boards/forms.py

from django import forms


class PostForm(forms.Form):
    MAX_TEXT_LENGTH = 10000
    MAX_IMAGE_SIZE = 8 * 1024 * 1024

    title = forms.CharField(max_length=50, required=False)
    text = forms.CharField(widget=forms.Textarea, required=False)
    image = forms.ImageField(required=False)

    def clean_text(self):
        text = self.cleaned_data['text']
        if text:
            if len(text) > self.MAX_TEXT_LENGTH:
                raise forms.ValidationError('Too many text')
        return text

    def clean_image(self):
        image = self.cleaned_data['image']
        if image:
            if image._size > self.MAX_IMAGE_SIZE:
                raise forms.ValidationError('Too large image: more than ' +
                                            str(self.MAX_IMAGE_SIZE) + ' bytes')
        return image

    def clean(self):
        cleaned_data = super(PostForm, self).clean()

        text = cleaned_data.get('text')
        image = cleaned_data.get('image')

        if (not text) and (not image):
            raise forms.ValidationError('Enter either text or image')

        return cleaned_data


class ThreadForm(PostForm):
    tags = forms.CharField(max_length=100)

    def clean_tags(self):
        tags = self.cleaned_data['tags']
        if tags:
            if ('+' in tags) or ('/' in tags):
                raise forms.ValidationError('Inappropriate characters in tags')

        return tags

    def clean(self):
        cleaned_data = super(ThreadForm, self).clean()

        return cleaned_data