package alertmanager

import (
	"flag"
	"fmt"
	"os"
	"time"

	"github.com/go-kit/kit/log/level"

	"github.com/cortexproject/cortex/pkg/ring"
	"github.com/cortexproject/cortex/pkg/ring/kv"
	"github.com/cortexproject/cortex/pkg/util"
	"github.com/cortexproject/cortex/pkg/util/flagext"
)

const (
	// RingKey is the key under which we store the alertmanager ring in the KVStore.
	RingKey = "alertmanager"

	// RingNameForServer is the name of the ring used by the alertmanager server.
	RingNameForServer = "alertmanager"

	// RingNumTokens is a safe default instead of exposing to config option to the user
	// in order to simplify the config.
	RingNumTokens = 128
)

// RingOp is the operation used for distributing tenants between alertmanagers.
var RingOp = ring.NewOp([]ring.IngesterState{ring.ACTIVE}, func(s ring.IngesterState) bool {
	// Only ACTIVE Alertmanager get requests. If instance is not ACTIVE, we need to find another Alertmanager.
	return s != ring.ACTIVE
})

// RingConfig masks the ring lifecycler config which contains
// many options not really required by the alertmanager ring. This config
// is used to strip down the config to the minimum, and avoid confusion
// to the user.
type RingConfig struct {
	KVStore           kv.Config     `yaml:"kvstore" doc:"description=The key-value store used to share the hash ring across multiple instances."`
	HeartbeatPeriod   time.Duration `yaml:"heartbeat_period"`
	HeartbeatTimeout  time.Duration `yaml:"heartbeat_timeout"`
	ReplicationFactor int           `yaml:"replication_factor"`

	// Instance details
	InstanceID             string   `yaml:"instance_id" doc:"hidden"`
	InstanceInterfaceNames []string `yaml:"instance_interface_names"`
	InstancePort           int      `yaml:"instance_port" doc:"hidden"`
	InstanceAddr           string   `yaml:"instance_addr" doc:"hidden"`

	// Injected internally
	ListenPort      int           `yaml:"-"`
	RingCheckPeriod time.Duration `yaml:"-"`

	// Used for testing
	SkipUnregister bool `yaml:"-"`
}

// RegisterFlags adds the flags required to config this to the given FlagSet
func (cfg *RingConfig) RegisterFlags(f *flag.FlagSet) {
	hostname, err := os.Hostname()
	if err != nil {
		level.Error(util.Logger).Log("msg", "failed to get hostname", "err", err)
		os.Exit(1)
	}

	// Prefix used by all the ring flags
	rfprefix := "alertmanager.sharding-ring."

	// Ring flags
	cfg.KVStore.RegisterFlagsWithPrefix(rfprefix, "alertmanagers/", f)
	f.DurationVar(&cfg.HeartbeatPeriod, rfprefix+"heartbeat-period", 15*time.Second, "Period at which to heartbeat to the ring.")
	f.DurationVar(&cfg.HeartbeatTimeout, rfprefix+"heartbeat-timeout", time.Minute, "The heartbeat timeout after which alertmanagers are considered unhealthy within the ring.")
	f.IntVar(&cfg.ReplicationFactor, rfprefix+"replication-factor", 3, "The replication factor to use when sharding the alertmanager.")

	// Instance flags
	cfg.InstanceInterfaceNames = []string{"eth0", "en0"}
	f.Var((*flagext.StringSlice)(&cfg.InstanceInterfaceNames), rfprefix+"instance-interface-names", "Name of network interface to read address from.")
	f.StringVar(&cfg.InstanceAddr, rfprefix+"instance-addr", "", "IP address to advertise in the ring.")
	f.IntVar(&cfg.InstancePort, rfprefix+"instance-port", 0, "Port to advertise in the ring (defaults to server.http-listen-port).")
	f.StringVar(&cfg.InstanceID, rfprefix+"instance-id", hostname, "Instance ID to register in the ring.")

	cfg.RingCheckPeriod = 5 * time.Second
}

// ToLifecyclerConfig returns a LifecyclerConfig based on the alertmanager
// ring config.
func (cfg *RingConfig) ToLifecyclerConfig() (ring.BasicLifecyclerConfig, error) {
	instanceAddr, err := ring.GetInstanceAddr(cfg.InstanceAddr, cfg.InstanceInterfaceNames)
	if err != nil {
		return ring.BasicLifecyclerConfig{}, err
	}

	instancePort := ring.GetInstancePort(cfg.InstancePort, cfg.ListenPort)

	return ring.BasicLifecyclerConfig{
		ID:                  cfg.InstanceID,
		Addr:                fmt.Sprintf("%s:%d", instanceAddr, instancePort),
		HeartbeatPeriod:     cfg.HeartbeatPeriod,
		TokensObservePeriod: 0,
		NumTokens:           RingNumTokens,
	}, nil
}

func (cfg *RingConfig) ToRingConfig() ring.Config {
	rc := ring.Config{}
	flagext.DefaultValues(&rc)

	rc.KVStore = cfg.KVStore
	rc.HeartbeatTimeout = cfg.HeartbeatTimeout
	rc.ReplicationFactor = cfg.ReplicationFactor

	return rc
}
