/*
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

    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.
*/

// The CAcert board voting software.
package main

import (
	"crypto/tls"
	"crypto/x509"
	"database/sql"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/alexedwards/scs/sqlite3store"
	"github.com/alexedwards/scs/v2"
	"github.com/jmoiron/sqlx"
	_ "github.com/mattn/go-sqlite3"

	u "git.cacert.org/cacert-boardvoting/internal/app"

	"git.cacert.org/cacert-boardvoting/internal"
)

const sessionHours = 12

var (
	version = "undefined"
	commit  = "undefined"
	date    = "undefined"
)

func main() {
	configFile := flag.String("config", "config.yaml", "Configuration file name")
	flag.Parse()

	infoLog := log.New(os.Stdout, "INFO\t", log.Ldate|log.Ltime)
	errorLog := log.New(os.Stderr, "ERROR\t", log.Ldate|log.Ltime)

	infoLog.Printf("CAcert Board Voting version %s, commit %s built at %s", version, commit, date)

	config, err := parseConfig(*configFile)
	if err != nil {
		errorLog.Fatal(err)
	}

	db, err := openDB(config.DatabaseFile)
	if err != nil {
		errorLog.Fatal(err)
	}

	defer func(db io.Closer) {
		_ = db.Close()
	}(db)

	if err != nil {
		errorLog.Fatalf("could not setup decision model: %v", err)
	}

	sessionManager := scs.New()
	sessionManager.Store = sqlite3store.New(db.DB)
	sessionManager.Lifetime = sessionHours * time.Hour
	sessionManager.Cookie.SameSite = http.SameSiteStrictMode
	sessionManager.Cookie.Secure = true

	application, err := u.New(errorLog, infoLog, db, config.MailConfig, sessionManager)
	if err != nil {
		errorLog.Fatalf("could not setup application: %v", err)
	}

	err = internal.InitializeDb(db.DB, infoLog)
	if err != nil {
		errorLog.Fatal(err)
	}

	defer func(application io.Closer) {
		_ = application.Close()
	}(application)

	infoLog.Printf("Starting server on %s", config.HTTPAddress)

	errChan := make(chan error, 1)

	infoLog.Printf("TLS config setup, starting TLS server on %s", config.HTTPSAddress)

	go setupHTTPRedirect(config, errChan)

	err = startHTTPSServer(config, errorLog, application.Routes(), func() { _ = application.Close() })
	if err != nil {
		errorLog.Fatalf("ListenAndServeTLS (HTTPS) failed: %v", err)
	}

	if err := <-errChan; err != nil {
		errorLog.Fatalf("ListenAndServe (HTTP) failed: %v", err)
	}
}

func startHTTPSServer(config *Config, errorLog *log.Logger, routes http.Handler, shutdownFunc func()) error {
	tlsConfig, err := setupTLSConfig(config)
	if err != nil {
		return fmt.Errorf("could not setup TLS configuration: %w", err)
	}

	srv := &http.Server{
		Addr:              config.HTTPSAddress,
		TLSConfig:         tlsConfig,
		ErrorLog:          errorLog,
		Handler:           routes,
		IdleTimeout:       config.Timeouts.Idle,
		ReadHeaderTimeout: config.Timeouts.ReadHeader,
		ReadTimeout:       config.Timeouts.Read,
		WriteTimeout:      config.Timeouts.Write,
	}

	srv.RegisterOnShutdown(shutdownFunc)

	err = srv.ListenAndServeTLS(config.ServerCert, config.ServerKey)
	if err != nil {
		return fmt.Errorf("")
	}

	return nil
}

func setupHTTPRedirect(config *Config, errChan chan error) {
	redirect := &http.Server{
		Addr: config.HTTPAddress,
		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			redirectURL := url.URL{
				Scheme: "https://",
				Host: strings.Join(
					[]string{
						strings.Split(r.URL.Host, ":")[0],
						strings.Split(config.HTTPSAddress, ":")[1],
					},
					":",
				),
				Path: r.URL.Path,
			}

			http.Redirect(w, r, redirectURL.String(), http.StatusMovedPermanently)
		}),
		IdleTimeout:       config.Timeouts.Idle,
		ReadHeaderTimeout: config.Timeouts.ReadHeader,
		ReadTimeout:       config.Timeouts.Read,
		WriteTimeout:      config.Timeouts.Write,
	}

	if err := redirect.ListenAndServe(); err != nil {
		errChan <- err
	}

	close(errChan)
}

func setupTLSConfig(config *Config) (*tls.Config, error) {
	caCert, err := os.ReadFile(config.ClientCACertificates)
	if err != nil {
		return nil, fmt.Errorf("could not read client certificate CAs %w", err)
	}

	caCertPool := x509.NewCertPool()
	if !caCertPool.AppendCertsFromPEM(caCert) {
		return nil, fmt.Errorf(
			"could not initialize client CA certificate pool from %s",
			config.ClientCACertificates,
		)
	}

	return &tls.Config{
		MinVersion: tls.VersionTLS12,
		ClientCAs:  caCertPool,
		ClientAuth: tls.VerifyClientCertIfGiven,
	}, nil
}

func openDB(dbFile string) (*sqlx.DB, error) {
	db, err := sql.Open("sqlite3", dbFile)
	if err != nil {
		return nil, fmt.Errorf("could not open database file %s: %w", dbFile, err)
	}

	if err = db.Ping(); err != nil {
		return nil, fmt.Errorf("could not ping database: %w", err)
	}

	return sqlx.NewDb(db, "sqlite3"), nil
}