package agent

import (
	"flag"
	"fmt"
	"github.com/armon/go-metrics"
	"github.com/hashicorp/logutils"
	"github.com/mitchellh/cli"
	"io"
	"net"
	"os"
	"os/signal"
	"runtime"
	"strings"
	"syscall"
	"time"
)

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

// Command is a Command implementation that runs a Consul 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 {
	Ui         cli.Ui
	ShutdownCh <-chan struct{}
	args       []string
	logFilter  *logutils.LevelFilter
	agent      *Agent
	rpcServer  *AgentRPC
	httpServer *HTTPServer
	dnsServer  *DNSServer
}

// readConfig is responsible for setup of our configuration using
// the command line and any file configs
func (c *Command) readConfig() *Config {
	var cmdConfig Config
	var configFiles []string
	cmdFlags := flag.NewFlagSet("agent", flag.ContinueOnError)
	cmdFlags.Usage = func() { c.Ui.Output(c.Help()) }
	cmdFlags.StringVar(&cmdConfig.SerfBindAddr, "serf-bind", "", "address to bind serf listeners to")
	cmdFlags.StringVar(&cmdConfig.ServerAddr, "server-addr", "", "address to bind server listeners to")
	cmdFlags.Var((*AppendSliceValue)(&configFiles), "config-file",
		"json file to read config from")
	cmdFlags.Var((*AppendSliceValue)(&configFiles), "config-dir",
		"directory of json files to read")
	cmdFlags.StringVar(&cmdConfig.EncryptKey, "encrypt", "", "encryption key")
	cmdFlags.StringVar(&cmdConfig.LogLevel, "log-level", "", "log level")
	cmdFlags.StringVar(&cmdConfig.NodeName, "node", "", "node name")
	cmdFlags.StringVar(&cmdConfig.RPCAddr, "rpc-addr", "",
		"address to bind RPC listener to")
	cmdFlags.StringVar(&cmdConfig.DataDir, "data-dir", "", "path to the data directory")
	cmdFlags.StringVar(&cmdConfig.Datacenter, "dc", "", "node datacenter")
	cmdFlags.StringVar(&cmdConfig.DNSRecursor, "recursor", "", "address of dns recursor")
	cmdFlags.StringVar(&cmdConfig.AdvertiseAddr, "advertise", "", "advertise address to use")
	cmdFlags.StringVar(&cmdConfig.HTTPAddr, "http-addr", "", "address to bind http server to")
	cmdFlags.StringVar(&cmdConfig.DNSAddr, "dns-addr", "", "address to bind dns server to")
	cmdFlags.BoolVar(&cmdConfig.Server, "server", false, "run agent as server")
	cmdFlags.BoolVar(&cmdConfig.Bootstrap, "bootstrap", false, "enable server bootstrap mode")
	cmdFlags.StringVar(&cmdConfig.StatsiteAddr, "statsite", "", "address of statsite instance")
	if err := cmdFlags.Parse(c.args); err != nil {
		return nil
	}

	config := DefaultConfig()
	if len(configFiles) > 0 {
		fileConfig, err := ReadConfigPaths(configFiles)
		if err != nil {
			c.Ui.Error(err.Error())
			return nil
		}

		config = MergeConfig(config, fileConfig)
	}

	config = MergeConfig(config, &cmdConfig)

	if config.NodeName == "" {
		hostname, err := os.Hostname()
		if err != nil {
			c.Ui.Error(fmt.Sprintf("Error determining hostname: %s", err))
			return nil
		}
		config.NodeName = hostname
	}

	if config.EncryptKey != "" {
		if _, err := config.EncryptBytes(); err != nil {
			c.Ui.Error(fmt.Sprintf("Invalid encryption key: %s", err))
			return nil
		}
	}

	// Ensure we have a data directory
	if config.DataDir == "" {
		c.Ui.Error("Must specify data directory using -data-dir")
		return nil
	}

	// Only allow bootstrap mode when acting as a server
	if config.Bootstrap && !config.Server {
		c.Ui.Error("Bootstrap mode cannot be enabled when server mode is not enabled")
		return nil
	}

	// Warn if we are in bootstrap mode
	if config.Bootstrap {
		c.Ui.Error("WARNING: Bootstrap mode enabled! Do not enable unless necessary")
	}

	return config
}

// setupLoggers is used to setup the logGate, logWriter, and our logOutput
func (c *Command) setupLoggers(config *Config) (*GatedWriter, *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: &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
	}

	// Create a log writer, and wrap a logOutput around it
	logWriter := NewLogWriter(512)
	logOutput := io.MultiWriter(c.logFilter, logWriter)
	return logGate, logWriter, logOutput
}

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

	// Setup the RPC listener
	rpcListener, err := net.Listen("tcp", config.RPCAddr)
	if err != nil {
		agent.Shutdown()
		c.Ui.Error(fmt.Sprintf("Error starting RPC listener: %s", err))
		return err
	}

	// Start the IPC layer
	c.Ui.Output("Starting Consul agent RPC...")
	c.rpcServer = NewAgentRPC(agent, rpcListener, logOutput, logWriter)

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

	if config.DNSAddr != "" {
		server, err := NewDNSServer(agent, logOutput, config.Domain,
			config.DNSAddr, config.DNSRecursor)
		if err != nil {
			agent.Shutdown()
			c.Ui.Error(fmt.Sprintf("Error starting dns server: %s", err))
			return err
		}
		c.dnsServer = server
	}

	return nil
}

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
	}
	c.args = args

	// Check GOMAXPROCS
	if runtime.GOMAXPROCS(0) == 1 {
		c.Ui.Error("WARNING: It is highly recommended to set GOMAXPROCS higher than 1")
	}

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

	/* 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)
	metricsConf := metrics.DefaultConfig("consul")

	// Optionally configure a statsite sink if provided
	if config.StatsiteAddr != "" {
		sink, err := metrics.NewStatsiteSink(config.StatsiteAddr)
		if err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to start statsite sink. Got: %s", err))
			return 1
		}
		fanout := metrics.FanoutSink{inm, sink}
		metrics.NewGlobal(metricsConf, fanout)

	} else {
		metricsConf.EnableHostname = false
		metrics.NewGlobal(metricsConf, inm)
	}

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

	// Register the services
	for _, service := range config.Services {
		ns := service.NodeService()
		chkType := service.CheckType()
		if err := c.agent.AddService(ns, chkType); err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to register service '%s': %v", service.Name, err))
			return 1
		}
	}

	// Register the checks
	for _, check := range config.Checks {
		health := check.HealthCheck(config.NodeName)
		chkType := &check.CheckType
		if err := c.agent.AddCheck(health, chkType); err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to register check '%s': %v %v", check.Name, err, check))
			return 1
		}
	}

	// Let the agent know we've finished registration
	c.agent.StartSync()

	c.Ui.Output("Consul agent running!")
	c.Ui.Info(fmt.Sprintf("     Node name: '%s'", config.NodeName))
	c.Ui.Info(fmt.Sprintf("    Datacenter: '%s'", config.Datacenter))
	c.Ui.Info(fmt.Sprintf("Advertise addr: '%s'", config.AdvertiseAddr))
	c.Ui.Info(fmt.Sprintf("      RPC addr: '%s'", config.RPCAddr))
	c.Ui.Info(fmt.Sprintf("     HTTP addr: '%s'", config.HTTPAddr))
	c.Ui.Info(fmt.Sprintf("      DNS addr: '%s'", config.DNSAddr))
	c.Ui.Info(fmt.Sprintf("     Encrypted: %#v", config.EncryptKey != ""))
	c.Ui.Info(fmt.Sprintf("        Server: %v (bootstrap: %v)", config.Server, config.Bootstrap))

	// Enable log streaming
	c.Ui.Info("")
	c.Ui.Output("Log data will now stream in as it occurs:\n")
	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
	case <-c.agent.ShutdownCh():
		// Agent is already shutdown!
		return 0
	}
	c.Ui.Output(fmt.Sprintf("Caught signal: %v", sig))

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

	// Check if we should do a graceful leave
	graceful := false
	if sig == os.Interrupt && !config.SkipLeaveOnInt {
		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
	}

	// Bulk update the services and checks
	c.agent.PauseSync()
	defer c.agent.ResumeSync()

	// Deregister the old services
	for _, service := range config.Services {
		ns := service.NodeService()
		c.agent.RemoveService(ns.ID)
	}

	// Deregister the old checks
	for _, check := range config.Checks {
		health := check.HealthCheck(config.NodeName)
		c.agent.RemoveCheck(health.CheckID)
	}

	// Register the services
	for _, service := range newConf.Services {
		ns := service.NodeService()
		chkType := service.CheckType()
		if err := c.agent.AddService(ns, chkType); err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to register service '%s': %v", service.Name, err))
		}
	}

	// Register the checks
	for _, check := range newConf.Checks {
		health := check.HealthCheck(config.NodeName)
		chkType := &check.CheckType
		if err := c.agent.AddCheck(health, chkType); err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to register check '%s': %v %v", check.Name, err, check))
		}
	}

	return newConf
}

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

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

  Starts the Consul agent and runs until an interrupt is received. The
  agent represents a single node in a cluster. An agent can also serve
  as a server by configuraiton.

Options:

  -rpc-addr=127.0.0.1:8400 Address to bind the RPC listener.

  -serf-bind - The address that the underlying Serf library will bind to.
  This is an IP address that should be reachable by all other nodes in the cluster.
  By default this is "0.0.0.0", meaning Consul will use the first available private
  IP address. Consul uses both TCP and UDP and use the same port for both, so if you
  have any firewalls be sure to allow both protocols.

 -server-addr - The address that the agent will bind to for handling RPC calls
 if running in server mode. This does not affect clients running in client mode.
 By default this is "0.0.0.0:8300". This port is used for TCP communications so any
 firewalls must be configured to allow this.

 -advertise - The advertise flag is used to change the address that we
  advertise to other nodes in the cluster. By default, the "-serf-bind" address is
  advertised. However, in some cases (specifically NAT traversal), there may
  be a routable address that cannot be bound to. This flag enables gossiping
  a different address to support this. If this address is not routable, the node
  will be in a constant flapping state, as other nodes will treat the non-routability
  as a failure.

 -config-file - A configuration file to load. For more information on
  the format of this file, read the "Configuration Files" section below.
  This option can be specified multiple times to load multiple configuration
  files. If it is specified multiple times, configuration files loaded later
  will merge with configuration files loaded earlier, with the later values
  overriding the earlier values.

 - config-dir - A directory of configuration files to load. Consul will
  load all files in this directory ending in ".json" as configuration files
  in alphabetical order. For more information on the format of the configuration
  files, see the "Configuration Files" section below.

 -encrypt - Specifies the secret key to use for encryption of Consul
  network traffic. This key must be 16-bytes that are base64 encoded. The
  easiest way to create an encryption key is to use "consul keygen". All
  nodes within a cluster must share the same encryption key to communicate.

 -log-level - The level of logging to show after the Consul agent has
  started. This defaults to "info". The available log levels are "trace",
  "debug", "info", "warn", "err". This is the log level that will be shown
  for the agent output, but note you can always connect via "consul monitor"
  to an agent at any log level. The log level can be changed during a
  config reload.

 -node - The name of this node in the cluster. This must be unique within
  the cluster. By default this is the hostname of the machine.

 -rpc-addr - The address that Consul will bind to for the agent's  RPC server.
  By default this is "127.0.0.1:8400", allowing only loopback connections.
  The RPC address is used by other Consul commands, such as  "consul members",
  in order to query a running Consul agent. It is also used by other applications
  to control Consul using it's [RPC protocol](/docs/agent/rpc.html).

 -data - This flag provides a data directory for the agent to store state.
  This is required for all agents. The directory should be durable across reboots.
  This is especially critical for agents that are running in server mode, as they
  must be able to persist the cluster state.

 -dc - This flag controls the datacenter the agent is running in. If not provided
  it defaults to "dc1". Consul has first class support for multiple data centers but
  it relies on proper configuration. Nodes in the same datacenter should be on a single
  LAN.

 -recursor - This flag provides an address of an upstream DNS server that is used to
  recursively resolve queries if they are not inside the service domain for consul. For example,
  a node can use Consul directly as a DNS server, and if the record is outside of the "consul." domain,
  the query will be resolved upstream using this server.

 -http-addr - This flag controls the address the agent listens on for HTTP requests.
  By default it is bound to "127.0.0.1:8500". This port must allow for TCP traffic.

 -dns-addr - This flag controls the address the agent listens on for DNS requests.
  By default it is bound to "127.0.0.1:8600". This port must allow for UDP and TCP traffic.

 -server - This flag is used to control if an agent is in server or client mode. When provided,
  an agent will act as a Consul server. Each Consul cluster must have at least one server, and ideally
  no more than 5 *per* datacenter. All servers participate in the Raft consensus algorithm, to ensure that
  transactions occur in a consistent, linearlizable manner. Transactions modify cluster state, which
  is maintained on all server nodes to ensure availability in the case of node failure. Server nodes also
  participate in a WAN gossip pool with server nodes in other datacenters. Servers act as gateways
  to other datacenters and forward traffic as appropriate.

 -bootstrap - This flag is used to control if a server is in "bootstrap" mode. It is important that
  no more than one server *per* datacenter be running in this mode. The initial server **must** be in bootstrap
  mode. Technically, a server in boostrap mode is allowed to self-elect as the Raft leader. It is important
  that only a single node is in this mode, because otherwise consistency cannot be guarenteed if multiple
  nodes are able to self-elect. Once there are multiple servers in a datacenter, it is generally a good idea
  to disable bootstrap mode on all of them.

 -statsite - This flag provides the address of a statsite instance. If provided Consul will stream
  various telemetry information to that instance for aggregation. This can be used to capture various
  runtime information.
`
	return strings.TrimSpace(helpText)
}