numerus/pkg/login.go

package pkg

import (
	"context"
	"net"
	"net/http"
	"time"

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

const (
	ContextUserKey   = "numerus-user"
	ContextCookieKey = "numerus-cookie"
	ContextConnKey   = "numerus-database"
	sessionCookie    = "numerus-session"
	defaultRole      = "guest"
)

type LoginPage struct {
	LoginError bool
	Email      string
	Password   string
}

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

func LoginHandler() http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user := getUser(r)
		if user.LoggedIn {
			http.Redirect(w, r, "/", http.StatusSeeOther)
			return
		}
		r.ParseForm()
		page := LoginPage{
			Email:    r.FormValue("email"),
			Password: r.FormValue("password"),
		}
		if r.Method == "POST" {
			conn := getConn(r)
			cookie := conn.MustGetText(r.Context(), "", "select login($1, $2, $3)", page.Email, page.Password, remoteAddr(r))
			if cookie != "" {
				setSessionCookie(w, cookie)
				http.Redirect(w, r, "/", http.StatusSeeOther)
				return
			}
			w.WriteHeader(http.StatusUnauthorized)
			page.LoginError = true
		} else {
			w.WriteHeader(http.StatusOK)
		}
		mustRenderWebTemplate(w, r, "login.gohtml", page)
	})
}

func LogoutHandler() http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		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 := r.Header.Get("X-Forwarded-For")
	if address == "" {
		address, _, _ = net.SplitHostPort(r.RemoteAddr)
	}
	return address
}

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,
	}
}

func CheckLogin(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 from user_profile")
		var langTag string
		if err := row.Scan(&user.Email, &user.Role, &langTag); 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 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 http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user := getUser(r)
		if user.LoggedIn {
			next.ServeHTTP(w, r)
		} else {
			http.Redirect(w, r, "/login", http.StatusSeeOther)
		}
	})
}