text: from attr import attrib, attrs, Factory
  from attr.validators import instance_of, optional
  from fractions import Fraction
  from typing import Optional
  from ..common import list_of, default_screen
  from ..fileio.adm.elements import (AudioProgramme, AudioContent, AudioObject, AudioPackFormat,
                                     AudioChannelFormat, AudioBlockFormatObjects, AudioBlockFormatDirectSpeakers,
                                     MatrixCoefficient, Frequency)
  
  
  class MetadataSource(object):
      """A source of metadata for some input channels."""
  
      def get_next_block(self) -> Optional["TypeMetadata"]:
          """Get the next metadata block, if one is available."""
          raise NotImplementedError()
  
  
  class MetadataSourceIter(MetadataSource):
      """Metadata source that iterates through a list of TypeMetadata objects.
  
      Args:
          type_metadatas (list of TypeMetadata): List of metadata to iterate through.
      """
  
      def __init__(self, type_metadatas):
          self.type_metadatas_iter = iter(type_metadatas)
  
      def get_next_block(self):
          return next(self.type_metadatas_iter, None)
  
  
  @attrs(slots=True)
  class TypeMetadata(object):
      """Base class for \\*TypeMetadata classes; these should represent all the
      parameters needed to render some set of audio channels within some time
      bounds.
      """
  
  
  @attrs(slots=True)
  class RenderingItem(object):
      """Base class for \\*RenderingItem classes; these should represent an item
      to be rendered, combining a MetadataSource that produces a sequence of
      TypeMetadata objects, and some indices into the tracks that this metadata
      applies to.
      """
  
  
  @attrs(slots=True)
  class ExtraData(object):
      """Common metadata from outside the ADM block format.
  
      Attributes:
          object_start (fractions.Fraction or None): Start time of audioObject.
          object_duration (fractions.Fraction or None): Duration of audioObject.
          reference_screen (CartesianScreen or PolarScreen): Reference screen from audioProgramme.
          channel_frequency (Frequency): Frequency information from audioChannel.
      """
      object_start = attrib(validator=optional(instance_of(Fraction)), default=None)
      object_duration = attrib(validator=optional(instance_of(Fraction)), default=None)
      reference_screen = attrib(default=default_screen)
      channel_frequency = attrib(validator=instance_of(Frequency), default=Factory(Frequency))
  
  
  @attrs(slots=True)
  class ADMPath(object):
      """Pointers to the ADM objects which a rendering item is derived from.
  
      Attributes:
          audioProgramme (Optional[AudioProgramme])
          audioContent (Optional[AudioContent])
          audioObjects (Optional[list[AudioObject]])
          audioPackFormats (Optional[list[AudioPackFormat]])
          audioChannelFormat (Optional[list[AudioChannelFormat]])
      """
      audioProgramme = attrib(validator=optional(instance_of(AudioProgramme)), default=None)
      audioContent = attrib(validator=optional(instance_of(AudioContent)), default=None)
      audioObjects = attrib(validator=optional(list_of(AudioObject)), default=None)
      audioPackFormats = attrib(validator=optional(list_of(AudioPackFormat)), default=None)
      audioChannelFormat = attrib(validator=optional(instance_of(AudioChannelFormat)), default=None)
  
      @property
      def first_audioObject(self):
          """Optional[AudioObject]: The first audioObject of this track in the
          chain, or None"""
          return self.audioObjects[0] if self.audioObjects is not None else None
  
      @property
      def last_audioObject(self):
          """Optional[AudioObject]: The last audioObject of this track in the
          chain, or None"""
          return self.audioObjects[-1] if self.audioObjects is not None else None
  
      @property
      def first_audioPackFormat(self):
          """Optional[AudioPackFormat]: The first audioPackFormat of this track
          in the chain, or None"""
          return self.audioPackFormats[0] if self.audioPackFormats is not None else None
  
      @property
      def last_audioPackFormat(self):
          """Optional[AudioPackFormat]: The last audioPackFormat of this track in
          the chain, or None"""
          return self.audioPackFormats[-1] if self.audioPackFormats is not None else None
  
  
  @attrs(slots=True)
  class ImportanceData(object):
      """Importance metadata for a single channel in a RenderingItem
  
      Attributes:
          audio_object (int or None): Importance that has been derived from the audioObject level
          audio_pack_format (int or None): Importance that has been derived from the audioPackFormat level
      """
      audio_object = attrib(validator=optional(instance_of(int)), default=None)
      audio_pack_format = attrib(validator=optional(instance_of(int)), default=None)
  
  
  @attrs(slots=True)
  class TrackSpec(object):
      """Represents a method for obtaining audio samples to be processed given
      multi-track input samples (from a WAV file for example).
  
      This is used to abstract over regular track references, silent channels and
      matrix channels, but could also be used for coded audio, fancy containers etc.
      """
  
  
  @attrs(slots=True)
  class DirectTrackSpec(TrackSpec):
      """Track obtained directly from the input audio stream.
  
      Attributes:
          track_index (int): Zero based input track index.
      """
      track_index = attrib(validator=instance_of(int))
  
  
  @attrs(slots=True)
  class SilentTrackSpec(TrackSpec):
      """A track whose samples are always 0."""
  
  
  @attrs(slots=True)
  class MatrixCoefficientTrackSpec(TrackSpec):
      """Track derived from a single channel and a matrix coefficient.
  
      Attributes:
          input_track (TrackSpec): track spec to obtain samples from before they
              are processed by parameters in coefficient.
          coefficient (MatrixCoefficient): matrix parameters to apply;
              inputChannelFormat should be ignored.
      """
      input_track = attrib(validator=instance_of(TrackSpec))
      coefficient = attrib(validator=instance_of(MatrixCoefficient))
  
  
  @attrs(slots=True)
  class MixTrackSpec(TrackSpec):
      """Track that is a mix of some other tracks.
  
      Attributes:
          input_tracks (list of TrackSpec): list of input tracks to mix
      """
      input_tracks = attrib(validator=list_of(TrackSpec))
  
  
  #################################################
  # type metadata and rendering items for each type
  #################################################
  
  # objects
  
  @attrs(slots=True)
  class ObjectTypeMetadata(TypeMetadata):
      """TypeMetadata for typeDefinition="Objects"
  
      Attributes:
          block_format (AudioBlockFormatObjects): Block format.
          extra_data (ExtraData): Extra parameters from outside block format.
      """
      block_format = attrib(validator=instance_of(AudioBlockFormatObjects))
  
      extra_data = attrib(validator=instance_of(ExtraData), default=Factory(ExtraData))
  
  
  @attrs(slots=True)
  class ObjectRenderingItem(RenderingItem):
      """RenderingItem for typeDefinition="Objects"
  
      Attributes:
          track_spec (TrackSpec): Zero based input track index for this item.
          metadata_source (MetadataSource): Source of ObjectTypeMetadata objects.
          importance (ImportanceData): Importance data for this item.
          adm_path (ADMPath): Pointers to the ADM objects which this is derived from.
      """
      track_spec = attrib(validator=instance_of(TrackSpec))
      metadata_source = attrib(validator=instance_of(MetadataSource))
  
      importance = attrib(validator=instance_of(ImportanceData), default=Factory(ImportanceData))
      adm_path = attrib(validator=optional(instance_of(ADMPath)), default=None, repr=False)
  
  
  # direct speakers
  
  @attrs(slots=True)
  class DirectSpeakersTypeMetadata(TypeMetadata):
      """TypeMetadata for typeDefinition="DirectSpeakers"
  
      Attributes:
          block_format (AudioBlockFormatDirectSpeakers): Block format.
          extra_data (ExtraData): Extra parameters from outside block format.
      """
      block_format = attrib(validator=instance_of(AudioBlockFormatDirectSpeakers))
      audioPackFormats = attrib(validator=optional(list_of(AudioPackFormat)), default=None)
  
      extra_data = attrib(validator=instance_of(ExtraData), default=Factory(ExtraData))
  
  
  @attrs(slots=True)
  class DirectSpeakersRenderingItem(RenderingItem):
      """RenderingItem for typeDefinition="DirectSpeakers"
  
      Attributes:
          track_spec (TrackSpec): Specification of input samples.
          metadata_source (MetadataSource): Source of DirectSpeakersTypeMetadata objects.
          importance (ImportanceData): Importance data for this item.
          adm_path (ADMPath): Pointers to the ADM objects which this is derived from.
      """
      track_spec = attrib(validator=instance_of(TrackSpec))
      metadata_source = attrib(validator=instance_of(MetadataSource))
  
      importance = attrib(validator=instance_of(ImportanceData), default=Factory(ImportanceData))
      adm_path = attrib(validator=optional(instance_of(ADMPath)), default=None, repr=False)
  
  
  # HOA
  
  @attrs(slots=True)
  class HOATypeMetadata(TypeMetadata):
      """TypeMetadata for typeDefinition="HOA"
  
      Attributes:
          orders (list of int): Order for each input channel.
          degrees (list of int): Degree for each channel.
          normalization (str): Normalization for all channels.
          nfcRefDist (float or None): NFC Reference distance for all channels.
          screenRef (bool): Are these channels screen related?
          rtime (fractions.Fraction or None): Start time of block.
          duration (fractions.Fraction or None): Duration of block.
          extra_data (ExtraData): Info from object and channels for all channels.
      """
      orders = attrib(validator=list_of(int))
      degrees = attrib(validator=list_of(int))
      normalization = attrib()
      nfcRefDist = attrib(validator=optional(instance_of(float)), default=None)
      screenRef = attrib(validator=instance_of(bool), default=False)
      rtime = attrib(default=None, validator=optional(instance_of(Fraction)))
      duration = attrib(default=None, validator=optional(instance_of(Fraction)))
  
      extra_data = attrib(validator=instance_of(ExtraData), default=Factory(ExtraData))
  
  
  @attrs(slots=True)
  class HOARenderingItem(RenderingItem):
      """RenderingItem for typeDefinition="HOA"
  
      Attributes:
          track_specs (list[TrackSpec]): Specification of n tracks of input samples.
          metadata_source (MetadataSource): Source of HOATypeMetadata objects;
              will usually contain only one object.
          importances (Optional[list[ImportanceData]]): Importance data for each
              track.
          adm_paths (Optional[list[ADMPath]]): Pointers to the ADM objects which
              each track is derived from.
      """
      track_specs = attrib(validator=list_of(TrackSpec))
      metadata_source = attrib(validator=instance_of(MetadataSource))
  
      importances = attrib(validator=optional(list_of(ImportanceData)), default=None)
      adm_paths = attrib(validator=optional(list_of(ADMPath)), repr=False, default=None)
  
      @importances.validator
      def importances_valid(self, attribute, value):
          if value is not None and len(value) != len(self.track_specs):
              raise ValueError("wrong number of ImportanceDatas provided")
  
      @adm_paths.validator
      def adm_paths_valid(self, attribute, value):
          if value is not None and len(value) != len(self.track_specs):
              raise ValueError("wrong number of ADMPaths provided")
  