Fix seek to end of stream (#73)

* Add Seek testdata & fix out-of-range check

Contains one fixed & one still failing test.

* Comment out still failing testcase

* flac: use upper case for TODO for consistency with other comments

---------

Co-authored-by: Robin <mewmew@users.noreply.github.com>

flac.go

@@ -323,7 +323,7 @@ func (stream *Stream) Seek(sampleNum uint64) (uint64, error) {
 
 	rs := stream.r.(io.ReadSeeker)
 
-	isBiggerThanStream := stream.Info.NSamples != 0 && sampleNum > stream.Info.NSamples
+	isBiggerThanStream := stream.Info.NSamples != 0 && sampleNum >= stream.Info.NSamples
 	if isBiggerThanStream || sampleNum < 0 {
 		return 0, fmt.Errorf("unable to seek to sample number %d", sampleNum)
 	}

flac_test.go

@@ -50,6 +50,8 @@ func TestSeek(t *testing.T) {
 		{seek: 100, expected: 0},
 		{seek: 8192, expected: 8192},
 		{seek: 8191, expected: 4096},
+		//{seek: 40960 + 2723 - 1, expected: 40960}, // last sample // TODO: re-enable when it works. See https://github.com/mewkiz/flac/pull/73
+		{seek: 40960 + 2723, expected: 0, err: "unable to seek to sample number 43683"}, // one after last sample
 	}
 
 	stream, err := flac.NewSeek(f)