import type { Sub as SubInt } from "./Int/Sub";
import type { _AddTrailingZeroesToSameLength } from "./internal/_AddTrailingZeroesToSameLength";
import type { _Div10 } from "./internal/_Div10";
import type { _ReplaceAllCharsWithZero } from "./internal/_ReplaceAllCharsWithZero";
import type { _StrToNum } from "./internal/_StrToNum";
import type { Args, Fn } from "../HKT";

/**
 * Subtract two numbers.
 *
 * Sig: `(n: number, m: number) => number`
 */
export type Sub<N extends number, M extends number> =
  `${N}` extends `${infer NIntPart}.${infer NFracPart}` ?
    `${M}` extends `${infer MIntPart}.${infer MFracPart}` ?
      _Div10<
        SubInt<
          _StrToNum<`${NIntPart extends "0" ? "" : NIntPart}${_AddTrailingZeroesToSameLength<NFracPart, MFracPart>}`>,
          _StrToNum<`${MIntPart extends "0" ? "" : MIntPart}${_AddTrailingZeroesToSameLength<MFracPart, NFracPart>}`>
        >,
        _AddTrailingZeroesToSameLength<NFracPart, MFracPart>
      >
    : _Div10<
        SubInt<
          _StrToNum<`${NIntPart extends "0" ? "" : NIntPart}${NFracPart}`>,
          _StrToNum<`${M}${_ReplaceAllCharsWithZero<NFracPart>}`>
        >,
        NFracPart
      >
  : `${M}` extends `${infer MIntPart}.${infer MFracPart}` ?
    _Div10<
      SubInt<
        _StrToNum<`${N}${_ReplaceAllCharsWithZero<MFracPart>}`>,
        _StrToNum<`${MIntPart extends "0" ? "" : MIntPart}${MFracPart}`>
      >,
      MFracPart
    >
  : SubInt<N, M>;

/**
 * [Fn] Subtract two numbers.
 *
 * Sig: `(n: number, m: number) => number`
 */
export default interface SubFn extends Fn<[number, number], number> {
  def: ([n, m]: Args<this>) => Sub<typeof n, typeof m>;
}