import os
import cherrypy
from photoapp.types import PhotoSet, PhotoStatus
import hashlib


def copysha(fpin, fpout):
    sha = hashlib.sha256()
    while True:
        b = fpin.read(1024 * 256)
        if not b:
            break
        fpout.write(b)
        sha.update(b)
    return sha.hexdigest()


def shasum(fpin):
    sha = hashlib.sha256()
    while True:
        b = fpin.read(4096)
        if not b:
            break
        sha.update(b)
    return sha.hexdigest()


def get_extension(fname):
    parts = os.path.basename(fname).split(".")
    if len(parts) == 1:
        return None
    return parts[-1].lower()


def auth():
    """
    Return the currently authorized username (per request) or None
    """
    return cherrypy.session.get('authed', None)


def require_auth(func):
    """
    Decorator: raise 403 unless session is authed
    """
    def wrapped(*args, **kwargs):
        if not auth():
            raise cherrypy.HTTPError(403)
        return func(*args, **kwargs)
    return wrapped


def photoset_auth_filter(query):
    """
    Sqlalchemy helper: filter the given PhotoSet query to items that match the authorized user's PhotoStatus access
    level. Currently, authed users can access ALL photos, and unauthed users can access only PhotoStatus.public
    status items.
    """
    return query.filter(PhotoSet.status == PhotoStatus.public) if not auth() else query


def slugify(words):
    return ''.join(letter for letter in '-'.join(words.lower().split())
                   if ('a' <= letter <= 'z') or ('0' <= letter <= '9') or letter == '-')


def cherryparam(v, type_=str):
    """
    Cherrypy handles duplicate or list field names in post/get/body parameters by setting the parameter value to
    a list of strings. However, if there is just one entry the parameter value is a string. Third, if the
    field isn't provided the value is None. This function always returns a list of values.
    """
    v = v or []
    if type(v) == type_:
        v = [v]  # one entry
    return v