(ims)
	if err != nil {
		return false, errors.New("skip: " + err.Error())
	}
	if modtime.UTC().Before(t.Add(1 * time.Second)) {
		return false, nil
	}
	return true, nil
}
func (ctx *Context) LocalIP() string {
	xForwardedFor := ctx.Request.Header.Get("X-Forwarded-For")
	ip := strings.TrimSpace(strings.Split(xForwardedFor, ",")[0])
	if ip != "" {
		return ip
	}
	ip = strings.TrimSpace(ctx.Request.Header.Get("X-Real-Ip"))
	if ip != "" {
		return ip
	}
	if ip, _, err := net.SplitHostPort(strings.TrimSpace(ctx.Request.RemoteAddr)); err == nil {
		return ip
	}
	return "127.0.0.1"
}
func (ctx *Context) SetCookie(cookie *http.Cookie) {
	if v := cookie.String(); v != "" {
		ctx.AddHeader("Set-Cookie", v)
	}
}
func (ctx *Context) Query(key string) string {
	return ctx.Request.URL.Query().Get(key)
}
func (ctx *Context) QueryAll(key string) []string {
	return ctx.Request.URL.Query()[key]
}
func (ctx *Context) QueryDefault(key, def string) string {
	value := ctx.Query(key)
	if value == "" {
		return def
	}
	return value
}
func (ctx *Context) Lang() string {
	return ctx.Query("__ga_lang")
}
func (ctx *Context) Headers(key string) string {
	return ctx.Request.Header.Get(key)
}
func (ctx *Context) Referer() string {
	return ctx.Headers("Referer")
}
func (ctx *Context) RefererURL() *url.URL {
	ref := ctx.Headers("Referer")
	if ref == "" {
		return nil
	}
	u, err := url.Parse(ref)
	if err != nil {
		return nil
	}
	return u
}
func (ctx *Context) RefererQuery(key string) string {
	if u := ctx.RefererURL(); u != nil {
		return u.Query().Get(key)
	}
	return ""
}
func (ctx *Context) FormValue(key string) string {
	return ctx.Request.FormValue(key)
}
func (ctx *Context) PostForm() url.Values {
	_ = ctx.Request.ParseMultipartForm(32 << 20)
	return ctx.Request.PostForm
}
func (ctx *Context) WantHTML() bool {
	return ctx.Method() == "GET" && strings.Contains(ctx.Headers("Accept"), "html")
}
func (ctx *Context) WantJSON() bool {
	return strings.Contains(ctx.Headers("Accept"), "json")
}
func (ctx *Context) AddHeader(key, value string) {
	ctx.Response.Header.Add(key, value)
}
func (ctx *Context) PjaxUrl(url string) {
	ctx.Response.Header.Add(constant.PjaxUrlHeader, url)
}
func (ctx *Context) IsPjax() bool {
	return ctx.Headers(constant.PjaxHeader) == "true"
}
func (ctx *Context) IsIframe() bool {
	return ctx.Query(constant.IframeKey) == "true" || ctx.Headers(constant.IframeKey) == "true"
}
func (ctx *Context) SetHeader(key, value string) {
	ctx.Response.Header.Set(key, value)
}
func (ctx *Context) GetContentType() string {
	return ctx.Request.Header.Get("Content-Type")
}
func (ctx *Context) Cookie(name string) string {
	for _, ck := range ctx.Request.Cookies() {
		if ck.Name == name {
			return ck.Value
		}
	}
	return ""
}
func (ctx *Context) User() interface{} {
	return ctx.UserValue["user"]
}
func (ctx *Context) ServeContent(content io.ReadSeeker, filename string, modtime time.Time, gzipCompression bool) error {
	if modified, err := ctx.CheckIfModifiedSince(modtime); !modified && err == nil {
		ctx.WriteNotModified()
		return nil
	}
	if ctx.GetContentType() == "" {
		ctx.SetContentType(filename)
	}
	buf, _ := ioutil.ReadAll(content)
	ctx.Response.Body = ioutil.NopCloser(bytes.NewBuffer(buf))
	return nil
}
func (ctx *Context) ServeFile(filename string, gzipCompression bool) error {
	f, err := os.Open(filename)
	if err != nil {
		return fmt.Errorf("%d", http.StatusNotFound)
	}
	defer func() {
		_ = f.Close()
	}()
	fi, _ := f.Stat()
	if fi.IsDir() {
		return ctx.ServeFile(path.Join(filename, "index.html"), gzipCompression)
	}
	return ctx.ServeContent(f, fi.Name(), fi.ModTime(), gzipCompression)
}
type HandlerMap map[Path]Handlers
type App struct {
	Requests    []Path
	Handlers    HandlerMap
	Middlewares Handlers
	Prefix      string
	Routers    RouterMap
	routeIndex int
	routeANY   bool
}
func NewApp() *App {
	return &App{
		Requests:    make([]Path, 0),
		Handlers:    make(HandlerMap),
		Prefix:      "/",
		Middlewares: make([]Handler, 0),
		routeIndex:  -1,
		Routers:     make(RouterMap),
	}
}
type Handler func(ctx *Context)
type Handlers []Handler
func (app *App) AppendReqAndResp(url, method string, handler []Handler) {
	app.Requests = append(app.Requests, Path{
		URL:    join(app.Prefix, url),
		Method: method,
	})
	app.routeIndex++
	app.Handlers[Path{
		URL:    join(app.Prefix, url),
		Method: method,
	}] = append(app.Middlewares, handler...)
}
func (app *App) Find(url, method string) []Handler {
	app.routeANY = false
	return app.Handlers[Path{URL: url, Method: method}]
}
func (app *App) POST(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "post", handler)
	return app
}
func (app *App) GET(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "get", handler)
	return app
}
func (app *App) DELETE(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "delete", handler)
	return app
}
func (app *App) PUT(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "put", handler)
	return app
}
func (app *App) OPTIONS(url string, handler ...Handler) *App {
	app.routeANY = false
	app.AppendReqAndResp(url, "options", handler)
	return app
}