#!/usr/bin/python3
"""
For more information see README.md

author: Sven Hauer
September, 2019
"""

import os
import sys
import io
import glob
import argparse
import PIL.Image

def read_logfile(filename):
    with open(filename, "rb") as binary_file:
        # Read the whole file at once
        return binary_file.read()

# find start and end of png based on:
# https://github.com/corkami/pics/blob/master/binary/PNG.png
def check_for_png(data):
    start_bytes = b'\x89PNG\r\n\x1a\n'
    end_bytes = b'IEND\xAE\x42\x60\x82'
    start = data.find(start_bytes)
    if start < 0:
        raise ValueError
    end = data.find(end_bytes)+len(end_bytes)
    return (start, end)

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    # a german bankleitzahl is a number beginning with [1-9] and has eight digits.
    parser.add_argument("--blz", type=str, metavar="BLZ", default = '*', help="enforce a bankleitzahl")
    parser.add_argument("-s", "--scaling", type=int, metavar="n", default=3, dest="img_scaling", help="Scale the output image.")
    parser.add_argument('--pngfile', metavar="filename", dest="png_outfile", default=None, type=argparse.FileType('wb'), help="Save image as png")
    args = parser.parse_args()

    log_path = "~/aqbanking/backends/aqhbci/data/banks/de/{}/logs/*.log".format(args.blz)
    #print(f"Using logfile glob pattern: '{log_path}'")

    # find all logfiles and sort them to find the newest file.
    input_log_file = sorted(glob.glob(os.path.expanduser(log_path)),
                            key = lambda x: os.path.getmtime(x))[-1]
    print(f"Using logfile: '{input_log_file}'")

    # read logfile
    data = read_logfile(input_log_file)
    # find the embedded png image
    try:
        start, end = check_for_png(data)
    except ValueError:
        print("No valid png found in logfile.")
        sys.exit(-3)

    # save png image into an in memory file
    png_data = io.BytesIO(data[start:end])

    # save image to a file
    if args.png_outfile:
        args.png_outfile.write(png_data.getbuffer())

    # show a scaled image into a window
    img = PIL.Image.open(png_data)
    img = img.resize((a*args.img_scaling for a in img.size), PIL.Image.NEAREST)
    img.show()