"""
Author: Lukas Heiligenbrunner
Matr.Nr.: K12104785
Exercise 2
"""

import os.path
from enum import Enum
from glob import glob
from typing import TextIO
import hashlib

import PIL
from PIL import Image, ImageStat


def mkdirIfNotExists(path: str):
    if not os.path.isdir(path):
        print(f"creating folder: {path}")
        os.makedirs(path)


def validSuffix(file: str) -> bool:
    return file.endswith((".jpg", ".jpeg", ".JPG", ".JPEG"))


def validFileSize(file: str) -> bool:
    return os.path.getsize(file) < 250_000


class ErrorCodes(Enum):
    Extension = 1
    FileSize = 2
    InvalidImage = 3
    ImageShape = 4
    VarianceLZero = 5
    Duplicate = 6


def log(filename: str, errorCode: ErrorCodes):
    print(f"[{filename}] :: {errorCode}")


class Singleton(type):
    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


class FileLogger(metaclass=Singleton):
    file: TextIO or None = None

    def init(self, log_file_path: str):
        self.file = open(log_file_path, 'a')

    def close(self):
        self.file.close()

    def log(self, filename: str, errorcode: ErrorCodes):
        # enforce a CRLF line ending with \r\n  !!
        self.file.write(f"{os.path.basename(filename)};{errorcode.value}\r\n")


def openImage(path: str) -> PIL.Image.Image or None:
    try:
        return Image.open(path)
    except (FileNotFoundError, PIL.UnidentifiedImageError, ValueError, TypeError) as e:
        return None


def validImageShape(img: PIL.Image.Image) -> bool:
    # check read mode of channels
    if img.mode != "RGB":
        return False

    # check if nr and order of channels is correct
    if img.getbands() != ('R', 'G', 'B'):
        return False

    # check if file format is jepeg
    if img.format != "JPEG":
        return False

    # check if height and length is > 96
    if img.height <= 96 or img.width <= 96:
        return False

    return True


def validVariance(img: PIL.Image.Image) -> bool:
    variances = ImageStat.Stat(img).var
    # variance cannot be negative!
    return min(variances) > .0


class FileCopy(metaclass=Singleton):
    format: str
    out_dir: str

    hashmap: [str]
    idx: int

    def init(self, out_dir: str, format: str):
        self.format = format
        self.out_dir = out_dir
        self.idx = 1
        self.hashmap = []

    def copyFile(self, img: PIL.Image.Image) -> bool:
        hexhash = hashlib.md5(img.__array__()).hexdigest()
        if hexhash in self.hashmap:
            return False
            # element already copied
        else:
            self.hashmap.append(hexhash)
            # apply format string
            filename = f"%{self.format}" % self.idx
            self.idx += 1
            # copy file
            im = PIL.Image.fromarray(img.__array__())
            im.save(os.path.join(self.out_dir, f"{filename}.jpg"), format="jpeg")
            im.close()
            return True


def processFile(f: str) -> bool:
    # check suffix
    if not validSuffix(f):
        log(f, ErrorCodes.Extension)
        FileLogger().log(f, ErrorCodes.Extension)
        return False

    # check file size
    if not validFileSize(f):
        log(f, ErrorCodes.FileSize)
        FileLogger().log(f, ErrorCodes.FileSize)
        return False

    img = openImage(f)
    if img is None:
        log(f, ErrorCodes.InvalidImage)
        FileLogger().log(f, ErrorCodes.InvalidImage)
        return False

    if not validImageShape(img):
        log(f, ErrorCodes.ImageShape)
        FileLogger().log(f, ErrorCodes.ImageShape)
        return False

    if not validVariance(img):
        log(f, ErrorCodes.VarianceLZero)
        FileLogger().log(f, ErrorCodes.VarianceLZero)
        return False

    # lets copy the image data
    if not FileCopy().copyFile(img):
        log(f, ErrorCodes.Duplicate)
        FileLogger().log(f, ErrorCodes.Duplicate)
        return False

    # ok nice if we are here we have successfully copied the img (:

    # close image
    img.close()
    return True


def validate_images(input_dir: str, output_dir: str, log_file: str, formatter: str = "05d") -> int:
    # check if out_put dir exists
    mkdirIfNotExists(output_dir)

    # check if logfile dir exists
    logdir = os.path.dirname(log_file)
    mkdirIfNotExists(logdir)

    # init file logger
    FileLogger().init(log_file)
    FileCopy().init(output_dir, formatter)

    # scan input dir for files
    files = glob(input_dir + '/**/*.*', recursive=True)

    # sort filenames
    files.sort()

    succcounter = 0
    for f in files:
        if processFile(f):
            succcounter += 1

    FileLogger().close()
    return succcounter


# Press the green button in the gutter to run the script.
if __name__ == '__main__':
    print(validate_images("unittest/unittest_input_0", "unittest/outputs/unittest_input_0",
                          "unittest/outputs/unittest_input_0.log", "06d"))