"""
Workflow Service
================

Switch different type of workflow service.
"""

from ows_accounting import response
from ows_accounting.utils import swf


AMAZON_SIMPLE_WORKFLOW = 'swf'


class WorkflowService(object):
    def __init__(self, service_name):
        """Switch to particular service.

        Args:
            service_name (str): workflow service name.

        Raises:
            Exception: if service is not supported or required method is not
                implemented in the particular service class.
        """

        if service_name == AMAZON_SIMPLE_WORKFLOW:
            self.service = swf
        else:
            raise Exception(
                'Service: {} is not supported.'.format(service_name))

    def execute_workflow(self, workflow_id, correlation_id, **params):
        """Execute simple workflow.

        Args:
            workflow_id (str): workflow id which uniquely identify each
                workflow.
            correlation_id (str): correlation_id in the header.
            params (dict): report specific params.

        Returns:
            response.Response: Response object with message for success or
                failure.
        """

        try:
            self.service.execute_workflow(
                workflow_id, correlation_id, **params)
            return response.Response(message='Workflow is executed.')
        except Exception as err:
            return response.create_fatal_response(str(err))

    def generate_workflow_id(self, prefix, **params):
        """Generate workflow id from params.

        Args:
            prefix (str): prefix of workflow id.
            params (dict): user params for the workflow.

        Returns:
            response.Response: Response object with message for success or
                failure. If success. Message will be the workflow_id.
        """

        try:
            workflow_id = self.service.generate_workflow_id(prefix, **params)
            return response.Response(message=workflow_id)
        except Exception as err:
            return response.Response(message=str(err), status=500)