#!/usr/bin/env python

import argparse

import hashlib

import pathlib

import sys

PARSER = argparse.ArgumentParser(

description="Helper for check file hashes in Makefile instead of bare timestamps"

)

PARSER.add_argument("dst", metavar="DST", type=pathlib.Path)

PARSER.add_argument("-d", "--debug", action="store_true", default=False)

def main(argv):

args = PARSER.parse_args(argv)

dst = args.dst

assert dst.suffix == ".hash"

dirname = dst.parent

if dirname.name != ".hash":

if args.debug:

print(f"Invalid name {dst} -> dirname {dirname}", file=sys.stderr)

return 0

dirname.mkdir(exist_ok=True)

src_dir = dirname.parent

src_name = dst.stem # drop .hash

full_src = src_dir / src_name

hasher = hashlib.sha256()

try:

hasher.update(full_src.read_bytes())

except OSError:

if args.debug:

print(f"Cannot open {full_src}", file=sys.stderr)

return 0

src_hash = hasher.hexdigest()

if dst.exists():

dst_hash = dst.read_text()

else:

dst_hash = ""

if src_hash != dst_hash:

dst.write_text(src_hash)

print(f"re-hash {src_hash}")

else:

if args.debug:

print(f"Skip {src_hash} checksum, up-to-date")

return 0

if __name__ == "__main__":

sys.exit(main(sys.argv[1:]))