import logging

from pythonosc import osc_message
from pythonosc.parsing import osc_types

_BUNDLE_PREFIX = b"#bundle\x00"


class ParseError(Exception):
  """Base exception raised when a datagram parsing error occurs."""


class OscBundle(object):
  """Bundles elements that should be triggered at the same time.

  An element can be another OscBundle or an OscMessage.
  """

  def __init__(self, dgram):
    """Initializes the OscBundle with the given datagram.

    Args:
      dgram: a UDP datagram representing an OscBundle.

    Raises:
      ParseError: if the datagram could not be parsed into an OscBundle.
    """
    # Interesting stuff starts after the initial b"#bundle\x00".
    self._dgram = dgram
    index = len(_BUNDLE_PREFIX)
    try:
      self._timestamp, index = osc_types.get_date(self._dgram, index)
    except osc_types.ParseError as pe:
      raise ParseError("Could not get the date from the datagram: %s" % pe)
    # Get the contents as a list of OscBundle and OscMessage.
    self._contents = self._parse_contents(index)

  def _parse_contents(self, index):
    contents = []

    try:
      # An OSC Bundle Element consists of its size and its contents.
      # The size is an int32 representing the number of 8-bit bytes in the
      # contents, and will always be a multiple of 4. The contents are either
      # an OSC Message or an OSC Bundle.
      while self._dgram[index:]:
        # Get the sub content size.
        content_size, index = osc_types.get_int(self._dgram, index)
        # Get the datagram for the sub content.
        content_dgram = self._dgram[index:index + content_size]
        # Increment our position index up to the next possible content.
        index += content_size
        # Parse the content into an OSC message or bundle.
        if OscBundle.dgram_is_bundle(content_dgram):
          contents.append(OscBundle(content_dgram))
        elif osc_message.OscMessage.dgram_is_message(content_dgram):
          contents.append(osc_message.OscMessage(content_dgram))
        else:
          logging.warning(
              "Could not identify content type of dgram %s" % content_dgram)
    except (osc_types.ParseError, osc_message.ParseError, IndexError) as e:
      raise ParseError("Could not parse a content datagram: %s" % e)

    return contents

  @staticmethod
  def dgram_is_bundle(dgram):
    """Returns whether this datagram starts like an OSC bundle."""
    return dgram.startswith(_BUNDLE_PREFIX)

  @property
  def timestamp(self):
    """Returns the timestamp associated with this bundle."""
    return self._timestamp

  @property
  def num_contents(self):
    """Shortcut for len(*bundle) returning the number of elements."""
    return len(self._contents)

  @property
  def size(self):
    """Returns the length of the datagram for this bundle."""
    return len(self._dgram)

  @property
  def dgram(self):
    """Returns the datagram from which this bundle was built."""
    return self._dgram

  def content(self, index):
    """Returns the bundle's content 0-indexed."""
    return self._contents[index]

  def __iter__(self):
    """Returns an iterator over the bundle's content."""
    return iter(self._contents)