golang-template/internal/handlers/handler.go

package handlers

import (
	"context"
	"go-backend/internal/auth"
	"go-backend/internal/database/sqlc"
	"go-backend/internal/services"
	"html/template"
	"log"
	"net/http"
)

// UserService and AuthService are defined here, on the consumer side, so
// handlers depend only on the methods they actually use and tests can swap
// in fakes without touching the services package.

type UserService interface {
	FindByID(ctx context.Context, id string) (*sqlc.UserAuth, error)
	FindByUsername(ctx context.Context, username string) (*sqlc.UserAuth, error)
	CreateUser(ctx context.Context, userInput sqlc.InsertUserParams) (*sqlc.UserAuth, error)
	PatchUser(ctx context.Context, id string, input services.PatchUserInput) (*sqlc.UserAuth, error)
}

type AuthService interface {
	CreateSession(ctx context.Context, userID string) (*services.SessionWithToken, error)
	ValidateSessionToken(ctx context.Context, token string) (*sqlc.UserSession, bool, error)
	DeleteSession(ctx context.Context, token string) error
}

type Handler struct {
	users         UserService
	auth          AuthService
	templateCache map[string]*template.Template
}

// PageData wraps every page render so base.tmpl always has a stable place
// to check whether a user is logged in (.User), regardless of what
// page-specific data (.Data) the page template itself needs.
type PageData struct {
	User *sqlc.UserAuth
	Data any
}

func NewHandler(users UserService, auth AuthService, templateCache map[string]*template.Template) *Handler {
	return &Handler{
		users:         users,
		auth:          auth,
		templateCache: templateCache,
	}
}

// render looks up the pre-parsed template for page (e.g. "index.tmpl") and
// executes it. It writes an error response itself on failure.
func (h *Handler) render(w http.ResponseWriter, page string, data PageData) {
	ts, ok := h.templateCache[page]
	if !ok {
		log.Printf("template %s not found in cache", page)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	if err := ts.ExecuteTemplate(w, "base", data); err != nil {
		log.Print(err.Error())
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
	}
}

func (h *Handler) HomePageHandler(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie("session")

	if err != nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	session, bump, err := h.auth.ValidateSessionToken(r.Context(), cookie.Value)

	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	if session == nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	if bump {
		http.SetCookie(w, auth.NewSessionCookie(cookie.Value, false))
	}

	user, err := h.users.FindByID(r.Context(), session.UserID)

	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	h.render(w, "index.tmpl", PageData{User: user, Data: user.Username})
}

func (h *Handler) LoginPageHandler(w http.ResponseWriter, r *http.Request) {
	cookie, _ := r.Cookie("session")

	if cookie != nil {
		session, bump, err := h.auth.ValidateSessionToken(r.Context(), cookie.Value)

		if err != nil {
			log.Print(err.Error())
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}

		if bump {
			http.SetCookie(w, auth.NewSessionCookie(cookie.Value, false))
		}

		if session != nil {
			http.Redirect(w, r, "/", http.StatusSeeOther)
			return
		}
	}

	h.render(w, "login.tmpl", PageData{})
}

func (h *Handler) SignUpPageHandler(w http.ResponseWriter, r *http.Request) {
	cookie, _ := r.Cookie("session")

	if cookie != nil {
		session, bump, err := h.auth.ValidateSessionToken(r.Context(), cookie.Value)

		if err != nil {
			log.Print(err.Error())
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}

		if bump {
			http.SetCookie(w, auth.NewSessionCookie(cookie.Value, false))
		}

		if session != nil {
			http.Redirect(w, r, "/", http.StatusSeeOther)
			return
		}
	}

	h.render(w, "signup.tmpl", PageData{})
}

func (h *Handler) SettingsPageHandler(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie("session")

	if err != nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	session, bump, err := h.auth.ValidateSessionToken(r.Context(), cookie.Value)

	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	if session == nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	if bump {
		http.SetCookie(w, auth.NewSessionCookie(cookie.Value, false))
	}

	user, err := h.users.FindByID(r.Context(), session.UserID)

	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	h.render(w, "settings.tmpl", PageData{User: user, Data: user})
}