#!/usr/bin/env python3
# Author: Theeko74
# Contributor(s): skjerns
# Oct, 2021
# MIT license -- free to use as you want, cheers.

"""
Simple python wrapper script to use ghoscript function to compress PDF files.

Compression levels:
    0: default
    1: prepress
    2: printer
    3: ebook
    4: screen

Dependency: Ghostscript.
On MacOSX install via command line `brew install ghostscript`.
"""

import argparse
import subprocess
import os.path
import sys
import shutil

def compress(input_file_path, output_file_path, power=0):
    """Function to compress PDF via Ghostscript command line interface"""
    quality = {
        0: '/default',
        1: '/prepress',
        2: '/printer',
        3: '/ebook',
        4: '/screen'
    }

    # Basic controls
    # Check if valid path
    if not os.path.isfile(input_file_path):
        print("Error: invalid path for input PDF file")
        sys.exit(1)

    # Check if file is a PDF by extension
    if input_file_path.split('.')[-1].lower() != 'pdf':
        print("Error: input file is not a PDF")
        sys.exit(1)

    gs = get_ghostscript_path()
    print("Compress PDF...")
    initial_size = os.path.getsize(input_file_path)
    subprocess.call([gs, '-sDEVICE=pdfwrite', '-dCompatibilityLevel=1.4',
                    '-dPDFSETTINGS={}'.format(quality[power]),
                    '-dNOPAUSE', '-dQUIET', '-dBATCH',
                    '-sOutputFile={}'.format(output_file_path),
                     input_file_path]
    )
    final_size = os.path.getsize(output_file_path)
    ratio = 1 - (final_size / initial_size)
    print("Compression by {0:.0%}.".format(ratio))
    print("Final file size is {0:.1f}MB".format(final_size / 1000000))
    print("Done.")


def get_ghostscript_path():
    gs_names = ['gs', 'gswin32', 'gswin64']
    for name in gs_names:
        if shutil.which(name):
            return shutil.which(name)
    raise FileNotFoundError(f'No GhostScript executable was found on path ({"/".join(gs_names)})')


def main():
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter
    )
    parser.add_argument('input', help='Relative or absolute path of the input PDF file')
    parser.add_argument('-o', '--out', help='Relative or absolute path of the output PDF file')
    parser.add_argument('-c', '--compress', type=int, help='Compression level from 0 to 4')
    parser.add_argument('-b', '--backup', action='store_true', help="Backup the old PDF file")
    parser.add_argument('--open', action='store_true', default=False,
                        help='Open PDF after compression')
    args = parser.parse_args()

    # In case no compression level is specified, default is 2 '/ printer'
    if not args.compress:
        args.compress = 2
    # In case no output file is specified, store in temp file
    if not args.out:
        args.out = 'temp.pdf'

    # Run
    compress(args.input, args.out, power=args.compress)

    # In case no output file is specified, erase original file
    if args.out == 'temp.pdf':
        if args.backup:
            shutil.copyfile(args.input, args.input.replace(".pdf", "_BACKUP.pdf"))
        shutil.copyfile(args.out, args.input)
        os.remove(args.out)

    # In case we want to open the file after compression
    if args.open:
        if args.out == 'temp.pdf' and args.backup:
            subprocess.call(['open', args.input])
        else:
            subprocess.call(['open', args.out])

if __name__ == '__main__':
    main()