adding merge transform

README.md

@@ -21,7 +21,7 @@ API Documentation is available at http://godoc.org/gopkg.in/qntfy/kazaam.v3.
 
 ## Features
 Kazaam is primarily designed to be used as a library for transforming arbitrary JSON.
-It ships with ten built-in transform types, and nineteen built-in converter types,
+It ships with eleven built-in transform types, and nineteen built-in converter types,
 described below, which provide significant flexibility in reshaping JSON data.
 
 Also included when you `go get` Kazaam, is a binary implementation, `kazaam` that can be used for
@@ -54,6 +54,7 @@ Kazaam currently supports the following built-in transforms:
 - default
 - pass
 - delete
+- merge
 
 ### Shift
 The shift transform is the current Kazaam workhorse used for remapping of fields. It supports a `"require"` field that when 
@@ -521,6 +522,75 @@ would result in
 A pass transform, as the name implies, passes the input data unchanged to the output. This is used internally
 when a null transform spec is specified, but may also be useful for testing.
 
+### Merge
+A merge transform will take multiple arrays and join them in to an array of objects joining them by keys. The arrays should be equal length.
+
+```json
+{
+  "operation": "merge",
+  "spec": {
+    "merge1": [
+      {
+        "name": "prop_1",
+        "array": "array_a"
+      },
+      {
+        "name": "prop_2",
+        "array": "array_b"
+      },
+      {
+        "name": "prop_3",
+        "array": "array_c"
+      }
+    ]
+  }
+}
+```
+
+executed on a json message with format:
+```json
+{
+  "array_a": [
+    "a_1",
+    "a_2",
+    "a_3"
+  ],
+  "array_b": [
+    "b_1",
+    "b_2",
+    "b_3"
+  ],
+  "array_c": [
+    "c_1",
+    "c_2",
+    "c_3"
+  ]
+}
+```
+
+would result in:
+```json
+{
+  "merge1": [
+    {
+      "prop_1": "a_1",
+      "prop_2": "b_1",
+      "prop_3": "c_1"
+    },
+    {
+      "prop_1": "a_2",
+      "prop_2": "b_2",
+      "prop_3": "c_2"
+    },
+    {
+      "prop_1": "a_3",
+      "prop_2": "b_3",
+      "prop_3": "c_3"
+    }
+  ]
+}
+```
+
 
 
 ## Converter Specification Support

kazaam.go

@@ -41,6 +41,7 @@ func init() {
 		"timestamp": transform.Timestamp,
 		"uuid":      transform.UUID,
 		"steps":     transform.Steps,
+		"merge":	 transform.Merge,
 	}
 
 	defaultConverters = map[string]registry.Converter{

transform/merge.go

@@ -0,0 +1,86 @@
+package transform
+
+import (
+	"encoding/json"
+)
+
+// Merge joins multiple array values into array of objects with property names containing their matching array. Arrays
+// should be the same length.
+func Merge(spec *Config, data []byte) ([]byte, error) {
+	var outData []byte
+
+	if spec.InPlace {
+		outData = data
+	} else {
+		outData = []byte(`{}`)
+	}
+
+	// iterate through the spec
+	for k, v := range *spec.Spec {
+
+		// map[prop_name] = [ values... ]
+		arrayVals := make(map[string][]interface{})
+		outVals := make([]map[string]interface{}, 0)
+
+		mergeSpec, ok := v.([]interface{})
+		if !ok {
+			return nil, SpecError("Invalid Spec for Merge")
+		}
+
+		l := 0
+
+		for i, v := range mergeSpec {
+			arraySpec := v.(map[string]interface{})
+			var name, array string
+			name, ok = arraySpec["name"].(string)
+			if !ok {
+				return nil, SpecError("Array spec missing name for Merge")
+			}
+			array, ok = arraySpec["array"].(string)
+			if !ok {
+				return nil, SpecError("Array spec missing array for Merge")
+			}
+
+			var dataForV []byte
+			var err error
+
+			dataForV, err = getJSONRaw(data, array, true)
+			if err != nil {
+				return nil, err
+			}
+
+			var arrayValues []interface{}
+			err = json.Unmarshal(dataForV, &arrayValues)
+
+			arrayVals[name] = arrayValues
+			if i == 0 {
+				l = len(arrayValues)
+			} else if l != len(arrayValues) {
+				return nil, SpecError("Arrays must be the same length for Merge")
+			}
+		}
+
+		for i := 0; i < l; i++ {
+			m := make(map[string]interface{})
+			for k, v := range arrayVals {
+				m[k] = v[0]
+				arrayVals[k] = v[1:]
+			}
+			outVals = append(outVals, m)
+		}
+
+		dataForV, err := json.Marshal(outVals)
+		if err != nil {
+			return nil, err
+		}
+
+		outData, err = setJSONRaw(outData, dataForV, k)
+		if err != nil {
+			return nil, err
+		}
+
+	}
+
+	return outData, nil
+
+}

transform/merge_test.go

@@ -0,0 +1,37 @@
+package transform
+
+import "testing"
+
+func TestMerge(t *testing.T) {
+	spec := `{"merge1":[{"name":"prop_1","array":"array_a"},{"name":"prop_2","array":"array_b"},{"name":"prop_3","array":"array_c"}]}`
+	jsonIn := `{"array_a":["a_1","a_2","a_3"],"array_b":["b_1","b_2","b_3"],"array_c":["c_1","c_2","c_3"]}`
+	jsonOut := `{"merge1":[{"prop_1":"a_1","prop_2":"b_1","prop_3":"c_1"},{"prop_1":"a_2","prop_2":"b_2","prop_3":"c_2"},{"prop_1":"a_3","prop_2":"b_3","prop_3":"c_3"}]}`
+
+	cfg := getConfig(spec, false)
+	kazaamOut, _ := getTransformTestWrapper(Merge, cfg, jsonIn)
+	areEqual, _ := checkJSONBytesEqual(kazaamOut, []byte(jsonOut))
+
+	if !areEqual {
+		t.Error("Transformed data does not match expectation.")
+		t.Log("Expected:   ", jsonOut)
+		t.Log("Actual:     ", kazaamOut)
+		t.FailNow()
+	}
+}
+
+func TestMergeSingleArray(t *testing.T) {
+	spec := `{"merge1":[{"name":"prop_1","array":"array_a"}]}`
+	jsonIn := `{"array_a":["a_1","a_2","a_3"]}`
+	jsonOut := `{"merge1":[{"prop_1":"a_1"},{"prop_1":"a_2"},{"prop_1":"a_3"}]}`
+
+	cfg := getConfig(spec, false)
+	kazaamOut, _ := getTransformTestWrapper(Merge, cfg, jsonIn)
+	areEqual, _ := checkJSONBytesEqual(kazaamOut, []byte(jsonOut))
+
+	if !areEqual {
+		t.Error("Transformed data does not match expectation.")
+		t.Log("Expected:   ", jsonOut)
+		t.Log("Actual:     ", kazaamOut)
+		t.FailNow()
+	}
+}