import { describe, expect, it } from 'vitest'
import {
  formatINR, fyOf, fyShort, uuidv7, timestampOfUuidv7,
  formatDocNo, nextDocNo, rolloverForFy, seriesPrefix, assertGstDocNo,
  gstinCheckDigit, validateGstin, deriveSupply,
  type DocSeries,
} from '@sims/domain'

describe('money — Indian grouping', () => {
  it('groups lakh/crore style', () => {
    expect(formatINR(123_456_789)).toBe('₹12,34,567.89')
    expect(formatINR(100)).toBe('₹1.00')
    expect(formatINR(-4_50)).toBe('-₹4.50')
    expect(formatINR(99_999, { symbol: false })).toBe('999.99')
  })
})

describe('financial year (Day Begin idiom)', () => {
  it('splits at 1 April', () => {
    expect(fyOf('2026-03-31')).toBe('2025-26')
    expect(fyOf('2026-04-01')).toBe('2026-27')
    expect(fyShort('2026-27')).toBe('26')
  })
})

describe('uuidv7', () => {
  it('is well-formed and carries its timestamp', () => {
    const at = 1_750_000_000_000
    const id = uuidv7(at)
    expect(id).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-7[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/)
    expect(timestampOfUuidv7(id)).toBe(at)
  })
  it('sorts by creation time', () => {
    expect(uuidv7(1000) < uuidv7(2000)).toBe(true)
  })
})

describe('document series — offline per-counter numbering', () => {
  const series: DocSeries = {
    tenantId: 't', storeId: 's', counterId: 'c', docType: 'SALE',
    fy: '2026-27', prefix: seriesPrefix('ST1', 'C2', '26'), nextSeq: 123,
  }
  it('formats within the GST 16-char rule', () => {
    const { docNo, series: bumped } = nextDocNo(series)
    expect(docNo).toBe('ST1C2/26-000123')
    expect(docNo.length).toBeLessThanOrEqual(16)
    expect(bumped.nextSeq).toBe(124)
  })
  it('rejects numbers that break the GST rule', () => {
    expect(() => assertGstDocNo('THIS/PREFIX/IS/TOO/LONG-000001')).toThrow(/16-char/)
    expect(() => formatDocNo('BAD_CHAR', 1)).toThrow(/16-char/) // underscore not allowed
  })
  it('FY rollover restarts the sequence', () => {
    const rolled = rolloverForFy(series, '2027-28', seriesPrefix('ST1', 'C2', '27'))
    expect(rolled.nextSeq).toBe(1)
    expect(rolloverForFy(series, '2026-27', series.prefix)).toBe(series)
  })
})

describe('GSTIN validation', () => {
  const body = '32ABCDE1234F1Z'
  const valid = body + gstinCheckDigit(body)
  it('accepts a checksum-correct GSTIN and extracts the state', () => {
    expect(validateGstin(valid)).toEqual({ ok: true, stateCode: '32' })
  })
  it('rejects wrong checksum and wrong shape', () => {
    const flipped = body + (valid[14] === 'A' ? 'B' : 'A')
    expect(validateGstin(flipped).ok).toBe(false)
    expect(validateGstin('not-a-gstin').ok).toBe(false)
  })
})

describe('deriveSupply — place of supply at the counter', () => {
  const store = '32' // MegaMart's state
  const intraGstin = '32ABCDE1234F1Z' + gstinCheckDigit('32ABCDE1234F1Z')
  const interGstin = '27ABCDE1234F1Z' + gstinCheckDigit('27ABCDE1234F1Z')

  it('no GSTIN → B2C, place of supply is the store state (intra)', () => {
    expect(deriveSupply(undefined, store)).toMatchObject({ b2b: false, placeOfSupplyStateCode: '32', interState: false })
    // A walk-in with only a state on file is still B2C — place of supply stays the store.
    expect(deriveSupply({ stateCode: '27' }, store)).toMatchObject({ b2b: false, placeOfSupplyStateCode: '32', interState: false })
  })
  it('GSTIN in the same state → B2B intra (CGST/SGST)', () => {
    expect(deriveSupply({ gstin: intraGstin }, store)).toMatchObject({
      b2b: true, placeOfSupplyStateCode: '32', interState: false, buyerGstin: intraGstin,
    })
  })
  it('GSTIN in another state → B2B inter (IGST)', () => {
    expect(deriveSupply({ gstin: interGstin }, store)).toMatchObject({
      b2b: true, placeOfSupplyStateCode: '27', interState: true, buyerGstin: interGstin,
    })
  })
})