Add experimental findprovs

Author: Kubuxu

package.json

@@ -12,3 +12,4 @@
   "name": "go-ipfs-api",
   "version": "1.0.0"
 }
+

shell.go

@@ -2,7 +2,9 @@
 package shell
 
 import (
+	"bufio"
 	"bytes"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -13,6 +15,8 @@ import (
 	"strings"
 	"time"
 
+	pstore "github.com/libp2p/go-libp2p-peerstore"
+	notif "github.com/libp2p/go-libp2p-routing/notifications"
 	ma "github.com/multiformats/go-multiaddr"
 	manet "github.com/multiformats/go-multiaddr-net"
 	files "github.com/whyrusleeping/go-multipart-files"
@@ -336,6 +340,42 @@ func (s *Shell) FindPeer(peer string) (*PeerInfo, error) {
 	return &str.Responses[0], nil
 }
 
+func (s *Shell) FindProvs(ctx context.Context, cid string) (<-chan pstore.PeerInfo, error) {
+	ctx, cancel := context.WithCancel(ctx)
+
+	resp, err := s.newRequest("dht/findprovs", cid).Send(s.httpcli)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.Error != nil {
+		return nil, resp.Error
+	}
+
+	outchan := make(chan pstore.PeerInfo, 4)
+
+	go func() {
+		var n notif.QueryEvent
+		scanner := bufio.NewScanner(resp.Output)
+		for scanner.Scan() {
+			json.Unmarshal(scanner.Bytes(), &n)
+			if n.Type == notif.Provider {
+				for _, p := range n.Responses {
+					outchan <- *p
+				}
+			}
+		}
+		cancel()
+	}()
+
+	go func() {
+		<-ctx.Done()
+		resp.Close()
+	}()
+
+	return outchan, nil
+}
+
 func (s *Shell) Refs(hash string, recursive bool) (<-chan string, error) {
 	req := s.newRequest("refs", hash)
 	if recursive {