package main

import (
	"html/template"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path"
	"runtime/debug"
	"strings"
)

const (
	//上传文件的位置
	uploadDir = "./uploads"
	//模板文件的位置
	templateDir = "./views"
	//
	listDir = 0x0001
)

//设置模板缓存，用的时候直接解析即可
var templates map[string]*template.Template = make(map[string]*template.Template)

func init() {
	//读取模板文件，设置模板缓存
	fileInfoArr, err := ioutil.ReadDir(templateDir)
	if err != nil {
		panic(err)
		return
	}
	var templateName, templatePath string
	for _, fileInfo := range fileInfoArr {
		templateName = fileInfo.Name()
		if ext := path.Ext(templateName); ext != ".html" {
			continue
		}
		templatePath = templateDir + "/" + templateName
		log.Println("Loading template:", templatePath)
		t := template.Must(template.ParseFiles(templatePath))
		//去除文件后面的".html"
		tmpl := strings.ReplaceAll(templateName, ".html", "")
		//把模板解析的缓存放到map里，用的时候直接就找到了
		templates[tmpl] = t
	}
}
func renderHTML(w http.ResponseWriter, tmpl string, locals map[string]interface{}) (err error) {
	err = templates[tmpl].Execute(w, locals)
	return err
}
func uploadHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		if err := renderHTML(w, "upload", nil); err != nil {
			http.Error(w, err.Error(),
				http.StatusInternalServerError)
			return
		}
	}
	if r.Method == "POST" {
		file, fileheader, err := r.FormFile("image")
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		filename := fileheader.Filename
		defer file.Close()
		serverFile, err := os.Create(uploadDir + "/" + filename)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		defer serverFile.Close()
		if _, err := io.Copy(serverFile, file); err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/view?id="+filename, http.StatusFound)
	}
}
func viewHandler(w http.ResponseWriter, r *http.Request) {
	imageID := r.FormValue("id")
	imagePath := uploadDir + "/" + imageID
	if exists := isExists(imagePath); !exists {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "image")
	http.ServeFile(w, r, imagePath)
}
func isExists(path string) bool {
	_, err := os.Stat(path)
	if err == nil {
		return true
	}
	return os.IsExist(err)
}

func listHandler(w http.ResponseWriter, r *http.Request) {
	fileInfoArr, err := ioutil.ReadDir("./uploads")
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	locals := make(map[string]interface{})
	images := []string{}
	for _, fileInfo := range fileInfoArr {
		images = append(images, fileInfo.Name())
	}
	locals["images"] = images
	// t, err := template.ParseFiles("list.html")
	// if err != nil {
	// 	http.Error(w, err.Error(),
	// 		http.StatusInternalServerError)
	// 	return
	// }
	// t.Execute(w, locals)
	if err = renderHTML(w, "list", locals); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}
func safeHandler(fn http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err, ok := recover().(error); ok {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				// 或者输出自定义的 50x 错误页面
				// w.WriteHeader(http.StatusInternalServerError)
				// renderHtml(w, "error", err)
				// logging
				log.Println("WARN: panic in %v - %v", fn, err)
				log.Println(string(debug.Stack()))
			}
		}()
		fn(w, r)
	}
}
func staticDirHandler(mux *http.ServeMux, prefix string, staticDir string, flags int) {
	mux.HandleFunc(prefix, func(w http.ResponseWriter, r *http.Request) {
		file := staticDir + r.URL.Path[len(prefix)-1:]
		if (flags & listDir) == 0 {
			if exists := isExists(file); !exists {
				http.NotFound(w, r)
				return
			}
		}
		http.ServeFile(w, r, file)
	})
}
func main() {
	mux := http.NewServeMux()
	staticDirHandler(mux, "/files/", "./public", 0)
	mux.HandleFunc("/list", safeHandler(listHandler))
	mux.HandleFunc("/view", safeHandler(viewHandler))
	mux.HandleFunc("/", safeHandler(uploadHandler))
	err := http.ListenAndServe(":8080", mux)
	if err != nil {
		log.Fatal("ListenAndServe: ", err.Error())
	}
}