#!/usr/bin/env python3
# SPDX-License-Identifier: Apache-2.0

"""Write subfolder list to a file

This script will walk the specified directory and write the file specified with
the list of all sub-directories found. If the output file already exists, the
file will only be updated in case sub-directories have been added or removed
since the previous invocation.

"""

import os
import argparse


def parse_args():
    """Parse command line arguments and options"""
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter)

    parser.add_argument('-d', '--directory', required=True,
                        help='Directory to walk for sub-directory discovery')
    parser.add_argument('-c', '--create-links', required=False,
                        help='Create links for each directory found in \
                              directory given')
    parser.add_argument('-o', '--out-file', required=True,
                        help='File to write containing a list of all \
                              directories found')
    parser.add_argument('-t', '--trigger-file', required=False,
                        help='Trigger file to be be touched to re-run CMake')

    args = parser.parse_args()

    return args


def get_subfolder_list(directory, create_links=None):
    """Return subfolder list of a directory"""
    dirlist = []

    if create_links is not None:
        if not os.path.exists(create_links):
            os.makedirs(create_links)
        symbase = os.path.basename(directory)
        symlink = create_links + os.path.sep + symbase
        if not os.path.exists(symlink):
            os.symlink(directory, symlink)
        dirlist.append(symlink)
    else:
        dirlist.append(directory)

    for root, dirs, _ in os.walk(directory, topdown=True):
        dirs.sort()
        for subdir in dirs:
            if create_links is not None:
                targetdirectory = os.path.join(root, subdir)
                reldir = os.path.relpath(targetdirectory, directory)
                linkname = symbase + '_' + reldir.replace(os.path.sep, '_')
                symlink = create_links + os.path.sep + linkname
                if not os.path.exists(symlink):
                    os.symlink(targetdirectory, symlink)
                dirlist.append(symlink)
            else:
                dirlist.append(os.path.join(root, subdir))

    return dirlist


def gen_out_file(out_file, dirs):
    """Generate file with the list of directories

    File won't be updated if it already exists and has the same content

    """
    dirs_nl = "\n".join(dirs) + "\n"

    if os.path.exists(out_file):
        with open(out_file, 'r', encoding="utf-8") as out_file_fo:
            out_file_dirs = out_file_fo.read()

        if out_file_dirs == dirs_nl:
            return

    with open(out_file, 'w', encoding="utf-8") as out_file_fo:
        out_file_fo.writelines(dirs_nl)


def touch(trigger):
    """Touch the trigger file

    If no trigger file is provided then do a return.

    """
    if trigger is None:
        return

    if os.path.exists(trigger):
        os.utime(trigger, None)
    else:
        with open(trigger, 'w') as trigger_fo:
            trigger_fo.write("")


def main():
    """Parse command line arguments and take respective actions"""
    args = parse_args()

    dirs = get_subfolder_list(args.directory, args.create_links)
    gen_out_file(args.out_file, dirs)

    # Always touch trigger file to ensure json files are updated
    touch(args.trigger_file)


if __name__ == "__main__":
    main()