// Copyright 2015 clair authors
//
// 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.

package api

import (
	"crypto/tls"
	"crypto/x509"
	"io/ioutil"
	"net"
	"net/http"
	"strconv"
	"time"

	"github.com/prometheus/common/log"
	"github.com/tylerb/graceful"

	"github.com/coreos/clair/api/context"
	"github.com/coreos/clair/config"
	"github.com/coreos/clair/utils"
)

const timeoutResponse = `{"Error":{"Message":"Clair failed to respond within the configured timeout window.","Type":"Timeout"}}`

func Run(config *config.APIConfig, ctx *context.RouteContext, st *utils.Stopper) {
	defer st.End()

	// Do not run the API service if there is no config.
	if config == nil {
		log.Infof("main API service is disabled.")
		return
	}
	log.Infof("starting main API on port %d.", config.Port)

	tlsConfig, err := tlsClientConfig(config.CAFile)
	if err != nil {
		log.Fatalf("could not initialize client cert authentication: %s\n", err)
	}
	if tlsConfig != nil {
		log.Info("main API configured with client certificate authentication")
	}

	srv := &graceful.Server{
		Timeout:          0,    // Already handled by our TimeOut middleware
		NoSignalHandling: true, // We want to use our own Stopper
		Server: &http.Server{
			Addr:      ":" + strconv.Itoa(config.Port),
			TLSConfig: tlsConfig,
			Handler:   http.TimeoutHandler(newAPIHandler(ctx), config.Timeout, timeoutResponse),
		},
	}

	listenAndServeWithStopper(srv, st, config.CertFile, config.KeyFile)

	log.Info("main API stopped")
}

func RunHealth(config *config.APIConfig, ctx *context.RouteContext, st *utils.Stopper) {
	// Do not run the API service if there is no config.
	if config == nil {
		log.Infof("health API service is disabled.")
		return
	}
	log.Infof("starting health API on port %d.", config.HealthPort)

	srv := &graceful.Server{
		Timeout:          10 * time.Second, // Interrupt health checks when stopping
		NoSignalHandling: true,             // We want to use our own Stopper
		Server: &http.Server{
			Addr:    ":" + strconv.Itoa(config.HealthPort),
			Handler: http.TimeoutHandler(newHealthHandler(ctx), config.Timeout, timeoutResponse),
		},
	}

	listenAndServeWithStopper(srv, st, "", "")

	log.Info("health API stopped")
}

// listenAndServeWithStopper wraps graceful.Server's
// ListenAndServe/ListenAndServeTLS and adds the ability to interrupt them with
// the provided utils.Stopper
func listenAndServeWithStopper(srv *graceful.Server, st *utils.Stopper, certFile, keyFile string) {
	go func() {
		<-st.Chan()
		srv.Stop(0)
	}()

	var err error
	if certFile != "" && keyFile != "" {
		log.Info("API: TLS Enabled")
		err = srv.ListenAndServeTLS(certFile, keyFile)
	} else {
		err = srv.ListenAndServe()
	}

	if opErr, ok := err.(*net.OpError); !ok || (ok && opErr.Op != "accept") {
		log.Fatal(err)
	}
}

// tlsClientConfig initializes a *tls.Config using the given CA. The resulting
// *tls.Config is meant to be used to configure an HTTP server to do client
// certificate authentication.
//
// If no CA is given, a nil *tls.Config is returned; no client certificate will
// be required and verified. In other words, authentication will be disabled.
func tlsClientConfig(caPath string) (*tls.Config, error) {
	if caPath == "" {
		return nil, nil
	}

	caCert, err := ioutil.ReadFile(caPath)
	if err != nil {
		return nil, err
	}

	caCertPool := x509.NewCertPool()
	caCertPool.AppendCertsFromPEM(caCert)

	tlsConfig := &tls.Config{
		ClientCAs:  caCertPool,
		ClientAuth: tls.RequireAndVerifyClientCert,
	}

	return tlsConfig, nil
}