package fingerprint

import (
	"fmt"
	"log"
	"sort"
	"time"

	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/nomad/structs"
)

// EmptyDuration is to be used by fingerprinters that are not periodic.
const (
	EmptyDuration = time.Duration(0)
)

func init() {
	builtinFingerprintMap["arch"] = NewArchFingerprint
	builtinFingerprintMap["cpu"] = NewCPUFingerprint
	builtinFingerprintMap["env_aws"] = NewEnvAWSFingerprint
	builtinFingerprintMap["env_gce"] = NewEnvGCEFingerprint
	builtinFingerprintMap["host"] = NewHostFingerprint
	builtinFingerprintMap["memory"] = NewMemoryFingerprint
	builtinFingerprintMap["network"] = NewNetworkFingerprint
	builtinFingerprintMap["nomad"] = NewNomadFingerprint
	builtinFingerprintMap["storage"] = NewStorageFingerprint

	// Initialize the list of available fingerprinters per platform.  Each
	// platform defines its own list of available fingerprinters.
	initPlatformFingerprints(builtinFingerprintMap)
}

// builtinFingerprintMap contains the built in registered fingerprints which are
// available for a given platform.
var builtinFingerprintMap = make(map[string]Factory, 16)

// BuiltinFingerprints is a slice containing the key names of all registered
// fingerprints available, to provided an ordered iteration
func BuiltinFingerprints() []string {
	fingerprints := make([]string, 0, len(builtinFingerprintMap))
	for k := range builtinFingerprintMap {
		fingerprints = append(fingerprints, k)
	}
	sort.Strings(fingerprints)
	return fingerprints
}

// NewFingerprint is used to instantiate and return a new fingerprint
// given the name and a logger
func NewFingerprint(name string, logger *log.Logger) (Fingerprint, error) {
	// Lookup the factory function
	factory, ok := builtinFingerprintMap[name]
	if !ok {
		return nil, fmt.Errorf("unknown fingerprint '%s'", name)
	}

	// Instantiate the fingerprint
	f := factory(logger)
	return f, nil
}

// Factory is used to instantiate a new Fingerprint
type Factory func(*log.Logger) Fingerprint

// Fingerprint is used for doing "fingerprinting" of the
// host to automatically determine attributes, resources,
// and metadata about it. Each of these is a heuristic, and
// many of them can be applied on a particular host.
type Fingerprint interface {
	// Fingerprint is used to update properties of the Node,
	// and returns if the fingerprint was applicable and a potential error.
	Fingerprint(*config.Config, *structs.Node) (bool, error)

	// Periodic is a mechanism for the fingerprinter to indicate that it should
	// be run periodically. The return value is a boolean indicating if it
	// should be periodic, and if true, a duration.
	Periodic() (bool, time.Duration)
}

// StaticFingerprinter can be embedded in a struct that has a Fingerprint method
// to make it non-periodic.
type StaticFingerprinter struct{}

func (s *StaticFingerprinter) Periodic() (bool, time.Duration) {
	return false, EmptyDuration
}