// Server entry point
// Copyright (C) 2022  Nguyễn Gia Phong
//
// This file is part of Phylactery.
//
// Phylactery is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Phylactery is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with Phylactery.  If not, see <https://www.gnu.org/licenses/>.

package main

import (
	"archive/zip"
	"embed"
	"html/template"
	"log"
	"io"
	"net/http"
	"os"
	"path"
	"strconv"
	"strings"
)

//go:embed static/*
var static embed.FS

//go:embed templates/*.html
var templates embed.FS

type Page struct {
	Index int
	Name string
}

type Archive struct {
	Path string
	Title string
	Entries []Page
}

func main() {
	http.Handle("/static/", http.FileServer(http.FS(static)))
	t, err := template.ParseFS(templates, "templates/*.html")
	if err != nil {
		log.Fatal(err)
	}
	lib := os.Getenv("PHYLACTERY_LIBRARY")
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		p := path.Clean(lib + r.URL.Path)
		stat, err := os.Stat(p)
		if err != nil {
			http.NotFound(w, r)
			return
		}

		if stat.IsDir() {
			// TODO
		}

		// TODO: LRU caching
		cbz, err := zip.OpenReader(p)
		if err != nil {
			http.Error(w, "invalid cbz", 406)
			return
		}
		defer cbz.Close()

		r.ParseForm()
		if entry, isImage := r.Form["entry"]; isImage {
			i, err := strconv.Atoi(entry[0])
			if err != nil || i < 0 || i >= len(cbz.File) {
				http.NotFound(w, r)
				return
			}
			image, _ := cbz.File[i].Open()
			defer image.Close()
			io.Copy(w, image)
			return
		}

		var pages []Page
		for i, f := range cbz.File {
			image, _ := cbz.File[i].Open()
			defer image.Close()
			buf := make([]byte, 512)
			n, _ := image.Read(buf)
			mime := http.DetectContentType(buf[:n])
			if strings.HasPrefix(mime, "image/") {
				pages = append(pages, Page{ i, f.Name })
			}
		}
		archive := Archive{ r.URL.Path, stat.Name(), pages }
		t.ExecuteTemplate(w, "archive.html", archive)
	})

	addr := os.Getenv("PHYLACTERY_ADDRESS")
	log.Println("Listening on", addr)
	log.Fatal(http.ListenAndServe(addr, nil))
}