Adding more filters

mino/option.go

@@ -5,6 +5,7 @@
 package mino
 
 import (
+	"math/rand"
 	"sort"
 )
 
@@ -68,6 +69,19 @@ func IndexFilter(index int) FilterUpdater {
 	}
 }
 
+// RejectFilter removes the given index
+func RejectFilter(index int) FilterUpdater {
+	return func(filters *Filter) {
+		arr := filters.Indices
+		i := sort.IntSlice(arr).Search(index)
+		// do nothing if the element is not there
+		if i == len(arr) || arr[i] != index {
+			return
+		}
+		filters.Indices = append(filters.Indices[0:i], filters.Indices[i+1:]...)
+	}
+}
+
 // RangeFilter is a filter to include a range of indices.
 // It will add all indices from start..end-1 to the existing
 // indices.
@@ -97,3 +111,17 @@ func ListFilter(indices []int) FilterUpdater {
 		filters.Indices = indices
 	}
 }
+
+// RandomFilter chooses 'count' random elements.
+func RandomFilter(count int) FilterUpdater {
+	return func(filters *Filter) {
+		if len(filters.Indices) >= count {
+			return
+		}
+		rand.Shuffle(len(filters.Indices),
+			func(i, j int) {
+				filters.Indices[i], filters.Indices[j] = filters.Indices[j], filters.Indices[i]
+			})
+		filters.Indices = filters.Indices[:count]
+	}
+}

mino/option_test.go

@@ -33,20 +33,44 @@ func TestFilter_RotateFilter(t *testing.T) {
 
 func TestFilter_IndexFilter(t *testing.T) {
 	filters := &Filter{Indices: []int{}}
-
 	IndexFilter(1)(filters)
-	require.Equal(t, filters.Indices, []int{1})
+	require.Equal(t, []int{1}, filters.Indices)
+
+	IndexFilter(2)(filters)
+	require.Equal(t, []int{1, 2}, filters.Indices)
 
 	IndexFilter(2)(filters)
-	require.Equal(t, filters.Indices, []int{1, 2})
+	require.Equal(t, []int{1, 2}, filters.Indices)
 
 	IndexFilter(0)(filters)
-	require.Equal(t, filters.Indices, []int{0, 1, 2})
+	require.Equal(t, []int{0, 1, 2}, filters.Indices)
 
 	IndexFilter(0)(filters)
 	IndexFilter(1)(filters)
 	IndexFilter(2)(filters)
-	require.Equal(t, filters.Indices, []int{0, 1, 2})
+	require.Equal(t, []int{0, 1, 2}, filters.Indices)
+}
+
+func TestFilter_RejectFilter(t *testing.T) {
+	filters := &Filter{Indices: []int{1, 2, 3, 4}}
+
+	testCases := []struct {
+		filterVal int
+		expected  []int
+	}{
+		{0, []int{1, 2, 3, 4}},
+		{5, []int{1, 2, 3, 4}},
+		{2, []int{1, 3, 4}},
+		{1, []int{3, 4}},
+		{4, []int{3}},
+		{4, []int{3}},
+		{3, []int{}},
+	}
+
+	for _, tc := range testCases {
+		RejectFilter(tc.filterVal)(filters)
+		require.Equal(t, tc.expected, filters.Indices)
+	}
 }
 
 func TestFilter_RangeFilter(t *testing.T) {