guard method

bool guard(
  1. String ptr,
  2. List<LicenseUsecase> usecases, {
  3. String? origin,
  4. List<String>? destinations,
  5. dynamic onPass()?,
  6. dynamic onFail(
    1. String
    )?,
})

Guard against an invalid LicenseRecord for a List of usecases and destinations.

Use this method to verify a non-expired LicenseRecord for the ptr exists and permits the listed usecases and destinations.

Parameters:

• ptr - The Pointer Record for the asset. Used to located the latest relevant LicenseRecord.

• origin - An optional override of the default origin specified in init.

• usecases - A List of usecases defining how the asset will be used.

• destinations - A List of destinations defining where the asset will be used. Often URLs

• onPass - A Function to execute automatically upon successfully resolving the LicenseRecord against the usecases and destinations

• onFail - A Function to execute automatically upon failure to resolve the LicenseRecord. Accepts a String parameter, holding an error message describing the reason for failure.

This method can be used in two forms, 1) as a traditional guard, returning a pass/fail boolean. Or 2) as a wrapper around function.

For example: An http that you want to run IF permitted by a LicenseRecord.

Option 1:

bool pass = guard('ptr', [LicenseUsecase.attribution()]);
if(pass) http.post(...);

Option 2:

guard('ptr', [LicenseUsecase.attribution()], onPass: () => http.post(...));

Returns the created TitleRecord

Implementation

bool guard(String ptr, List<LicenseUsecase> usecases,
    {String? origin,
    List<String>? destinations,
    Function()? onPass,
    Function(String)? onFail}) {
  TitleRecord? title = this.title.get(ptr, origin: origin);
  if (title == null) {
    if (onFail != null) onFail('Missing title for ptr: $ptr');
    return false;
  }
  LicenseRecord? license = this.license.latest(title);
  if (license == null) {
    if (onFail != null) onFail('Missing license for ptr: $ptr');
    return false;
  }
  String? guardMessage = Guard.check(
      license, [LicenseUse(usecases, destinations: destinations)]);
  if (guardMessage == null) {
    if (onPass != null) onPass();
    return true;
  } else {
    if (onFail != null) onFail(guardMessage);
    return false;
  }
}