#!/usr/local/cpython-3.7/bin/python3

"""Manage timestamps files, to see if a directory's contents have changed."""

import os
import sys
import typing
import filecmp
import subprocess

TIMESTAMP_FILENAME = '.file-timestamps'
TEMP_TIMESTAMP_FILENAME = TIMESTAMP_FILENAME + '.temp'

def usage(retval: int) -> None:
    """Output a usage message."""
    if retval == 0:
        write = sys.stdout.write
    else:
        write = sys.stderr.write

    # write('Usage: {} --generate dir --compare dir1 dir2 --help'.format(sys.argv[0]))
    write('Usage: {} --help --verbose --generate dir1 dir2 ... dirn\n'.format(sys.argv[0]))

    sys.exit(retval)


def run(command: str) -> None:
    """Run shell command."""
    retval = subprocess.call(command, shell=True)

    if retval:
        sys.stderr.write('Command {} failed with exit code {}\n'.format(command, retval))
        sys.exit(1)


def generate(directory: str) -> bool:
    """Generate a fts file for directory."""
    filenames = [filename for filename in os.listdir(directory) if not filename.startswith('.')]
#    filenames = []
#    for filename in os.listdir(directory):
#        if filename.startswith('.'):
#            continue
#        filenames.append(filename)

    # I doubt filenames are guaranteed to come back sorted from os.listdir(), so we sort them ourselves.
    filenames.sort()

    temp_ts_fn = os.path.join(directory, TEMP_TIMESTAMP_FILENAME)
    ts_fn = os.path.join(directory, TIMESTAMP_FILENAME)

    with open(temp_ts_fn, 'w') as file_:
        for filename in filenames:
            fn = os.path.join(directory, filename)
            # We intentionally use a naked filename instead of fn in the 3rd field of 3.
            file_.write('{} {} {}\n'.format(os.path.getmtime(fn), os.path.getsize(fn), filename))

    # The "original" file does not exist - rename, output equal, and exit 0
    if not os.path.exists(ts_fn):
        os.rename(temp_ts_fn, ts_fn)
        return True
        
    # We exit 0 whether things look the same or not, because an error would look like exit 1, and
    # we want to be able to tell the difference.
    if filecmp.cmp(ts_fn, temp_ts_fn, shallow=False):
        os.unlink(temp_ts_fn)
        return True
    else:
        os.rename(temp_ts_fn, ts_fn)
        return False


# def inhale(filename: str) -> None:
#     """Return filename's mtime and a list of lines within it."""
#     dir_stamps = []
#     with open(filename, 'r') as file_:
#         for line in file_.readline():
#             dir_stamps.append(line)
#     return (os.path.getmtime(filename), dir_stamps)


def main() -> None:
    """Manage timestamps files, to see if a directory's contains have changed."""
    directories: typing.List[str] = []
    verbose = False

    while sys.argv[1:]:
        if sys.argv[1] == '--generate':
            directories = sys.argv[2:]
            del sys.argv[1]
            break
        elif sys.argv[1] == '--verbose':
            verbose = True
#        elif sys.argv[1] == '--compare':
#            directory1 = sys.argv[2]
#            directory2 = sys.argv[3]
#            del sys.argv[1]
#            del sys.argv[1]
#            compare(initial_cwd, directory1, directory2)
        elif sys.argv[1] in ('-h', '--help'):
            usage(0)
        else:
            sys.stderr.write('{}: Unrecognized option: {}\n'.format(sys.argv[0], sys.argv[1]))
            usage(1)
        del sys.argv[1]

    if not directories:
        sys.stderr.write('{}: --generate is a required option\n'.format(sys.argv[0]))
        usage(1)

    all_equal = True
    for directory in directories:
        if verbose:
            sys.stderr.write('Generating timestamp file for {}\n'.format(directory))
        subresult = generate(directory)
        all_equal &= subresult
        if subresult:
            print('equal')
        else:
            print('unequal')

    if all_equal:
        if verbose:
            sys.stderr.write('All equal\n')
    else:
        sys.stderr.write('One or more not equal\n')

    sys.exit(0)

if __name__ == '__main__':
    main()