coreapi: implement dht api

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

coreapi.go

@@ -31,6 +31,9 @@ type CoreAPI interface {
 	// ObjectAPI returns an implementation of Object API
 	Object() ObjectAPI
 
+	// Dht returns an implementation of Dht API
+	Dht() DhtAPI
+
 	// ResolvePath resolves the path using Unixfs resolver
 	ResolvePath(context.Context, Path) (ResolvedPath, error)
 

dht.go

@@ -17,7 +17,11 @@ type DhtAPI interface {
 
 	// FindProviders finds peers in the DHT who can provide a specific value
 	// given a key.
-	FindProviders(context.Context, Path) (<-chan peer.ID, error) //TODO: is path the right choice here?
+	FindProviders(context.Context, Path, ...options.DhtFindProvidersOption) (<-chan peer.ID, error) //TODO: is path the right choice here?
+
+	// WithNumProviders is an option for FindProviders which specifies the
+	// number of peers to look for. Default is 20
+	WithNumProviders(numProviders int) options.DhtFindProvidersOption
 
 	// Provide announces to the network that you are providing given values
 	Provide(context.Context, Path, ...options.DhtProvideOption) error

options/dht.go

@@ -4,7 +4,12 @@ type DhtProvideSettings struct {
 	Recursive bool
 }
 
+type DhtFindProvidersSettings struct {
+	NumProviders int
+}
+
 type DhtProvideOption func(*DhtProvideSettings) error
+type DhtFindProvidersOption func(*DhtFindProvidersSettings) error
 
 func DhtProvideOptions(opts ...DhtProvideOption) (*DhtProvideSettings, error) {
 	options := &DhtProvideSettings{
@@ -20,6 +25,20 @@ func DhtProvideOptions(opts ...DhtProvideOption) (*DhtProvideSettings, error) {
 	return options, nil
 }
 
+func DhtFindProvidersOptions(opts ...DhtFindProvidersOption) (*DhtFindProvidersSettings, error) {
+	options := &DhtFindProvidersSettings{
+		NumProviders: 20,
+	}
+
+	for _, opt := range opts {
+		err := opt(options)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return options, nil
+}
+
 type DhtOptions struct{}
 
 func (api *DhtOptions) WithRecursive(recursive bool) DhtProvideOption {
@@ -28,3 +47,10 @@ func (api *DhtOptions) WithRecursive(recursive bool) DhtProvideOption {
 		return nil
 	}
 }
+
+func (api *DhtOptions) WithNumProviders(numProviders int) DhtFindProvidersOption {
+	return func(settings *DhtFindProvidersSettings) error {
+		settings.NumProviders = numProviders
+		return nil
+	}
+}