package agent

import (
	"os"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/drone/drone/queue"
	"github.com/drone/mq/stomp"

	"github.com/Sirupsen/logrus"
	"github.com/codegangsta/cli"
	"github.com/samalba/dockerclient"
)

// AgentCmd is the exported command for starting the drone agent.
var AgentCmd = cli.Command{
	Name:   "agent",
	Usage:  "starts the drone agent",
	Action: start,
	Flags: []cli.Flag{
		cli.StringFlag{
			EnvVar: "DOCKER_HOST",
			Name:   "docker-host",
			Usage:  "docker deamon address",
			Value:  "unix:///var/run/docker.sock",
		},
		cli.BoolFlag{
			EnvVar: "DOCKER_TLS_VERIFY",
			Name:   "docker-tls-verify",
			Usage:  "docker daemon supports tlsverify",
		},
		cli.StringFlag{
			EnvVar: "DOCKER_CERT_PATH",
			Name:   "docker-cert-path",
			Usage:  "docker certificate directory",
			Value:  "",
		},
		cli.IntFlag{
			EnvVar: "DOCKER_MAX_PROCS",
			Name:   "docker-max-procs",
			Usage:  "limit number of running docker processes",
			Value:  2,
		},
		cli.StringFlag{
			EnvVar: "DOCKER_OS",
			Name:   "docker-os",
			Usage:  "docker operating system",
			Value:  "linux",
		},
		cli.StringFlag{
			EnvVar: "DOCKER_ARCH",
			Name:   "docker-arch",
			Usage:  "docker architecture system",
			Value:  "amd64",
		},
		cli.StringFlag{
			EnvVar: "DRONE_SERVER",
			Name:   "drone-server",
			Usage:  "drone server address",
			Value:  "ws://localhost:8000/ws/broker",
		},
		cli.StringFlag{
			EnvVar: "DRONE_TOKEN",
			Name:   "drone-token",
			Usage:  "drone authorization token",
		},
		cli.StringFlag{
			EnvVar: "DRONE_SECRET,DRONE_AGENT_SECRET",
			Name:   "drone-secret",
			Usage:  "drone agent secret",
		},
		cli.DurationFlag{
			EnvVar: "DRONE_BACKOFF",
			Name:   "backoff",
			Usage:  "drone server backoff interval",
			Value:  time.Second * 15,
		},
		cli.DurationFlag{
			EnvVar: "DRONE_PING",
			Name:   "ping",
			Usage:  "drone server ping frequency",
			Value:  time.Minute * 5,
		},
		cli.BoolFlag{
			EnvVar: "DRONE_DEBUG",
			Name:   "debug",
			Usage:  "start the agent in debug mode",
		},
		cli.DurationFlag{
			EnvVar: "DRONE_TIMEOUT",
			Name:   "timeout",
			Usage:  "drone timeout due to log inactivity",
			Value:  time.Minute * 5,
		},
		cli.StringFlag{
			EnvVar: "DRONE_FILTER",
			Name:   "filter",
			Usage:  "filter jobs processed by this agent",
		},
		cli.IntFlag{
			EnvVar: "DRONE_MAX_LOGS",
			Name:   "max-log-size",
			Usage:  "drone maximum log size in megabytes",
			Value:  5,
		},
		cli.StringSliceFlag{
			EnvVar: "DRONE_PLUGIN_PRIVILEGED",
			Name:   "privileged",
			Usage:  "plugins that require privileged mode",
			Value: &cli.StringSlice{
				"plugins/docker",
				"plugins/docker:*",
				"plugins/gcr",
				"plugins/gcr:*",
				"plugins/ecr",
				"plugins/ecr:*",
			},
		},
		cli.StringFlag{
			EnvVar: "DRONE_PLUGIN_NAMESPACE",
			Name:   "namespace",
			Value:  "plugins",
			Usage:  "default plugin image namespace",
		},
		cli.BoolTFlag{
			EnvVar: "DRONE_PLUGIN_PULL",
			Name:   "pull",
			Usage:  "always pull latest plugin images",
		},
	},
}

func start(c *cli.Context) {

	// debug level if requested by user
	if c.Bool("debug") {
		logrus.SetLevel(logrus.DebugLevel)
	} else {
		logrus.SetLevel(logrus.WarnLevel)
	}

	var accessToken string
	if c.String("drone-secret") != "" {
		// secretToken := c.String("drone-secret")
		accessToken = c.String("drone-secret")
		// accessToken, _ = token.New(token.AgentToken, "").Sign(secretToken)
	} else {
		accessToken = c.String("drone-token")
	}

	logrus.Infof("Connecting to %s with token %s",
		c.String("drone-server"),
		accessToken,
	)

	server := strings.TrimRight(c.String("drone-server"), "/")

	tls, err := dockerclient.TLSConfigFromCertPath(c.String("docker-cert-path"))
	if err == nil {
		tls.InsecureSkipVerify = c.Bool("docker-tls-verify")
	}
	docker, err := dockerclient.NewDockerClient(c.String("docker-host"), tls)
	if err != nil {
		logrus.Fatal(err)
	}

	var client *stomp.Client

	handler := func(m *stomp.Message) {
		running.Add(1)
		defer func() {
			running.Done()
			client.Ack(m.Ack)
		}()

		r := pipeline{
			drone:  client,
			docker: docker,
			config: config{
				platform:   c.String("docker-os") + "/" + c.String("docker-arch"),
				timeout:    c.Duration("timeout"),
				namespace:  c.String("namespace"),
				privileged: c.StringSlice("privileged"),
				pull:       c.BoolT("pull"),
				logs:       int64(c.Int("max-log-size")) * 1000000,
			},
		}

		work := new(queue.Work)
		m.Unmarshal(work)
		r.run(work)
	}

	handleSignals()

	backoff := c.Duration("backoff")

	for {
		// dial the drone server to establish a TCP connection.
		client, err = stomp.Dial(server)
		if err != nil {
			logrus.Errorf("Failed to establish server connection, %s, retry in %v", err, backoff)
			<-time.After(backoff)
			continue
		}
		opts := []stomp.MessageOption{
			stomp.WithCredentials("x-token", accessToken),
		}

		// initialize the stomp session and authenticate.
		if err = client.Connect(opts...); err != nil {
			logrus.Errorf("Failed to establish server session, %s, retry in %v", err, backoff)
			<-time.After(backoff)
			continue
		}

		opts = []stomp.MessageOption{
			stomp.WithAck("client"),
			stomp.WithPrefetch(
				c.Int("docker-max-procs"),
			),
		}
		if filter := c.String("filter"); filter != "" {
			opts = append(opts, stomp.WithSelector(filter))
		}

		// subscribe to the pending build queue.
		client.Subscribe("/queue/pending", stomp.HandlerFunc(func(m *stomp.Message) {
			go handler(m) // HACK until we a channel based Subscribe implementation
		}), opts...)

		logrus.Infof("Server connection establish, ready to process builds.")
		<-client.Done()

		logrus.Warnf("Server connection interrupted, attempting to reconnect.")
	}
}

// tracks running builds
var running sync.WaitGroup

func handleSignals() {
	// Graceful shut-down on SIGINT/SIGTERM
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	signal.Notify(c, syscall.SIGTERM)

	go func() {
		<-c
		logrus.Debugln("SIGTERM received.")
		logrus.Debugln("wait for running builds to finish.")
		running.Wait()
		logrus.Debugln("done.")
		os.Exit(0)
	}()
}