import os

from SpiffWorkflow.bpmn.BpmnScriptEngine import BpmnScriptEngine
from SpiffWorkflow.bpmn.serializer.BpmnSerializer import BpmnSerializer
from SpiffWorkflow.bpmn.serializer.CompactWorkflowSerializer import CompactWorkflowSerializer
from SpiffWorkflow.bpmn.workflow import BpmnWorkflow
from SpiffWorkflow.camunda.serializer.CamundaSerializer import CamundaSerializer
from SpiffWorkflow.serializer.json import JSONSerializer

from crc import app
from crc.models import WorkflowModel, WorkflowStatus, WorkflowSpecModel


class CustomBpmnScriptEngine(BpmnScriptEngine):
    """This is a custom script processor that can be easily injected into Spiff Workflow.
    Rather than execute arbitrary code, this assumes the script references a fully qualified python class
    such as myapp.RandomFact. """

    def execute(self, task, script, **kwargs):
        """
        Assume that the script read in from the BPMN file is a fully qualified python class. Instantiate
        that class, pass in any data available to the current task so that it might act on it.
        Assume that the class implements the "do_task" method.

        This allows us to reference custom code from the BPMN diagram.
        """
        module_name = "crc." + script
        class_name = module_name.split(".")[-1]
        mod = __import__(module_name, fromlist=[class_name])
        klass = getattr(mod, class_name)
        klass().do_task(task.data)


class WorkflowProcessor:

    _script_engine = CustomBpmnScriptEngine()
    _serializer = CompactWorkflowSerializer()

    def __init__(self, workflow_spec_id, bpmn_json):
        self.bpmn_workflow = self._serializer.deserialize_workflow(bpmn_json, self.get_spec(workflow_spec_id))
        self.bpmn_workflow.script_engine = self._script_engine

    @staticmethod
    def get_spec(workflow_spec_id):
        filename = os.path.join(app.root_path, 'static', 'bpmn', workflow_spec_id)
        return CamundaSerializer().deserialize_workflow_spec(filename)

    @classmethod
    def create(cls, workflow_spec_id):
        spec = cls.get_spec(workflow_spec_id)
        bpmn_workflow = BpmnWorkflow(spec, script_engine=cls._script_engine)
        bpmn_workflow.do_engine_steps()
        json = cls._serializer.serialize_workflow(bpmn_workflow)
        processor = cls(workflow_spec_id, json)
        return processor

    def get_status(self):
        if self.bpmn_workflow.is_completed():
            return WorkflowStatus.complete
        user_tasks = self.bpmn_workflow.get_ready_user_tasks()
        if len(user_tasks) > 0:
            return WorkflowStatus.user_input_required
        else:
            return WorkflowStatus.waiting

    def do_engine_steps(self):
        self.bpmn_workflow.do_engine_steps()

    def serialize(self):
        return self.bpmn_workflow.serialize(JSONSerializer())

    def next_user_tasks(self):
        return self.bpmn_workflow.get_ready_user_tasks()

    def complete_task(self, task):
        self.bpmn_workflow.complete_task_from_id(task.id)

    def get_data(self):
        return self.bpmn_workflow.data