refactor: reduce code duplication in FloodFill

Recursive/FloodFill.js

@@ -9,7 +9,7 @@
  * @see https://www.techiedelight.com/flood-fill-algorithm/
  */
 
-const neighbors = [
+const neighborOffsets = [
   [-1, -1],
   [-1, 0],
   [-1, 1],
@@ -20,6 +20,27 @@ const neighbors = [
   [1, 1]
 ]
 
+function isInside(rgbData, location) {
+  const x = location[0]
+  const y = location[1]
+  return x >= 0 && x < rgbData.length && y >= 0 && y < rgbData[0].length
+}
+
+function checkLocation(rgbData, location) {
+  if (!isInside(rgbData, location)) {
+    throw new Error('location should point to a pixel within the rgbData')
+  }
+}
+
+function* neighbors(rgbData, location) {
+  for (const offset of neighborOffsets) {
+    const neighborLocation = [location[0] + offset[0], location[1] + offset[1]]
+    if (isInside(rgbData, neighborLocation)) {
+      yield neighborLocation
+    }
+  }
+}
+
 /**
  * Implements the flood fill algorithm through a breadth-first approach using a queue.
  *
@@ -34,14 +55,7 @@ export function breadthFirstSearch(
   targetColor,
   replacementColor
 ) {
-  if (
-    location[0] < 0 ||
-    location[0] >= rgbData.length ||
-    location[1] < 0 ||
-    location[1] >= rgbData[0].length
-  ) {
-    throw new Error('location should point to a pixel within the rgbData')
-  }
+  checkLocation(rgbData, location)
 
   const queue = []
   queue.push(location)
@@ -65,14 +79,7 @@ export function depthFirstSearch(
   targetColor,
   replacementColor
 ) {
-  if (
-    location[0] < 0 ||
-    location[0] >= rgbData.length ||
-    location[1] < 0 ||
-    location[1] >= rgbData[0].length
-  ) {
-    throw new Error('location should point to a pixel within the rgbData')
-  }
+  checkLocation(rgbData, location)
 
   depthFirstFill(rgbData, location, targetColor, replacementColor)
 }
@@ -98,13 +105,8 @@ function breadthFirstFill(
 
   if (rgbData[currentLocation[0]][currentLocation[1]] === targetColor) {
     rgbData[currentLocation[0]][currentLocation[1]] = replacementColor
-
-    for (let i = 0; i < neighbors.length; i++) {
-      const x = currentLocation[0] + neighbors[i][0]
-      const y = currentLocation[1] + neighbors[i][1]
-      if (x >= 0 && x < rgbData.length && y >= 0 && y < rgbData[0].length) {
-        queue.push([x, y])
-      }
+    for (const neighborLocation of neighbors(rgbData, currentLocation)) {
+      queue.push(neighborLocation)
     }
   }
 }
@@ -120,13 +122,8 @@ function breadthFirstFill(
 function depthFirstFill(rgbData, location, targetColor, replacementColor) {
   if (rgbData[location[0]][location[1]] === targetColor) {
     rgbData[location[0]][location[1]] = replacementColor
-
-    for (let i = 0; i < neighbors.length; i++) {
-      const x = location[0] + neighbors[i][0]
-      const y = location[1] + neighbors[i][1]
-      if (x >= 0 && x < rgbData.length && y >= 0 && y < rgbData[0].length) {
-        depthFirstFill(rgbData, [x, y], targetColor, replacementColor)
-      }
+    for (const neighborLocation of neighbors(rgbData, location)) {
+      depthFirstFill(rgbData, neighborLocation, targetColor, replacementColor)
     }
   }
 }

Recursive/test/FloodFill.test.js

@@ -21,6 +21,19 @@ describe('FloodFill', () => {
   })
 })
 
+describe.each([breadthFirstSearch, depthFirstSearch])('%o', (floodFillFun) => {
+  it.each([
+    [1, -1],
+    [-1, 1],
+    [0, 7],
+    [7, 0]
+  ])('throws for start position [%i, %i]', (location) => {
+    expect(() =>
+      floodFillFun(generateTestRgbData(), location, green, orange)
+    ).toThrowError()
+  })
+})
+
 /**
  * Utility-function to test the function "breadthFirstSearch".
  *