package pkg

import (
	"context"
	"errors"
	"github.com/julienschmidt/httprouter"
	"html/template"
	"net"
	"net/http"
	"strings"
	"time"

	"golang.org/x/text/language"
)

const (
	ContextUserKey   = "numerus-user"
	ContextCookieKey = "numerus-cookie"
	ContextConnKey   = "numerus-database"
	sessionCookie    = "numerus-session"
	defaultRole      = "guest"
	csrfTokenField   = "csfrToken"
	csrfTokenHeader  = "X-CSRFToken"
)

type loginForm struct {
	locale   *Locale
	Errors   []error
	Email    *InputField
	Password *InputField
}

func newLoginForm(demo bool, locale *Locale) *loginForm {
	form := &loginForm{
		locale: locale,
		Email: &InputField{
			Name:     "email",
			Label:    pgettext("input", "Email", locale),
			Type:     "email",
			Required: true,
			Attributes: []template.HTMLAttr{
				`autofocus="autofocus"`,
				`autocomplete="username"`,
				`autocapitalize="none"`,
			},
		},
		Password: &InputField{
			Name:     "password",
			Label:    pgettext("input", "Password", locale),
			Type:     "password",
			Required: true,
			Attributes: []template.HTMLAttr{
				`autocomplete="current-password"`,
			},
		},
	}
	if demo {
		form.Email.Val = "admin@numerus"
		form.Password.Val = "admin"
	}
	return form
}

func (form *loginForm) Parse(r *http.Request) error {
	err := r.ParseForm()
	if err != nil {
		return err
	}
	form.Email.FillValue(r)
	form.Password.FillValue(r)
	return nil
}

func (form *loginForm) Validate() bool {
	validator := newFormValidator()
	if validator.CheckRequiredInput(form.Email, gettext("Email can not be empty.", form.locale)) {
		validator.CheckValidEmailInput(form.Email, gettext("This value is not a valid email. It should be like name@domain.com.", form.locale))
	}
	validator.CheckRequiredInput(form.Password, gettext("Password can not be empty.", form.locale))
	return validator.AllOK()
}

func GetLoginForm(w http.ResponseWriter, r *http.Request, demo bool) {
	user := getUser(r)
	if user.LoggedIn {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}
	locale := getLocale(r)
	form := newLoginForm(demo, locale)
	w.WriteHeader(http.StatusOK)
	mustRenderLoginForm(w, r, form)
}

func HandleLoginForm(w http.ResponseWriter, r *http.Request, demo bool) {
	user := getUser(r)
	if user.LoggedIn {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}
	locale := getLocale(r)
	form := newLoginForm(demo, locale)
	if err := form.Parse(r); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if form.Validate() {
		conn := getConn(r)
		cookie := conn.MustGetText(r.Context(), "", "select login($1, $2, $3)", form.Email, form.Password, remoteAddr(r))
		if cookie != "" {
			setSessionCookie(w, cookie)
			http.Redirect(w, r, "/", http.StatusSeeOther)
			return
		}
		form.Errors = append(form.Errors, errors.New(gettext("Invalid user or password.", locale)))
		w.WriteHeader(http.StatusUnauthorized)
	} else {
		w.WriteHeader(http.StatusUnprocessableEntity)
	}
	mustRenderLoginForm(w, r, form)
}

func mustRenderLoginForm(w http.ResponseWriter, r *http.Request, form *loginForm) {
	mustRenderWebTemplate(w, r, "login.gohtml", form)
}

func HandleLogout(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	if err := verifyCsrfTokenValid(r); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}
	conn := getConn(r)
	conn.MustExec(r.Context(), "select logout()")
	http.SetCookie(w, createSessionCookie("", -24*time.Hour))
	http.Redirect(w, r, "/login", http.StatusSeeOther)
}

func remoteAddr(r *http.Request) string {
	address, _, _ := net.SplitHostPort(r.RemoteAddr)
	if address != "localhost" && address != "127.0.0.1" && address != "::1" {
		return address
	}
	forwarded := r.Header.Get("X-Forwarded-For")
	if forwarded == "" {
		return address
	}
	ips := strings.Split(forwarded, ", ")
	forwarded = ips[0]
	if forwarded == "" {
		return address
	}
	return forwarded
}

func setSessionCookie(w http.ResponseWriter, cookie string) {
	http.SetCookie(w, createSessionCookie(cookie, 8766*24*time.Hour))
}

func createSessionCookie(value string, duration time.Duration) *http.Cookie {
	return &http.Cookie{
		Name:     sessionCookie,
		Value:    value,
		Path:     "/",
		Expires:  time.Now().Add(duration),
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	}
}

type AppUser struct {
	Email     string
	LoggedIn  bool
	Role      string
	Language  language.Tag
	CsrfToken string
}

func LoginChecker(db *Db, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		var ctx = r.Context()
		if cookie, err := r.Cookie(sessionCookie); err == nil {
			ctx = context.WithValue(ctx, ContextCookieKey, cookie.Value)
		}

		conn := db.MustAcquire(ctx)
		defer conn.Release()
		ctx = context.WithValue(ctx, ContextConnKey, conn)

		user := &AppUser{
			Email:    "",
			LoggedIn: false,
			Role:     defaultRole,
		}
		row := conn.QueryRow(ctx, "select coalesce(email, ''), role, lang_tag, csrf_token from user_profile")
		var langTag string
		if err := row.Scan(&user.Email, &user.Role, &langTag, &user.CsrfToken); err != nil {
			panic(err)
		}
		user.LoggedIn = user.Email != ""
		user.Language, _ = language.Parse(langTag)
		ctx = context.WithValue(ctx, ContextUserKey, user)

		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func verifyCsrfTokenValid(r *http.Request) error {
	user := getUser(r)
	token := r.Header.Get(csrfTokenHeader)
	if token == "" {
		token = r.FormValue(csrfTokenField)
	}
	if user.CsrfToken == token {
		return nil
	}
	locale := getLocale(r)
	return errors.New(locale.Get("Cross-site request forgery detected."))
}

func getUser(r *http.Request) *AppUser {
	return r.Context().Value(ContextUserKey).(*AppUser)
}

func getConn(r *http.Request) *Conn {
	return r.Context().Value(ContextConnKey).(*Conn)
}

func Authenticated(next httprouter.Handle) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		user := getUser(r)
		if user.LoggedIn {
			next(w, r, params)
		} else {
			http.Redirect(w, r, "/login", http.StatusSeeOther)
		}
	}
}