/*
Copyright 2020-2023 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

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

    https://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.
*/

package main

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"encoding/base64"
	"fmt"
	"net/http"
	"os"
	"time"

	"github.com/knadh/koanf"
	"github.com/knadh/koanf/parsers/toml"
	"github.com/knadh/koanf/providers/confmap"
	log "github.com/sirupsen/logrus"

	"code.cacert.org/cacert/oidc-demo-app/ui"

	"code.cacert.org/cacert/oidc-demo-app/internal/handlers"
	"code.cacert.org/cacert/oidc-demo-app/internal/services"
)

const (
	defaultReadTimeout  = 5 * time.Second
	defaultWriteTimeout = 10 * time.Second
	defaultIdleTimeout  = 15 * time.Second

	sessionKeyLength     = 32
	sessionAuthKeyLength = 64
)

func main() {
	logger := log.New()

	config, err := services.ConfigureApplication(
		logger,
		"RESOURCE_APP",
		services.DefaultConfiguration,
	)
	if err != nil {
		log.Fatalf("error loading configuration: %v", err)
	}

	oidcServer := config.MustString("oidc.server")
	oidcClientID := config.MustString("oidc.client-id")
	oidcClientSecret := config.MustString("oidc.client-secret")

	if level := config.String("log.level"); level != "" {
		logLevel, err := log.ParseLevel(level)
		if err != nil {
			logger.WithError(err).Fatal("could not parse log level")
		}

		logger.SetLevel(logLevel)
	}

	if config.Bool("log.json") {
		logger.SetFormatter(&log.JSONFormatter{})
	}

	bundle, catalog := services.InitI18n(logger, config.Strings("i18n.languages"))

	services.AddMessages(catalog)

	tlsClientConfig := &tls.Config{
		MinVersion: tls.VersionTLS12,
	}

	if config.Exists("api-client.rootCAs") {
		rootCAFile := config.MustString("api-client.rootCAs")
		caCertPool := x509.NewCertPool()

		pemBytes, err := os.ReadFile(rootCAFile)
		if err != nil {
			log.Fatalf("could not read CA certificate file: %v", err)
		}

		caCertPool.AppendCertsFromPEM(pemBytes)
		tlsClientConfig.RootCAs = caCertPool
	}

	apiTransport := &http.Transport{TLSClientConfig: tlsClientConfig}
	apiClient := &http.Client{Transport: apiTransport}

	oidcInfo, err := services.DiscoverOIDC(logger, &services.OidcParams{
		OidcServer:       oidcServer,
		OidcClientID:     oidcClientID,
		OidcClientSecret: oidcClientSecret,
		APIClient:        apiClient,
	})
	if err != nil {
		log.Fatalf("OpenID Connect discovery failed: %s", err)
	}

	sessionPath, sessionAuthKey, sessionEncKey := configureSessionParameters(config)
	services.InitSessionStore(logger, sessionPath, sessionAuthKey, sessionEncKey)

	authMiddleware := handlers.Authenticate(logger, oidcInfo.OAuth2Config, oidcClientID)

	publicURL := buildPublicURL(config.MustString("server.name"), config.MustInt("server.port"))

	indexHandler, err := handlers.NewIndexHandler(bundle, catalog, ui.Templates, oidcInfo, publicURL)
	if err != nil {
		logger.Fatalf("could not initialize index handler: %v", err)
	}

	callbackHandler := handlers.NewCallbackHandler(logger, oidcInfo.KeySet, oidcInfo.OAuth2Config)
	afterLogoutHandler := handlers.NewAfterLogoutHandler(logger)
	staticFiles := http.FileServer(http.FS(ui.Static))

	router := http.NewServeMux()
	router.Handle("/", authMiddleware(indexHandler))
	router.Handle("/callback", callbackHandler)
	router.Handle("/after-logout", afterLogoutHandler)
	router.Handle("/health", handlers.NewHealthHandler())
	router.Handle("/images/", staticFiles)
	router.Handle("/css/", staticFiles)
	router.Handle("/js/", staticFiles)

	nextRequestID := func() string {
		return fmt.Sprintf("%d", time.Now().UnixNano())
	}

	tracing := handlers.Tracing(nextRequestID)
	logging := handlers.Logging(logger)
	hsts := handlers.EnableHSTS()

	errorMiddleware, err := handlers.ErrorHandling(logger, ui.Templates, bundle, catalog)
	if err != nil {
		logger.Fatalf("could not initialize request error handling: %v", err)
	}

	tlsConfig := &tls.Config{
		ServerName: config.String("server.name"),
		MinVersion: tls.VersionTLS12,
	}

	server := &http.Server{
		Addr:         fmt.Sprintf("%s:%d", config.String("server.bind_address"), config.Int("server.port")),
		Handler:      tracing(logging(hsts(errorMiddleware(router)))),
		ReadTimeout:  defaultReadTimeout,
		WriteTimeout: defaultWriteTimeout,
		IdleTimeout:  defaultIdleTimeout,
		TLSConfig:    tlsConfig,
	}

	handlers.StartApplication(context.Background(), logger, server, publicURL, config)
}

func buildPublicURL(hostname string, port int) string {
	const defaultHTTPSPort = 443

	if port != defaultHTTPSPort {
		return fmt.Sprintf("https://%s:%d", hostname, port)
	}

	return fmt.Sprintf("https://%s", hostname)
}

func configureSessionParameters(config *koanf.Koanf) (string, []byte, []byte) {
	sessionPath := config.MustString("session.path")

	sessionAuthKey, err := base64.StdEncoding.DecodeString(config.String("session.auth-key"))
	if err != nil {
		log.WithError(err).Fatal("could not decode session auth key")
	}

	sessionEncKey, err := base64.StdEncoding.DecodeString(config.String("session.enc-key"))
	if err != nil {
		log.WithError(err).Fatal("could not decode session encryption key")
	}

	generated := false

	if len(sessionAuthKey) != sessionAuthKeyLength {
		sessionAuthKey = services.GenerateKey(sessionAuthKeyLength)
		generated = true
	}

	if len(sessionEncKey) != sessionKeyLength {
		sessionEncKey = services.GenerateKey(sessionKeyLength)
		generated = true
	}

	if generated {
		_ = config.Load(confmap.Provider(map[string]interface{}{
			"session.auth-key": sessionAuthKey,
			"session.enc-key":  sessionEncKey,
		}, "."), nil)

		tomlData, err := config.Marshal(toml.Parser())
		if err != nil {
			log.WithError(err).Fatal("could not encode session config")
		}

		log.Infof("put the following in your resource_app.toml:\n%s", string(tomlData))
	}

	return sessionPath, sessionAuthKey, sessionEncKey
}