import type { PasskeySignature, SignatureValue } from '../types/signatures.js'

export function isSignatureImage(value: string | undefined | null): boolean {
  return typeof value === 'string' && value.startsWith('data:image/')
}

export function isPasskeySignature(value: unknown): value is PasskeySignature {
  return (
    typeof value === 'object' &&
    value !== null &&
    (value as PasskeySignature).kind === 'passkey' &&
    (value as PasskeySignature).version === 1
  )
}

export function normalizeSignature(value: unknown): SignatureValue | undefined {
  if (value === null || value === undefined || value === '') return undefined
  if (isPasskeySignature(value)) return value
  if (typeof value === 'string') return value
  return undefined
}

export function hasAnySignature(
  skipper: SignatureValue | '' | undefined,
  crew: SignatureValue | '' | undefined
): boolean {
  return !!(skipper || crew)
}

export function isSignatureValidForEntry(sig: PasskeySignature, entryHash: string): boolean {
  return sig.entryHash === entryHash
}

export interface SignatureExportLabels {
  imagePlaceholder: string
  passkeyLabel: (username: string, signedAt: string) => string
}

export function formatSignatureForExport(
  value: SignatureValue | undefined | null,
  labels: SignatureExportLabels
): string {
  if (!value) return ''
  if (isPasskeySignature(value)) {
    return labels.passkeyLabel(value.username, value.signedAt)
  }
  if (isSignatureImage(value)) return labels.imagePlaceholder
  return value
}

export function serializeSignature(value: SignatureValue | '' | undefined): SignatureValue | undefined {
  if (!value) return undefined
  if (isPasskeySignature(value)) return value
  if (isSignatureImage(value)) return value
  const trimmed = value.trim()
  return trimmed || undefined
}