import { describe, it, expect } from 'vitest';
import {
  parseDecimal,
  formatDecimal,
  addDecimals,
  compareDecimals,
  negateDecimal,
  subtractDecimals,
  multiplyDecimals,
  divideDecimals,
} from '../src/domain/decimal';


describe('parseDecimal', () => {
  it('parses positive integer', () => {
    expect(parseDecimal('123')).toEqual({ coefficient: 123n, scale: 0 });
  });

  it('parses negative integer', () => {
    expect(parseDecimal('-456')).toEqual({ coefficient: -456n, scale: 0 });
  });

  it('parses positive decimal', () => {
    expect(parseDecimal('12.34')).toEqual({ coefficient: 1234n, scale: 2 });
  });

  it('parses negative decimal', () => {
    expect(parseDecimal('-56.78')).toEqual({ coefficient: -5678n, scale: 2 });
  });

  it('parses zero', () => {
    expect(parseDecimal('0')).toEqual({ coefficient: 0n, scale: 0 });
  });

  it('parses -0 as zero', () => {
    expect(parseDecimal('-0')).toEqual({ coefficient: 0n, scale: 0 });
  });

  it('parses with commas', () => {
    expect(parseDecimal('1,234.56')).toEqual({ coefficient: 123456n, scale: 2 });
  });

  it('parses with leading/trailing whitespace', () => {
    expect(parseDecimal('  123.45  ')).toEqual({ coefficient: 12345n, scale: 2 });
  });

  it('parses large numbers', () => {
    expect(parseDecimal('99999999999999999.99')).toEqual({ coefficient: 9999999999999999999n, scale: 2 });
  });

  it('throws on empty string', () => {
    expect(() => parseDecimal('')).toThrow('Invalid decimal');
  });

  it('throws on non-numeric', () => {
    expect(() => parseDecimal('abc')).toThrow('Invalid decimal');
  });

  it('throws on double sign', () => {
    expect(() => parseDecimal('+-5')).toThrow('Invalid decimal');
  });
});

describe('formatDecimal', () => {
  it('formats integer', () => {
    expect(formatDecimal(123n, 0)).toBe('123');
  });

  it('formats negative integer', () => {
    expect(formatDecimal(-456n, 0)).toBe('-456');
  });

  it('formats decimal with scale', () => {
    expect(formatDecimal(1234n, 2)).toBe('12.34');
  });

  it('formats zero', () => {
    expect(formatDecimal(0n, 0)).toBe('0');
  });

  it('formats zero with scale', () => {
    expect(formatDecimal(0n, 2)).toBe('0');
  });

  it('strips trailing zeros', () => {
    expect(formatDecimal(1200n, 4)).toBe('0.12');
  });

  it('strips trailing zeros after decimal point', () => {
    expect(formatDecimal(1200n, 2)).toBe('12');
  });

  it('formats negative decimal', () => {
    expect(formatDecimal(-5678n, 2)).toBe('-56.78');
  });
});

describe('addDecimals', () => {
  it('adds two positive integers', () => {
    expect(addDecimals(['100', '200'])).toBe('300');
  });

  it('adds positive and negative', () => {
    expect(addDecimals(['100', '-100'])).toBe('0');
  });

  it('adds decimals with different scales', () => {
    expect(addDecimals(['1.5', '2.33'])).toBe('3.83');
  });

  it('handles empty array', () => {
    expect(addDecimals([])).toBe('0');
  });

  it('handles single value', () => {
    expect(addDecimals(['42'])).toBe('42');
  });

  it('adds multiple values', () => {
    expect(addDecimals(['10', '20', '30'])).toBe('60');
  });

  it('handles carry', () => {
    expect(addDecimals(['0.99', '0.01'])).toBe('1');
  });

  it('handles large numbers', () => {
    expect(addDecimals(['999999999', '1'])).toBe('1000000000');
  });
});

describe('compareDecimals', () => {
  it('returns 0 for equal values', () => {
    expect(compareDecimals('100', '100')).toBe(0);
  });

  it('returns 1 when a > b', () => {
    expect(compareDecimals('200', '100')).toBe(1);
  });

  it('returns -1 when a < b', () => {
    expect(compareDecimals('100', '200')).toBe(-1);
  });

  it('compares decimals correctly', () => {
    expect(compareDecimals('1.1', '1.01')).toBe(1);
  });

  it('compares negative numbers', () => {
    expect(compareDecimals('-100', '-200')).toBe(1);
  });

  it('compares zero', () => {
    expect(compareDecimals('0', '0')).toBe(0);
  });
});

describe('negateDecimal', () => {
  it('negates positive to negative', () => {
    expect(negateDecimal('100')).toBe('-100');
  });

  it('negates negative to positive', () => {
    expect(negateDecimal('-100')).toBe('100');
  });

  it('negates zero', () => {
    expect(negateDecimal('0')).toBe('0');
  });

  it('negates decimal', () => {
    expect(negateDecimal('12.34')).toBe('-12.34');
  });
});

describe('subtractDecimals', () => {
  it('subtracts two positive integers', () => {
    expect(subtractDecimals('300', '100')).toBe('200');
  });

  it('subtracts to negative', () => {
    expect(subtractDecimals('100', '300')).toBe('-200');
  });

  it('subtracts to zero', () => {
    expect(subtractDecimals('100', '100')).toBe('0');
  });

  it('subtracts decimals', () => {
    expect(subtractDecimals('3.5', '1.2')).toBe('2.3');
  });
});

describe('multiplyDecimals', () => {
  it('multiplies two integers', () => {
    expect(multiplyDecimals('10', '20')).toBe('200');
  });

  it('multiplies by zero', () => {
    expect(multiplyDecimals('100', '0')).toBe('0');
  });

  it('multiplies negative numbers', () => {
    expect(multiplyDecimals('-10', '20')).toBe('-200');
  });

  it('multiplies decimals', () => {
    expect(multiplyDecimals('1.5', '2')).toBe('3');
  });

  it('multiplies decimals with scale', () => {
    expect(multiplyDecimals('1.1', '1.1')).toBe('1.21');
  });
});

describe('divideDecimals', () => {
  it('divides integers', () => {
    expect(divideDecimals('10', '2')).toBe('5');
  });

  it('divides integers to decimal results', () => {
    expect(divideDecimals('5', '2')).toBe('2.5');
  });

  it('divides decimals where numerator has a scale', () => {
    expect(divideDecimals('10.0', '2.0')).toBe('5');
  });

  it('divides to recurring decimals with maxScale limit', () => {
    expect(divideDecimals('10', '3', 4)).toBe('3.3333');
  });

  it('throws on division by zero', () => {
    expect(() => divideDecimals('5', '0')).toThrow('除数不能为零');
  });
});