Move first-click mines to random places

Fixes #106.

package.json

@@ -1,6 +1,6 @@
 {
     "name": "minesweeper",
-    "version": "0.86.9",
+    "version": "0.86.10",
     "description": "Just Minesweeper!",
     "author": "Florine W. Dekker",
     "browser": "dist/bundle.js",

src/main/js/Field.ts

@@ -168,20 +168,10 @@ export class Field {
 
         this.runUndoably(() => {
             const square = this.getSquare(coords);
-            if (square.hasMine) {
-                const target = this.squareList.find(it => !it.hasMine && it !== square)!;
-                this.runAction(swapAction(square, target));
-            }
+            const from = [square].concat(square.neighbors).filter(it => it.hasMine);
+            const to = this.squareList.filter(it => !it.hasMine && from.indexOf(it) < 0).slice(0, from.length);
 
-            square.neighbors
-                .filter(it => it.hasMine)
-                .forEach(it => {
-                    const target = this.squareList
-                        .find(it => !it.hasMine && it !== square && square.neighbors.indexOf(it) < 0);
-
-                    if (target !== undefined)
-                        this.runAction(swapAction(it, target));
-                });
+            from.slice(0, to.length).forEach(it => this.runAction(swapAction(it, this.random.pop(to)!)));
         });
     }
 

src/main/js/Random.ts

@@ -31,12 +31,24 @@ export class Random {
     /**
      * Returns a random element from `array`, or `undefined` if the array is empty.
      *
-     * @param array the array to return a random element from
+     * @param array the array to return a random element of
      */
-    pick<T>(array: T[]): T | undefined {
+    get<T>(array: T[]): T | undefined {
         return array[this.uniform(0, array.length)];
     }
 
+    /**
+     * Removes and returns a random element from `array`, or returns `undefined` if the array is empty.
+     *
+     * @param array the array to remove and return a random element of
+     */
+    pop<T>(array: T[]): T | undefined {
+        const idx = this.uniform(0, array.length);
+        const item = array[idx];
+        if (idx >= 0) array.splice(idx, 1);
+        return item;
+    }
+
     /**
      * Shuffles the elements of `array` in-place.
      *