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)
	}
}

func TestGetBadNothing(t *testing.T) {
	m := mount.New([]mount.Mount{})

	_, err := m.Get(datastore.NewKey("/quux/thud"))
	if g, e := err, datastore.ErrNotFound; g != e {
		t.Fatalf("expected ErrNotFound, got: %v\n", g)
	}
}

func TestPutBadNothing(t *testing.T) {
	m := mount.New(nil)

	err := m.Put(datastore.NewKey("quux"), []byte("foobar"))
	if g, e := err, mount.ErrNoMount; g != e {
		t.Fatalf("Put got wrong error: %v != %v", g, e)
	}
}

// openDatastore returns an error if the config file is not present.
func (r *FSRepo) openDatastore() error {
	leveldbPath := path.Join(r.path, leveldbDirectory)
	var err error
	// save leveldb reference so it can be neatly closed afterward
	r.leveldbDS, err = levelds.NewDatastore(leveldbPath, &levelds.Options{
		Compression: ldbopts.NoCompression,
	})
	if err != nil {
		return errors.New("unable to open leveldb datastore")
	}

	// 4TB of 256kB objects ~=17M objects, splitting that 256-way
	// leads to ~66k objects per dir, splitting 256*256-way leads to
	// only 256.
	//
	// The keys seen by the block store have predictable prefixes,
	// including "/" from datastore.Key and 2 bytes from multihash. To
	// reach a uniform 256-way split, we need approximately 4 bytes of
	// prefix.
	blocksDS, err := flatfs.New(path.Join(r.path, flatfsDirectory), 4)
	if err != nil {
		return errors.New("unable to open flatfs datastore")
	}

	// Add our PeerID to metrics paths to keep them unique
	//
	// As some tests just pass a zero-value Config to fsrepo.Init,
	// cope with missing PeerID.
	id := r.config.Identity.PeerID
	if id == "" {
		// the tests pass in a zero Config; cope with it
		id = fmt.Sprintf("uninitialized_%p", r)
	}
	prefix := "fsrepo." + id + ".datastore."
	r.metricsBlocks = measure.New(prefix+"blocks", blocksDS)
	r.metricsLevelDB = measure.New(prefix+"leveldb", r.leveldbDS)
	mountDS := mount.New([]mount.Mount{
		{
			Prefix:    ds.NewKey("/blocks"),
			Datastore: r.metricsBlocks,
		},
		{
			Prefix:    ds.NewKey("/"),
			Datastore: r.metricsLevelDB,
		},
	})
	// Make sure it's ok to claim the virtual datastore from mount as
	// threadsafe. There's no clean way to make mount itself provide
	// this information without copy-pasting the code into two
	// variants. This is the same dilemma as the `[].byte` attempt at
	// introducing const types to Go.
	var _ ds.ThreadSafeDatastore = blocksDS
	var _ ds.ThreadSafeDatastore = r.leveldbDS
	r.ds = ds2.ClaimThreadSafe{mountDS}
	return nil
}

func TestGetNotFound(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
	})

	_, err := m.Get(datastore.NewKey("/quux/thud"))
	if g, e := err, datastore.ErrNotFound; g != e {
		t.Fatalf("expected ErrNotFound, got: %v\n", g)
	}
}

func TestPutBadNoMount(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/redherring"), Datastore: mapds},
	})

	err := m.Put(datastore.NewKey("/quux/thud"), []byte("foobar"))
	if g, e := err, mount.ErrNoMount; g != e {
		t.Fatalf("expected ErrNoMount, got: %v\n", g)
	}
}

func TestHasBadNothing(t *testing.T) {
	m := mount.New([]mount.Mount{})

	found, err := m.Has(datastore.NewKey("/quux/thud"))
	if err != nil {
		t.Fatalf("Has error: %v", err)
	}
	if g, e := found, false; g != e {
		t.Fatalf("wrong value: %v != %v", g, e)
	}
}

func TestHasNotFound(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
	})

	found, err := m.Has(datastore.NewKey("/quux/thud"))
	if err != nil {
		t.Fatalf("Has error: %v", err)
	}
	if g, e := found, false; g != e {
		t.Fatalf("wrong value: %v != %v", g, e)
	}
}

func TestHas(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
	})

	if err := mapds.Put(datastore.NewKey("/thud"), []byte("foobar")); err != nil {
		t.Fatalf("Put error: %v", err)
	}

	found, err := m.Has(datastore.NewKey("/quux/thud"))
	if err != nil {
		t.Fatalf("Has error: %v", err)
	}
	if g, e := found, true; g != e {
		t.Fatalf("wrong value: %v != %v", g, e)
	}
}

func TestPut(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
	})

	if err := m.Put(datastore.NewKey("/quux/thud"), []byte("foobar")); err != nil {
		t.Fatalf("Put error: %v", err)
	}

	val, err := mapds.Get(datastore.NewKey("/thud"))
	if err != nil {
		t.Fatalf("Get error: %v", err)
	}
	buf, ok := val.([]byte)
	if !ok {
		t.Fatalf("Get value is not []byte: %T %v", val, val)
	}
	if g, e := string(buf), "foobar"; g != e {
		t.Errorf("wrong value: %q != %q", g, e)
	}
}

func TestDelete(t *testing.T) {
	mapds := datastore.NewMapDatastore()
	m := mount.New([]mount.Mount{
		{Prefix: datastore.NewKey("/quux"), Datastore: mapds},
	})

	if err := mapds.Put(datastore.NewKey("/thud"), []byte("foobar")); err != nil {
		t.Fatalf("Put error: %v", err)
	}

	err := m.Delete(datastore.NewKey("/quux/thud"))
	if err != nil {
		t.Fatalf("Delete error: %v", err)
	}

	// make sure it disappeared
	found, err := mapds.Has(datastore.NewKey("/thud"))
	if err != nil {
		t.Fatalf("Has error: %v", err)
	}
	if g, e := found, false; g != e {
		t.Fatalf("wrong value: %v != %v", g, e)
	}
}