goma-gateway/internal/handler.go

package pkg

/*
Copyright 2024 Jonas Kaninda

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
import (
	"context"
	"encoding/json"
	"github.com/gorilla/mux"
	"github.com/jkaninda/goma-gateway/pkg/logger"
	"net/http"
	"sync"
)

// CORSHandler handles CORS headers for incoming requests
//
// Adds CORS headers to the response dynamically based on the provided headers map[string]string
func CORSHandler(cors Cors) mux.MiddlewareFunc {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			// Set CORS headers from the cors config
			//Update Cors Headers
			for k, v := range cors.Headers {
				w.Header().Set(k, v)
			}
			//Update Origin Cors Headers
			if allowedOrigin(cors.Origins, r.Header.Get("Origin")) {
				// Handle preflight requests (OPTIONS)
				if r.Method == "OPTIONS" {
					w.Header().Set(accessControlAllowOrigin, r.Header.Get("Origin"))
					w.WriteHeader(http.StatusNoContent)
					return
				} else {
					w.Header().Set(accessControlAllowOrigin, r.Header.Get("Origin"))
				}
			}
			// Pass the request to the next handler
			next.ServeHTTP(w, r)
		})
	}
}

// ProxyErrorHandler catches backend errors and returns a custom response
func ProxyErrorHandler(w http.ResponseWriter, r *http.Request, err error) {
	logger.Error("Proxy error: %v", err)
	w.WriteHeader(http.StatusBadGateway)
	_, err = w.Write([]byte("Bad Gateway"))
	if err != nil {
		return
	}
	return
}

// HealthCheckHandler handles health check of routes
func (heathRoute HealthCheckRoute) HealthCheckHandler(w http.ResponseWriter, r *http.Request) {
	logger.Info("%s %s %s %s", r.Method, r.RemoteAddr, r.URL, r.UserAgent())
	wg := sync.WaitGroup{}
	wg.Add(len(heathRoute.Routes))
	var routes []HealthCheckRouteResponse
	for _, route := range heathRoute.Routes {
		go func() {
			defer wg.Done()
			if route.HealthCheck != "" {
				err := healthCheck(route.Destination + route.HealthCheck)
				if err != nil {
					if heathRoute.DisableRouteHealthCheckError {
						routes = append(routes, HealthCheckRouteResponse{Name: route.Name, Status: "unhealthy", Error: "Route healthcheck errors disabled"})
					}
					routes = append(routes, HealthCheckRouteResponse{Name: route.Name, Status: "unhealthy", Error: "Error: " + err.Error()})
				} else {
					logger.Info("Route %s is healthy", route.Name)
					routes = append(routes, HealthCheckRouteResponse{Name: route.Name, Status: "healthy", Error: ""})
				}
			} else {
				logger.Warn("Route %s's healthCheck is undefined", route.Name)
				routes = append(routes, HealthCheckRouteResponse{Name: route.Name, Status: "undefined", Error: ""})
			}
		}()

	}
	wg.Wait() // Wait for all requests to complete
	response := HealthCheckResponse{
		Status: "healthy", //Goma proxy
		Routes: routes,    // Routes health check
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	err := json.NewEncoder(w).Encode(response)
	if err != nil {
		return
	}
}
func (heathRoute HealthCheckRoute) HealthReadyHandler(w http.ResponseWriter, r *http.Request) {
	logger.Info("%s %s %s %s", r.Method, r.RemoteAddr, r.URL, r.UserAgent())
	response := HealthCheckRouteResponse{
		Name:   "Service Gateway",
		Status: "healthy",
		Error:  "",
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	err := json.NewEncoder(w).Encode(response)
	if err != nil {
		return
	}
}
func allowedOrigin(origins []string, origin string) bool {
	for _, o := range origins {
		if o == origin {
			return true
		}
		continue
	}
	return false

}

// callbackHandler handles oauth callback
func (oauth *OauthRulerMiddleware) callbackHandler(w http.ResponseWriter, r *http.Request) {
	oauthConfig := oauth2Config(oauth)
	// Verify the state to protect against CSRF
	if r.URL.Query().Get("state") != oauth.State {
		http.Error(w, "Invalid state", http.StatusBadRequest)
		return
	}
	// Exchange the authorization code for an access token
	code := r.URL.Query().Get("code")
	token, err := oauthConfig.Exchange(context.Background(), code)
	if err != nil {
		logger.Error("Failed to exchange token: %v", err.Error())
		http.Error(w, "Failed to exchange token", http.StatusInternalServerError)
		return
	}

	// Get user info from the token
	userInfo, err := oauth.getUserInfo(token)
	if err != nil {
		logger.Error("Error getting user info: %v", err)
		http.Error(w, "Error getting user info: ", http.StatusInternalServerError)
		return
	}
	// Generate JWT with user's email
	jwtToken, err := createJWT(userInfo.Email, oauth.JWTSecret)
	if err != nil {
		logger.Error("Error creating JWT: %v", err)
		http.Error(w, "Error creating JWT ", http.StatusInternalServerError)
		return
	}
	// Save token to a cookie for simplicity
	http.SetCookie(w, &http.Cookie{
		Name:  "goma.oauth",
		Value: jwtToken,
		Path:  oauth.CookiePath,
	})

	// Redirect to the home page or another protected route
	http.Redirect(w, r, oauth.RedirectPath, http.StatusSeeOther)
}