Add ‘purge’ SQL function

sql/funcs.go

@@ -88,6 +88,12 @@ var funcs = map[string]map[int]interface{}{
 	"count.if":  {2: nil},
 	"count.not": {2: nil},
 
+	// Purge implementation
+
+	"purge":     {1: nil},
+	"purge.if":  {2: nil},
+	"purge.not": {2: nil},
+
 	// Json implementation
 	"json.decode": {1: nil},
 	"json.encode": {1: nil},

util/fncs/args.go

@@ -25,6 +25,12 @@ import (
 
 var defaultTime = time.Unix(0, 0)
 
+func copySlice(arr []interface{}) (out []interface{}) {
+	out = make([]interface{}, len(arr))
+	copy(out, arr)
+	return
+}
+
 func outputFloat(val float64) (interface{}, error) {
 	switch {
 	case math.IsNaN(val):
@@ -176,20 +182,18 @@ func ensureDuration(val interface{}) (out time.Duration, ok bool) {
 
 func ensureSlice(args interface{}) (out []interface{}, ok bool) {
 	if i, ok := args.([]interface{}); ok {
-		out = i
+		return i, true
 	} else {
-		out = []interface{}{args}
+		return []interface{}{args}, false
 	}
-	return out, true
 }
 
 func ensureObject(args interface{}) (out map[string]interface{}, ok bool) {
 	if i, ok := args.(map[string]interface{}); ok {
-		out = i
+		return i, true
 	} else {
-		out = map[string]interface{}{}
+		return map[string]interface{}{}, false
 	}
-	return out, true
 }
 
 func ensureInts(args interface{}) (out []int64) {

util/fncs/fnc.go

@@ -55,6 +55,14 @@ func Run(ctx context.Context, name string, args ...interface{}) (interface{}, er
 	case "count.not":
 		return countNot(ctx, args...)
 
+	// Purge implementation
+	case "purge":
+		return purge(ctx, args...)
+	case "purge.if":
+		return purgeIf(ctx, args...)
+	case "purge.not":
+		return purgeNot(ctx, args...)
+
 	// Json implementation
 	case "json.decode":
 		return jsonDecode(ctx, args...)

util/fncs/purge.go

@@ -0,0 +1,73 @@
+// Copyright © 2016 Abcum Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fncs
+
+import (
+	"context"
+)
+
+func purge(ctx context.Context, args ...interface{}) (interface{}, error) {
+	if arr, ok := ensureSlice(args[0]); ok {
+		arr = copySlice(arr)
+		for i := len(arr) - 1; i >= 0; i-- {
+			if arr[i] == nil {
+				copy(arr[i:], arr[i+1:])
+				arr[len(arr)-1] = nil
+				arr = arr[:len(arr)-1]
+			}
+		}
+		return arr, nil
+	}
+	if args[0] == nil {
+		return nil, nil
+	}
+	return args[0], nil
+}
+
+func purgeIf(ctx context.Context, args ...interface{}) (interface{}, error) {
+	if arr, ok := ensureSlice(args[0]); ok {
+		arr = copySlice(arr)
+		for i := len(arr) - 1; i >= 0; i-- {
+			if arr[i] == args[1] {
+				copy(arr[i:], arr[i+1:])
+				arr[len(arr)-1] = nil
+				arr = arr[:len(arr)-1]
+			}
+		}
+		return arr, nil
+	}
+	if args[0] == args[1] {
+		return nil, nil
+	}
+	return args[0], nil
+}
+
+func purgeNot(ctx context.Context, args ...interface{}) (interface{}, error) {
+	if arr, ok := ensureSlice(args[0]); ok {
+		arr = copySlice(arr)
+		for i := len(arr) - 1; i >= 0; i-- {
+			if arr[i] != args[1] {
+				copy(arr[i:], arr[i+1:])
+				arr[len(arr)-1] = nil
+				arr = arr[:len(arr)-1]
+			}
+		}
+		return arr, nil
+	}
+	if args[0] != args[1] {
+		return nil, nil
+	}
+	return args[0], nil
+}

util/fncs/purge_test.go

@@ -0,0 +1,69 @@
+// Copyright © 2016 Abcum Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fncs
+
+import (
+	"context"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestPurge(t *testing.T) {
+
+	var res interface{}
+
+	var test = []interface{}{int(1), int(2), nil, float64(3.5), "testing string"}
+
+	Convey("purge() works properly", t, func() {
+		res, _ = Run(context.Background(), "purge", nil)
+		So(res, ShouldResemble, nil)
+		res, _ = Run(context.Background(), "purge", "test")
+		So(res, ShouldResemble, "test")
+		res, _ = Run(context.Background(), "purge", test)
+		So(res, ShouldResemble, []interface{}{int(1), int(2), float64(3.5), "testing string"})
+	})
+
+	Convey("purge.if() works properly", t, func() {
+		res, _ = Run(context.Background(), "purge.if", "test", nil)
+		So(res, ShouldResemble, "test")
+		res, _ = Run(context.Background(), "purge.if", "test", "none")
+		So(res, ShouldResemble, "test")
+		res, _ = Run(context.Background(), "purge.if", "test", "test")
+		So(res, ShouldResemble, nil)
+		res, _ = Run(context.Background(), "purge.if", test, "testing string")
+		So(res, ShouldResemble, []interface{}{int(1), int(2), nil, float64(3.5)})
+		res, _ = Run(context.Background(), "purge.if", test, 3.5)
+		So(res, ShouldResemble, []interface{}{int(1), int(2), nil, "testing string"})
+		res, _ = Run(context.Background(), "purge.if", test, nil)
+		So(res, ShouldResemble, []interface{}{int(1), int(2), float64(3.5), "testing string"})
+	})
+
+	Convey("purge.not() works properly", t, func() {
+		res, _ = Run(context.Background(), "purge.not", "test", nil)
+		So(res, ShouldResemble, nil)
+		res, _ = Run(context.Background(), "purge.not", "test", "none")
+		So(res, ShouldResemble, nil)
+		res, _ = Run(context.Background(), "purge.not", "test", "test")
+		So(res, ShouldResemble, "test")
+		res, _ = Run(context.Background(), "purge.not", test, "testing string")
+		So(res, ShouldResemble, []interface{}{"testing string"})
+		res, _ = Run(context.Background(), "purge.not", test, 3.5)
+		So(res, ShouldResemble, []interface{}{float64(3.5)})
+		res, _ = Run(context.Background(), "purge.not", test, nil)
+		So(res, ShouldResemble, []interface{}{nil})
+	})
+
+}