package agent

import (
	"flag"
	"fmt"
	"io"
	"os"
	"os/signal"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/armon/go-metrics"
	"github.com/hashicorp/go-checkpoint"
	"github.com/hashicorp/go-syslog"
	"github.com/hashicorp/logutils"
	"github.com/hashicorp/nomad/helper/flag-slice"
	"github.com/hashicorp/nomad/helper/gated-writer"
	scada "github.com/hashicorp/scada-client"
	"github.com/mitchellh/cli"
)

// gracefulTimeout controls how long we wait before forcefully terminating
const gracefulTimeout = 5 * time.Second

// Command is a Command implementation that runs a Nomad agent.
// The command will not end unless a shutdown message is sent on the
// ShutdownCh. If two messages are sent on the ShutdownCh it will forcibly
// exit.
type Command struct {
	Revision          string
	Version           string
	VersionPrerelease string
	Ui                cli.Ui
	ShutdownCh        <-chan struct{}

	args       []string
	agent      *Agent
	httpServer *HTTPServer
	logFilter  *logutils.LevelFilter
	logOutput  io.Writer

	scadaProvider *scada.Provider
	scadaHttp     *HTTPServer
}

func (c *Command) readConfig() *Config {
	var dev bool
	var configPath []string
	var logLevel string
	flags := flag.NewFlagSet("agent", flag.ContinueOnError)
	flags.BoolVar(&dev, "dev", false, "")
	flags.StringVar(&logLevel, "log-level", "info", "")
	flags.Usage = func() { c.Ui.Error(c.Help()) }
	flags.Var((*sliceflag.StringFlag)(&configPath), "config", "config")
	if err := flags.Parse(c.args); err != nil {
		return nil
	}

	// Load the configuration
	var config *Config
	if dev {
		config = DevConfig()
	} else {
		config = DefaultConfig()
	}
	for _, path := range configPath {
		current, err := LoadConfig(path)
		if err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error loading configuration from %s: %s", path, err))
			return nil
		}

		if config == nil {
			config = current
		} else {
			config = config.Merge(current)
		}
	}

	// Ensure the sub-structs at least exist
	if config.Client == nil {
		config.Client = &ClientConfig{}
	}
	if config.Server == nil {
		config.Server = &ServerConfig{}
	}

	// Set the version info
	config.Revision = c.Revision
	config.Version = c.Version
	config.VersionPrerelease = c.VersionPrerelease

	return config
}

// setupLoggers is used to setup the logGate, logWriter, and our logOutput
func (c *Command) setupLoggers(config *Config) (*gatedwriter.Writer, *logWriter, io.Writer) {
	// Setup logging. First create the gated log writer, which will
	// store logs until we're ready to show them. Then create the level
	// filter, filtering logs of the specified level.
	logGate := &gatedwriter.Writer{
		Writer: &cli.UiWriter{Ui: c.Ui},
	}

	c.logFilter = LevelFilter()
	c.logFilter.MinLevel = logutils.LogLevel(strings.ToUpper(config.LogLevel))
	c.logFilter.Writer = logGate
	if !ValidateLevelFilter(c.logFilter.MinLevel, c.logFilter) {
		c.Ui.Error(fmt.Sprintf(
			"Invalid log level: %s. Valid log levels are: %v",
			c.logFilter.MinLevel, c.logFilter.Levels))
		return nil, nil, nil
	}

	// Check if syslog is enabled
	var syslog io.Writer
	if config.EnableSyslog {
		l, err := gsyslog.NewLogger(gsyslog.LOG_NOTICE, config.SyslogFacility, "nomad")
		if err != nil {
			c.Ui.Error(fmt.Sprintf("Syslog setup failed: %v", err))
			return nil, nil, nil
		}
		syslog = &SyslogWrapper{l, c.logFilter}
	}

	// Create a log writer, and wrap a logOutput around it
	logWriter := NewLogWriter(512)
	var logOutput io.Writer
	if syslog != nil {
		logOutput = io.MultiWriter(c.logFilter, logWriter, syslog)
	} else {
		logOutput = io.MultiWriter(c.logFilter, logWriter)
	}
	c.logOutput = logOutput
	return logGate, logWriter, logOutput
}

// setupAgent is used to start the agent and various interfaces
func (c *Command) setupAgent(config *Config, logOutput io.Writer) error {
	c.Ui.Output("Starting Nomad agent...")
	agent, err := NewAgent(config, logOutput)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error starting agent: %s", err))
		return err
	}
	c.agent = agent

	// Enable the SCADA integration
	if err := c.setupSCADA(config); err != nil {
		agent.Shutdown()
		c.Ui.Error(fmt.Sprintf("Error starting SCADA: %s", err))
		return err
	}

	// Setup the HTTP server
	http, err := NewHTTPServer(agent, config, logOutput)
	if err != nil {
		agent.Shutdown()
		c.Ui.Error(fmt.Sprintf("Error starting http server: %s", err))
		return err
	}
	c.httpServer = http

	// Setup update checking
	if !config.DisableUpdateCheck {
		version := config.Version
		if config.VersionPrerelease != "" {
			version += fmt.Sprintf("-%s", config.VersionPrerelease)
		}
		updateParams := &checkpoint.CheckParams{
			Product: "nomad",
			Version: version,
		}
		if !config.DisableAnonymousSignature {
			updateParams.SignatureFile = filepath.Join(config.DataDir, "checkpoint-signature")
		}

		// Schedule a periodic check with expected interval of 24 hours
		checkpoint.CheckInterval(updateParams, 24*time.Hour, c.checkpointResults)

		// Do an immediate check within the next 30 seconds
		go func() {
			time.Sleep(randomStagger(30 * time.Second))
			c.checkpointResults(checkpoint.Check(updateParams))
		}()
	}
	return nil
}

// checkpointResults is used to handler periodic results from our update checker
func (c *Command) checkpointResults(results *checkpoint.CheckResponse, err error) {
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Failed to check for updates: %v", err))
		return
	}
	if results.Outdated {
		c.Ui.Error(fmt.Sprintf("Newer Nomad version available: %s", results.CurrentVersion))
	}
	for _, alert := range results.Alerts {
		switch alert.Level {
		case "info":
			c.Ui.Info(fmt.Sprintf("Bulletin [%s]: %s (%s)", alert.Level, alert.Message, alert.URL))
		default:
			c.Ui.Error(fmt.Sprintf("Bulletin [%s]: %s (%s)", alert.Level, alert.Message, alert.URL))
		}
	}
}

func (c *Command) Run(args []string) int {
	c.Ui = &cli.PrefixedUi{
		OutputPrefix: "==> ",
		InfoPrefix:   "    ",
		ErrorPrefix:  "==> ",
		Ui:           c.Ui,
	}

	// Parse our configs
	c.args = args
	config := c.readConfig()
	if config == nil {
		return 1
	}

	// Setup the log outputs
	logGate, _, logOutput := c.setupLoggers(config)
	if logGate == nil {
		return 1
	}

	// Initialize the telemetry
	if err := c.setupTelementry(config); err != nil {
		c.Ui.Error(fmt.Sprintf("Error initializing telemetry: %s", err))
		return 1
	}

	// Create the agent
	if err := c.setupAgent(config, logOutput); err != nil {
		return 1
	}
	defer c.agent.Shutdown()

	// Check and shut down the SCADA listeners at the end
	defer func() {
		if c.httpServer != nil {
			c.httpServer.Shutdown()
		}
		if c.scadaHttp != nil {
			c.scadaHttp.Shutdown()
		}
		if c.scadaProvider != nil {
			c.scadaProvider.Shutdown()
		}
	}()

	// Compile agent information for output later
	info := make(map[string]string)
	info["client"] = strconv.FormatBool(config.Client.Enabled)
	info["log level"] = config.LogLevel
	info["server"] = strconv.FormatBool(config.Server.Enabled)
	info["region"] = fmt.Sprintf("%s (DC: %s)", config.Region, config.Datacenter)
	if config.Atlas != nil && config.Atlas.Infrastructure != "" {
		info["atlas"] = fmt.Sprintf("(Infrastructure: '%s' Join: %v)",
			config.Atlas.Infrastructure, config.Atlas.Join)
	} else {
		info["atlas"] = "<disabled>"
	}

	// Sort the keys for output
	infoKeys := make([]string, 0, len(info))
	for key := range info {
		infoKeys = append(infoKeys, key)
	}
	sort.Strings(infoKeys)

	// Agent configuration output
	padding := 18
	c.Ui.Output("Nomad agent configuration:\n")
	for _, k := range infoKeys {
		c.Ui.Info(fmt.Sprintf(
			"%s%s: %s",
			strings.Repeat(" ", padding-len(k)),
			strings.Title(k),
			info[k]))
	}
	c.Ui.Output("")

	// Output the header that the server has started
	c.Ui.Output("Nomad agent started! Log data will stream in below:\n")

	// Enable log streaming
	logGate.Flush()

	// Wait for exit
	return c.handleSignals(config)
}

// handleSignals blocks until we get an exit-causing signal
func (c *Command) handleSignals(config *Config) int {
	signalCh := make(chan os.Signal, 4)
	signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM, syscall.SIGHUP)

	// Wait for a signal
WAIT:
	var sig os.Signal
	select {
	case s := <-signalCh:
		sig = s
	case <-c.ShutdownCh:
		sig = os.Interrupt
	}
	c.Ui.Output(fmt.Sprintf("Caught signal: %v", sig))

	// Check if this is a SIGHUP
	if sig == syscall.SIGHUP {
		if conf := c.handleReload(config); conf != nil {
			config = conf
		}
		goto WAIT
	}

	// Check if we should do a graceful leave
	graceful := false
	if sig == os.Interrupt && !config.LeaveOnInt {
		graceful = true
	} else if sig == syscall.SIGTERM && config.LeaveOnTerm {
		graceful = true
	}

	// Bail fast if not doing a graceful leave
	if !graceful {
		return 1
	}

	// Attempt a graceful leave
	gracefulCh := make(chan struct{})
	c.Ui.Output("Gracefully shutting down agent...")
	go func() {
		if err := c.agent.Leave(); err != nil {
			c.Ui.Error(fmt.Sprintf("Error: %s", err))
			return
		}
		close(gracefulCh)
	}()

	// Wait for leave or another signal
	select {
	case <-signalCh:
		return 1
	case <-time.After(gracefulTimeout):
		return 1
	case <-gracefulCh:
		return 0
	}
}

// handleReload is invoked when we should reload our configs, e.g. SIGHUP
func (c *Command) handleReload(config *Config) *Config {
	c.Ui.Output("Reloading configuration...")
	newConf := c.readConfig()
	if newConf == nil {
		c.Ui.Error(fmt.Sprintf("Failed to reload configs"))
		return config
	}

	// Change the log level
	minLevel := logutils.LogLevel(strings.ToUpper(newConf.LogLevel))
	if ValidateLevelFilter(minLevel, c.logFilter) {
		c.logFilter.SetMinLevel(minLevel)
	} else {
		c.Ui.Error(fmt.Sprintf(
			"Invalid log level: %s. Valid log levels are: %v",
			minLevel, c.logFilter.Levels))

		// Keep the current log level
		newConf.LogLevel = config.LogLevel
	}
	return newConf
}

// setupTelementry is used ot setup the telemetry sub-systems
func (c *Command) setupTelementry(config *Config) error {
	/* Setup telemetry
	Aggregate on 10 second intervals for 1 minute. Expose the
	metrics over stderr when there is a SIGUSR1 received.
	*/
	inm := metrics.NewInmemSink(10*time.Second, time.Minute)
	metrics.DefaultInmemSignal(inm)

	var telConfig *Telemetry
	if config.Telemetry == nil {
		telConfig = &Telemetry{}
	} else {
		telConfig = config.Telemetry
	}

	metricsConf := metrics.DefaultConfig("nomad")
	metricsConf.EnableHostname = !telConfig.DisableHostname

	// Configure the statsite sink
	var fanout metrics.FanoutSink
	if telConfig.StatsiteAddr != "" {
		sink, err := metrics.NewStatsiteSink(telConfig.StatsiteAddr)
		if err != nil {
			return err
		}
		fanout = append(fanout, sink)
	}

	// Configure the statsd sink
	if telConfig.StatsdAddr != "" {
		sink, err := metrics.NewStatsdSink(telConfig.StatsdAddr)
		if err != nil {
			return err
		}
		fanout = append(fanout, sink)
	}

	// Initialize the global sink
	if len(fanout) > 0 {
		fanout = append(fanout, inm)
		metrics.NewGlobal(metricsConf, fanout)
	} else {
		metricsConf.EnableHostname = false
		metrics.NewGlobal(metricsConf, inm)
	}
	return nil
}

// setupSCADA is used to start a new SCADA provider and listener,
// replacing any existing listeners.
func (c *Command) setupSCADA(config *Config) error {
	// Shut down existing SCADA listeners
	if c.scadaProvider != nil {
		c.scadaProvider.Shutdown()
	}
	if c.scadaHttp != nil {
		c.scadaHttp.Shutdown()
	}

	// No-op if we don't have an infrastructure
	if config.Atlas == nil || config.Atlas.Infrastructure == "" {
		return nil
	}

	// Create the new provider and listener
	c.Ui.Output("Connecting to Atlas: " + config.Atlas.Infrastructure)
	provider, list, err := NewProvider(config, c.logOutput)
	if err != nil {
		return err
	}
	c.scadaProvider = provider
	c.scadaHttp = newScadaHttp(c.agent, list)
	return nil
}

func (c *Command) Synopsis() string {
	return "Runs a Nomad agent"
}

func (c *Command) Help() string {
	helpText := `
Usage: nomad agent [options]

  Starts the Nomad agent and runs until an interrupt is received.
  The agent may be a client and/or server.

Options:

  -advertise=addr          Sets the advertise address to use
  -atlas=org/name          Sets the Atlas infrastructure name, enables SCADA.
  -atlas-join              Enables auto-joining the Atlas cluster
  -atlas-token=token       Provides the Atlas API token
  -bootstrap               Sets server to bootstrap mode
  -bind=0.0.0.0            Sets the bind address for cluster communication
  -bootstrap-expect=0      Sets server to expect bootstrap mode.
  -client=127.0.0.1        Sets the address to bind for client access.
                           This includes RPC, DNS, HTTP and HTTPS (if configured)
  -config-file=foo         Path to a JSON file to read configuration from.
                           This can be specified multiple times.
  -config-dir=foo          Path to a directory to read configuration files
                           from. This will read every file ending in ".json"
                           as configuration in this directory in alphabetical
                           order. This can be specified multiple times.
  -data-dir=path           Path to a data directory to store agent state
  -recursor=1.2.3.4        Address of an upstream DNS server.
                           Can be specified multiple times.
  -dc=east-aws             Datacenter of the agent
  -encrypt=key             Provides the gossip encryption key
  -join=1.2.3.4            Address of an agent to join at start time.
                           Can be specified multiple times.
  -join-wan=1.2.3.4        Address of an agent to join -wan at start time.
                           Can be specified multiple times.
  -retry-join=1.2.3.4      Address of an agent to join at start time with
                           retries enabled. Can be specified multiple times.
  -retry-interval=30s      Time to wait between join attempts.
  -retry-max=0             Maximum number of join attempts. Defaults to 0, which
                           will retry indefinitely.
  -retry-join-wan=1.2.3.4  Address of an agent to join -wan at start time with
                           retries enabled. Can be specified multiple times.
  -retry-interval-wan=30s  Time to wait between join -wan attempts.
  -retry-max-wan=0         Maximum number of join -wan attempts. Defaults to 0, which
                           will retry indefinitely.
  -log-level=info          Log level of the agent.
  -node=hostname           Name of this node. Must be unique in the cluster
  -protocol=N              Sets the protocol version. Defaults to latest.
  -rejoin                  Ignores a previous leave and attempts to rejoin the cluster.
  -server                  Switches agent to server mode.
  -syslog                  Enables logging to syslog
  -ui-dir=path             Path to directory containing the Web UI resources
  -pid-file=path           Path to file to store agent PID
 `
	return strings.TrimSpace(helpText)
}