"""This module is responsible for constructing schemas for validation."""

import audio_schemas
from constants import transcoding_types


def get_audio_validation_schema(mime_type):
    """Return validation schema for provided codec and MIME type.

    Args:
        mime_type (str): audio file MIME type.
    Returns:
        trafaret.Dict: trafaret schema for validation of audio meta data.

    """
    if mime_type in transcoding_types.WAV_MIME_TYPES:
        return audio_schemas.BASE_SCHEMA.append(
            audio_schemas.WAV_SCHEMA)
    return audio_schemas.BASE_SCHEMA


def extract_errors(validation_error):
    """Extract errors and generate one error message.

    Args:
        validation_error (trafaret.DataError): Validation error.
    Returns:
        str: error descriptions separated by newline escape character.

    """
    exception_description = validation_error.as_dict()
    errors = []
    for key, value in exception_description.items():
        error = '{key} {error}.'.format(key=key, error=value)
        errors.append(error)
    result_error = '\n'.join(errors)
    return result_error