package main

import (
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"regexp"
)

type Item struct {
	ISBN string
	Filename string
}

func (i Item) imageURL() string {
	return "https://medien.ubitweb.de/bildzentrale_original/" +
		i.ISBN[0:3] + "/" +
		i.ISBN[3:6] + "/" +
		i.ISBN[6:9] + "/" +
		i.ISBN[9:13] +
		".jpg"
}

func (i Item) targetFilename() string {
	return "covers/" + i.ISBN + ".jpg"
}

func (i Item) downloadCover() error {
	resp, err := http.Get(i.imageURL())

	if err != nil {
		return err
	}

	defer resp.Body.Close()

	out, err := os.Create(i.targetFilename())
	if err != nil {
		return err
	}

	defer out.Close()

	_, err = io.Copy(out, resp.Body)

	return err
}

var filename string
var force bool

func getItems(filename string) []Item {
	var items []Item
	// Get all book URLS
	url := "https://git.okoyono.de/mezzo/buch_des_monats/raw/branch/master/" + filename
	resp, err := http.Get(url)

	if err != nil {
		panic(filename + " is missing")
	}

	defer resp.Body.Close()

	content, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		panic("Can not download the file. Network problem?")
	}

	re := regexp.MustCompile(`[0-9]{13}`)
	matches := re.FindAllString(string(content), -1)

	for _, isbn := range matches {
		items = append(items, Item{ISBN: isbn, Filename: filename})
	}

	return items
}

func main() {
	// Get all items from the git repo
	items := getItems(filename)

	for _, item := range items {
		_, err := os.Stat(item.targetFilename())
		if os.IsNotExist(err) || force {
			fmt.Printf("Downloading %v ...\n", item.imageURL())
			err := item.downloadCover()

			if err != nil {
				fmt.Printf("ERROR: File %s not found\n", item.imageURL())
			}
		}
	}

	// TODO: use template to generate the restulting HTML
}

func init() {
	flag.StringVar(&filename, "filename", "COMIC.mkd", "The filename to use")
	flag.BoolVar(&force, "force", false, "Ignore cache, download all covers")
	flag.Parse()
}