// Copyright 2020 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package cmd

import (
	"net/http"
	"strconv"
	"strings"

	"code.gitea.io/gitea/modules/graceful"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"

	"github.com/caddyserver/certmagic"
)

func runLetsEncrypt(listenAddr, domain, directory, email string, m http.Handler) error {

	// If HTTP Challenge enabled, needs to be serving on port 80. For TLSALPN needs 443.
	// Due to docker port mapping this can't be checked programmatically
	// TODO: these are placeholders until we add options for each in settings with appropriate warning
	enableHTTPChallenge := true
	enableTLSALPNChallenge := true
	altHTTPPort := 0
	altTLSALPNPort := 0

	if p, err := strconv.Atoi(setting.PortToRedirect); err == nil {
		altHTTPPort = p
	}
	if p, err := strconv.Atoi(setting.HTTPPort); err == nil {
		altTLSALPNPort = p
	}

	magic := certmagic.NewDefault()
	magic.Storage = &certmagic.FileStorage{Path: directory}
	myACME := certmagic.NewACMEManager(magic, certmagic.ACMEManager{
		Email:                   email,
		Agreed:                  setting.LetsEncryptTOS,
		DisableHTTPChallenge:    !enableHTTPChallenge,
		DisableTLSALPNChallenge: !enableTLSALPNChallenge,
		ListenHost:              setting.HTTPAddr,
		AltTLSALPNPort:          altTLSALPNPort,
		AltHTTPPort:             altHTTPPort,
	})

	magic.Issuers = []certmagic.Issuer{myACME}

	// this obtains certificates or renews them if necessary
	err := magic.ManageSync(graceful.GetManager().HammerContext(), []string{domain})
	if err != nil {
		return err
	}

	tlsConfig := magic.TLSConfig()
	tlsConfig.NextProtos = append(tlsConfig.NextProtos, "h2")

	if version := toTLSVersion(setting.SSLMinimumVersion); version != 0 {
		tlsConfig.MinVersion = version
	}
	if version := toTLSVersion(setting.SSLMaximumVersion); version != 0 {
		tlsConfig.MaxVersion = version
	}

	// Set curve preferences
	if curves := toCurvePreferences(setting.SSLCurvePreferences); len(curves) > 0 {
		tlsConfig.CurvePreferences = curves
	}

	// Set cipher suites
	if ciphers := toTLSCiphers(setting.SSLCipherSuites); len(ciphers) > 0 {
		tlsConfig.CipherSuites = ciphers
	}

	if enableHTTPChallenge {
		go func() {
			log.Info("Running Let's Encrypt handler on %s", setting.HTTPAddr+":"+setting.PortToRedirect)
			// all traffic coming into HTTP will be redirect to HTTPS automatically (LE HTTP-01 validation happens here)
			var err = runHTTP("tcp", setting.HTTPAddr+":"+setting.PortToRedirect, "Let's Encrypt HTTP Challenge", myACME.HTTPChallengeHandler(http.HandlerFunc(runLetsEncryptFallbackHandler)))
			if err != nil {
				log.Fatal("Failed to start the Let's Encrypt handler on port %s: %v", setting.PortToRedirect, err)
			}
		}()
	}

	return runHTTPSWithTLSConfig("tcp", listenAddr, "Web", tlsConfig, m)
}

func runLetsEncryptFallbackHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "GET" && r.Method != "HEAD" {
		http.Error(w, "Use HTTPS", http.StatusBadRequest)
		return
	}
	// Remove the trailing slash at the end of setting.AppURL, the request
	// URI always contains a leading slash, which would result in a double
	// slash
	target := strings.TrimSuffix(setting.AppURL, "/") + r.URL.RequestURI()
	http.Redirect(w, r, target, http.StatusFound)
}
