add: LastIndexOf type

source/last-index-of.d.ts

@@ -0,0 +1,80 @@
+import type {GreaterThanOrEqual} from './greater-than-or-equal.d.ts';
+import type {ApplyDefaultOptions} from './internal/object.d.ts';
+import type {IsOptionalKeyOf} from './is-optional-key-of.d.ts';
+import type {Inc, Neg, IndexOfOptions} from './index-of.d.ts';
+import type {UnknownArray} from './unknown-array.d.ts';
+import type {IsAnyOrNever} from './internal/type.d.ts';
+import type {LiteralUnion} from './literal-union.d.ts';
+import type {GreaterThan} from './greater-than.d.ts';
+import type {IsEqual} from './is-equal.d.ts';
+
+type DefaultLastIndexOfOptions = {
+    ignoreOptionalModifier: false;
+    fromIndex: 0;
+}
+
+type IsLastOptional<T extends UnknownArray> =
+    T extends [...infer Rest, (infer _)?]
+        ? [...Rest] extends T
+            ? true
+            : false
+        : false;
+
+export type LastIndexOf<
+    Array_ extends UnknownArray, Item,
+    Options extends IndexOfOptions = {},
+> = IsAnyOrNever<Array_> extends true ? Array_
+    : _LastIndexOf<Array_, Item,
+        ApplyDefaultOptions<
+            IndexOfOptions,
+            DefaultLastIndexOfOptions,
+            Options
+        >
+    >;
+
+type _LastIndexOf<
+    Array_ extends UnknownArray, Item,
+    Options extends Required<IndexOfOptions>,
+    F_Index extends number[] = [],
+    B_Index extends number[] = [1],
+    T_Index extends number = never,
+> =
+    number extends Array_['length']
+        ? keyof Array_ & `${number}` extends never
+
+            ? Array_ extends readonly [...infer Rest, infer Last]
+                ? GreaterThan<B_Index['length'], Options['fromIndex']> extends true
+                    ? IsEqual<Last, Item> extends true ? Neg<B_Index>
+                        : _LastIndexOf<Rest, Item, Options, F_Index, Inc<B_Index>, T_Index>
+                    : _LastIndexOf<Rest, Item, Options, F_Index, Inc<B_Index>, T_Index>
+
+                : Array_ extends readonly [] ? T_Index
+                    : IsEqual<Array_[number], Item> extends false ? T_Index
+                        : LiteralUnion<F_Index['length'], number>
+
+            : Array_ extends readonly [(infer First)?, ...infer Rest]
+                ? IsEqual<First, Item> extends true
+                    ? _LastIndexOf<Rest, Item, Options, Inc<F_Index>, B_Index,
+                        F_Index['length'] | (
+                            Options['ignoreOptionalModifier'] extends true ? never
+                                : IsOptionalKeyOf<Array_, '0'> extends false ? never
+                                    : _LastIndexOf<Rest, Item, Options, Inc<F_Index>, B_Index, T_Index>)>
+                    : _LastIndexOf<Rest, Item, Options, Inc<F_Index>, B_Index, T_Index>
+                : never
+
+        : Array_ extends readonly [...infer Rest, (infer Last)?]
+            ? GreaterThanOrEqual<F_Index['length'], Options['fromIndex']> extends true
+                ? IsEqual<Last, Item> extends true
+                    ? Required<Rest>['length'] | (
+                        Options['ignoreOptionalModifier'] extends true ? never
+                            : IsLastOptional<Array_> extends false ? never
+                                : _LastIndexOf<Rest, Item, Options, Inc<F_Index>>)
+                    : _LastIndexOf<Rest, Item, Options, Inc<F_Index>>
+                : _LastIndexOf<Rest, Item, Options, Inc<F_Index>>
+            : never
+
+
+type T = LastIndexOf<[1, 3, 6, 6, ...10[], 8, 10, 4, 2, 4, 6], 4, {fromIndex: 0, ignoreOptionalModifier: false}>
+//    ^?
+
+export {};