Implement mount Query, in a dumb way

mount/mount.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/jbenet/go-datastore"
+	"github.com/jbenet/go-datastore/keytransform"
 	"github.com/jbenet/go-datastore/query"
 )
 
@@ -34,19 +35,19 @@ type Datastore struct {
 
 var _ datastore.Datastore = (*Datastore)(nil)
 
-func (d *Datastore) lookup(key datastore.Key) (datastore.Datastore, datastore.Key) {
+func (d *Datastore) lookup(key datastore.Key) (ds datastore.Datastore, mountpoint, rest datastore.Key) {
 	for _, m := range d.mounts {
-		if m.Prefix.IsAncestorOf(key) {
+		if m.Prefix.Equal(key) || m.Prefix.IsAncestorOf(key) {
 			s := strings.TrimPrefix(key.String(), m.Prefix.String())
 			k := datastore.NewKey(s)
-			return m.Datastore, k
+			return m.Datastore, m.Prefix, k
 		}
 	}
-	return nil, key
+	return nil, datastore.NewKey("/"), key
 }
 
 func (d *Datastore) Put(key datastore.Key, value interface{}) error {
-	ds, k := d.lookup(key)
+	ds, _, k := d.lookup(key)
 	if ds == nil {
 		return ErrNoMount
 	}
@@ -54,7 +55,7 @@ func (d *Datastore) Put(key datastore.Key, value interface{}) error {
 }
 
 func (d *Datastore) Get(key datastore.Key) (value interface{}, err error) {
-	ds, k := d.lookup(key)
+	ds, _, k := d.lookup(key)
 	if ds == nil {
 		return nil, datastore.ErrNotFound
 	}
@@ -62,7 +63,7 @@ func (d *Datastore) Get(key datastore.Key) (value interface{}, err error) {
 }
 
 func (d *Datastore) Has(key datastore.Key) (exists bool, err error) {
-	ds, k := d.lookup(key)
+	ds, _, k := d.lookup(key)
 	if ds == nil {
 		return false, nil
 	}
@@ -70,7 +71,7 @@ func (d *Datastore) Has(key datastore.Key) (exists bool, err error) {
 }
 
 func (d *Datastore) Delete(key datastore.Key) error {
-	ds, k := d.lookup(key)
+	ds, _, k := d.lookup(key)
 	if ds == nil {
 		return datastore.ErrNotFound
 	}
@@ -78,5 +79,38 @@ func (d *Datastore) Delete(key datastore.Key) error {
 }
 
 func (d *Datastore) Query(q query.Query) (query.Results, error) {
-	return nil, errors.New("TODO")
+	if len(q.Filters) > 0 ||
+		len(q.Orders) > 0 ||
+		q.Limit > 0 ||
+		q.Offset > 0 {
+		// TODO this is overly simplistic, but the only caller is
+		// `ipfs refs local` for now, and this gets us moving.
+		return nil, errors.New("mount only supports listing all prefixed keys in random order")
+	}
+	key := datastore.NewKey(q.Prefix)
+	ds, mount, k := d.lookup(key)
+	if ds == nil {
+		return nil, errors.New("mount only supports listing a mount point")
+	}
+	// TODO support listing cross mount points too
+
+	// delegate the query to the mounted datastore, while adjusting
+	// keys in and out
+	q2 := q
+	q2.Prefix = k.String()
+	wrapDS := keytransform.Wrap(ds, &keytransform.Pair{
+		Convert: func(datastore.Key) datastore.Key {
+			panic("this should never be called")
+		},
+		Invert: func(k datastore.Key) datastore.Key {
+			return mount.Child(k)
+		},
+	})
+
+	r, err := wrapDS.Query(q2)
+	if err != nil {
+		return nil, err
+	}
+	r = query.ResultsReplaceQuery(r, q)
+	return r, nil
 }

mount/mount_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/jbenet/go-datastore"
 	"github.com/jbenet/go-datastore/mount"
+	"github.com/jbenet/go-datastore/query"
 )
 
 func TestPutBadNothing(t *testing.T) {
@@ -205,3 +206,36 @@ func TestDelete(t *testing.T) {
 		t.Fatalf("wrong value: %v != %v", g, e)
 	}
 }
+
+func TestQuerySimple(t *testing.T) {
+	mapds := datastore.NewMapDatastore()
+	m := mount.New([]mount.Mount{
+		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
+	})
+
+	const myKey = "/quux/thud"
+	if err := m.Put(datastore.NewKey(myKey), []byte("foobar")); err != nil {
+		t.Fatalf("Put error: %v", err)
+	}
+
+	res, err := m.Query(query.Query{Prefix: "/quux"})
+	if err != nil {
+		t.Fatalf("Query fail: %v\n", err)
+	}
+	entries, err := res.Rest()
+	if err != nil {
+		t.Fatalf("Query Results.Rest fail: %v\n", err)
+	}
+	seen := false
+	for _, e := range entries {
+		switch e.Key {
+		case datastore.NewKey(myKey).String():
+			seen = true
+		default:
+			t.Errorf("saw unexpected key: %q", e.Key)
+		}
+	}
+	if !seen {
+		t.Errorf("did not see wanted key %q in %+v", myKey, entries)
+	}
+}