/*
Copyright 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"
	"log/slog"
	"net/http"
	"os"
	"time"

	"code.cacert.org/cacert/oidc-demo-app/ui"
	"github.com/knadh/koanf"
	"github.com/knadh/koanf/parsers/toml"
	"github.com/knadh/koanf/providers/confmap"

	"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
)

var (
	version = "local"
	commit  = "unknown"
	date    = "unknown"
)

type StaticFSWrapper struct {
	http.FileSystem
	ModTime time.Time
}

func (f *StaticFSWrapper) Open(name string) (http.File, error) {
	file, err := f.FileSystem.Open(name)

	return &StaticFileWrapper{File: file, fixedModTime: f.ModTime}, err //nolint:wrapcheck
}

type StaticFileWrapper struct {
	http.File
	fixedModTime time.Time
}

func (f *StaticFileWrapper) Stat() (os.FileInfo, error) {
	fileInfo, err := f.File.Stat()

	return &StaticFileInfoWrapper{FileInfo: fileInfo, fixedModTime: f.fixedModTime}, err //nolint:wrapcheck
}

type StaticFileInfoWrapper struct {
	os.FileInfo
	fixedModTime time.Time
}

func (f *StaticFileInfoWrapper) ModTime() time.Time {
	return f.fixedModTime
}

func main() {
	var (
		logLevel   = new(slog.LevelVar)
		logHandler slog.Handler
		logger     *slog.Logger
	)

	logHandler = slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{Level: logLevel})
	logger = slog.New(logHandler)
	slog.SetDefault(logger)

	config, err := services.ConfigureApplication("RESOURCE_APP", services.DefaultConfiguration)
	if err != nil {
		logger.Error("error loading configuration", "error", err)
		os.Exit(1)
	}

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

	if level := config.Bytes("log.level"); level != nil {
		if err := logLevel.UnmarshalText(level); err != nil {
			logger.Error("could not parse log level", "error", err)
			os.Exit(1)
		}

		slog.SetLogLoggerLevel(logLevel.Level())
	}

	if config.Bool("log.json") {
		logHandler = slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: logLevel})
		logger = slog.New(logHandler)
		slog.SetDefault(logger)
	}

	logLogger := slog.NewLogLogger(logger.Handler(), logLevel.Level())

	logger.Info(
		"Starting CAcert OpenID Connect demo application",
		"version", version, "commit", commit, "date", date,
	)
	logger.Info("Server is starting")

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

	services.AddMessages(catalog)

	tlsClientConfig, err := getTLSConfig(config)
	if err != nil {
		logger.Error("error loading tls config", "error", err)
		os.Exit(1)
	}

	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 {
		logger.Error("OpenID Connect discovery failed", "error", err)
		os.Exit(1)
	}

	sessionPath, sessionAuthKey, sessionEncKey, err := configureSessionParameters(logger, config)
	if err := services.InitSessionStore(logger, sessionPath, sessionAuthKey, sessionEncKey); err != nil {
		logger.Error("could not initialize session store", "error", err)

		os.Exit(1)
	}

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

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

	tokenInfoService, err := services.InitTokenInfoService(logger, oidcInfo)
	if err != nil {
		logger.Error("could not initialize token info service", "error", err)

		os.Exit(1)
	}

	indexHandler, err := handlers.NewIndexHandler(logger, bundle, catalog, oidcInfo, publicURL, tokenInfoService)
	if err != nil {
		logger.Error("could not initialize index handler", "error", err)
		os.Exit(1)
	}

	protectedResource, err := handlers.NewProtectedResourceHandler(
		logger, bundle, catalog, oidcInfo, publicURL, tokenInfoService,
	)
	if err != nil {
		logger.Error("could not initialize protected resource handler", "error", err)
	}

	callbackHandler := handlers.NewCallbackHandler(logger, oidcInfo.KeySet, oidcInfo.OAuth2Config)
	afterLogoutHandler := handlers.NewAfterLogoutHandler(logger)

	staticFiles, err := staticFileHandler()
	if err != nil {
		logger.Error("could not initialize static file handler", "error", err)

		os.Exit(1)
	}

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

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

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

	errorMiddleware, err := handlers.ErrorHandling(logger, bundle, catalog)
	if err != nil {
		logger.Error("could not initialize request error handling", "error", err)
		os.Exit(1)
	}

	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,
	}

	if err := handlers.StartApplication(context.Background(), logger, server, publicURL, config); err != nil {
		logger.Error("could not start application", "error", err)
		os.Exit(1)
	}
}

func staticFileHandler() (func(w http.ResponseWriter, r *http.Request), error) {
	stat, err := os.Stat(os.Args[0])
	if err != nil {
		return nil, fmt.Errorf("could not use stat on binary: %w", err)
	}

	fileServer := http.FileServer(&StaticFSWrapper{FileSystem: http.FS(ui.Static), ModTime: stat.ModTime()})

	staticFiles := func(w http.ResponseWriter, r *http.Request) {
		w.Header().Del("Expires")
		w.Header().Del("Pragma")
		w.Header().Set("Cache-Control", "max-age=3600")

		fileServer.ServeHTTP(w, r)
	}

	return staticFiles, nil
}

func getTLSConfig(config *koanf.Koanf) (*tls.Config, error) {
	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 {
			return nil, fmt.Errorf("could not read CA certificate file: %w", err)
		}

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

	return tlsClientConfig, nil
}

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(logger *slog.Logger, config *koanf.Koanf) (string, []byte, []byte, error) {
	sessionPath := config.MustString("session.path")

	sessionAuthKey, err := base64.StdEncoding.DecodeString(config.String("session.auth-key"))
	if err != nil {
		return "", nil, nil, fmt.Errorf("could not decode session authentication key: %w", err)
	}

	sessionEncKey, err := base64.StdEncoding.DecodeString(config.String("session.enc-key"))
	if err != nil {
		return "", nil, nil, fmt.Errorf("could not decode session encryption key: %w", err)
	}

	generated := false

	if len(sessionAuthKey) != sessionAuthKeyLength {
		sessionAuthKey, err = services.GenerateKey(sessionAuthKeyLength)
		if err != nil {
			return "", nil, nil, fmt.Errorf("could not generate session authentication key: %w", err)
		}

		generated = true
	}

	if len(sessionEncKey) != sessionKeyLength {
		sessionEncKey, err = services.GenerateKey(sessionKeyLength)
		if err != nil {
			return "", nil, nil, fmt.Errorf("could not generate session encryption key: %w", err)
		}

		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 {
			return "", nil, nil, fmt.Errorf("could not encode session configuration: %w", err)
		}

		logger.Info("put the following in your resource_app.toml")
		fmt.Print(string(tomlData)) //nolint:forbidigo
	}

	return sessionPath, sessionAuthKey, sessionEncKey, nil
}