// gtranslate - Better front-end for Google Translate
// Copyright (C) 2021-present Alexey Yerin
//
// This program 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.
//
// This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.

package main

import (
	"fmt"
	"html/template"
	"log"
	"net/http"
	"net/url"
	"path"

	"github.com/gorilla/mux"
	"github.com/spf13/pflag"
)

func main() {
	bind := pflag.StringP("bind", "b", ":5000", "Address to bind the server to, [addr]:port")
	templateDir := pflag.String("template-dir", "./templates", "Templates directory")
	staticDir := pflag.String("static-dir", "./static", "Static files directory")
	proxy := pflag.String("proxy", "", "Proxy URL, with no scheme http is assumed")
	userAgent := pflag.String("user-agent", "", "User-Agent header to use")
	pflag.Parse()

	var proxyUrl *url.URL
	if *proxy != "" {
		u, err := url.Parse(*proxy)

		if err != nil {
			log.Fatalln("Invalid proxy URL:", err)
		}

		proxyUrl = u
	}

	tmpl := template.Must(template.ParseGlob(path.Join(*templateDir, "*.html")))

	r := mux.NewRouter()

	r.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
		if req.Method == "GET" {
			tmpl.ExecuteTemplate(w, "index", nil)
			return
		}

		from := req.FormValue("from")
		to := req.FormValue("to")
		text := req.FormValue("text")

		translation, err := Translate(from, to, text, *userAgent, proxyUrl)
		if err != nil {
			writeError(w, 500, err)
		}

		type indexPageData struct {
			From        string
			To          string
			Text        string
			Translation string
		}

		tmpl.ExecuteTemplate(w, "index", indexPageData{from, to, text, translation})
	}).Methods("GET", "POST")

	r.HandleFunc("/api", func(w http.ResponseWriter, req *http.Request) {
		from := req.FormValue("from")
		if from == "" {
			writeError(w, 400, "'from' field is missing")
			return
		}
		to := req.FormValue("to")
		if to == "" {
			writeError(w, 400, "'to' field is missing")
			return
		}
		text := req.FormValue("text")
		if text == "" {
			writeError(w, 400, "'text' field is missing")
			return
		}

		translation, err := Translate(from, to, text, *userAgent, proxyUrl)
		if err != nil {
			writeError(w, 500, err)
		}

		w.Write([]byte(translation))
	}).Methods("POST")

	// Static files
	fs := http.FileServer(http.Dir(*staticDir))
	r.PathPrefix("/static/").Handler(http.StripPrefix("/static/", fs))

	log.Println("Starting on", *bind)
	log.Fatalln(http.ListenAndServe(*bind, r))
}

func writeError(w http.ResponseWriter, status int, err interface{}) {
	w.WriteHeader(status)
	w.Write([]byte(fmt.Sprintln(err)))
}