feat: add user generation logic to oauth login

backend/internal/api/oauth.go

@@ -2,17 +2,19 @@ package api
 
 import (
 	"context"
+	"crypto/rand"
 	"errors"
 	"net/http"
 
 	"github.com/danielgtaylor/huma/v2"
+	"github.com/forfarm/backend/internal/domain"
 	"github.com/forfarm/backend/internal/utilities"
 	"github.com/go-chi/chi/v5"
+	"golang.org/x/crypto/bcrypt"
 )
 
 func (a *api) registerOauthRoutes(_ chi.Router, apiInstance huma.API) {
 	tags := []string{"oauth"}
-
 	huma.Register(apiInstance, huma.Operation{
 		OperationID: "oauth_exchange",
 		Method:      http.MethodPost,
@@ -34,8 +36,24 @@ type ExchangeTokenOutput struct {
 	}
 }
 
-// exchangeHandler now assumes the provided access token is a Google ID token.
-// It verifies the token with Google and then generates your own JWT.
+func generateRandomPassword(length int) (string, error) {
+	const charset = "abcdefghijklmnopqrstuvwxyz" +
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!@#$%^&*()-_=+[]{}<>?,./"
+
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", err
+	}
+
+	for i, b := range bytes {
+		bytes[i] = charset[b%byte(len(charset))]
+	}
+	return string(bytes), nil
+}
+
+// exchangeHandler assumes the provided access token is a Google ID token.
+// It verifies the token with Google, and if the user doesn't exist,
+// it creates a new user with a randomly generated password before issuing your JWT.
 func (a *api) exchangeHandler(ctx context.Context, input *ExchangeTokenInput) (*ExchangeTokenOutput, error) {
 	if input.Body.AccessToken == "" {
 		return nil, errors.New("access token is required")
@@ -46,13 +64,38 @@ func (a *api) exchangeHandler(ctx context.Context, input *ExchangeTokenInput) (*
 		return nil, errors.New("invalid Google ID token")
 	}
 
-	newJWT, err := utilities.CreateJwtToken(googleUserID)
+	user, err := a.userRepo.GetByEmail(ctx, email)
+	if err == domain.ErrNotFound {
+		newPassword, err := generateRandomPassword(12)
+		if err != nil {
+			return nil, err
+		}
+
+		hashedPassword, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
+		if err != nil {
+			return nil, err
+		}
+
+		newUser := &domain.User{
+			Email:    email,
+			Password: string(hashedPassword),
+		}
+		if err := a.userRepo.CreateOrUpdate(ctx, newUser); err != nil {
+			return nil, err
+		}
+		user = *newUser
+	} else if err != nil {
+		return nil, err
+	}
+
+	token, err := utilities.CreateJwtToken(user.UUID)
 	if err != nil {
 		return nil, err
 	}
 
-	resp := &ExchangeTokenOutput{}
-	resp.Body.JWT = newJWT
-	resp.Body.Email = email
-	return resp, nil
+	output := &ExchangeTokenOutput{}
+	output.Body.JWT = token
+	output.Body.Email = email
+	_ = googleUserID // Maybe need in the future
+	return output, nil
 }