export const DEFAULT_VALID_DAYS = 365;
export const SECONDS_PER_DAY = 86400;

export function isPeriodKey(pk) {
  return pk.validDays != null && pk.validDays > 0;
}

export function isFixedKey(pk) {
  return pk.expiresAtSec != null && Number.isFinite(pk.expiresAtSec) && !isPeriodKey(pk);
}

/** @returns {{ ok: true, expiresAtSec?: number, validDays?: number } | { ok: false, error: string }} */
export function parseProductKeyExpiry(body, nowSec = Math.floor(Date.now() / 1000)) {
  const hasExpiresAtSec = body.expiresAtSec != null && body.expiresAtSec !== '';
  const hasValidDays = body.validDays != null && body.validDays !== '';

  if (hasExpiresAtSec && hasValidDays) {
    return { ok: false, error: 'conflicting_expiry' };
  }

  if (hasExpiresAtSec) {
    const expiresAtSec = Number(body.expiresAtSec);
    if (!Number.isFinite(expiresAtSec) || expiresAtSec <= 0) {
      return { ok: false, error: 'invalid_expiresAtSec' };
    }
    return { ok: true, expiresAtSec };
  }

  if (hasValidDays) {
    const validDays = Number(body.validDays);
    if (!Number.isInteger(validDays) || validDays < 1) {
      return { ok: false, error: 'invalid_validDays' };
    }
    return { ok: true, validDays };
  }

  return { ok: true, validDays: DEFAULT_VALID_DAYS };
}

export function getExpiryMode(pk) {
  return isPeriodKey(pk) ? 'period' : 'fixed';
}

export function getEffectiveExpSec(pk) {
  if (isFixedKey(pk)) return pk.expiresAtSec;
  if (isPeriodKey(pk) && pk.licenseExpSec != null) return pk.licenseExpSec;
  return null;
}

/**
 * On first activation of a period key, sets activatedAtSec and licenseExpSec on pk.
 * @returns {{ changed: boolean, exp: number }}
 */
export function ensurePeriodActivated(pk, nowSec) {
  if (isFixedKey(pk)) {
    return { changed: false, exp: pk.expiresAtSec };
  }

  if (!isPeriodKey(pk)) {
    throw new Error('invalid_product_key_expiry');
  }

  if (pk.licenseExpSec != null && pk.activatedAtSec != null) {
    return { changed: false, exp: pk.licenseExpSec };
  }

  pk.activatedAtSec = nowSec;
  pk.licenseExpSec = nowSec + pk.validDays * SECONDS_PER_DAY;
  return { changed: true, exp: pk.licenseExpSec };
}

export function resolveTokenExp(pk, nowSec) {
  if (isFixedKey(pk)) return pk.expiresAtSec;
  if (isPeriodKey(pk)) {
    if (pk.licenseExpSec != null) return pk.licenseExpSec;
    return nowSec + pk.validDays * SECONDS_PER_DAY;
  }
  throw new Error('invalid_product_key_expiry');
}

export function enrichLicenseEntry(pk, devices, revoked) {
  return {
    key: pk.key,
    sub: pk.sub,
    pid: pk.pid,
    maxDevices: pk.maxDevices,
    expiryMode: getExpiryMode(pk),
    expiresAtSec: pk.expiresAtSec ?? null,
    validDays: pk.validDays ?? null,
    activatedAtSec: pk.activatedAtSec ?? null,
    licenseExpSec: pk.licenseExpSec ?? null,
    effectiveExpSec: getEffectiveExpSec(pk),
    revoked,
    activatedDevices: devices,
    activatedCount: devices.length,
  };
}