pdfdiff.py

# file: pdfdiff.py
# vim:fileencoding=utf-8:ft=python
#
# Copyright © 2019 R.F. Smith <rsmith@xs4all.nl>
# SPDX-License-Identifier: MIT
# Created: 2019-07-11T00:22:30+0200
# Last modified: 2020-04-23T19:03:32+0200
"""
Script to try and show a diff between two PDF files.

Requires pdftotext from the poppler utilities,
and a diff that supports the -w option to ignore whitespace.
"""

from types import SimpleNamespace
import binascii
import os
import subprocess as sp
import sys

# Standard ANSI colors.
fgcolor = SimpleNamespace(
    brightred="\033[31;1m",
    brightgreen="\033[32;1m",
    brightyellow="\033[33;1m",
    brightmagenta="\033[35;1m",
    reset="\033[0m",
)


def main(argv):
    """
    Entry point for pdfdiff.py.

    Arguments:
        argv: command line arguments
    """
    if len(argv) != 2:
        print("Usage: pdfdiff.py first second")
        sys.exit(1)
    tmpnam = []
    for j in range(2):
        tmpnam.append(binascii.hexlify(os.urandom(10)).decode("ascii") + ".txt")
        with open(tmpnam[j], "w") as f:
            f.write(pdftotext(argv[j]))
    diffargs = ["diff", "-d", "-u", "-w"] + tmpnam
    result = sp.run(diffargs, stdout=sp.PIPE, stderr=sp.DEVNULL, check=True, text=True)
    lines = result.stdout.splitlines()
    os.remove(tmpnam[0])
    os.remove(tmpnam[1])
    lines[0] = lines[0].replace(tmpnam[0], argv[0])
    lines[1] = lines[1].replace(tmpnam[1], argv[1])
    try:
        colordiff(lines)
    except BrokenPipeError:
        pass


def pdftotext(path):
    """
    Generate a text rendering of a PDF file in the form of a list of lines.
    """
    args = ["pdftotext", "-layout", path, "-"]
    cp = sp.run(args, stdout=sp.PIPE, stderr=sp.DEVNULL, check=True, text=True)
    return cp.stdout


def colordiff(txt):
    """
    Print a colored diff.

    Arguments:
        txt: diff list or generator to print
    """
    for line in txt:
        line = line.rstrip()
        if line.startswith(("+++ ", "--- ")):
            print(fgcolor.brightyellow, line)
            continue
        if line.startswith("+"):
            print(fgcolor.brightgreen, line)
            continue
        if line.startswith("-"):
            print(fgcolor.brightred, line)
            continue
        if line.startswith("@@"):
            print(fgcolor.brightmagenta, line)
            continue
        print(fgcolor.reset, line)


if __name__ == "__main__":
    main(sys.argv[1:])