accounted/lib/email/reminder-templates.ts

import type { Invoice, Customer, CompanySettings, ReminderTextOverrides } from '@/types'
import { formatCurrency, formatDate, getCompanyDisplayName, getCompanyPrimaryName } from '@/lib/utils'
import { getAmountToPay } from '@/lib/invoices/rounding'
import { companyWithInvoicePaymentAccount } from '@/lib/invoices/payment-accounts'
import { applyPlaceholders, escapeHtml, sanitizeSubjectLine } from './user-text'

/**
 * What the customer was asked to pay on the original invoice: the öre-rounded
 * "Att betala" minus any ROT/RUT-avdrag (fakturamodellen: the deduction is a
 * claim on Skatteverket, never on the customer). Reminders, dröjsmålsränta and
 * the amount-to-pay line must all start from this figure, not invoice.total,
 * or a privatperson is dunned for the SKV share and charged interest on it.
 */
export function reminderPrincipal(invoice: Invoice, company: CompanySettings): number {
  return getAmountToPay(invoice, company).toPay
}

export interface ReminderEmailData {
  invoice: Invoice
  customer: Customer
  company: CompanySettings
  reminderLevel: 1 | 2 | 3
  daysOverdue: number
  actionUrl: string // URL for customer to mark as paid or dispute
  // Dröjsmålsränta + lagstadgad påminnelseavgift (Räntelagen §6, Lag 1981:739).
  // When the reminder is generated by the cron, these are computed and persisted
  // on the invoice_reminders row and then passed in here.
  //
  // interestAmount is a share of the invoice total, so it carries the INVOICE
  // currency. reminderFee is a fixed statutory krona amount and always carries
  // SEK (see REMINDER_FEE_CURRENCY). The two are deliberately not summed here:
  // the amount to pay is derived per currency by calculateReminderAmounts().
  interestAmount: number
  interestRate: number    // annual rate as decimal (0.105 = 10.5%)
  interestFromDate: string
  interestDays: number
  reminderFee: number     // always SEK, never the invoice currency
}

/**
 * The lagstadgad påminnelseavgift is a Swedish-krona statute: Lag (1981:739) om
 * ersättning för inkassokostnader m.m. 2 §, with the amount fixed at 60 kr by
 * förordning (1981:1057) 1 §. There is no conversion rule for a foreign-currency
 * claim, and Accounted books the fee 1510/3990 in SEK regardless of the invoice
 * currency (lib/bookkeeping/reminder-fee-entries.ts).
 *
 * So the fee is always quoted in SEK. Rendering "60" with the invoice's currency
 * code would demand roughly ten times the statutory amount from a EUR customer
 * and would not match the receivable recorded in the books.
 */
export const REMINDER_FEE_CURRENCY = 'SEK'

export interface ReminderAmounts {
  /** Invoice currency (uppercased ISO code). Carries the invoice total + interest. */
  currency: string
  /** invoice.total + dröjsmålsränta, plus the fee only when the invoice is itself in SEK. */
  totalDue: number
  /**
   * The påminnelseavgift in SEK when the invoice is in another currency, so it
   * has to be demanded alongside rather than inside `totalDue`. 0 when the fee
   * is already folded into `totalDue`.
   */
  feeDueSeparately: number
}

/**
 * Split the amount to pay per currency. Never returns a single scalar that mixes
 * a foreign invoice currency with the SEK statutory fee.
 */
export function calculateReminderAmounts(input: {
  invoiceTotal: number
  interestAmount: number
  reminderFee: number
  currency?: string | null
}): ReminderAmounts {
  const currency = (input.currency || REMINDER_FEE_CURRENCY).toUpperCase()
  const feeSharesInvoiceCurrency = currency === REMINDER_FEE_CURRENCY
  const fee = input.reminderFee > 0 ? Math.round(input.reminderFee * 100) / 100 : 0

  const totalDue =
    Math.round(
      (input.invoiceTotal + input.interestAmount + (feeSharesInvoiceCurrency ? fee : 0)) * 100,
    ) / 100

  return {
    currency,
    totalDue,
    feeDueSeparately: feeSharesInvoiceCurrency ? 0 : fee,
  }
}

/**
 * Render the amount to pay. When the statutory fee is in a different currency
 * than the invoice it is appended as its own amount ("1 010,00 € + 60 kr")
 * instead of being folded into a misleading single figure.
 */
export function formatReminderTotalDue(amounts: ReminderAmounts): string {
  const base = formatCurrency(amounts.totalDue, amounts.currency)
  if (amounts.feeDueSeparately <= 0) {
    return base
  }
  return `${base} + ${formatCurrency(amounts.feeDueSeparately, REMINDER_FEE_CURRENCY)}`
}

/** Shown whenever a SEK fee rides along with a foreign-currency invoice. */
export const REMINDER_FEE_CURRENCY_NOTE =
  'Påminnelseavgiften är lagstadgad (Lag 1981:739) och anges i svenska kronor. '
  + 'Den räknas inte om till fakturans valuta utan betalas som ett separat belopp i SEK.'

// Reminder level configurations
const REMINDER_CONFIG = {
  1: {
    title: 'Vänlig påminnelse',
    tone: 'friendly',
    daysAfterDue: 15
  },
  2: {
    title: 'Andra påminnelsen',
    tone: 'firm',
    daysAfterDue: 30
  },
  3: {
    title: 'Slutlig påminnelse',
    tone: 'urgent',
    daysAfterDue: 45
  }
} as const

export type ReminderLevelKey = 'level_1' | 'level_2' | 'level_3'

function levelKey(reminderLevel: 1 | 2 | 3): ReminderLevelKey {
  return `level_${reminderLevel}` as ReminderLevelKey
}

// Placeholder keys available in company-editable reminder texts
// (company_settings.reminder_text_overrides). Rendered as a legend in the
// settings UI; kept here rather than in messages/*.json because ICU message
// syntax treats literal braces as interpolation.
export const REMINDER_EMAIL_PLACEHOLDER_KEYS = [
  'fakturanummer',
  'kundnamn',
  'förnamn',
  'företag',
  'fakturadatum',
  'förfallodatum',
  'belopp',
  'dagar',
] as const

/**
 * Default subject/body per reminder level, in placeholder-pattern form.
 * Single source of truth: the stock mail renders these same patterns through
 * the same substitution pipeline as company overrides, so the settings-UI
 * prefill is exactly what goes out and cannot drift from the send path.
 *
 * Level 3 is deliberately an inkassovarning (final notice before collection),
 * as Swedish practice expects: it names the 8-day window and that the claim
 * is handed to inkasso with added statutory costs (lag 1981:739). TEXT only:
 * fee and interest math live in the reminder processor and are unaffected by
 * anything here or in company overrides.
 *
 * The stock subject additionally gets ' (inkl. dröjsmålsränta)' appended when
 * surcharges apply (see generateReminderEmailSubject); an override replaces
 * the whole line and gets no automatic suffix.
 */
export const REMINDER_EMAIL_DEFAULT_TEXTS: Record<
  ReminderLevelKey,
  { subject: string; body: string }
> = {
  level_1: {
    subject: 'Vänlig påminnelse: Faktura {fakturanummer} - {belopp}',
    body:
      'Vi vill påminna dig om att faktura {fakturanummer} förföll till betalning den {förfallodatum}. '
      + 'Om du redan har betalat kan du bortse från denna påminnelse.',
  },
  level_2: {
    subject: 'Andra påminnelsen: Faktura {fakturanummer} - {belopp}',
    body:
      'Trots vår tidigare påminnelse har vi ännu inte mottagit betalning för faktura {fakturanummer} '
      + 'som förföll den {förfallodatum}.\n\n'
      + 'Vi ber dig vänligen att omgående reglera detta belopp för att undvika ytterligare åtgärder.',
  },
  level_3: {
    subject: 'Slutlig påminnelse: Faktura {fakturanummer} - {belopp}',
    body:
      'Detta är en slutlig påminnelse och inkassovarning gällande faktura {fakturanummer}.\n\n'
      + 'Fakturan förföll till betalning den {förfallodatum} och vi har trots tidigare påminnelser '
      + 'ännu inte mottagit din betalning.\n\n'
      + 'Om full betalning inte har kommit oss tillhanda inom 8 dagar från detta meddelande '
      + 'överlämnas fordran till inkasso, vilket medför ytterligare kostnader för dig enligt '
      + 'lag (1981:739) om ersättning för inkassokostnader m.m.',
  },
}

// Values for the fixed placeholder set. {belopp} is the amount to pay incl.
// surcharges via formatReminderTotalDue, so a foreign-currency invoice with a
// SEK fee renders the two-amount form here too, never one mixed scalar.
function buildReminderPlaceholderValues(data: ReminderEmailData): Record<string, string> {
  const { invoice, customer, company, daysOverdue, interestAmount, reminderFee } = data
  const fullName = (customer.name || '').trim()
  const amounts = calculateReminderAmounts({
    invoiceTotal: reminderPrincipal(invoice, company),
    interestAmount,
    reminderFee,
    currency: invoice.currency,
  })
  return {
    fakturanummer: invoice.invoice_number ?? '',
    kundnamn: fullName,
    förnamn: fullName ? fullName.split(' ')[0] : '',
    företag: getCompanyPrimaryName(company),
    fakturadatum: formatDate(invoice.invoice_date),
    förfallodatum: formatDate(invoice.due_date),
    belopp: formatReminderTotalDue(amounts),
    dagar: String(daysOverdue),
  }
}

interface ResolvedReminderTexts {
  subject?: string
  body?: string
}

// Resolves the company's custom reminder texts for one level. Per-field
// fallback: missing / non-string / whitespace-only values return undefined
// and the caller renders the default pattern instead. Returns RAW substituted
// strings: escaping is the caller's job per output variant (HTML vs text vs
// subject). Defensive typeof checks: rows can be written outside Zod
// (scripts, SQL).
function resolveReminderTexts(
  company: CompanySettings,
  reminderLevel: 1 | 2 | 3,
  values: Record<string, string>,
): ResolvedReminderTexts {
  const overrides: ReminderTextOverrides | null | undefined = company.reminder_text_overrides
  const levelTexts =
    overrides && typeof overrides === 'object' ? overrides[levelKey(reminderLevel)] : undefined
  if (!levelTexts || typeof levelTexts !== 'object') return {}
  const pick = (v: unknown): string | undefined =>
    typeof v === 'string' && v.trim() !== '' ? applyPlaceholders(v.trim(), values) : undefined
  return {
    subject: pick(levelTexts.subject),
    body: pick(levelTexts.body),
  }
}

// Effective body for one level: override if present, else the default
// pattern, both substituted through the same pipeline.
function resolveReminderBody(data: ReminderEmailData): string {
  const values = buildReminderPlaceholderValues(data)
  const custom = resolveReminderTexts(data.company, data.reminderLevel, values)
  return (
    custom.body
    ?? applyPlaceholders(REMINDER_EMAIL_DEFAULT_TEXTS[levelKey(data.reminderLevel)].body, values)
  )
}

// Blank-line separated paragraphs -> <p> blocks; single newlines -> <br>.
// Escape FIRST so user-authored overrides cannot inject markup. The final
// level's opening paragraph keeps the red emphasis regardless of override:
// the inkassovarning must not look like a routine note.
function reminderBodyToHtml(body: string, reminderLevel: 1 | 2 | 3): string {
  return body
    .split(/(?:\r?\n){2,}/)
    .map((paragraph, index) => {
      const emphasis =
        reminderLevel === 3 && index === 0 ? ' color: #dc2626; font-weight: 500;' : ''
      const html = escapeHtml(paragraph).replace(/\r\n|\r|\n/g, '<br>')
      return `<p style="margin: 0 0 15px 0;${emphasis}">${html}</p>`
    })
    .join('\n        ')
}

/**
 * Generate HTML email for payment reminder
 */
export function generateReminderEmailHtml(data: ReminderEmailData): string {
  const {
    invoice,
    customer,
    reminderLevel,
    daysOverdue,
    actionUrl,
    interestAmount,
    interestRate,
    interestDays,
    reminderFee,
  } = data
  // Payment details follow the invoice currency, same as the invoice email
  // and PDF: a EUR reminder must never print the SEK account's IBAN.
  const company = companyWithInvoicePaymentAccount(data.company, invoice.currency)
  const config = REMINDER_CONFIG[reminderLevel]
  const interestRatePercent = (interestRate * 100).toLocaleString('sv-SE', {
    minimumFractionDigits: 0,
    maximumFractionDigits: 2,
  })
  const hasInterest = interestAmount > 0
  const hasFee = reminderFee > 0
  const hasSurcharges = hasInterest || hasFee
  const amounts = calculateReminderAmounts({
    invoiceTotal: reminderPrincipal(invoice, company),
    interestAmount,
    reminderFee,
    currency: invoice.currency,
  })
  const feeInOtherCurrency = amounts.feeDueSeparately > 0

  // Different styling based on urgency
  const headerColor = reminderLevel === 3 ? '#dc2626' : reminderLevel === 2 ? '#ea580c' : '#2563eb'
  const buttonColor = reminderLevel === 3 ? '#dc2626' : reminderLevel === 2 ? '#ea580c' : '#2563eb'

  return `
<!DOCTYPE html>
<html lang="sv">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>${config.title} - Faktura ${invoice.invoice_number}</title>
</head>
<body style="margin: 0; padding: 0; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif; line-height: 1.6; color: #333; background-color: #f9fafb;">
  <div style="max-width: 600px; margin: 0 auto; padding: 40px 20px;">
    <div style="background: white; border-radius: 12px; padding: 40px; box-shadow: 0 1px 3px rgba(0,0,0,0.1);">
      <!-- Header -->
      <div style="text-align: center; margin-bottom: 30px;">
        <div style="display: inline-block; background: ${headerColor}15; color: ${headerColor}; padding: 8px 16px; border-radius: 20px; font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.5px;">
          ${config.title}
        </div>
      </div>

      <!-- Title -->
      <h1 style="margin: 0 0 20px 0; font-size: 22px; font-weight: 600; color: #111; text-align: center;">
        Faktura ${invoice.invoice_number} förföll för ${daysOverdue} dagar sedan
      </h1>

      <!-- Greeting and Message -->
      <div style="margin-bottom: 30px;">
        <p style="margin: 0 0 15px 0;">
          Hej${customer.name ? ` ${customer.name.split(' ')[0]}` : ''},
        </p>

        ${reminderBodyToHtml(resolveReminderBody(data), reminderLevel)}
      </div>

      <!-- Invoice Summary Box -->
      <div style="background: #f8f9fa; border-radius: 8px; padding: 25px; margin-bottom: 30px; border-left: 4px solid ${headerColor};">
        <table style="width: 100%; border-collapse: collapse;">
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">Fakturanummer:</td>
            <td style="padding: 8px 0; text-align: right; font-weight: 500;">${invoice.invoice_number}</td>
          </tr>
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">Fakturadatum:</td>
            <td style="padding: 8px 0; text-align: right;">${formatDate(invoice.invoice_date)}</td>
          </tr>
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">Förfallodatum:</td>
            <td style="padding: 8px 0; text-align: right; color: #dc2626; font-weight: 500;">
              ${formatDate(invoice.due_date)}
            </td>
          </tr>
          <tr>
            <td colspan="2" style="padding: 15px 0 8px 0; border-top: 1px solid #e5e7eb;"></td>
          </tr>
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">Ursprungligt belopp:</td>
            <td style="padding: 8px 0; text-align: right; font-weight: 500;">${formatCurrency(reminderPrincipal(invoice, company), invoice.currency)}</td>
          </tr>
          ${hasInterest ? `
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">
              Dröjsmålsränta (${interestRatePercent}% per år, ${interestDays} dagar):
            </td>
            <td style="padding: 8px 0; text-align: right; font-weight: 500;">${formatCurrency(interestAmount, invoice.currency)}</td>
          </tr>
          ` : ''}
          ${hasFee ? `
          <tr>
            <td style="padding: 8px 0; color: #666; font-size: 14px;">Påminnelseavgift:</td>
            <td style="padding: 8px 0; text-align: right; font-weight: 500;">${formatCurrency(reminderFee, REMINDER_FEE_CURRENCY)}</td>
          </tr>
          ` : ''}
          ${hasSurcharges ? `
          <tr>
            <td colspan="2" style="padding: 12px 0 8px 0; border-top: 1px solid #e5e7eb;"></td>
          </tr>
          ` : ''}
          <tr>
            <td style="padding: 8px 0; font-size: 18px; font-weight: 600;">Att betala:</td>
            <td style="padding: 8px 0; text-align: right; font-size: 18px; font-weight: 600; color: ${headerColor};">
              ${formatReminderTotalDue(amounts)}
            </td>
          </tr>
          ${feeInOtherCurrency ? `
          <tr>
            <td colspan="2" style="padding: 10px 0 0 0; color: #666; font-size: 12px; line-height: 1.5;">
              ${REMINDER_FEE_CURRENCY_NOTE}
            </td>
          </tr>
          ` : ''}
        </table>
      </div>

      <!-- Payment Details -->
      <div style="margin-bottom: 30px;">
        <h2 style="margin: 0 0 15px 0; font-size: 16px; font-weight: 600; color: #111;">
          Betalningsinformation
        </h2>
        <table style="width: 100%; border-collapse: collapse;">
          ${company.bank_name ? `
          <tr>
            <td style="padding: 6px 0; color: #666; font-size: 14px; width: 140px;">Bank:</td>
            <td style="padding: 6px 0;">${company.bank_name}</td>
          </tr>
          ` : ''}
          ${company.clearing_number && company.account_number ? `
          <tr>
            <td style="padding: 6px 0; color: #666; font-size: 14px;">Kontonummer:</td>
            <td style="padding: 6px 0;">${company.clearing_number}-${company.account_number}</td>
          </tr>
          ` : ''}
          ${company.iban ? `
          <tr>
            <td style="padding: 6px 0; color: #666; font-size: 14px;">IBAN:</td>
            <td style="padding: 6px 0;">${company.iban}</td>
          </tr>
          ` : ''}
          ${company.bic ? `
          <tr>
            <td style="padding: 6px 0; color: #666; font-size: 14px;">BIC/SWIFT:</td>
            <td style="padding: 6px 0;">${company.bic}</td>
          </tr>
          ` : ''}
          <tr>
            <td style="padding: 6px 0; color: #666; font-size: 14px;">Meddelande:</td>
            <td style="padding: 6px 0; font-weight: 500;">${invoice.invoice_number}</td>
          </tr>
        </table>
      </div>

      <!-- Action Buttons -->
      <div style="text-align: center; margin-bottom: 30px;">
        <p style="margin: 0 0 20px 0; color: #666; font-size: 14px;">
          Har du redan betalat eller har frågor om fakturan?
        </p>
        <a href="${actionUrl}" style="display: inline-block; background: ${buttonColor}; color: white; padding: 14px 28px; border-radius: 8px; text-decoration: none; font-weight: 500; font-size: 14px;">
          Hantera faktura
        </a>
      </div>

      <!-- Footer -->
      <div style="padding-top: 20px; border-top: 1px solid #e5e7eb;">
        <p style="margin: 0 0 10px 0; color: #666; font-size: 14px;">
          Har du frågor? Svara direkt på detta mejl så hjälper vi dig.
        </p>
        <p style="margin: 0; color: #666; font-size: 14px;">
          Med vänliga hälsningar,<br>
          <strong>${getCompanyPrimaryName(company)}</strong>
        </p>
        ${company.org_number ? `
        <p style="margin: 10px 0 0 0; color: #999; font-size: 12px;">
          Org.nr: ${company.org_number}
          ${company.vat_number ? ` | VAT: ${company.vat_number}` : ''}
        </p>
        ` : ''}
      </div>
    </div>

    <!-- Unsubscribe note -->
    <p style="text-align: center; margin-top: 20px; color: #999; font-size: 12px;">
      Detta är ett automatiskt meddelande angående en obetald faktura.
    </p>
  </div>
</body>
</html>
`
}

/**
 * Generate plain text email for payment reminder
 */
export function generateReminderEmailText(data: ReminderEmailData): string {
  const {
    invoice,
    customer,
    reminderLevel,
    daysOverdue,
    actionUrl,
    interestAmount,
    interestRate,
    interestDays,
    reminderFee,
  } = data
  // Payment details follow the invoice currency, same as the invoice email
  // and PDF: a EUR reminder must never print the SEK account's IBAN.
  const company = companyWithInvoicePaymentAccount(data.company, invoice.currency)
  const config = REMINDER_CONFIG[reminderLevel]
  const interestRatePercent = (interestRate * 100).toLocaleString('sv-SE', {
    minimumFractionDigits: 0,
    maximumFractionDigits: 2,
  })
  const hasInterest = interestAmount > 0
  const hasFee = reminderFee > 0
  const amounts = calculateReminderAmounts({
    invoiceTotal: reminderPrincipal(invoice, company),
    interestAmount,
    reminderFee,
    currency: invoice.currency,
  })

  let text = `${config.title.toUpperCase()}\n`
  text += `Faktura ${invoice.invoice_number} förföll för ${daysOverdue} dagar sedan\n`
  text += `=`.repeat(50) + `\n\n`

  text += `Hej${customer.name ? ` ${customer.name.split(' ')[0]}` : ''},\n\n`

  text += `${resolveReminderBody(data)}\n\n`

  text += `Fakturasammanfattning:\n`
  text += `-`.repeat(30) + `\n`
  text += `Fakturanummer: ${invoice.invoice_number}\n`
  text += `Fakturadatum: ${formatDate(invoice.invoice_date)}\n`
  text += `Förfallodatum: ${formatDate(invoice.due_date)}\n`
  text += `Ursprungligt belopp: ${formatCurrency(reminderPrincipal(invoice, company), invoice.currency)}\n`
  if (hasInterest) {
    text += `Dröjsmålsränta (${interestRatePercent}% per år, ${interestDays} dagar): ${formatCurrency(interestAmount, invoice.currency)}\n`
  }
  if (hasFee) {
    text += `Påminnelseavgift: ${formatCurrency(reminderFee, REMINDER_FEE_CURRENCY)}\n`
  }
  text += `Att betala: ${formatReminderTotalDue(amounts)}\n`
  text += `-`.repeat(30) + `\n`
  if (amounts.feeDueSeparately > 0) {
    text += `${REMINDER_FEE_CURRENCY_NOTE}\n`
  }
  text += `\n`

  text += `Betalningsinformation:\n`
  if (company.bank_name) text += `Bank: ${company.bank_name}\n`
  if (company.clearing_number && company.account_number) {
    text += `Kontonummer: ${company.clearing_number}-${company.account_number}\n`
  }
  if (company.iban) text += `IBAN: ${company.iban}\n`
  if (company.bic) text += `BIC/SWIFT: ${company.bic}\n`
  text += `Meddelande: ${invoice.invoice_number}\n\n`

  text += `Har du redan betalat eller har frågor om fakturan?\n`
  text += `Hantera faktura: ${actionUrl}\n\n`

  text += `Har du frågor? Svara direkt på detta mejl så hjälper vi dig.\n\n`
  text += `Med vänliga hälsningar,\n`
  text += `${getCompanyDisplayName(company)}\n`

  if (company.org_number) {
    text += `\nOrg.nr: ${company.org_number}`
    if (company.vat_number) text += ` | VAT: ${company.vat_number}`
    text += `\n`
  }

  return text
}

/**
 * Generate email subject for payment reminder.
 *
 * When dröjsmålsränta or påminnelseavgift apply we surface them in the
 * subject so the customer sees the true amount to pay before opening
 * the email.
 */
export function generateReminderEmailSubject(data: ReminderEmailData): string {
  const { company, reminderLevel, interestAmount, reminderFee } = data
  const hasSurcharges = interestAmount > 0 || reminderFee > 0

  // {belopp} comes from formatReminderTotalDue: a SEK fee on a foreign-currency
  // invoice renders as "1 010,00 € + 60 kr", two amounts in two currencies,
  // never one mixed scalar.
  const values = buildReminderPlaceholderValues(data)
  const custom = resolveReminderTexts(company, reminderLevel, values)
  if (custom.subject !== undefined) {
    // An override owns the whole line: no automatic surcharge suffix.
    return sanitizeSubjectLine(custom.subject)
  }

  const suffix = hasSurcharges ? ' (inkl. dröjsmålsränta)' : ''
  const stock = applyPlaceholders(
    REMINDER_EMAIL_DEFAULT_TEXTS[levelKey(reminderLevel)].subject,
    values,
  )
  return sanitizeSubjectLine(`${stock}${suffix}`)
}

/**
 * Get the number of days after due date for each reminder level
 */
export type ReminderDaysConfig = Record<1 | 2 | 3, number>

type ReminderDaysSettings = Partial<
  Pick<
    CompanySettings,
    'reminder_days_level_1' | 'reminder_days_level_2' | 'reminder_days_level_3'
  >
>

export function getReminderDaysConfig(
  settings?: ReminderDaysSettings | null,
): ReminderDaysConfig {
  const defaults: ReminderDaysConfig = {
    1: REMINDER_CONFIG[1].daysAfterDue,
    2: REMINDER_CONFIG[2].daysAfterDue,
    3: REMINDER_CONFIG[3].daysAfterDue,
  }

  const configured: ReminderDaysConfig = {
    1: settings?.reminder_days_level_1 ?? defaults[1],
    2: settings?.reminder_days_level_2 ?? defaults[2],
    3: settings?.reminder_days_level_3 ?? defaults[3],
  }

  const valid =
    Object.values(configured).every((days) => Number.isInteger(days) && days >= 1 && days <= 365)
    && configured[1] < configured[2]
    && configured[2] < configured[3]

  return valid ? configured : defaults
}