package main

import (
	"context"
	"fmt"
	"github.com/gorilla/mux"
	"log"
	"net/http"
)

type FilterFunc func(http.Handler) http.Handler

func FilterChain(filters ...FilterFunc) FilterFunc {
	return func(next http.Handler) http.Handler {
		for i := len(filters) - 1; i >= 0; i-- {
			next = filters[i](next)
		}
		return next
	}
}

type Context struct {
	context.Context
	req *http.Request
	res http.ResponseWriter
}

func (c *Context) String(code int, str string) error {
	c.res.WriteHeader(code)
	_, err := c.res.Write([]byte(str))
	return err
}

func (c *Context) Result(code int, str string) error {
	c.res.WriteHeader(code)
	_, err := c.res.Write([]byte(str))
	return err
}

type HandleFunc func(Context) error

func IndexPage(ctx Context) error {
	//return errors.New("xxx")
	return ctx.String(200, "hello index")
}
func Logger() HandleFunc {
	return func(c Context) error {
		return nil
	}
}

func main() {
	app := mux.NewRouter()
	next := http.Handler(http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
		ctx := Context{
			res: res,
			req: req,
		}
		h := Logger()
		h(ctx)
		if err := IndexPage(ctx); err != nil {
			ctx.Result(500, "err:"+err.Error())
		}
	}))
	next = FilterChain(func(handler http.Handler) http.Handler {
		return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
			fmt.Println("start")
			handler.ServeHTTP(writer, request)
			fmt.Println("end")
		})
	})(next)
	app.Handle("/", next).Methods("GET")
	srv := http.Server{
		Addr:    ":9999",
		Handler: app,
	}
	log.Fatal(srv.ListenAndServe())
}