From bcabb0dd78770055f756c1470c68a9b5c62d1efe Mon Sep 17 00:00:00 2001
From: kazuya kawaguchi <kawakazu80@gmail.com>
Date: Wed, 20 Sep 2023 12:44:48 +0900
Subject: [PATCH] feat: add `parseAcceptLanguage` (#2)

---
 deno/mod.ts        |  1 +
 mod.ts             |  3 +++
 src/index.ts       | 13 +++++++++++++
 test/index.test.ts | 33 ++++++++++++++++++++++++++++++++-
 4 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 mod.ts

diff --git a/deno/mod.ts b/deno/mod.ts
index fc5653f..d9e6183 100644
--- a/deno/mod.ts
+++ b/deno/mod.ts
@@ -1 +1,2 @@
+// TODO: we must change package structure for deno
 export * from '../src/index.ts'
diff --git a/mod.ts b/mod.ts
new file mode 100644
index 0000000..7f67017
--- /dev/null
+++ b/mod.ts
@@ -0,0 +1,3 @@
+import { isLocale } from 'https://deno.land/x/intlify_utils'
+
+console.log('isLocale', isLocale(new Intl.Locale('en-US')))
diff --git a/src/index.ts b/src/index.ts
index 0e9b1b3..50ecb93 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -11,3 +11,16 @@ const toTypeString = (value: unknown): string => objectToString.call(value)
 export function isLocale(val: unknown): val is Intl.Locale {
   return toTypeString(val) === '[object Intl.Locale]'
 }
+
+/**
+ * parse `accept-language` header string
+ *
+ * @param {string} value The accept-language header string
+ *
+ * @returns {Array<string>} The array of language tags, if `*` (any language) or empty string is detected, return an empty array.
+ */
+export function parseAcceptLanguage(value: string): string[] {
+  return value.split(',').map((tag) => tag.split(';')[0]).filter((tag) =>
+    !(tag === '*' || tag === '')
+  )
+}
diff --git a/test/index.test.ts b/test/index.test.ts
index ad5cc2a..e2930d0 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, test } from 'vitest'
-import { isLocale } from '../src/index.ts'
+import { isLocale, parseAcceptLanguage } from '../src/index.ts'
 
 describe('isLocale', () => {
   test('Locale instance', () => {
@@ -10,3 +10,34 @@ describe('isLocale', () => {
     expect(isLocale('en-US')).toBe(false)
   })
 })
+
+describe('parseAcceptLanguage', () => {
+  test('basic: ja,en-US;q=0.7,en;q=0.3', () => {
+    expect(parseAcceptLanguage('ja,en-US;q=0.7,en;q=0.3')).toEqual([
+      'ja',
+      'en-US',
+      'en',
+    ])
+  })
+
+  test('q-factor nothing: ja,en-US', () => {
+    expect(parseAcceptLanguage('ja,en-US')).toEqual([
+      'ja',
+      'en-US',
+    ])
+  })
+
+  test('single: ja', () => {
+    expect(parseAcceptLanguage('ja')).toEqual([
+      'ja',
+    ])
+  })
+
+  test('any language: *', () => {
+    expect(parseAcceptLanguage('*')).toEqual([])
+  })
+
+  test('empty: ""', () => {
+    expect(parseAcceptLanguage('')).toEqual([])
+  })
+})