package main

import (
	"fmt"
	"html/template"
	"io"
	"io/ioutil"
	"log"
	"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
}

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 {
		log.Fatal(filename + " is missing")
	}

	defer resp.Body.Close()

	content, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatal("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 getHTML(filename string, w http.ResponseWriter) {
	// Get all items from the git repo
	items := getItems(filename)

	// Generate the restulting HTML
	t, err := template.ParseFiles("templates/" + filename + ".html")
	if err != nil {
		panic(err)
	}

	err = t.Execute(w, items)
	if err != nil {
		panic(err)
	}
}

func main() {
	// All static files (CSS, JS)
	fileServer := http.FileServer(http.Dir("./static"))
	http.Handle("/static/", http.StripPrefix("/static", fileServer))

	// Cover images
	imageServer := http.FileServer(http.Dir("./covers/"))
	http.Handle("/covers/", http.StripPrefix("/covers", imageServer))

	// Update "Hook" /update?filename=COMIC.mkd
	http.HandleFunc("/update", func(w http.ResponseWriter, r *http.Request) {
		filename := r.URL.Query().Get("filename")
		log.Printf("Update hook triggered for %v", filename)

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

		for _, item := range items {
			fmt.Printf("Downloading %v ...\n", item.ImageURL())
			err := item.downloadCover()

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

	http.HandleFunc("/book", func(w http.ResponseWriter, r *http.Request) {
		log.Print("/book")
		getHTML("BOOK.mkd", w)
	})
	http.HandleFunc("/comic", func(w http.ResponseWriter, r *http.Request) {
		log.Print("/comic")
		getHTML("COMIC.mkd", w)
	})

	// Spawn the webserver (blocking)
	log.Print("Spawn webserver on port :9783 and waiting for requests ...")
	err := http.ListenAndServe(":9783", nil)
	if err != nil {
		panic(err)
	}
}