package main

import (
	"crypto/md5"
	"fmt"
	"golang.org/x/image/webp"
	"image/jpeg"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"time"
)

func main() {
	_, err := os.Stat("cache")
	if err == nil {
		err := os.RemoveAll("cache")
		if err != nil {
			log.Fatal(err)
		}
	}
	err = os.Mkdir("cache", os.ModeDir|os.ModePerm)
	if err != nil {
		log.Fatal(err)
	}

	http.HandleFunc("/", webp2jpgHandler)
	err = http.ListenAndServe(":9999", nil)
	if err != nil {
		log.Fatal(err)
	}
}

func hitCache(md5Path string, writer http.ResponseWriter) bool {
	startTime := time.Now().UnixNano()
	_, err := os.Stat("cache/" + md5Path)
	if err != nil {
		return false
	}

	file, err := os.OpenFile("cache/"+md5Path, os.O_RDONLY, os.FileMode(0644))
	defer file.Close()
	if err != nil {
		log.Fatal(err)
	}

	header := writer.Header()
	header.Set("Access-Control-Allow-Origin", "*")
	header.Set("content-type", "image/jpeg")

	if _, err := io.Copy(writer, file); err != nil {
		log.Fatal(err)
	}
	endTime := time.Now().UnixNano()
	fmt.Printf("命中缓存：%dμs\n", (endTime-startTime)/1e3)

	return true
}

func webp2jpg(path string, md5Path string, writer http.ResponseWriter) {
	startTime := time.Now().UnixNano()

	resp, getErr := http.Get(path)
	if getErr != nil {
		log.Print(getErr)
		writer.WriteHeader(404)
		return
	}
	endTime := time.Now().UnixNano()

	fmt.Printf("下载耗时：%dms\n", (endTime-startTime)/1e6)

	startTime = time.Now().UnixNano()
	m, err := webp.Decode(resp.Body)
	if err != nil {
		log.Fatal(err)
	}
	endTime = time.Now().UnixNano()
	fmt.Printf("解码耗时：%dms\n", (endTime-startTime)/1e6)

	header := writer.Header()
	header.Set("Access-Control-Allow-Origin", "*")
	header.Set("content-type", "image/jpeg")

	file, err := os.OpenFile("cache/"+md5Path, os.O_CREATE|os.O_WRONLY, os.FileMode(0644))
	defer file.Close()
	if err != nil {
		log.Fatal(err)
	}
	startTime = time.Now().UnixNano()
	err = jpeg.Encode(io.MultiWriter(writer, file), m, &jpeg.Options{Quality: 50})
	if err != nil {
		log.Fatal(err)
	}
	endTime = time.Now().UnixNano()
	fmt.Printf("编码耗时：%dms\n", (endTime-startTime)/1e6)
}

func webp2jpgHandler(writer http.ResponseWriter, request *http.Request) {
	if !(strings.HasPrefix(request.URL.RawQuery, "http") && strings.HasSuffix(request.URL.RawQuery, ".webp")) {
		writer.WriteHeader(404)
		return
	}

	m := md5.Sum([]byte(request.URL.RawQuery))
	md5Path := fmt.Sprintf("%x", m)

	if hitCache(md5Path, writer) {
		return
	}

	webp2jpg(request.URL.RawQuery, md5Path, writer)
}