numerus/pkg/login.go

package pkg

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

	"github.com/jackc/pgx/v4"
)

const (
	ContextUserKey = "numerus-user"
	sessionCookie  = "numerus-session"
	defaultRole    = "guest"
)

type LoginPage struct {
	LoginError bool
	Email      string
	Password   string
}

type AppUser struct {
	Email    string
	LoggedIn bool
	Role     string
}

func LoginHandler(db *Db) 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" {
			cookie := db.Text(r, "", "select login($1, $2, $3)", page.Email, page.Password, remoteAddr(r))
			if cookie != "" {
				http.SetCookie(w, createSessionCookie(cookie, 8766*24*time.Hour))
				http.Redirect(w, r, "/", http.StatusSeeOther)
				return
			}
			w.WriteHeader(http.StatusUnauthorized)
			page.LoginError = true
		} else {
			w.WriteHeader(http.StatusOK)
		}
		renderTemplate(w, r, "login.html", page)
	})
}

func LogoutHandler(db *Db) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user := getUser(r)
		if user.LoggedIn {
			db.Exec(r, "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 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) {
		user := &AppUser{
			Email:    "",
			LoggedIn: false,
			Role:     defaultRole,
		}
		if cookie, err := r.Cookie(sessionCookie); err == nil {
			row := db.pool.QueryRow(r.Context(), "select * from check_cookie($1) as (email text, role name)", cookie.Value)
			if err := row.Scan(&user.Email, &user.Role); err != nil {
				if err != pgx.ErrNoRows {
					panic(err)
				}
			} else {
				user.LoggedIn = user.Role != "guest"
			}
		}
		ctx := context.WithValue(r.Context(), ContextUserKey, user)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

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