import Personnummer from 'personnummer'
import { normalizePidSearchValue } from '../composables/useIsPid'

export interface SsnValidationOptions {
  allowCoordinationNumber?: boolean
  allowInterimNumber?: boolean
}

export interface SsnValidationResult {
  isValid: boolean
  /** Normalized value without separators; `null` when empty or invalid. */
  digits: string | null
}

const INVALID_RESULT: SsnValidationResult = {
  isValid: false,
  digits: null,
}

const DEFAULT_SSN_VALIDATION_OPTIONS = {
  allowCoordinationNumber: true,
  allowInterimNumber: true,
} as const

function resolveSsnValidationOptions(options?: SsnValidationOptions) {
  return {
    ...DEFAULT_SSN_VALIDATION_OPTIONS,
    ...options,
  }
}

/** Strip separators; keeps alphanumeric characters for interim numbers. */
export function stripSsnSeparators(value: string): string {
  return normalizePidSearchValue(value)
}

/** Validate a Swedish personal identity number. */
export function validateSsnNumber(value: string, options?: SsnValidationOptions): SsnValidationResult {
  const trimmed = value.trim()
  if (!trimmed) {
    return INVALID_RESULT
  }

  const resolvedOptions = resolveSsnValidationOptions(options)
  const isValid = Personnummer.valid(trimmed, resolvedOptions)

  return {
    isValid,
    digits: isValid ? stripSsnSeparators(trimmed) : null,
  }
}

export function validateSsn(value: string, options?: SsnValidationOptions): boolean {
  return validateSsnNumber(value, options).isValid
}

/** `null` when empty, otherwise whether the value is a valid personnummer. */
export function getSsnValidationState(value: string, options?: SsnValidationOptions): boolean | null {
  if (!value.trim()) {
    return null
  }
  return validateSsn(value, options)
}