✨ Enable to calculate the number of indent

Author: takker99

is.ts

@@ -0,0 +1,10 @@
+// These code are based on https://deno.land/x/unknownutil@v1.1.0/is.ts
+
+export const isNone = (value: unknown): value is undefined | null =>
+  value === null || value === undefined;
+export const isString = (value: unknown): value is string =>
+  typeof value === "string";
+export const isNumber = (value: unknown): value is number =>
+  typeof value === "number";
+export const isArray = <T>(value: unknown): value is T[] =>
+  Array.isArray(value);

text.test.ts

@@ -0,0 +1,9 @@
+import { getIndentCount } from "./text.ts";
+import { assertStrictEquals } from "./deps/testing.ts";
+
+Deno.test("getIndentCount()", () => {
+  assertStrictEquals(getIndentCount("sample text "), 0);
+  assertStrictEquals(getIndentCount("  sample text "), 2);
+  assertStrictEquals(getIndentCount("　　 sample text"), 3);
+  assertStrictEquals(getIndentCount("\t \t　　sample text"), 5);
+});

text.ts

@@ -0,0 +1,29 @@
+import { isString } from "./is.ts";
+
+export const getIndentCount = (text: string): number =>
+  text.match(/^(\s*)/)?.[1]?.length ?? 0;
+
+/** 指定した行の配下にある行の数を返す
+ *
+ * @param index 指定したい行の行番号
+ * @param lines 行のリスト
+ */
+export function getIndentLineCount(
+  index: number,
+  lines: string[] | { text: string }[],
+): number {
+  const base = getIndentCount(getText(index, lines));
+  let count = 0;
+  while (
+    index + count + 1 < lines.length &&
+    (getIndentCount(getText(index + count + 1, lines))) > base
+  ) {
+    count++;
+  }
+  return count;
+}
+
+function getText(index: number, lines: string[] | { text: string }[]) {
+  const line = lines[index];
+  return isString(line) ? line : line.text;
+}