package main

import (
	"image"
	"image/gif"
	"log"
	"net/http"
	"os"

	"regexp"
	"strconv"

	"github.com/chai2010/webp"
	"github.com/disintegration/imaging"
)

// 实现一个 web api 服务(获取指定尺寸的图片)
func main() {

	http.HandleFunc("/img/", func(w http.ResponseWriter, r *http.Request) {

		// URL 格式: /img/{id}-{version}@{倍图}{宽度}.{格式}
		reg := regexp.MustCompile(`^/img/([0-9a-zA-Z]+)-([0-9a-zA-Z]+)@([0-9]{1,4})x([0-9]{1,4}).(jpg|jpeg|png|webp)$`)
		matches := reg.FindStringSubmatch(r.URL.Path)
		if len(matches) != 6 {
			log.Println("URL 格式错误", matches)
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		// 正则表达式获取参数
		id, version, multiple_str, width_str, format := matches[1], matches[2], matches[3], matches[4], matches[5]
		multiple, err := strconv.Atoi(multiple_str)
		if err != nil {
			log.Println("倍图参数错误", multiple_str)
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		width, err := strconv.Atoi(width_str)
		if err != nil {
			log.Println("宽度参数错误", width_str)
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		log.Println(id, version, multiple, width, format)

		// 打開輸入文件
		file, err := os.Open("data/test.gif")
		if err != nil {
			log.Println("打开文件失败", err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		defer file.Close()

		// 將輸入文件解碼為 image.Image
		img, ext, err := image.Decode(file)
		if err != nil {
			log.Println("解码图像失败", err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		// 如果是 GIF 格式的动态图片，直接返回
		if ext == "gif" {
			giffile, err := os.Open("data/test.gif")
			if err != nil {
				log.Println("打开文件失败", err)
				w.WriteHeader(http.StatusBadRequest)
				return
			}
			defer giffile.Close()
			gifimg, err := gif.DecodeAll(giffile)
			if err != nil {
				log.Println("解码图像失败", err)
				w.WriteHeader(http.StatusBadRequest)
				return
			}
			gif.EncodeAll(w, gifimg)
			return
		}

		// 將圖像轉換為 RGBA 格式（如果尚未採用該格式）
		if _, ok := img.(*image.RGBA); !ok {
			img = imaging.Clone(img)
		}

		// 將圖像調整為指定宽度的 WebP 格式並將其寫入輸出到瀏覽器(高度自适应)
		if err = webp.Encode(w, imaging.Resize(img, multiple*width, 0, imaging.Lanczos), &webp.Options{Quality: 80}); err != nil {
			log.Println("编码图像失败", err.Error())
			w.WriteHeader(http.StatusBadRequest)
			return
		}
	})
	log.Println("Server is running at http://localhost:6001")
	http.ListenAndServe(":6001", nil)
}