package dhtopts

import (
	"fmt"

	ds "github.com/ipfs/go-datastore"
	dssync "github.com/ipfs/go-datastore/sync"
	record "github.com/libp2p/go-libp2p-record"
)

// Options is a structure containing all the options that can be used when constructing a DHT.
type Options struct {
	Datastore ds.Batching
	Validator record.Validator
	Client    bool
}

// Apply applies the given options to this Option
func (o *Options) Apply(opts ...Option) error {
	for i, opt := range opts {
		if err := opt(o); err != nil {
			return fmt.Errorf("dht option %d failed: %s", i, err)
		}
	}
	return nil
}

// Option DHT option type.
type Option func(*Options) error

// Defaults are the default DHT options. This option will be automatically
// prepended to any options you pass to the DHT constructor.
var Defaults = func(o *Options) error {
	o.Validator = record.NamespacedValidator{
		"pk": record.PublicKeyValidator{},
	}
	o.Datastore = dssync.MutexWrap(ds.NewMapDatastore())
	return nil
}

// Datastore configures the DHT to use the specified datastore.
//
// Defaults to an in-memory (temporary) map.
func Datastore(ds ds.Batching) Option {
	return func(o *Options) error {
		o.Datastore = ds
		return nil
	}
}

// Client configures whether or not the DHT operates in client-only mode.
//
// Defaults to false.
func Client(only bool) Option {
	return func(o *Options) error {
		o.Client = only
		return nil
	}
}

// Validator configures the DHT to use the specified validator.
//
// Defaults to a namespaced validator that can only validate public keys.
func Validator(v record.Validator) Option {
	return func(o *Options) error {
		o.Validator = v
		return nil
	}
}

// NamespacedValidator adds a validator namespaced under `ns`. This option fails
// if the DHT is not using a `record.NamespacedValidator` as it's validator (it
// uses one by default but this can be overridden with the `Validator` option).
//
// Example: Given a validator registered as `NamespacedValidator("ipns",
// myValidator)`, all records with keys starting with `/ipns/` will be validated
// with `myValidator`.
func NamespacedValidator(ns string, v record.Validator) Option {
	return func(o *Options) error {
		nsval, ok := o.Validator.(record.NamespacedValidator)
		if !ok {
			return fmt.Errorf("can only add namespaced validators to a NamespacedValidator")
		}
		nsval[ns] = v
		return nil
	}
}