"""A class to manage fetching and caching of images by URL"""

# Copyright 2012-2014 Anthony Beville

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import datetime
import logging
import os
import shutil
import sqlite3 as lite
import tempfile
from typing import Union

import requests

from comictaggerlib import ctversion
from comictaggerlib.settings import ComicTaggerSettings

try:
    from PyQt5 import QtCore, QtNetwork

    qt_available = True
except ImportError:
    qt_available = False

logger = logging.getLogger(__name__)


class ImageFetcherException(Exception):
    pass


def fetch_complete(image_data: Union[bytes, QtCore.QByteArray]) -> None:
    ...


class ImageFetcher:

    image_fetch_complete = fetch_complete

    def __init__(self) -> None:

        self.settings_folder = ComicTaggerSettings.get_settings_folder()
        self.db_file = os.path.join(self.settings_folder, "image_url_cache.db")
        self.cache_folder = os.path.join(self.settings_folder, "image_cache")

        self.user_data = None
        self.fetched_url = ""

        if not os.path.exists(self.db_file):
            self.create_image_db()

        if qt_available:
            self.nam = QtNetwork.QNetworkAccessManager()

    def clear_cache(self) -> None:
        os.unlink(self.db_file)
        if os.path.isdir(self.cache_folder):
            shutil.rmtree(self.cache_folder)

    def fetch(self, url: str, blocking: bool = False) -> bytes:
        """
        If called with blocking=True, this will block until the image is
        fetched.
        If called with blocking=False, this will run the fetch in the
        background, and emit a signal when done
        """

        self.fetched_url = url

        # first look in the DB
        image_data = self.get_image_from_cache(url)
        if blocking or not qt_available:
            if not image_data:
                try:
                    image_data = requests.get(url, headers={"user-agent": "comictagger/" + ctversion.version}).content
                except Exception as e:
                    logger.exception("Fetching url failed: %s")
                    raise ImageFetcherException("Network Error!") from e

            # save the image to the cache
            self.add_image_to_cache(self.fetched_url, image_data)
            return image_data

        if qt_available:
            # if we found it, just emit the signal asap
            if image_data:
                ImageFetcher.image_fetch_complete(QtCore.QByteArray(image_data))
                return bytes()

            # didn't find it.  look online
            self.nam.finished.connect(self.finish_request)
            self.nam.get(QtNetwork.QNetworkRequest(QtCore.QUrl(url)))

            # we'll get called back when done...
        return bytes()

    def finish_request(self, reply: QtNetwork.QNetworkReply) -> None:
        # read in the image data
        logger.debug("request finished")
        image_data = reply.readAll()

        # save the image to the cache
        self.add_image_to_cache(self.fetched_url, image_data)

        ImageFetcher.image_fetch_complete(image_data)

    def create_image_db(self) -> None:

        # this will wipe out any existing version
        open(self.db_file, "wb").close()

        # wipe any existing image cache folder too
        if os.path.isdir(self.cache_folder):
            shutil.rmtree(self.cache_folder)
        os.makedirs(self.cache_folder)

        con = lite.connect(self.db_file)

        # create tables
        with con:
            cur = con.cursor()

            cur.execute("CREATE TABLE Images(url TEXT,filename TEXT,timestamp TEXT,PRIMARY KEY (url))")

    def add_image_to_cache(self, url: str, image_data: Union[bytes, QtCore.QByteArray]) -> None:

        con = lite.connect(self.db_file)

        with con:
            cur = con.cursor()

            timestamp = datetime.datetime.now()

            tmp_fd, filename = tempfile.mkstemp(dir=self.cache_folder, prefix="img")
            with os.fdopen(tmp_fd, "w+b") as f:
                f.write(bytes(image_data))

            cur.execute("INSERT or REPLACE INTO Images VALUES(?, ?, ?)", (url, filename, timestamp))

    def get_image_from_cache(self, url: str) -> bytes:

        con = lite.connect(self.db_file)
        with con:
            cur = con.cursor()

            cur.execute("SELECT filename FROM Images WHERE url=?", [url])
            row = cur.fetchone()

            if row is None:
                return bytes()

            filename = row[0]
            image_data = bytes()

            try:
                with open(filename, "rb") as f:
                    image_data = f.read()
                    f.close()
            except IOError:
                pass

            return image_data