package main

import (
	"context"
	"database/sql"
	"encoding/gob"
	"errors"
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"strconv"

	"github.com/gorilla/handlers"
	"github.com/gorilla/schema"
	"github.com/gorilla/securecookie"
	"github.com/gorilla/sessions"
	"golang.org/x/crypto/bcrypt"

	"gosten/model"
	"gosten/templ"
)

// flags
var (
	port uint64
	host string
)

func init() {
	flag.StringVar(&host, "h", "localhost", "address to listen on")
	flag.Uint64Var(&port, "p", 8080, "port to listen on")

	gob.Register(SessionData{})
}

var Q *model.Queries
var s *schema.Decoder
var sessionStore sessions.Store

const sessionCookie = "sessionKeks"

func main() {
	flag.Parse()

	db := openDB("")

	if err := db.Ping(); err != nil {
		log.Fatal(err)
	}

	Q = model.New(db)
	s = schema.NewDecoder()
	sessionStore = sessions.NewCookieStore(securecookie.GenerateRandomKey(32))

	mux := http.NewServeMux()

	mux.Handle("/{$}", showTemplate("index", nil))
	mux.HandleFunc("GET /login", loginPage)
	mux.HandleFunc("POST /login", handleLogin)
	mux.HandleFunc("GET /logout", handleLogout)

	handler := sessionHandler(mux)
	handler = handlers.CombinedLoggingHandler(os.Stderr, handler)
	handler = handlers.ProxyHeaders(handler)

	address := net.JoinHostPort(host, strconv.FormatUint(port, 10))
	log.Fatal(http.ListenAndServe(address, handler))
}

type User struct {
	Name       string  `form:"options=required"`
	Password   string  `form:"type=password;options=required"`
	RememberMe bool    `form:"type=checkbox;value=y;options=checked"`
	Errors     []error `form:"-"`
}

type fieldError struct {
	Field string
	Issue string
}

func (fe fieldError) Error() string {
	return fmt.Sprintf("%s: %v", fe.Field, fe.Issue)
}

func (fe fieldError) FieldError() (field, err string) {
	return fe.Field, fe.Issue
}

func showTemplate(tpl string, data any) http.HandlerFunc {
	return func(w http.ResponseWriter, _ *http.Request) {
		if err := templ.Lookup(tpl).Execute(w, data); err != nil {
			log.Panicf("Executing '%s' with %+v: %v", tpl, data, err)
		}
	}
}

func parseForm[T any](r *http.Request, data *T) {
	if err := r.ParseForm(); err != nil {
		log.Panic("Parsing form: ", err)
	}
	if err := s.Decode(data, r.PostForm); err != nil {
		log.Panic("Decoding form: ", err)
	}
}

func loginPage(w http.ResponseWriter, r *http.Request) {
	s := session(r)

	if !s.s.IsNew && s.Authenticated {
		u, err := Q.GetUserById(r.Context(), s.UserID)
		if err != nil {
			s.Authenticated = false
			s.Save(w, r)
		} else {
			u2 := User{Name: u.Name}
			showTemplate("login2", u2).ServeHTTP(w, r)
			return
		}
	}

	showTemplate("login", User{}).ServeHTTP(w, r)
}

func handleLogin(w http.ResponseWriter, r *http.Request) {
	u := User{}
	parseForm(r, &u)

	invalid := false

	dbUser, err := Q.GetUserByName(r.Context(), u.Name)
	if err == nil {
		hash := []byte(dbUser.Pwd)
		pwd := []byte(u.Password)

		if bcrypt.CompareHashAndPassword(hash, pwd) != nil {
			invalid = true
		}
	} else if errors.Is(err, sql.ErrNoRows) {
		invalid = true
	} else {
		log.Panicf("Could not load user '%s': %v", u.Name, err)
	}

	if invalid {
		u.Errors = []error{fieldError{"Password", "Invalid"}}
		showTemplate("login", u).ServeHTTP(w, r)
		return
	}

	s := session(r)
	if u.RememberMe {
		s.MaxAge(86400 * 7) // 1 week
	} else {
		s.MaxAge(0)
	}

	s.UserID = dbUser.ID
	s.Authenticated = true
	s.Save(w, r)

	showTemplate("login2", u).ServeHTTP(w, r)
}

func handleLogout(w http.ResponseWriter, r *http.Request) {
	s := session(r)
	s.Authenticated = false
	s.MaxAge(-1)
	s.Save(w, r)
}

func sessionHandler(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		session, err := sessionStore.Get(r, sessionCookie)
		if err != nil {
		}

		ctx := context.WithValue(r.Context(), "_session", session)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

type Session struct {
	*SessionData
	s *sessions.Session
}

type SessionData struct {
	UserID        int64
	Authenticated bool
}

func (s *Session) Save(w http.ResponseWriter, r *http.Request) {
	s.s.Values["data"] = *s.SessionData
	if err := s.s.Save(r, w); err != nil {
		log.Panic("Storing session: ", err)
	}
}

func (s *Session) MaxAge(maxAge int) {
	s.s.Options.MaxAge = maxAge
}

func session(r *http.Request) Session {
	s := r.Context().Value("_session").(*sessions.Session)
	s.Options.HttpOnly = true

	sd, ok := s.Values["data"].(SessionData)
	if !ok {
		sd = SessionData{}
	}
	return Session{&sd, s}
}