feat(vanilla): add testing infrastructure and tests (NK-wjnczv)

1 files changed, 115 insertions, 0 deletions

diff --git a/vanilla/node_modules/@jridgewell/trace-mapping/src/binary-search.ts b/vanilla/node_modules/@jridgewell/trace-mapping/src/binary-search.ts
new file mode 100644
index 0000000..c1144ad
--- /dev/null
+++ b/vanilla/node_modules/@jridgewell/trace-mapping/src/binary-search.ts
@@ -0,0 +1,115 @@
+import type { SourceMapSegment, ReverseSegment } from './sourcemap-segment';
+import { COLUMN } from './sourcemap-segment';
+
+export type MemoState = {
+  lastKey: number;
+  lastNeedle: number;
+  lastIndex: number;
+};
+
+export let found = false;
+
+/**
+ * A binary search implementation that returns the index if a match is found.
+ * If no match is found, then the left-index (the index associated with the item that comes just
+ * before the desired index) is returned. To maintain proper sort order, a splice would happen at
+ * the next index:
+ *
+ * ```js
+ * const array = [1, 3];
+ * const needle = 2;
+ * const index = binarySearch(array, needle, (item, needle) => item - needle);
+ *
+ * assert.equal(index, 0);
+ * array.splice(index + 1, 0, needle);
+ * assert.deepEqual(array, [1, 2, 3]);
+ * ```
+ */
+export function binarySearch(
+  haystack: SourceMapSegment[] | ReverseSegment[],
+  needle: number,
+  low: number,
+  high: number,
+): number {
+  while (low <= high) {
+    const mid = low + ((high - low) >> 1);
+    const cmp = haystack[mid][COLUMN] - needle;
+
+    if (cmp === 0) {
+      found = true;
+      return mid;
+    }
+
+    if (cmp < 0) {
+      low = mid + 1;
+    } else {
+      high = mid - 1;
+    }
+  }
+
+  found = false;
+  return low - 1;
+}
+
+export function upperBound(
+  haystack: SourceMapSegment[] | ReverseSegment[],
+  needle: number,
+  index: number,
+): number {
+  for (let i = index + 1; i < haystack.length; index = i++) {
+    if (haystack[i][COLUMN] !== needle) break;
+  }
+  return index;
+}
+
+export function lowerBound(
+  haystack: SourceMapSegment[] | ReverseSegment[],
+  needle: number,
+  index: number,
+): number {
+  for (let i = index - 1; i >= 0; index = i--) {
+    if (haystack[i][COLUMN] !== needle) break;
+  }
+  return index;
+}
+
+export function memoizedState(): MemoState {
+  return {
+    lastKey: -1,
+    lastNeedle: -1,
+    lastIndex: -1,
+  };
+}
+
+/**
+ * This overly complicated beast is just to record the last tested line/column and the resulting
+ * index, allowing us to skip a few tests if mappings are monotonically increasing.
+ */
+export function memoizedBinarySearch(
+  haystack: SourceMapSegment[] | ReverseSegment[],
+  needle: number,
+  state: MemoState,
+  key: number,
+): number {
+  const { lastKey, lastNeedle, lastIndex } = state;
+
+  let low = 0;
+  let high = haystack.length - 1;
+  if (key === lastKey) {
+    if (needle === lastNeedle) {
+      found = lastIndex !== -1 && haystack[lastIndex][COLUMN] === needle;
+      return lastIndex;
+    }
+
+    if (needle >= lastNeedle) {
+      // lastIndex may be -1 if the previous needle was not found.
+      low = lastIndex === -1 ? 0 : lastIndex;
+    } else {
+      high = lastIndex;
+    }
+  }
+  state.lastKey = key;
+  state.lastNeedle = needle;
+
+  return (state.lastIndex = binarySearch(haystack, needle, low, high));
+}