feat: add API to generate FB custom token from Kakao

cmd/server/handler/auth_handler.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 
 	"github.com/go-chi/render"
-	app "github.com/pet-sitter/pets-next-door-api/api"
 	pnd "github.com/pet-sitter/pets-next-door-api/api"
 	"github.com/pet-sitter/pets-next-door-api/internal/configs"
 	"github.com/pet-sitter/pets-next-door-api/internal/domain/auth"
@@ -51,13 +50,13 @@ func (h *authHandler) KakaoCallback(w http.ResponseWriter, r *http.Request) {
 	code := pnd.ParseOptionalStringQuery(r, "code")
 	tokenView, err := h.kakaoClient.FetchAccessToken(*code)
 	if err != nil {
-		render.Render(w, r, app.ErrUnknown(err))
+		render.Render(w, r, pnd.ErrUnknown(err))
 		return
 	}
 
 	userProfile, err := h.kakaoClient.FetchUserProfile(tokenView.AccessToken)
 	if err != nil {
-		render.Render(w, r, app.ErrUnknown(err))
+		render.Render(w, r, pnd.ErrUnknown(err))
 		return
 	}
 
@@ -76,3 +75,42 @@ func (h *authHandler) KakaoCallback(w http.ResponseWriter, r *http.Request) {
 		PhotoURL:             userProfile.Properties.ProfileImage,
 	})
 }
+
+// GenerateFBCustomTokenFromKakao godoc
+// @Summary Kakao OAuth 토큰 기반 Firebase Custom Token 생성 API
+// @Description 주어진 카카오 토큰으로 사용자 기본 정보를 검증하고 Firebase Custom Token을 발급합니다.
+// @Tags auth
+// @Accept json
+// @Produce json
+// @Param request body auth.GenerateFBCustomTokenRequest true "Firebase Custom Token 생성 요청"
+// @Success 201 {object} auth.GenerateFBCustomTokenResponse
+// @Failure 400 {object} pnd.AppError
+// @Router /auth/custom-tokens/kakao [post]
+func (h *authHandler) GenerateFBCustomTokenFromKakao(w http.ResponseWriter, r *http.Request) {
+	var tokenRequest auth.GenerateFBCustomTokenRequest
+	if err := pnd.ParseBody(r, &tokenRequest); err != nil {
+		render.Render(w, r, err)
+		return
+	}
+
+	userProfile, err2 := h.kakaoClient.FetchUserProfile(tokenRequest.OAuthToken)
+	if err2 != nil {
+		render.Render(w, nil, pnd.ErrBadRequest(fmt.Errorf("유효하지 않은 Kakao 인증 정보입니다")))
+		return
+	}
+
+	customToken, err := h.authService.CustomToken(r.Context(), fmt.Sprintf("%d", userProfile.ID))
+	if err != nil {
+		render.Render(w, r, err)
+		return
+	}
+
+	render.Status(r, http.StatusCreated)
+	render.JSON(w, r, auth.GenerateFBCustomTokenResponse{
+		AuthToken:            *customToken,
+		FirebaseProviderType: user.FirebaseProviderTypeKakao,
+		FirebaseUID:          fmt.Sprintf("%d", userProfile.ID),
+		Email:                userProfile.KakaoAccount.Email,
+		PhotoURL:             userProfile.Properties.ProfileImage,
+	})
+}

cmd/server/main.go

@@ -11,7 +11,7 @@ import (
 )
 
 // @title 이웃집멍냥 API 문서
-// @version 0.7.0
+// @version 0.8.0
 // @description 이웃집멍냥 백엔드 API 문서입니다.
 // @termsOfService http://swagger.io/terms/
 

cmd/server/router.go

@@ -97,6 +97,7 @@ func NewRouter(app *firebaseinfra.FirebaseApp) *chi.Mux {
 		r.Route("/auth", func(r chi.Router) {
 			r.Get("/login/kakao", authHandler.KakaoLogin)
 			r.Get("/callback/kakao", authHandler.KakaoCallback)
+			r.Post("/custom-tokens/kakao", authHandler.GenerateFBCustomTokenFromKakao)
 		})
 		r.Route("/media", func(r chi.Router) {
 			r.Get("/{id}", mediaHandler.FindMediaByID)

internal/domain/auth/view.go

@@ -9,3 +9,17 @@ type KakaoCallbackView struct {
 	Email                string                    `json:"email"`
 	PhotoURL             string                    `json:"photoURL"`
 }
+
+// GenerateFBCustomTokenRequest는 OAuth 토큰 정보를 기반으로 Firebase Custom Token을 생성하기 위한 요청이다.
+type GenerateFBCustomTokenRequest struct {
+	OAuthToken string `json:"oauthToken"`
+}
+
+// GenerateFBCustomTokenResponse는 Firebase Custom Token을 생성하기 위한 응답이다.
+type GenerateFBCustomTokenResponse struct {
+	AuthToken            string                    `json:"authToken"`
+	FirebaseProviderType user.FirebaseProviderType `json:"fbProviderType"`
+	FirebaseUID          string                    `json:"fbUid"`
+	Email                string                    `json:"email"`
+	PhotoURL             string                    `json:"photoURL"`
+}

internal/infra/kakao/client.go

@@ -2,6 +2,7 @@ package kakaoinfra
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"strings"
@@ -70,7 +71,7 @@ func (kakaoClient *KakaoDefaultClient) FetchUserProfile(code string) (*kakaoUser
 	}
 
 	if res.StatusCode != http.StatusOK {
-		return nil, err
+		return nil, fmt.Errorf("failed to fetch user profile from Kakao server")
 	}
 
 	body, err := io.ReadAll(res.Body)