#! /usr/bin/env python3
""" Move files and directories to custom trash directories, taking the
corresponding mount points into account.
"""

from pathlib import Path
import argparse
import logging
import sys
import os
import json
from datetime import datetime
from subprocess import check_output

DEFAULT_CONFIG = {
    'trashes': [
        '$HOME/trash/',
    ]
}


def parse_args():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('names', nargs='*')
    parser.add_argument('-d', '--dry-run', action='store_true')
    parser.add_argument('-l', '--list', action='store_true')
    return parser.parse_args()


def lowest_mount(path: Path) -> Path:
    """Find lowest level mount point of given path"""
    while not path.is_mount() and path.parent != path:
        return lowest_mount(path.parent)

    return path


def getconfig() -> dict:
    config_file = Path('~/.config/trash.json').expanduser()
    config = DEFAULT_CONFIG
    if config_file.is_file():
        with open(config_file) as f:
            config.update(json.load(f))
    return config


def get_trashes(config):
    trashes: list[Path] = []
    for trashdir in config['trashes']:
        trashdir = Path(os.path.expandvars(trashdir)).expanduser().resolve()
        trashes.append(trashdir)
    return trashes


def write_meta(original_dir, trash_timestamp_dir, calc_size=False):
    if calc_size:
        size = check_output(['du', '-sh', original_dir]).split()[0].decode('utf8')
    else:
        size = '?'
    with open(trash_timestamp_dir / '.trash_meta', 'w') as f:
        f.writelines([l + '\n' for l in [str(original_dir), size]])


def read_meta(meta_file: Path) -> tuple:
    with open(meta_file) as f:
        try:
            trashed_dir, size = f.readlines()
            trashed_dir = trashed_dir.strip()
            size = size.strip()
        except ValueError:
            logging.info(f'Meta information at {meta_file} outdated or corrupt')
            trashed_dir = size = None
    return trashed_dir, size


def trash(names, config, dry_run=False):
    for name in names:
        name = Path(os.path.expandvars(name))

        if not (name.is_file() or name.is_dir()):
            logging.warning(f'{name} is not a file nor directory')
            continue

        name = name.absolute()

        trashed = False
        for trashdir in get_trashes(config):
            try:
                if lowest_mount(trashdir) == lowest_mount(name):
                    timestamp_prefix = trashdir / datetime.now().isoformat(
                        timespec='seconds').replace(':', '_')
                    newname = timestamp_prefix / '/'.join(name.parts[1:])
                    newname.parent.mkdir(parents=True, exist_ok=True)
                    logging.debug(f'Will move {name} to {newname}')
                    if not dry_run:
                        write_meta(name, timestamp_prefix)
                        name.rename(newname)
                    trashed = True
                    break
            except ValueError:
                pass

        if not trashed:
            logging.warning(f'Unable to trash {name}')


def extract_timestamp(trashed_path: Path) -> datetime:
    # length of the used ISO format is 19!
    date_string = trashed_path.parts[-1][-19:].replace('_', ':')
    logging.debug(f'Extracted {date_string} from {trashed_path}')
    return datetime.fromisoformat(date_string)


def trashed_sort_key(trashed_path: Path) -> int:
    return extract_timestamp(trashed_path).timestamp()


def list_trashed(config) -> str:
    """ Yield trashed entries for trashdirs of given config
    """
    for trashdir in get_trashes(config):
        for entry in sorted(trashdir.iterdir(), key=trashed_sort_key):
            meta_file = entry / '.trash_meta'
            if meta_file.is_file():
                trashed_dir, size = read_meta(meta_file)
                yield f'{trashed_dir or entry} ({extract_timestamp(entry)}, {size})'
            else:
                yield entry


def main():
    args = parse_args()
    logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)

    config = getconfig()
    logging.debug(config)

    if args.list:
        print(*list(list_trashed(config)), sep='\n')
        sys.exit()

    trash(args.names, config, dry_run=args.dry_run)

    if args.dry_run:
        logging.info('Dry run. Nothin happened. I guess.')


if __name__ == '__main__':
    main()