general_model.py

"""
General functions mostly used in models (models.py)
"""
import re
import uuid

from django.core.exceptions import PermissionDenied
from django.db.models import ProtectedError
from django.utils.html import strip_tags


def get_ext(filename):
    """
    Get the extension of a given filename

    :param filename: a filename
    :return:
    """
    return filename.split(".")[-1].lower()


def file_delete_default(sender, instance, **kwargs):
    """
    Delete a file

    :param sender:
    :param instance: the file object to delete the file from
    :param kwargs:
    :return:
    """
    try:
        instance.File.delete(False)
    except:
        # in case the file is locked by another process.
        print("Error in removing the file. Only the object will be removed.")


def delete_object(obj):
    """
    Try to delete an object. Raise permissiondenied if obj is protected

    :param obj:
    :return:
    """
    try:
        obj.delete()
    except ProtectedError as e:
        raise PermissionDenied('This object ({}) can not be deleted, as other objects depend on it. Please remove the others first. Depending objects: {}'.format(obj, print_list(e.protected_objects)))


def metro_icon_default(fobject):
    """
    Gives an icon name from metro ui icon font based on the extension of the filename.

    :param fobject: file object
    :return: icon name
    """
    extension = get_ext(fobject.File.name)
    if extension == 'pdf':
        return 'pdf'
    elif extension in ['doc', 'docx', 'odf', 'rtf']:
        return 'word'
    elif extension in ['jpg', 'jpeg', 'png', 'bmp', 'gif']:
        return 'image'
    elif extension in ['xls', 'xlsx', 'ods']:
        return 'excel'
    elif extension in ['ppt', 'pptx', 'odp']:
        return 'powerpoint'
    elif extension in ['tex']:
        return 'code'
    elif extension in ['zip', 'rar', 'gz']:
        return 'archive'
    elif extension in ['txt']:
        return 'text'
    return 'empty'


def filename_default(filename):
    """
    Generate a random unique filename.

    :param filename: the original filename, used to get extension from.
    :return:
    """
    ext = get_ext(filename)
    return "%s.%s" % (uuid.uuid4(), ext)


def clean_text(text):
    """
    Clean ascii control characters and non-breaking-spaces from text.

    :param text: The string to clean.
    :return:
    """
    # almost all except \n \t and \r
    control = r'([\x00-\x08])|([\x0b-\x0c])|([\x0e-\x1f])|([\uFFF0-\uFFFF])|([\u2000-\u200F])|([\u2028-\u202F])|([\x80-\x9F])|([\uE000-\uF8FF])'
    nbsp = r'\xa0'
    try:
        # remove ascii control characters, including replacement character FFFD
        text = re.sub(control, '', text)
        # convert non breaking spaces to regular spaces
        text = re.sub(nbsp, ' ', text)
        # convert curly braces to straight braces (prevents messing with django variables)
        text = text.replace('{', '[').replace('}', ']')
        return strip_tags(text)  # strip_tags removes most common HTML, but not all. Therefore, database text fiels are not safe.
    except:
        return ''


def print_list(lst):
    """
    list of strings to pretty inline enumeration.
    ['a', 'b', 'c'] to 'a, b & c'

    :param lst: input list
    :return: string
    """
    if len(lst) == 0:
        return 'None'
    elif len(lst) == 1:
        return lst[0]
    else:
        tx = ''
        for item in lst:
            tx += str(item) + ', '
        tx = tx[:-2]
        i = tx.rfind(',')
        return tx[:i] + ' &' + tx[i + 1:]