accounted/lib/email/__tests__/reminder-templates.test.ts

import { describe, it, expect } from 'vitest'
import {
  generateReminderEmailHtml,
  generateReminderEmailText,
  generateReminderEmailSubject,
  calculateReminderAmounts,
  formatReminderTotalDue,
  REMINDER_FEE_CURRENCY,
  reminderPrincipal,
} from '../reminder-templates'
import { formatCurrency } from '@/lib/utils'
import { makeCustomer, makeInvoice, makeCompanySettings } from '@/tests/helpers'

const company = makeCompanySettings({ company_name: 'Acme AB' })
const customer = makeCustomer({ name: 'Erik Andersson', email: 'erik@example.se' })
const invoice = makeInvoice({
  invoice_number: 'F2026010',
  invoice_date: '2026-04-15',
  due_date: '2026-05-01',
  currency: 'SEK',
  total: 10_000,
})

const eurInvoice = makeInvoice({
  invoice_number: 'F2026011',
  invoice_date: '2026-04-15',
  due_date: '2026-05-01',
  currency: 'EUR',
  total: 1_000,
})

const baseData = {
  invoice,
  customer,
  company,
  reminderLevel: 1 as const,
  daysOverdue: 25,
  actionUrl: 'https://example.com/invoice-action/abc',
}

const eurBaseData = { ...baseData, invoice: eurInvoice }

describe('reminder email templates: surcharges', () => {
  it('renders dröjsmålsränta + påminnelseavgift in HTML when set', () => {
    const html = generateReminderEmailHtml({
      ...baseData,
      interestAmount: 86.3,
      interestRate: 0.105,
      interestFromDate: '2026-05-01',
      interestDays: 30,
      reminderFee: 60,
    })
    expect(html).toContain('Ursprungligt belopp:')
    expect(html).toContain('Dröjsmålsränta')
    expect(html).toContain('Påminnelseavgift:')
    expect(html).toContain('Att betala:')
    expect(html).toContain('10,5%') // rate display (sv-SE format)
    expect(html).toContain('30 dagar')
  })

  it('omits surcharge rows when both are zero', () => {
    const html = generateReminderEmailHtml({
      ...baseData,
      interestAmount: 0,
      interestRate: 0.105,
      interestFromDate: '2026-05-01',
      interestDays: 0,
      reminderFee: 0,
    })
    expect(html).not.toContain('Dröjsmålsränta')
    expect(html).not.toContain('Påminnelseavgift:')
    expect(html).toContain('Att betala:')
  })

  it('renders surcharges in plain text', () => {
    const text = generateReminderEmailText({
      ...baseData,
      interestAmount: 86.3,
      interestRate: 0.105,
      interestFromDate: '2026-05-01',
      interestDays: 30,
      reminderFee: 60,
    })
    expect(text).toContain('Ursprungligt belopp')
    expect(text).toContain('Dröjsmålsränta')
    expect(text).toContain('Påminnelseavgift')
    expect(text).toContain('Att betala')
  })

  it('subject includes surcharge note when surcharges apply', () => {
    const subject = generateReminderEmailSubject({
      ...baseData,
      interestAmount: 86.3,
      interestRate: 0.105,
      interestFromDate: '2026-05-01',
      interestDays: 30,
      reminderFee: 60,
    })
    expect(subject).toContain('F2026010')
    expect(subject).toContain('inkl. dröjsmålsränta')
  })

  it('subject is unchanged when no surcharges apply', () => {
    const subject = generateReminderEmailSubject({
      ...baseData,
      interestAmount: 0,
      interestRate: 0,
      interestFromDate: '2026-05-01',
      interestDays: 0,
      reminderFee: 0,
    })
    expect(subject).not.toContain('inkl. dröjsmålsränta')
    expect(subject).toContain('F2026010')
  })
})

describe('calculateReminderAmounts', () => {
  it('folds the fee into the total for a SEK invoice', () => {
    expect(
      calculateReminderAmounts({
        invoiceTotal: 10_000,
        interestAmount: 86.3,
        reminderFee: 60,
        currency: 'SEK',
      }),
    ).toEqual({ currency: 'SEK', totalDue: 10_146.3, feeDueSeparately: 0 })
  })

  it('keeps the SEK fee out of a foreign-currency total', () => {
    expect(
      calculateReminderAmounts({
        invoiceTotal: 1_000,
        interestAmount: 10,
        reminderFee: 60,
        currency: 'EUR',
      }),
    ).toEqual({ currency: 'EUR', totalDue: 1_010, feeDueSeparately: 60 })
  })

  it('treats a missing currency as SEK', () => {
    expect(
      calculateReminderAmounts({
        invoiceTotal: 100,
        interestAmount: 0,
        reminderFee: 60,
        currency: null,
      }),
    ).toEqual({ currency: 'SEK', totalDue: 160, feeDueSeparately: 0 })
  })

  it('rounds with Math.round(x * 100) / 100, not toFixed', () => {
    const amounts = calculateReminderAmounts({
      invoiceTotal: 1_000.005,
      interestAmount: 0.011,
      reminderFee: 0,
      currency: 'SEK',
    })
    expect(amounts.totalDue).toBe(1_000.02)
  })

  it('renders a split total as two amounts, never one mixed scalar', () => {
    const amounts = calculateReminderAmounts({
      invoiceTotal: 1_000,
      interestAmount: 10,
      reminderFee: 60,
      currency: 'EUR',
    })
    expect(formatReminderTotalDue(amounts)).toBe(
      `${formatCurrency(1_010, 'EUR')} + ${formatCurrency(60, 'SEK')}`,
    )
  })
})

describe('reminder email templates: statutory fee currency (Lag 1981:739)', () => {
  const eurSurcharges = {
    interestAmount: 10,
    interestRate: 0.105,
    interestFromDate: '2026-05-01',
    interestDays: 30,
    reminderFee: 60,
  }

  it('the fee is a SEK statute, not the invoice currency', () => {
    expect(REMINDER_FEE_CURRENCY).toBe('SEK')
  })

  it('never labels the 60 kr fee with the invoice currency in HTML', () => {
    const html = generateReminderEmailHtml({ ...eurBaseData, ...eurSurcharges })

    expect(
      html,
      'the påminnelseavgift is capped at 60 kr by Lag 1981:739; rendering it as 60 EUR demands roughly 690 kr',
    ).not.toContain(formatCurrency(60, 'EUR'))
    expect(html).toContain(formatCurrency(60, 'SEK'))
  })

  it('never sums a SEK fee into a EUR total in HTML', () => {
    const html = generateReminderEmailHtml({ ...eurBaseData, ...eurSurcharges })

    // 1000 EUR invoice + 10 EUR interest = 1010 EUR, plus 60 kr alongside.
    expect(html).toContain(formatCurrency(1_010, 'EUR'))
    expect(html).not.toContain(formatCurrency(1_070, 'EUR'))
    expect(html).toContain('Lag 1981:739')
  })

  it('never labels the fee with the invoice currency in plain text', () => {
    const text = generateReminderEmailText({ ...eurBaseData, ...eurSurcharges })

    expect(text).toContain(`Påminnelseavgift: ${formatCurrency(60, 'SEK')}`)
    expect(text).not.toContain(formatCurrency(60, 'EUR'))
    expect(text).toContain(
      `Att betala: ${formatCurrency(1_010, 'EUR')} + ${formatCurrency(60, 'SEK')}`,
    )
  })

  it('never quotes a mixed-currency amount in the subject', () => {
    const subject = generateReminderEmailSubject({ ...eurBaseData, ...eurSurcharges })

    expect(subject).not.toContain(formatCurrency(1_070, 'EUR'))
    expect(subject).toContain(
      `${formatCurrency(1_010, 'EUR')} + ${formatCurrency(60, 'SEK')}`,
    )
  })

  it('leaves a SEK invoice untouched: one currency, one total, no split note', () => {
    const data = {
      ...baseData,
      interestAmount: 86.3,
      interestRate: 0.105,
      interestFromDate: '2026-05-01',
      interestDays: 30,
      reminderFee: 60,
    }
    const html = generateReminderEmailHtml(data)
    const text = generateReminderEmailText(data)
    const subject = generateReminderEmailSubject(data)

    expect(html).toContain(formatCurrency(60, 'SEK'))
    expect(html).toContain(formatCurrency(10_146.3, 'SEK'))
    expect(html).not.toContain('Lag 1981:739')
    expect(text).toContain(`Påminnelseavgift: ${formatCurrency(60, 'SEK')}`)
    expect(text).toContain(`Att betala: ${formatCurrency(10_146.3, 'SEK')}`)
    expect(text).not.toContain(' + ')
    expect(subject).toContain(formatCurrency(10_146.3, 'SEK'))
  })

  it('does not append a SEK note when the fee is disabled on a EUR invoice', () => {
    const html = generateReminderEmailHtml({
      ...eurBaseData,
      ...eurSurcharges,
      reminderFee: 0,
    })
    expect(html).not.toContain('Lag 1981:739')
    expect(html).toContain(formatCurrency(1_010, 'EUR'))
  })
})

describe('reminder email templates: ROT/RUT-avdrag (fakturamodellen)', () => {
  // 12 500 total with a 3 750 ROT deduction: the customer was asked for
  // 8 750; the 3 750 is a claim on Skatteverket and must never be dunned.
  const rotInvoice = makeInvoice({
    invoice_number: 'F2026012',
    invoice_date: '2026-04-15',
    due_date: '2026-05-01',
    currency: 'SEK',
    total: 12_500,
    deduction_total: 3_750,
  } as Parameters<typeof makeInvoice>[0])
  const rotData = { ...baseData, invoice: rotInvoice, interestAmount: 0, interestRate: 0, interestFromDate: '2026-05-02', interestDays: 0, reminderFee: 0 }

  it('reminderPrincipal is the customer share', () => {
    expect(reminderPrincipal(rotInvoice, company)).toBe(8_750)
    expect(reminderPrincipal(invoice, company)).toBe(10_000)
  })

  it('HTML, text and subject never quote the pre-deduction total', () => {
    const html = generateReminderEmailHtml(rotData)
    const text = generateReminderEmailText(rotData)
    const subject = generateReminderEmailSubject({ ...rotData, reminderFee: 60 })
    for (const out of [html, text]) {
      expect(out).toContain(formatCurrency(8_750, 'SEK'))
      expect(out).not.toContain(formatCurrency(12_500, 'SEK'))
    }
    expect(subject).not.toContain(formatCurrency(12_500, 'SEK'))
  })

  it('folds interest and fee onto the customer share', () => {
    const amounts = calculateReminderAmounts({
      invoiceTotal: reminderPrincipal(rotInvoice, company),
      interestAmount: 12.5,
      reminderFee: 60,
      currency: 'SEK',
    })
    expect(amounts.totalDue).toBe(8_822.5)
  })
})