From c2c5d7726ced85bc4d38e0bdec686b941f365036 Mon Sep 17 00:00:00 2001
From: Anthony Fu <anthonyfu117@hotmail.com>
Date: Wed, 8 May 2024 02:42:57 +0200
Subject: [PATCH] feat: add `unindent` function

---
 src/__snapshots__/string.test.ts.snap | 31 +++++++++++++++++++
 src/string.test.ts                    | 44 ++++++++++++++++++++++++++-
 src/string.ts                         | 39 ++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 src/__snapshots__/string.test.ts.snap

diff --git a/src/__snapshots__/string.test.ts.snap b/src/__snapshots__/string.test.ts.snap
new file mode 100644
index 0000000..7666bdc
--- /dev/null
+++ b/src/__snapshots__/string.test.ts.snap
@@ -0,0 +1,31 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`unindent > base 1`] = `
+"if (a) {
+  b()
+}"
+`;
+
+exports[`unindent > indent deep 1`] = `
+"    if (a) {
+    b()
+}"
+`;
+
+exports[`unindent > multi-start and end 1`] = `
+"    if (a) {
+  b()
+}"
+`;
+
+exports[`unindent > no start or end 1`] = `
+"if (a) {
+  b()
+}"
+`;
+
+exports[`unindent > with leading indent 1`] = `
+"    if (a) {
+  b()
+}"
+`;
diff --git a/src/string.test.ts b/src/string.test.ts
index fdc89de..6821e6d 100644
--- a/src/string.test.ts
+++ b/src/string.test.ts
@@ -1,5 +1,5 @@
 import { expect, it } from 'vitest'
-import { capitalize, ensurePrefix, ensureSuffix, slash, template } from './string'
+import { capitalize, ensurePrefix, ensureSuffix, slash, template, unindent } from './string'
 
 it('template', () => {
   expect(
@@ -119,3 +119,45 @@ it('capitalize', () => {
   expect(capitalize('āÁĂÀ')).toEqual('Āáăà')
   expect(capitalize('\a')).toEqual('A')
 })
+
+it('unindent', () => {
+  expect(
+    unindent`
+      if (a) {
+        b()
+      }
+    `,
+  ).toMatchSnapshot('base')
+
+  expect(
+    unindent`
+          if (a) {
+        b()
+      }
+    `,
+  ).toMatchSnapshot('with leading indent')
+
+  expect(
+    unindent`
+
+          if (a) {
+        b()
+      }
+
+    `,
+  ).toMatchSnapshot('multi-start and end')
+
+  expect(
+    unindent`if (a) {
+  b()
+}`,
+  ).toMatchSnapshot('no start or end')
+
+  expect(
+    unindent`
+                  if (a) {
+                  b()
+              }
+    `,
+  ).toMatchSnapshot('indent deep')
+})
diff --git a/src/string.ts b/src/string.ts
index 8d066b3..edde718 100644
--- a/src/string.ts
+++ b/src/string.ts
@@ -106,3 +106,42 @@ export function randomStr(size = 16, dict = urlAlphabet) {
 export function capitalize(str: string): string {
   return str[0].toUpperCase() + str.slice(1).toLowerCase()
 }
+
+const _reFullWs = /^\s*$/
+
+/**
+ * Remove common leading whitespace from a template string.
+ * Will also remove empty lines at the beginning and end.
+ * @category string
+ * @example
+ * ```ts
+ * const str = unindent`
+ *   if (a) {
+ *     b()
+ *   }
+ * `
+ */
+export function unindent(str: TemplateStringsArray | string) {
+  const lines = (typeof str === 'string' ? str : str[0]).split('\n')
+  const whitespaceLines = lines.map(line => _reFullWs.test(line))
+
+  const commonIndent = lines
+    .reduce((min, line, idx) => {
+      if (whitespaceLines[idx])
+        return min
+      const indent = line.match(/^\s*/)?.[0].length
+      return indent === undefined ? min : Math.min(min, indent)
+    }, Number.POSITIVE_INFINITY)
+
+  let emptyLinesHead = 0
+  while (emptyLinesHead < lines.length && whitespaceLines[emptyLinesHead])
+    emptyLinesHead++
+  let emptyLinesTail = 0
+  while (emptyLinesTail < lines.length && whitespaceLines[lines.length - emptyLinesTail - 1])
+    emptyLinesTail++
+
+  return lines
+    .slice(emptyLinesHead, lines.length - emptyLinesTail)
+    .map(line => line.slice(commonIndent))
+    .join('\n')
+}