Implemented spliceEsonArray

package.json

@@ -23,6 +23,7 @@
     "flow": "flow; test $? -eq 0 -o $? -eq 2",
     "test": "ava --verbose",
     "test-eson": "ava --verbose test/eson.test.js",
+    "test-patch": "ava --verbose test/patchEson.test.js",
     "watch:test": "ava --verbose --watch"
   },
   "dependencies": {

src/eson.js

@@ -71,6 +71,33 @@ export function mapEsonArray (esonArray, callback) {
   return result
 }
 
+/**
+ * Splice an eson Array: delete items and insert items
+ * @param {ESON} esonArray
+ * @param {number} start
+ * @param {number} deleteCount
+ * @param {Array} [insertItems]
+ */
+export function spliceEsonArray(esonArray, start, deleteCount, insertItems = []) {
+  let splicedArray = {}
+  const originalLength = esonArray._meta.length
+
+  for (let i = 0; i < start; i++) {
+    splicedArray[i] = esonArray[i]
+  }
+  for (let i = 0; i < insertItems.length; i++) {
+    splicedArray[i + start] = insertItems[i]
+  }
+  for (let i = start + deleteCount; i < originalLength; i++) {
+    splicedArray[i - deleteCount] = esonArray[i]
+  }
+
+  const length = originalLength - deleteCount + insertItems.length
+  splicedArray._meta = setIn(esonArray._meta, ['length'], length)
+
+  return splicedArray
+}
+
 /**
  * Expand function which will expand all nodes
  * @param {Path} path

test/eson.test.js

@@ -3,11 +3,12 @@ import test from 'ava'
 import { setIn, getIn, deleteIn } from '../src/utils/immutabilityHelpers'
 import {
   esonToJson, toEsonPath, toJsonPath, pathExists, transform, traverse,
-    parseJSONPointer, compileJSONPointer,
+  parseJSONPointer, compileJSONPointer,
   jsonToEson,
-    expand, expandOne, expandPath, applyErrors, search, nextSearchResult, previousSearchResult,
-    applySelection, pathsFromSelection,
-    SELECTED, SELECTED_END
+  expand, expandOne, expandPath, applyErrors, search, nextSearchResult,
+  previousSearchResult,
+  applySelection, pathsFromSelection,
+  SELECTED, SELECTED_END, spliceEsonArray
 } from '../src/eson'
 import deepMap from "deep-map/lib/index"
 
@@ -530,6 +531,15 @@ test('pathsFromSelection (after)', t => {
   t.deepEqual(pathsFromSelection(ESON1, selection), [])
 })
 
+test('spliceEsonArray', t => {
+  const eson = jsonToEson([1,2,3])
+
+  t.deepEqual(replaceIds(spliceEsonArray(eson, 1, 1)), replaceIds(jsonToEson([1,3])))
+  t.deepEqual(replaceIds(spliceEsonArray(eson, 1, 5)), replaceIds(jsonToEson([1])))
+  t.deepEqual(replaceIds(spliceEsonArray(eson, 1, 0, [10])), replaceIds(jsonToEson([1,5,3])))
+  t.deepEqual(replaceIds(spliceEsonArray(eson, 1, 0, [10,20])), replaceIds(jsonToEson([1,10,20,3])))
+})
+
 // helper function to replace all id properties with a constant value
 function replaceIds (eson, value = '[ID]') {
   eson._meta.id = value