boards/forms/fields.py

from django import forms
from django.utils.translation import ugettext_lazy as _

ATTRIBUTE_PLACEHOLDER = 'placeholder'
ATTRIBUTE_ROWS = 'rows'

URL_ROWS = 2
URL_PLACEHOLDER = _('Insert URLs on separate lines.')


class MultipleFileInput(forms.FileInput):
    """
    Input that allows to enter many files at once, utilizing the html5 "multiple"
    attribute of a file input.
    """
    def value_from_datadict(self, data, files, name):
        if len(files) == 0:
            return None
        else:
            return files.getlist(name)


class MultipleFileField(forms.FileField):
    """
    Field that allows to enter multiple files from one input.
    """
    def to_python(self, data):
        if not data or len(data) == 0:
            return None

        for file in data:
            super().to_python(file)

        return data


class UrlFileWidget(forms.MultiWidget):
    """
    Widget with a file input and a text input that allows to enter either a
    file from a local system, or a URL from which the file would be downloaded.
    """
    def __init__(self, *args, **kwargs):
        widgets = (
                MultipleFileInput(attrs={
                    'accept': 'file/*',
                    'multiple': ''
                }),
                forms.Textarea(attrs={
                    ATTRIBUTE_PLACEHOLDER: URL_PLACEHOLDER,
                    ATTRIBUTE_ROWS: URL_ROWS,
                }),
        )
        super().__init__(widgets, *args, **kwargs)

    def decompress(self, value):
        return [None, None]


class UrlFileField(forms.MultiValueField):
    """
    Field with a file input and a text input that allows to enter either a
    file from a local system, or a URL from which the file would be downloaded.
    """
    widget = UrlFileWidget

    def __init__(self, *args, **kwargs):
        fields = (
                MultipleFileField(required=False, label=_('File')),
                forms.CharField(required=False, label=_('File URL')),
        )

        super().__init__(
                fields=fields,
                require_all_fields=False, *args, **kwargs)

    def compress(self, data_list):
        all_data = []
        for data in data_list:
            if type(data) == list:
                all_data += data
            elif type(data) == str and len(data) > 0:
                file_input = data.replace('\r\n', '\n')
                url_list = file_input.split('\n')
                all_data += url_list

        return all_data