From 4ed75021ca30e8fb592744ee85bfb91dbc4f0e5a Mon Sep 17 00:00:00 2001
From: Adam Laycock <adam@arcath.net>
Date: Mon, 6 Dec 2021 15:35:55 +0000
Subject: [PATCH] feat: update createMap so that setRange can take a function

---
 src/functions/create-map.spec.ts | 14 ++++++++++++++
 src/functions/create-map.ts      | 14 +++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/functions/create-map.spec.ts b/src/functions/create-map.spec.ts
index 15259e1..e173cd1 100644
--- a/src/functions/create-map.spec.ts
+++ b/src/functions/create-map.spec.ts
@@ -19,5 +19,19 @@ describe('Create Map', () => {
     t2.setRange(2, 4, 2, 4, true)
 
     expect(t2.get(3, 4)).toBe(true)
+
+    const t3 = createMap(9, 9, 0)
+
+    t3.setRange(0, 2, 1, 1, v => {
+      return v + 1
+    })
+
+    t3.setRange(1, 1, 0, 2, v => {
+      return v + 1
+    })
+
+    expect(t3.get(0, 0)).toBe(0)
+    expect(t3.get(1, 1)).toBe(2)
+    expect(t3.get(0, 1)).toBe(1)
   })
 })
diff --git a/src/functions/create-map.ts b/src/functions/create-map.ts
index 6cdcbca..d1d7782 100644
--- a/src/functions/create-map.ts
+++ b/src/functions/create-map.ts
@@ -3,13 +3,13 @@ export interface Map<T> {
   get(x: number, y: number): T
   /** Set the value of X,Y to `value` */
   set(x: number, y: number, value: T): void
-  /** Set all the cells in the range to `value` */
+  /** Set all the cells in the range to `value` or pass a function that takes the current value as its only argument and returns a new value. */
   setRange(
     minX: number,
     maxX: number,
     minY: number,
     maxY: number,
-    value: T
+    value: T | ((current: T) => T)
   ): void
   /** The underlying map. Be warned this map maybe shifted so that 0 = minX etc... */
   map: T[][]
@@ -20,7 +20,7 @@ export interface Map<T> {
  *
  * @param maxX The maximum X value.
  * @param maxY The maximum Y value.
- * @param initialValue THe default value for all cells.
+ * @param initialValue The default value for all cells.
  * @param minX (Optional) The minimum X value, defaults to 0
  * @param minY (Optional) The minimum Y value, defaults to 0
  */
@@ -61,11 +61,15 @@ export const createMap = <T>(
     highX: number,
     lowY: number,
     highY: number,
-    value: T
+    value: T | ((current: T) => T)
   ) => {
     for (let y = lowY; y <= highY; y++) {
       for (let x = lowX; x <= highX; x++) {
-        set(x, y, value)
+        if (typeof value === 'function') {
+          set(x, y, (value as (current: T) => T)(get(x, y)))
+        } else {
+          set(x, y, value)
+        }
       }
     }
   }