# Process trace events and create ROS model

import sys
from .lttng_models import EventMetadata, get_field, get_name

def ros_process(events):
    """
    Process unpickled events and create ROS model
    :param events (list(dict(str:str:))): the list of events
    :return the processor object
    """
    processor = RosProcessor()
    processor.process_events(events)
    return processor

class RosProcessor():
    """
    ROS-aware event processing/handling class.
    Handles a trace's events and builds a model with the data.
    """
    def __init__(self):
        # TODO add other stuff
        # Instances of callback_start for eventual matching
        self._callback_starts = {}
        # Callback instances, callback_address: end - start
        self.callbacks_instances = {}

        # Link a ROS trace event to its corresponding handling method
        self._handler_map = {
            'ros2:rcl_subscription_init': self._handle_subscription_init,
            'ros2:rclcpp_subscription_callback_added': self._handle_subscription_callback_added,
            'ros2:rclcpp_subscription_callback_start': self._handle_subscription_callback_start,
            'ros2:rclcpp_subscription_callback_end': self._handle_subscription_callback_end,
        }

    def process_events(self, events):
        """
        Process events
        :param events (list(dict(str:str))): the events to process
        """
        for event in events:
            self._handle(event)

    def _handle(self, event):
        event_name = get_name(event)
        handler_function = self._handler_map.get(event_name, None)
        if handler_function is not None:
            pid = get_field(event, 'vpid', default=get_field(event, 'pid'))
            tid = get_field(event, 'vtid', default=get_field(event, 'tid'))
            timestamp = get_field(event, '_timestamp')
            procname = get_field(event, 'procname')
            metadata = EventMetadata(event_name, pid, tid, timestamp, procname)
            handler_function(event, metadata)
        else:
            print(f'unhandled event name: {event_name}', file=sys.stderr)

    def _handle_subscription_init(self, event, metadata):
        # TODO
        pass

    def _handle_subscription_callback_added(self, event, metadata):
        # Add the callback address key and create an empty list
        callback_addr = get_field(event, 'callback')
        self.callbacks_instances[callback_addr] = []

    def _handle_subscription_callback_start(self, event, metadata):
        callback_addr = get_field(event, 'callback')
        self._callback_starts[callback_addr] = metadata.timestamp

    def _handle_subscription_callback_end(self, event, metadata):
        callback_addr = get_field(event, 'callback')
        start_timestamp = self._callback_starts.pop(callback_addr, None)
        if start_timestamp is not None:
            duration = metadata.timestamp - start_timestamp
            self.callbacks_instances[callback_addr].append(duration)