package main

import (
	"crypto/md5"
	"crypto/subtle"
	"encoding/hex"
	"flag"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"time"
)

type App struct {
	Store
	Template *template.Template
	Domain   string
}

func logMux(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		t := time.Now()
		handler.ServeHTTP(w, r)
		log.Println(r.Method, r.URL.Path, time.Since(t))
	})
}

func (app *App) validateHandler(w http.ResponseWriter, r *http.Request) {
	c, err := r.Cookie("id")
	//log.Println(r.Header.Get("X-Original-URI"))
	//log.Println(r.Host)
	if err != nil {
		w.WriteHeader(http.StatusUnauthorized)
	} else {
		if s, ok := app.GetSession(c.Value); ok {
			w.Header().Set("X-Remote-User", strconv.FormatInt(s.UserId, 10))
			w.WriteHeader(http.StatusOK)
		} else {
			log.Println("Session does not exist:", c.Value)
			w.WriteHeader(http.StatusUnauthorized)
		}
	}
}

func (app *App) loginHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		username := r.FormValue("username")
		password := r.FormValue("password")
		next := r.FormValue("next")
		hash := md5.Sum([]byte(password))
		dst := make([]byte, hex.EncodedLen(md5.Size))
		hex.Encode(dst, hash[:])
		u, ok := app.GetUser(username)
		if ok && subtle.ConstantTimeCompare(u.Password, dst) == 1 {
			s := app.NewSession(u.Id)
			c := http.Cookie{Name: "id", Value: s.Id, Domain: "." + app.Domain}
			http.SetCookie(w, &c)
			http.Redirect(w, r, next, http.StatusSeeOther)
		} else {
			app.Template.ExecuteTemplate(w, "login.tmpl", struct {
				Next string
			}{next})
		}
	} else if r.Method == http.MethodGet {
		next := r.FormValue("next")
		app.Template.ExecuteTemplate(w, "login.tmpl", struct {
			Next string
		}{next})
	}
}

func (app *App) logoutHandler(w http.ResponseWriter, r *http.Request) {
	c := http.Cookie{Name: "id", Value: "", Domain: "." + app.Domain, MaxAge: 0}
	http.SetCookie(w, &c)
	http.Redirect(w, r, "/login", http.StatusSeeOther)
}

func main() {

	flag.Usage = func() {
		fmt.Fprintf(
			flag.CommandLine.Output(),
			"Usage: %s [OPTIONS] [DATABASE] [DOMAIN]\n",
			os.Args[0],
		)
		flag.PrintDefaults()
	}
	address := flag.String("a", ":8080", "bind the server to `address`")
	templateDir := flag.String("t", "templates", "template `directory`")
	flag.Parse()
	if flag.NArg() < 2 {
		fmt.Print("Argument missing. ")
		flag.Usage()
		os.Exit(1)
	}

	store := NewPgStore(flag.Args()[0])
	template := template.Must(template.New("").ParseGlob(filepath.Join(*templateDir, "*.tmpl")))
	app := &App{store, template, flag.Args()[1]}
	http.HandleFunc("/validate", app.validateHandler)
	http.HandleFunc("/login", app.loginHandler)
	http.HandleFunc("/logout", app.logoutHandler)
	if err := http.ListenAndServe(*address, logMux(http.DefaultServeMux)); err != nil {
		panic(err)
	}
}