def handle_command(self, request: HandleCommandRequest):
'''
general command handler that matches on command type url
and runs appropriate handler method
'''
# unpack current state
prior_state = None
prior_state_any: Any = get_field(request, "prior_state")
validate(prior_state_any is not None,
"missing prior state",
error_code=StatusCode.INTERNAL)(self.context)
if not prior_state_any.type_url.endswith("google.protobuf.Empty"):
prior_state = unpack_any(prior_state_any, BankAccount)
# get the handler by type url
handler_key = request.command.type_url.split('.')[-1]
logger.info(f"handling command {handler_key}")
handler = self.command_router.get(handler_key)
if not handler:
raise Exception(f"unknown type {request.command.type_url}")
return handler(request, prior_state, request.prior_event_meta)
def _cos_unpack_state(any_state):
'''return state or None if a proto Empty message'''
assert isinstance(any_state, Any), 'expecting Any'
if any_state.type_url.endswith('google.protobuf.Empty'):
logger.debug('converting google.protobuf.Empty to None')
return None
else:
return unpack_any(any_state, BankAccount)
def _debit_account(self, request: HandleCommandRequest,
prior_state: BankAccount, prior_event_meta: MetaData):
'''handle debit'''
validate(prior_event_meta.revision_number > 0, "account not found",
StatusCode.NOT_FOUND)(self.context)
command: DebitAccountRequest = unpack_any(request.command,
DebitAccountRequest)
validate(prior_state.account_balance - command.amount >= 0,
"insufficient funds")(self.context)
event = AccountDebited(account_id=prior_state.account_id,
amount=command.amount)
return HandleCommandResponse(event=pack_any(event))
def _credit_account(self, request: HandleCommandRequest,
prior_state: BankAccount, prior_event_meta: MetaData):
'''handle credit'''
validate(prior_event_meta.revision_number > 0, "account not found",
StatusCode.NOT_FOUND)(self.context)
command: CreditAccountRequest = unpack_any(request.command,
CreditAccountRequest)
validate(command.amount >= 0, "credit must be positive")(self.context)
# if crediting $0, return a no-op
if command.amount == 0:
return HandleCommandResponse()
event = AccountCredited(account_id=prior_state.account_id,
amount=command.amount)
return HandleCommandResponse(event=pack_any(event))
def _open_account(self, request: HandleCommandRequest,
prior_state: BankAccount, prior_event_meta: MetaData):
'''handle open account command'''
# the first event results in revision 1, so it can expect revision 0 prior
validate(prior_event_meta.revision_number == 0,
"account already exists",
StatusCode.ALREADY_EXISTS)(self.context)
command: OpenAccountRequest = unpack_any(request.command,
OpenAccountRequest)
validate(command.account_owner,
"missing account owner",
field_name="account_owner")(self.context)
event = AccountOpened(account_id=prior_event_meta.entity_id,
balance=command.balance,
account_owner=command.account_owner)
return HandleCommandResponse(event=pack_any(event))
def HandleReadSide(self, request, context):
state = unpack_any(request.state, BankAccount)
logger.info(f"readSideId={request.read_side_id}, entity={request.meta.entity_id}, revision={request.meta.revision_number}, balance={state.account_balance}, eventType={request.event.type_url}")
return HandleReadSideResponse(successful=True)