1 files changed, 105 insertions, 0 deletions
diff --git a/packages/excalidraw/binaryheap.ts b/packages/excalidraw/binaryheap.ts
new file mode 100644
index 0000000..0bacadc
--- /dev/null
+++ b/packages/excalidraw/binaryheap.ts
@@ -0,0 +1,105 @@
+export default class BinaryHeap<T> {
+  private content: T[] = [];
+
+  constructor(private scoreFunction: (node: T) => number) {}
+
+  sinkDown(idx: number) {
+    const node = this.content[idx];
+    while (idx > 0) {
+      const parentN = ((idx + 1) >> 1) - 1;
+      const parent = this.content[parentN];
+      if (this.scoreFunction(node) < this.scoreFunction(parent)) {
+        this.content[parentN] = node;
+        this.content[idx] = parent;
+        idx = parentN; // TODO: Optimize
+      } else {
+        break;
+      }
+    }
+  }
+
+  bubbleUp(idx: number) {
+    const length = this.content.length;
+    const node = this.content[idx];
+    const score = this.scoreFunction(node);
+
+    while (true) {
+      const child2N = (idx + 1) << 1;
+      const child1N = child2N - 1;
+      let swap = null;
+      let child1Score = 0;
+
+      if (child1N < length) {
+        const child1 = this.content[child1N];
+        child1Score = this.scoreFunction(child1);
+        if (child1Score < score) {
+          swap = child1N;
+        }
+      }
+
+      if (child2N < length) {
+        const child2 = this.content[child2N];
+        const child2Score = this.scoreFunction(child2);
+        if (child2Score < (swap === null ? score : child1Score)) {
+          swap = child2N;
+        }
+      }
+
+      if (swap !== null) {
+        this.content[idx] = this.content[swap];
+        this.content[swap] = node;
+        idx = swap; // TODO: Optimize
+      } else {
+        break;
+      }
+    }
+  }
+
+  push(node: T) {
+    this.content.push(node);
+    this.sinkDown(this.content.length - 1);
+  }
+
+  pop(): T | null {
+    if (this.content.length === 0) {
+      return null;
+    }
+
+    const result = this.content[0];
+    const end = this.content.pop()!;
+
+    if (this.content.length > 0) {
+      this.content[0] = end;
+      this.bubbleUp(0);
+    }
+
+    return result;
+  }
+
+  remove(node: T) {
+    if (this.content.length === 0) {
+      return;
+    }
+
+    const i = this.content.indexOf(node);
+    const end = this.content.pop()!;
+
+    if (i < this.content.length) {
+      this.content[i] = end;
+
+      if (this.scoreFunction(end) < this.scoreFunction(node)) {
+        this.sinkDown(i);
+      } else {
+        this.bubbleUp(i);
+      }
+    }
+  }
+
+  size(): number {
+    return this.content.length;
+  }
+
+  rescoreElement(node: T) {
+    this.sinkDown(this.content.indexOf(node));
+  }
+}