package nomad

import (
	"fmt"
	"io"
	"net"
	"os"
	"runtime"
	"time"

	"github.com/hashicorp/memberlist"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/hashicorp/nomad/scheduler"
	"github.com/hashicorp/raft"
	"github.com/hashicorp/serf/serf"
)

const (
	DefaultRegion   = "region1"
	DefaultDC       = "dc1"
	DefaultSerfPort = 4648
)

// These are the protocol versions that Nomad can understand
const (
	ProtocolVersionMin uint8 = 1
	ProtocolVersionMax       = 1
)

// ProtocolVersionMap is the mapping of Nomad protocol versions
// to Serf protocol versions. We mask the Serf protocols using
// our own protocol version.
var protocolVersionMap map[uint8]uint8

func init() {
	protocolVersionMap = map[uint8]uint8{
		1: 5,
	}
}

var (
	DefaultRPCAddr = &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 4647}
)

// Config is used to parameterize the server
type Config struct {
	// Bootstrap mode is used to bring up the first Consul server.
	// It is required so that it can elect a leader without any
	// other nodes being present
	Bootstrap bool

	// BootstrapExpect mode is used to automatically bring up a collection of
	// Consul servers. This can be used to automatically bring up a collection
	// of nodes.
	BootstrapExpect int

	// DataDir is the directory to store our state in
	DataDir string

	// DevMode is used for development purposes only and limits the
	// use of persistence or state.
	DevMode bool

	// DevDisableBootstrap is used to disable bootstrap mode while
	// in DevMode. This is largely used for testing.
	DevDisableBootstrap bool

	// LogOutput is the location to write logs to. If this is not set,
	// logs will go to stderr.
	LogOutput io.Writer

	// ProtocolVersion is the protocol version to speak. This must be between
	// ProtocolVersionMin and ProtocolVersionMax.
	ProtocolVersion uint8

	// RPCAddr is the RPC address used by Nomad. This should be reachable
	// by the other servers and clients
	RPCAddr *net.TCPAddr

	// RPCAdvertise is the address that is advertised to other nodes for
	// the RPC endpoint. This can differ from the RPC address, if for example
	// the RPCAddr is unspecified "0.0.0.0:4646", but this address must be
	// reachable
	RPCAdvertise *net.TCPAddr

	// RaftConfig is the configuration used for Raft in the local DC
	RaftConfig *raft.Config

	// RaftTimeout is applied to any network traffic for raft. Defaults to 10s.
	RaftTimeout time.Duration

	// RequireTLS ensures that all RPC traffic is protected with TLS
	RequireTLS bool

	// SerfConfig is the configuration for the serf cluster
	SerfConfig *serf.Config

	// Node name is the name we use to advertise. Defaults to hostname.
	NodeName string

	// Region is the region this Nomad server belongs to.
	Region string

	// Datacenter is the datacenter this Nomad server belongs to.
	Datacenter string

	// Build is a string that is gossiped around, and can be used to help
	// operators track which versions are actively deployed
	Build string

	// NumSchedulers is the number of scheduler thread that are run.
	// This can be as many as one per core, or zero to disable this server
	// from doing any scheduling work.
	NumSchedulers int

	// EnabledSchedulers controls the set of sub-schedulers that are
	// enabled for this server to handle. This will restrict the evaluations
	// that the workers dequeue for processing.
	EnabledSchedulers []string

	// ReconcileInterval controls how often we reconcile the strongly
	// consistent store with the Serf info. This is used to handle nodes
	// that are force removed, as well as intermittent unavailability during
	// leader election.
	ReconcileInterval time.Duration

	// EvalGCInterval is how often we dispatch a job to GC evaluations
	EvalGCInterval time.Duration

	// EvalGCThreshold is how "old" an evaluation must be to be eligible
	// for GC. This gives users some time to debug a failed evaluation.
	EvalGCThreshold time.Duration

	// NodeGCInterval is how often we dispatch a job to GC failed nodes.
	NodeGCInterval time.Duration

	// NodeGCThreshold is how "old" a nodemust be to be eligible
	// for GC. This gives users some time to view and debug a failed nodes.
	NodeGCThreshold time.Duration

	// EvalNackTimeout controls how long we allow a sub-scheduler to
	// work on an evaluation before we consider it failed and Nack it.
	// This allows that evaluation to be handed to another sub-scheduler
	// to work on. Defaults to 60 seconds. This should be long enough that
	// no evaluation hits it unless the sub-scheduler has failed.
	EvalNackTimeout time.Duration

	// EvalDeliveryLimit is the limit of attempts we make to deliver and
	// process an evaluation. This is used so that an eval that will never
	// complete eventually fails out of the system.
	EvalDeliveryLimit int

	// MinHeartbeatTTL is the minimum time between heartbeats.
	// This is used as a floor to prevent excessive updates.
	MinHeartbeatTTL time.Duration

	// MaxHeartbeatsPerSecond is the maximum target rate of heartbeats
	// being processed per second. This allows the TTL to be increased
	// to meet the target rate.
	MaxHeartbeatsPerSecond float64

	// HeartbeatGrace is the additional time given as a grace period
	// beyond the TTL to account for network and processing delays
	// as well as clock skew.
	HeartbeatGrace time.Duration

	// FailoverHeartbeatTTL is the TTL applied to heartbeats after
	// a new leader is elected, since we no longer know the status
	// of all the heartbeats.
	FailoverHeartbeatTTL time.Duration
}

// CheckVersion is used to check if the ProtocolVersion is valid
func (c *Config) CheckVersion() error {
	if c.ProtocolVersion < ProtocolVersionMin {
		return fmt.Errorf("Protocol version '%d' too low. Must be in range: [%d, %d]",
			c.ProtocolVersion, ProtocolVersionMin, ProtocolVersionMax)
	} else if c.ProtocolVersion > ProtocolVersionMax {
		return fmt.Errorf("Protocol version '%d' too high. Must be in range: [%d, %d]",
			c.ProtocolVersion, ProtocolVersionMin, ProtocolVersionMax)
	}
	return nil
}

// DefaultConfig returns the default configuration
func DefaultConfig() *Config {
	hostname, err := os.Hostname()
	if err != nil {
		panic(err)
	}

	c := &Config{
		Region:                 DefaultRegion,
		Datacenter:             DefaultDC,
		NodeName:               hostname,
		ProtocolVersion:        ProtocolVersionMax,
		RaftConfig:             raft.DefaultConfig(),
		RaftTimeout:            10 * time.Second,
		RPCAddr:                DefaultRPCAddr,
		SerfConfig:             serf.DefaultConfig(),
		NumSchedulers:          1,
		ReconcileInterval:      60 * time.Second,
		EvalGCInterval:         5 * time.Minute,
		EvalGCThreshold:        1 * time.Hour,
		NodeGCInterval:         5 * time.Minute,
		NodeGCThreshold:        24 * time.Hour,
		EvalNackTimeout:        60 * time.Second,
		EvalDeliveryLimit:      3,
		MinHeartbeatTTL:        10 * time.Second,
		MaxHeartbeatsPerSecond: 50.0,
		HeartbeatGrace:         10 * time.Second,
		FailoverHeartbeatTTL:   300 * time.Second,
	}

	// Enable all known schedulers by default
	c.EnabledSchedulers = make([]string, 0, len(scheduler.BuiltinSchedulers))
	for name := range scheduler.BuiltinSchedulers {
		c.EnabledSchedulers = append(c.EnabledSchedulers, name)
	}
	c.EnabledSchedulers = append(c.EnabledSchedulers, structs.JobTypeCore)

	// Default the number of schedulers to match the coores
	c.NumSchedulers = runtime.NumCPU()

	// Increase our reap interval to 3 days instead of 24h.
	c.SerfConfig.ReconnectTimeout = 3 * 24 * time.Hour

	// Serf should use the WAN timing, since we are using it
	// to communicate between DC's
	c.SerfConfig.MemberlistConfig = memberlist.DefaultWANConfig()
	c.SerfConfig.MemberlistConfig.BindPort = DefaultSerfPort

	// Disable shutdown on removal
	c.RaftConfig.ShutdownOnRemove = false
	return c
}