Implements Path.PopLastSegment().

This allows a path (/ipfs/foo/bar) to be separated between its head
(/ipfs/foo) and its tail (bar).

License: MIT
Signed-off-by: Stephen Whitmore <noffle@ipfs.io>

path/path.go

@@ -50,6 +50,24 @@ func (p Path) IsJustAKey() bool {
 	return (len(parts) == 2 && parts[0] == "ipfs")
 }
 
+// PopLastSegment returns a new Path without its final segment, and the final
+// segment, separately. If there is no more to pop (the path is just a key),
+// the original path is returned.
+func (p Path) PopLastSegment() (Path, string, error) {
+
+	if p.IsJustAKey() {
+		return p, "", nil
+	}
+
+	segs := p.Segments()
+	newPath, err := ParsePath("/" + strings.Join(segs[:len(segs)-1], "/"))
+	if err != nil {
+		return "", "", err
+	}
+
+	return newPath, segs[len(segs)-1], nil
+}
+
 func FromSegments(prefix string, seg ...string) (Path, error) {
 	return ParsePath(prefix + strings.Join(seg, "/"))
 }

path/path_test.go

@@ -49,3 +49,31 @@ func TestIsJustAKey(t *testing.T) {
 		}
 	}
 }
+
+func TestPopLastSegment(t *testing.T) {
+	cases := map[string][]string{
+		"QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n":             []string{"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n", ""},
+		"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n":       []string{"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n", ""},
+		"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n/a":     []string{"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n", "a"},
+		"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n/a/b":   []string{"/ipfs/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n/a", "b"},
+		"/ipns/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n/x/y/z": []string{"/ipns/QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n/x/y", "z"},
+	}
+
+	for p, expected := range cases {
+		path, err := ParsePath(p)
+		if err != nil {
+			t.Fatalf("ParsePath failed to parse \"%s\", but should have succeeded", p)
+		}
+		head, tail, err := path.PopLastSegment()
+		if err != nil {
+			t.Fatalf("PopLastSegment failed, but should have succeeded: %s", err)
+		}
+		headStr := head.String()
+		if headStr != expected[0] {
+			t.Fatalf("expected head of PopLastSegment(%s) to return %v, not %v", p, expected[0], headStr)
+		}
+		if tail != expected[1] {
+			t.Fatalf("expected tail of PopLastSegment(%s) to return %v, not %v", p, expected[1], tail)
+		}
+	}
+}