feat: type utilites for unicode language id

src/locale.ts

@@ -0,0 +1,230 @@
+export interface UnicodeLocaleId {
+  lang: UnicodeLanguageId
+  extensions: Array<
+    UnicodeExtension | TransformedExtension | PuExtension | OtherExtension
+  >
+}
+
+export interface UnicodeLanguageId {
+  lang: string
+  script?: string
+  region?: string
+  variants: string[]
+}
+
+// -----
+
+type IsNever<T> = [T] extends [never] ? true : false
+type Split<S extends string, SEP extends string> = string extends S ? string[]
+  : S extends `${infer A}${SEP}${infer B}`
+    ? [A, ...(B extends '' ? [] : Split<B, SEP>)]
+  : SEP extends '' ? []
+  : [S]
+type Shift<T extends unknown[]> = T extends [unknown, ...infer U] ? U : never
+type First<T extends unknown[]> = T extends [infer A, ...infer rest] ? A : never
+type Last<T extends unknown[]> = [unknown, ...T][T['length']]
+type Length<T extends readonly unknown[]> = T['length']
+type IsEqual<X, Y> = (<T>() => T extends X ? 1 : 2) extends
+  (<T>() => T extends Y ? 1 : 2) ? true : false
+type Push<T extends unknown[], U> = [...T, U]
+type Includes<Value extends unknown[], Item> = IsEqual<Value[0], Item> extends
+  true ? true
+  : Value extends [Value[0], ...infer rest] ? Includes<rest, Item>
+  : false
+type UnionToIntersection<U> = (
+  U extends unknown ? (arg: U) => 0 : never
+) extends (arg: infer I) => 0 ? I
+  : never
+type LastInUnion<U> = UnionToIntersection<
+  U extends unknown ? (x: U) => 0 : never
+> extends (x: infer L) => 0 ? L
+  : never
+type UnionToTuple<U, Last = LastInUnion<U>> = [U] extends [never] ? []
+  : [...UnionToTuple<Exclude<U, Last>>, Last]
+type StrintToUnion<T extends string> = T extends `${infer Letter}${infer Rest}`
+  ? Letter | StrintToUnion<Rest>
+  : never
+type StringToTuple<T extends string> = UnionToTuple<StrintToUnion<T>>
+
+type Alphabets =
+  | 'a'
+  | 'b'
+  | 'c'
+  | 'd'
+  | 'e'
+  | 'f'
+  | 'g'
+  | 'h'
+  | 'i'
+  | 'j'
+  | 'k'
+  | 'l'
+  | 'm'
+  | 'n'
+  | 'o'
+  | 'p'
+  | 'q'
+  | 'r'
+  | 's'
+  | 'v'
+  | 'w'
+  | 'y'
+  | 'z'
+
+type Numbers = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
+
+type ParseUnicodeLanguageId<
+  T extends string,
+  S extends unknown[] = Split<T, '-'>,
+  Lang extends unknown[] = ParseLangSubtag<First<S>>,
+  Rest1 extends unknown[] = Shift<S>,
+  Script extends unknown[] = ParseScriptSubtag<First<Rest1>>,
+  Rest2 extends unknown[] = Shift<Rest1>,
+  Region extends unknown[] = ParseRegionSubtag<First<Rest2>>,
+  Rest3 extends unknown[] = Shift<Rest2>,
+  Variants extends { variants: string[]; error?: string } = ParseVariantsSubtag<
+    Rest3
+  >,
+> = [
+  {
+    lang: First<Lang>
+    script: First<Script>
+    region: First<Region>
+    variants: Variants['variants']
+  },
+  Last<Lang>,
+]
+
+type ParseLangSubtag<
+  T,
+  L = T extends string ? IsUnicodeLanguageSubtag<T> extends true ? [T, never]
+    : [never, 'Missing unicode language subtag']
+    : T extends 'root' ? ['root', never]
+    : [never, 'Malformed unicode language subtag'],
+> = L
+
+type IsUnicodeLanguageSubtag<T> = true
+
+/**
+ * Range of Unicode language subtag (EBNF: = alpha{2,3} | alpha{5,8};)
+ * https://unicode.org/reports/tr35/#unicode_language_subtag
+ */
+export type LangSubtagRange<
+  T extends unknown[],
+> = Includes<[2, 3, 5, 6, 7, 8], Length<T>> extends true ? true : false
+
+type _IsUnicodeLanguageSubtag<
+  T extends string,
+  Chars extends unknown[] = StringToTuple<T>,
+> = Length<Chars> extends 2 ? true : false
+
+type ParseScriptSubtag<
+  T,
+  S = T extends string ? IsUnicodeScriptSubtag<T> extends true ? [T, never]
+    : [never, 'error']
+    : [never, 'error'],
+> = S
+
+type IsUnicodeScriptSubtag<T> = true
+
+type ParseRegionSubtag<
+  T,
+  S = T extends string ? IsUnicodeRegionSubtag<T> extends true ? [T, never]
+    : [never, 'error']
+    : [never, 'error'],
+> = S
+
+type IsUnicodeRegionSubtag<T> = true
+
+type ParseVariantsSubtag<
+  T extends unknown[],
+  S extends { variants: string[]; error?: string } = _ParseVariantsSubtag<T>,
+> = S
+
+type _ParseVariantsSubtag<
+  T extends unknown[] = [],
+  Accumrator extends { variants: string[]; error?: string } = { variants: [] },
+  HasVariants = Length<T> extends 0 ? false : true,
+  Target = First<T>,
+  HasVariantSubTag = HasVariants extends true ? IsUnicodeVariantSubtag<Target>
+    : false,
+  Rest extends unknown[] = Shift<T>,
+  Variant = HasVariants extends true
+    ? HasVariantSubTag extends true ? Target : never
+    : never,
+  Duplicate = IsNever<Variant> extends false
+    ? Includes<Accumrator['variants'], Variant> extends true ? true
+    : false
+    : false,
+  VariantStr extends string = Variant extends string ? Variant : never,
+> = Accumrator['error'] extends string ? {
+    variants: [...Accumrator['variants']]
+    error: Accumrator['error']
+  }
+  : Duplicate extends true ? {
+      variants: [...Accumrator['variants']]
+      error: `Duplicate variant "${VariantStr}"`
+    }
+  : IsNever<VariantStr> extends true ? { variants: [...Accumrator['variants']] }
+  : _ParseVariantsSubtag<
+    Rest,
+    { variants: Push<Accumrator['variants'], VariantStr> }
+  >
+
+type IsUnicodeVariantSubtag<T> = true
+type _S = _ParseVariantsSubtag<['a', 'b', 'b', 'c']>
+
+type UnicodeLangId = ParseUnicodeLanguageId<'ja-Kana-JP-t-it-latn-it'>
+type id2 = ParseUnicodeLanguageId<''>
+
+// -----
+
+export type KV = [string, string] | [string]
+
+export interface Extension {
+  type: string
+}
+
+export interface UnicodeExtension extends Extension {
+  type: 'u'
+  keywords: KV[]
+  attributes: string[]
+}
+
+export interface TransformedExtension extends Extension {
+  type: 't'
+  fields: KV[]
+  lang?: UnicodeLanguageId
+}
+export interface PuExtension extends Extension {
+  type: 'x'
+  value: string
+}
+
+export interface OtherExtension extends Extension {
+  type:
+    | 'a'
+    | 'b'
+    | 'c'
+    | 'd'
+    | 'e'
+    | 'f'
+    | 'g'
+    | 'h'
+    | 'i'
+    | 'j'
+    | 'k'
+    | 'l'
+    | 'm'
+    | 'n'
+    | 'o'
+    | 'p'
+    | 'q'
+    | 'r'
+    | 's'
+    | 'v'
+    | 'w'
+    | 'y'
+    | 'z'
+  value: string
+}