import { Unique } from './Unique.js';

/**
 * 获取函数的所有重载类型，返回一个包含所有重载签名的联合类型。
 * 这个类型解决了 TypeScript 中 `typeof` 操作符只能获取第一个重载签名的问题。
 *
 * @template T - 要获取重载的函数类型
 *
 * @example
 * ```typescript
 * // 基本用法
 * function parseInput(input: string): string;
 * function parseInput(input: number): number;
 * function parseInput(input: boolean): boolean;
 * function parseInput(input: any): any {
 *   // 实现
 * }
 *
 * // 使用 typeof 只能获取第一个重载
 * type FirstOverload = typeof parseInput;  // (input: string) => string
 *
 * // 使用 Overloads 获取所有重载
 * type AllOverloads = Overloads<typeof parseInput>;
 * // 结果：
 * // ((input: string) => string) |
 * // ((input: number) => number) |
 * // ((input: boolean) => boolean) |
 * // ((input: any) => any)
 *
 * // 实际应用场景
 * interface StringOrNumber {
 *   (value: string): string;
 *   (value: number): number;
 * }
 *
 * const fn: StringOrNumber = (value: any) => value;
 *
 * type FnOverloads = Overloads<typeof fn>;
 * // 结果：
 * // ((value: string) => string) | ((value: number) => number)
 *
 * // 高级用法：创建类型安全的调用函数
 * function callWithOverloads<T extends (...args: any[]) => any>(
 *   fn: T,
 *   ...args: Parameters<Overloads<T>>
 * ): ReturnType<Overloads<T>> {
 *   return fn(...args);
 * }
 *
 * // 可以安全地调用所有重载
 * const result1 = callWithOverloads(parseInput, "hello");  // string
 * const result2 = callWithOverloads(parseInput, 42);      // number
 * const result3 = callWithOverloads(parseInput, true);     // boolean
 *
 * // 内置方法示例
 * type ParseIntOverloads = Overloads<typeof parseInt>;
 * // 结果：
 * // ((string: string, radix?: number) => number) |
 * // ((string: string) => number)
 *
 * // 类方法重载
 * class Calculator {
 *   add(x: number, y: number): number;
 *   add(x: string, y: string): string;
 *   add(x: any, y: any): any {
 *     return x + y;
 *   }
 * }
 *
 * type AddOverloads = Overloads<Calculator['add']>;
 * // 结果：
 * // ((x: number, y: number) => number) |
 * // ((x: string, y: string) => string)
 *
 * // 实用工具类型
 * type OverloadParameters<T> = Parameters<Overloads<T>>;
 * type OverloadReturnType<T> = ReturnType<Overloads<T>>;
 * ```
 */

type Overloads<T> = Unique<T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
    (...args: infer A4): infer R4;
    (...args: infer A5): infer R5;
    (...args: infer A6): infer R6;
    (...args: infer A7): infer R7;
    (...args: infer A8): infer R8;
} ? [
    (...args: A1) => R1,
    ((...args: A2) => R2),
    ((...args: A3) => R3),
    ((...args: A4) => R4),
    ((...args: A5) => R5),
    ((...args: A6) => R6),
    ((...args: A7) => R7),
    ((...args: A8) => R8)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
    (...args: infer A4): infer R4;
    (...args: infer A5): infer R5;
    (...args: infer A6): infer R6;
    (...args: infer A7): infer R7;
} ? [
    (...args: A1) => R1,
    ((...args: A2) => R2),
    ((...args: A3) => R3),
    ((...args: A4) => R4),
    ((...args: A5) => R5),
    ((...args: A6) => R6),
    ((...args: A7) => R7)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
    (...args: infer A4): infer R4;
    (...args: infer A5): infer R5;
    (...args: infer A6): infer R6;
} ? [
    (...args: A1) => R1,
    ((...args: A2) => R2),
    ((...args: A3) => R3),
    ((...args: A4) => R4),
    ((...args: A5) => R5),
    ((...args: A6) => R6)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
    (...args: infer A4): infer R4;
    (...args: infer A5): infer R5;
} ? [
    (...args: A1) => R1,
    ((...args: A2) => R2),
    ((...args: A3) => R3),
    ((...args: A4) => R4),
    ((...args: A5) => R5)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
    (...args: infer A4): infer R4;
} ? [
    (...args: A1) => R1,
    ((...args: A2) => R2),
    ((...args: A3) => R3),
    ((...args: A4) => R4)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
    (...args: infer A3): infer R3;
} ? [
    ((...args: A1) => R1),
    ((...args: A2) => R2),
    ((...args: A3) => R3)
] : T extends {
    (...args: infer A1): infer R1;
    (...args: infer A2): infer R2;
} ? [
    ((...args: A1) => R1),
    ((...args: A2) => R2)
] : T extends {
    (...args: infer A1): infer R1;
} ? [
    (...args: A1) => R1
] : [
    T
]>;

export type { Overloads };