package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path"
	"strconv"
	"strings"

	"github.com/julienschmidt/httprouter"
)

var files map[string]map[int][]string
var IMAGE_TYPES map[string]int

func serveImage(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
	log.Printf("GET %s", r.URL.Path)
	abort := func(code int, reason string) {
		http.Error(w, reason, code)
		log.Printf("GET failed: %d %s", code, reason)
	}

	file, ok := files[p.ByName("type")]
	if !ok {
		abort(400, "Invalid Type")
		return
	}

	simageType := p.ByName("image_type")
	id := p.ByName("id")

	localPath := path.Join("./", p.ByName("type"), simageType, id)
	if _, err := os.Stat(localPath); err == nil {
		log.Println("-> Serving from local file")
		f, err := os.Open(localPath)
		defer f.Close()
		if err != nil {
			abort(500, "Could not open File")
			return
		}
		w.WriteHeader(200)
		io.Copy(w, f)
		return
	}

	if idx := strings.Index(id, ".jpg"); idx != -1 {
		id = id[:idx]
	}

	numId, err := strconv.ParseInt(id, 10, 0)
	if err != nil {
		abort(400, "Invalid ID")
		return
	}

	imageType, ok := IMAGE_TYPES[simageType]
	if !ok {
		abort(400, "Invalid image type")
		return
	}

	images, ok := file[int(numId)]
	if !ok {
		abort(404, "Invalid Target")
		return
	}

	if imageType < 0 || int(imageType) >= len(images) {
		abort(400, "Invalid image type")
		return
	}
	log.Println("-> downloading from acd")

	res, err := http.Get(images[int(imageType)])
	if err != nil {
		abort(500, err.Error())
		return
	}

	data, err := ioutil.ReadAll(res.Body)
	if err != nil {
		abort(500, err.Error())
		return
	}

	if err := ioutil.WriteFile(localPath, data, 0755); err != nil {
		abort(500, err.Error())
		return
	}

	w.Write(data)
}

func loadList(name string) error {
	data, err := ioutil.ReadFile(fmt.Sprintf("%s.list", name))
	if err != nil {
		return err
	}

	files[name] = make(map[int][]string)

	entries := strings.Split(string(data), "\n")

	for _, entry := range entries {
		if entry == "" {
			continue
		}
		data := strings.Split(entry, " ")

		id, err := strconv.ParseInt(data[0], 10, 0)
		if err != nil {
			return err
		}

		if e, ok := files[name][int(id)]; ok {
			files[name][int(id)] = append(e, data[1])
		} else {
			files[name][int(id)] = []string{data[1]}
		}
	}
	return nil
}

func main() {
	IMAGE_TYPES = make(map[string]int)
	IMAGE_TYPES["full"] = 0
	IMAGE_TYPES["thumb"] = 1
	files = make(map[string]map[int][]string)
	if err := loadList("gril"); err != nil {
		log.Fatal(err)
	}
	if err := loadList("series"); err != nil {
		log.Fatal(err)
	}

	router := httprouter.New()
	router.GET("/:type/:image_type/:id", serveImage)
	log.Println("starting image-on-demand on localhost:8081")
	log.Fatal(http.ListenAndServe("localhost:8081", router))
}