import { parsePhoneNumberFromString } from 'libphonenumber-js'

const VALID_SOURCE = new Set(['manual', 'account-profile', 'phone-prefix', 'unknown'])

export function normalizeCountryCode(value) {
  const code = String(value || '').trim().toUpperCase()
  return /^[A-Z]{2}$/.test(code) ? code : ''
}

export function inferCountryFromPhone(value) {
  const raw = String(value || '').trim()
  if (!raw) return ''
  const normalized = raw.startsWith('+') ? raw : `+${raw.replace(/[^\d]/g, '')}`
  try {
    return normalizeCountryCode(parsePhoneNumberFromString(normalized)?.country)
  } catch {
    return ''
  }
}

export function resolveCustomerCountry(input = {}, existing = {}, options = {}) {
  const manualCountry = normalizeCountryCode(input.country)
  if (options.manual === true) {
    return {
      country: manualCountry,
      countrySource: manualCountry ? 'manual' : 'unknown',
      countryConfidence: manualCountry ? 1 : 0,
      countryInferredAt: new Date().toISOString(),
    }
  }

  const existingSource = VALID_SOURCE.has(existing.countrySource)
    ? existing.countrySource
    : 'unknown'
  if (existingSource === 'manual' && normalizeCountryCode(existing.country)) {
    return {
      country: normalizeCountryCode(existing.country),
      countrySource: 'manual',
      countryConfidence: 1,
      countryInferredAt: existing.countryInferredAt || existing.updatedAt,
    }
  }

  const accountCountry = normalizeCountryCode(
    input.accountCountry || input.countryCode || input.profileCountry,
  )
  if (accountCountry) {
    return {
      country: accountCountry,
      countrySource: 'account-profile',
      countryConfidence: 0.98,
      countryInferredAt: new Date().toISOString(),
    }
  }

  const phoneCountry = inferCountryFromPhone(input.phone || existing.phone)
  if (phoneCountry) {
    return {
      country: phoneCountry,
      countrySource: 'phone-prefix',
      countryConfidence: 0.92,
      countryInferredAt: new Date().toISOString(),
    }
  }

  const preserved = normalizeCountryCode(input.country || existing.country)
  const preservedSource = VALID_SOURCE.has(input.countrySource)
    ? input.countrySource
    : existingSource
  if (preserved && preservedSource !== 'unknown') {
    return {
      country: preserved,
      countrySource: preservedSource,
      countryConfidence: Number(input.countryConfidence ?? existing.countryConfidence ?? 0.7),
      countryInferredAt: input.countryInferredAt || existing.countryInferredAt,
    }
  }

  return {
    country: '',
    countrySource: 'unknown',
    countryConfidence: 0,
    countryInferredAt: null,
  }
}