from __future__ import absolute_import
from typing import Optional, Tuple, Mapping, Any

from django.utils.translation import ugettext as _
from django.conf import settings
from django.template.defaultfilters import slugify
from django.core.files import File
from django.http import HttpRequest
from jinja2 import Markup as mark_safe
import unicodedata

from zerver.lib.avatar_hash import user_avatar_hash
from zerver.lib.request import JsonableError
from zerver.lib.str_utils import force_text, force_str, NonBinaryStr

from boto.s3.bucket import Bucket
from boto.s3.key import Key
from boto.s3.connection import S3Connection
from mimetypes import guess_type, guess_extension

from zerver.models import get_user_profile_by_id
from zerver.models import Attachment
from zerver.models import Realm, UserProfile, Message

from six.moves import urllib
import base64
import os
import re
from PIL import Image, ImageOps
from six import binary_type, text_type
import io
import random
import logging

DEFAULT_AVATAR_SIZE = 100

# Performance Note:
#
# For writing files to S3, the file could either be stored in RAM
# (if it is less than 2.5MiB or so) or an actual temporary file on disk.
#
# Because we set FILE_UPLOAD_MAX_MEMORY_SIZE to 0, only the latter case
# should occur in practice.
#
# This is great, because passing the pseudofile object that Django gives
# you to boto would be a pain.

# To come up with a s3 key we randomly generate a "directory". The
# "file name" is the original filename provided by the user run
# through a sanitization function.

attachment_url_re = re.compile(u'[/\-]user[\-_]uploads[/\.-].*?(?=[ )]|\Z)')

def attachment_url_to_path_id(attachment_url):
    # type: (text_type) -> text_type
    path_id_raw = re.sub(u'[/\-]user[\-_]uploads[/\.-]', u'', attachment_url)
    # Remove any extra '.' after file extension. These are probably added by the user
    return re.sub(u'[.]+$', u'', path_id_raw, re.M)

def sanitize_name(raw_value):
    # type: (NonBinaryStr) -> text_type
    """
    Sanitizes a value to be safe to store in a Linux filesystem, in
    S3, and in a URL.  So unicode is allowed, but not special
    characters other than ".", "-", and "_".

    This implementation is based on django.utils.text.slugify; it is
    modified by:
    * hardcoding allow_unicode=True.
    * adding '.' and '_' to the list of allowed characters.
    * preserving the case of the value.
    """
    value = force_text(raw_value)
    value = unicodedata.normalize('NFKC', value)
    value = re.sub('[^\w\s._-]', '', value, flags=re.U).strip()
    return mark_safe(re.sub('[-\s]+', '-', value, flags=re.U))

def random_name(bytes=60):
    # type: (int) -> text_type
    return base64.urlsafe_b64encode(os.urandom(bytes)).decode('utf-8')

class BadImageError(JsonableError):
    pass

def resize_avatar(image_data, size=DEFAULT_AVATAR_SIZE):
    # type: (binary_type, int) -> binary_type
    try:
        im = Image.open(io.BytesIO(image_data))
        im = ImageOps.fit(im, (size, size), Image.ANTIALIAS)
    except IOError:
        raise BadImageError("Could not decode avatar image; did you upload an image file?")
    out = io.BytesIO()
    im.save(out, format='png')
    return out.getvalue()

### Common

class ZulipUploadBackend(object):
    def upload_message_image(self, uploaded_file_name, content_type, file_data, user_profile, target_realm=None):
        # type: (text_type, Optional[text_type], binary_type, UserProfile, Optional[Realm]) -> text_type
        raise NotImplementedError()

    def upload_avatar_image(self, user_file, user_profile, email):
        # type: (File, UserProfile, text_type) -> None
        raise NotImplementedError()

    def delete_message_image(self, path_id):
        # type: (text_type) -> bool
        raise NotImplementedError()

    def get_avatar_url(self, hash_key):
        # type: (text_type) -> text_type
        raise NotImplementedError()

### S3

def get_bucket(conn, bucket_name):
    # type: (S3Connection, text_type) -> Bucket
    # Calling get_bucket() with validate=True can apparently lead
    # to expensive S3 bills:
    #    http://www.appneta.com/blog/s3-list-get-bucket-default/
    # The benefits of validation aren't completely clear to us, and
    # we want to save on our bills, so we set the validate flag to False.
    # (We think setting validate to True would cause us to fail faster
    #  in situations where buckets don't exist, but that shouldn't be
    #  an issue for us.)
    bucket = conn.get_bucket(bucket_name, validate=False)
    return bucket

def upload_image_to_s3(
        bucket_name,
        file_name,
        content_type,
        user_profile,
        contents,
    ):
    # type: (NonBinaryStr, text_type, Optional[text_type], UserProfile, binary_type) -> None

    conn = S3Connection(settings.S3_KEY, settings.S3_SECRET_KEY)
    bucket = get_bucket(conn, force_str(bucket_name))
    key = Key(bucket)
    key.key = force_str(file_name)
    key.set_metadata("user_profile_id", str(user_profile.id))
    key.set_metadata("realm_id", str(user_profile.realm.id))

    if content_type is not None:
        headers = {'Content-Type': force_str(content_type)}
    else:
        headers = None

    key.set_contents_from_string(contents, headers=headers)

def get_file_info(request, user_file):
    # type: (HttpRequest, File) -> Tuple[text_type, Optional[text_type]]

    uploaded_file_name = user_file.name
    assert isinstance(uploaded_file_name, str)

    content_type = request.GET.get('mimetype')
    if content_type is None:
        guessed_type = guess_type(uploaded_file_name)[0]
        if guessed_type is not None:
            content_type = force_text(guessed_type)
    else:
        uploaded_file_name = uploaded_file_name + guess_extension(content_type)

    uploaded_file_name = urllib.parse.unquote(uploaded_file_name)
    return uploaded_file_name, content_type


def get_signed_upload_url(path):
    # type: (text_type) -> text_type
    conn = S3Connection(settings.S3_KEY, settings.S3_SECRET_KEY)
    return force_text(conn.generate_url(15, 'GET', bucket=settings.S3_AUTH_UPLOADS_BUCKET, key=force_str(path)))

def get_realm_for_filename(path):
    # type: (text_type) -> Optional[int]
    conn = S3Connection(settings.S3_KEY, settings.S3_SECRET_KEY)
    key = get_bucket(conn, settings.S3_AUTH_UPLOADS_BUCKET).get_key(path)
    if key is None:
        # This happens if the key does not exist.
        return None
    return get_user_profile_by_id(key.metadata["user_profile_id"]).realm.id

class S3UploadBackend(ZulipUploadBackend):
    def upload_message_image(self, uploaded_file_name, content_type, file_data, user_profile, target_realm=None):
        # type: (text_type, Optional[text_type], binary_type, UserProfile, Optional[Realm]) -> text_type
        bucket_name = settings.S3_AUTH_UPLOADS_BUCKET
        s3_file_name = "/".join([
            str(target_realm.id if target_realm is not None else user_profile.realm.id),
            random_name(18),
            sanitize_name(uploaded_file_name)
        ])
        url = "/user_uploads/%s" % (s3_file_name)

        upload_image_to_s3(
                bucket_name,
                s3_file_name,
                content_type,
                user_profile,
                file_data
        )

        create_attachment(uploaded_file_name, s3_file_name, user_profile)
        return url

    def delete_message_image(self, path_id):
        # type: (text_type) -> bool
        conn = S3Connection(settings.S3_KEY, settings.S3_SECRET_KEY)
        bucket = get_bucket(conn, settings.S3_AUTH_UPLOADS_BUCKET)

        # check if file exists
        key = bucket.get_key(path_id)
        if key is not None:
            bucket.delete_key(key)
            return True

        file_name = path_id.split("/")[-1]
        logging.warning("%s does not exist. Its entry in the database will be removed." % (file_name,))
        return False

    def upload_avatar_image(self, user_file, user_profile, email):
        # type: (File, UserProfile, text_type) -> None
        content_type = guess_type(user_file.name)[0]
        bucket_name = settings.S3_AVATAR_BUCKET
        s3_file_name = user_avatar_hash(email)

        image_data = user_file.read()
        upload_image_to_s3(
            bucket_name,
            s3_file_name + ".original",
            content_type,
            user_profile,
            image_data,
        )

        resized_data = resize_avatar(image_data)
        upload_image_to_s3(
            bucket_name,
            s3_file_name,
            'image/png',
            user_profile,
            resized_data,
        )
        # See avatar_url in avatar.py for URL.  (That code also handles the case
        # that users use gravatar.)

    def get_avatar_url(self, hash_key):
        # type: (text_type) -> text_type
        bucket = settings.S3_AVATAR_BUCKET
        # ?x=x allows templates to append additional parameters with &s
        return u"https://%s.s3.amazonaws.com/%s?x=x" % (bucket, hash_key)

### Local

def mkdirs(path):
    # type: (text_type) -> None
    dirname = os.path.dirname(path)
    if not os.path.isdir(dirname):
        os.makedirs(dirname)

def write_local_file(type, path, file_data):
    # type: (text_type, text_type, binary_type) -> None
    file_path = os.path.join(settings.LOCAL_UPLOADS_DIR, type, path)
    mkdirs(file_path)
    with open(file_path, 'wb') as f:
        f.write(file_data)

def get_local_file_path(path_id):
    # type: (text_type) -> Optional[text_type]
    local_path = os.path.join(settings.LOCAL_UPLOADS_DIR, 'files', path_id)
    if os.path.isfile(local_path):
        return local_path
    else:
        return None

class LocalUploadBackend(ZulipUploadBackend):
    def upload_message_image(self, uploaded_file_name, content_type, file_data, user_profile, target_realm=None):
        # type: (text_type, Optional[text_type], binary_type, UserProfile, Optional[Realm]) -> text_type
        # Split into 256 subdirectories to prevent directories from getting too big
        path = "/".join([
            str(user_profile.realm.id),
            format(random.randint(0, 255), 'x'),
            random_name(18),
            sanitize_name(uploaded_file_name)
        ])

        write_local_file('files', path, file_data)
        create_attachment(uploaded_file_name, path, user_profile)
        return '/user_uploads/' + path

    def delete_message_image(self, path_id):
        # type: (text_type) -> bool
        file_path = os.path.join(settings.LOCAL_UPLOADS_DIR, 'files', path_id)
        if os.path.isfile(file_path):
            # This removes the file but the empty folders still remain.
            os.remove(file_path)
            return True

        file_name = path_id.split("/")[-1]
        logging.warning("%s does not exist. Its entry in the database will be removed." % (file_name,))
        return False

    def upload_avatar_image(self, user_file, user_profile, email):
        # type: (File, UserProfile, text_type) -> None
        email_hash = user_avatar_hash(email)

        image_data = user_file.read()
        write_local_file('avatars', email_hash+'.original', image_data)

        resized_data = resize_avatar(image_data)
        write_local_file('avatars', email_hash+'.png', resized_data)

    def get_avatar_url(self, hash_key):
        # type: (text_type) -> text_type
        # ?x=x allows templates to append additional parameters with &s
        return u"/user_avatars/%s.png?x=x" % (hash_key)

# Common and wrappers
if settings.LOCAL_UPLOADS_DIR is not None:
    upload_backend = LocalUploadBackend() # type: ZulipUploadBackend
else:
    upload_backend = S3UploadBackend()

def delete_message_image(path_id):
    # type: (text_type) -> bool
    return upload_backend.delete_message_image(path_id)

def upload_avatar_image(user_file, user_profile, email):
    # type: (File, UserProfile, text_type) -> None
    upload_backend.upload_avatar_image(user_file, user_profile, email)

def upload_message_image(uploaded_file_name, content_type, file_data, user_profile, target_realm=None):
    # type: (text_type, Optional[text_type], binary_type, UserProfile, Optional[Realm]) -> text_type
    return upload_backend.upload_message_image(uploaded_file_name, content_type, file_data,
                                               user_profile, target_realm=target_realm)

def claim_attachment(user_profile, path_id, message, is_message_realm_public):
    # type: (UserProfile, text_type, Message, bool) -> bool
    try:
        attachment = Attachment.objects.get(path_id=path_id)
        attachment.messages.add(message)
        # Only the owner of the file has the right to elevate the permissions of a file.
        # This makes sure that a private file is not accidently made public by another user
        # by sending a message to a public stream that refers the private file.
        if attachment.owner == user_profile:
            attachment.is_realm_public = attachment.is_realm_public or is_message_realm_public
        attachment.save()
        return True
    except Attachment.DoesNotExist:
        raise JsonableError(_("The upload was not successful. Please reupload the file again in a new message."))
    return False

def create_attachment(file_name, path_id, user_profile):
    # type: (text_type, text_type, UserProfile) -> bool
    Attachment.objects.create(file_name=file_name, path_id=path_id, owner=user_profile, realm=user_profile.realm)
    return True

def upload_message_image_from_request(request, user_file, user_profile):
    # type: (HttpRequest, File, UserProfile) -> text_type
    uploaded_file_name, content_type = get_file_info(request, user_file)
    return upload_message_image(uploaded_file_name, content_type, user_file.read(), user_profile)
