"""Module containing a preprocessor that converts outputs in the notebook from 
one format to another.
"""

# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.


from .base import Preprocessor
from traitlets import Unicode


class ConvertFiguresPreprocessor(Preprocessor):
    """
    Converts all of the outputs in a notebook from one format to another.
    """

    from_format = Unicode(help='Format the converter accepts').tag(config=True)
    to_format = Unicode(help='Format the converter writes').tag(config=True)

    def __init__(self, **kw):
        """
        Public constructor
        """
        super().__init__(**kw)


    def convert_figure(self, data_format, data):
        raise NotImplementedError()


    def preprocess_cell(self, cell, resources, cell_index):
        """
        Apply a transformation on each cell,

        See base.py
        """

        # Loop through all of the datatypes of the outputs in the cell.
        for output in cell.get('outputs', []):
            if output.output_type in {'execute_result', 'display_data'} \
                    and self.from_format in output.data \
                    and self.to_format not in output.data:

                output.data[self.to_format] = self.convert_figure(
                            self.from_format, output.data[self.from_format])

        return cell, resources
