#!/usr/bin/env python3
"""extract_odf_links.py - Tool to extract links from ODF documents

Given one or more ODF documents, this tool finds links that refer to the local
filesystem, and writes their full paths to stdout.
"""
# Copyright © 2020 Brett Smith
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import argparse
import concurrent.futures as futmod
import logging
import multiprocessing
import os
import sys
import urllib.parse

from pathlib import Path
from zipfile import BadZipFile

import odf.opendocument  # type:ignore[import]
import odf.text  # type:ignore[import]

from typing import (
    Dict,
    Hashable,
    Iterator,
    Optional,
    Sequence,
    Set,
    TextIO,
)

from .. import cliutil

# This should be Queue[Optional[Path]] but that requires newer typeshed
PathQ = multiprocessing.SimpleQueue

PROGNAME = 'extract-odf-links'
_QUEUES: Dict[Hashable, PathQ] = {}
logger = logging.getLogger('conservancy_beancount.tools.extract_odf_links')

def parse_delimiter(arg: str) -> str:
    try:
        retval = eval('"{}"'.format(arg.replace('"', r'\"')), {})
    except SyntaxError:
        retval = None
    if isinstance(retval, str):
        return retval
    else:
        raise ValueError(f"not a valid string: {arg!r}")

def parse_arguments(arglist: Optional[Sequence[str]]=None) -> argparse.Namespace:
    parser = argparse.ArgumentParser(prog=PROGNAME)
    cliutil.add_version_argument(parser)
    cliutil.add_loglevel_argument(parser)
    cliutil.add_jobs_argument(parser)
    parser.add_argument(
        '--delimiter', '-d',
        metavar='TEXT',
        type=parse_delimiter,
        default='\\n',
        help="""String to output between links. Accepts all backslash escapes
supported in Python like \\n, \\t, \\0, \\u, etc. Default `%(default)s`.
""")
    parser.add_argument(
        '--zero', '--null', '-z', '-0',
        action='store_const',
        dest='delimiter',
        const='\0',
        help="""Shortcut for --delimiter=\\0
""")
    parser.add_argument(
        '--relative-to', '-r',
        metavar='PATH',
        type=Path,
        help="""Try to resolve all links relative to this path, rather than each
spreadsheet's path
""")
    parser.add_argument(
        'odf_paths',
        metavar='ODF_PATH',
        type=Path,
        nargs=argparse.ONE_OR_MORE,
        help="""ODF file(s) to extract links from
""")
    args = parser.parse_args(arglist)
    paths_count = len(args.odf_paths)
    args.odf_paths = [path for path in args.odf_paths if path != cliutil.STDSTREAM_PATH]
    args.read_stdin = paths_count > len(args.odf_paths)
    if args.relative_to is None:
        if args.read_stdin:
            parser.error("--relative-to is required to read from stdin")
    elif args.relative_to.is_dir() or not args.relative_to.exists():
        args.relative_to /= 'PathStub.ods'
    return args

def extract_links(odf_doc: odf.opendocument.OpenDocument, rel_path: Path) -> Iterator[Path]:
    for a_elem in odf_doc.getElementsByType(odf.text.A):
        parts = urllib.parse.urlparse(a_elem.getAttribute('href') or '')
        if (parts.scheme and parts.scheme != 'file') or not parts.path:
            continue
        path = Path(urllib.parse.unquote(parts.path))
        if not path.is_absolute():
            path = (rel_path / path).resolve()
            try:
                path.relative_to(rel_path)
            except ValueError:
                pass
            else:
                # Link points to another document inside the ODF. Skip it.
                continue
        yield path

def enqueue_links(odf_path: Path,
                  rel_path: Optional[Path],
                  queue_key: Hashable,
                  stdin_fd: int,
) -> None:
    queue = _QUEUES[queue_key]
    try:
        with cliutil.bytes_output(odf_path, stdin_fd, 'r') as odf_file:
            odf_doc = odf.opendocument.load(odf_file)
        for path in extract_links(odf_doc, rel_path or odf_path):
            queue.put(path)
    finally:
        queue.put(None)

def main(arglist: Optional[Sequence[str]]=None,
         stdout: TextIO=sys.stdout,
         stderr: TextIO=sys.stderr,
) -> int:
    args = parse_arguments(arglist)
    cliutil.set_loglevel(logger, args.loglevel)
    args.odf_paths.sort(key=lambda path: path.stat().st_size)
    if not args.read_stdin:
        # Set a value that passes type checking but will crash if opened.
        stdin_fd = -1
    else:
        # multiprocessing closes subprocesses' stdin.
        # Migrate it to a new fd they can read.
        stdin_fd = os.dup(sys.stdin.fileno())
        os.set_inheritable(stdin_fd, True)
        args.odf_paths.append(cliutil.STDSTREAM_PATH)
    args.odf_paths.reverse()

    queue_key = id(args)
    queue = _QUEUES[queue_key] = multiprocessing.SimpleQueue()
    # `args.jobs - 1` because the main process does enough work to count as one.
    max_procs = max(1, min(args.jobs - 1, len(args.odf_paths)))
    with futmod.ProcessPoolExecutor(max_procs) as pool:
        procs = {pool.submit(
            enqueue_links, odf_path, args.relative_to, queue_key, stdin_fd,
        ) for odf_path in args.odf_paths}
        procs_left = len(procs)
        seen: Set[Path] = set()
        while procs_left:
            path = queue.get()
            if path is None:
                procs_left -= 1
            elif path not in seen:
                seen.add(path)
                if not path.exists():
                   logger.warning("path %s not found", path)
                print(path, end=args.delimiter, file=stdout)

    returncode = 0
    for odf_path, proc in zip(args.odf_paths, procs):
        try:
            proc.result()
        except IOError as error:
            logger.error("error reading %s: %s", odf_path, error.strerror)
            returncode = os.EX_DATAERR
        except BadZipFile as error:
            logger.error("error parsing %s: %s", odf_path, error.args[0])
            returncode = os.EX_DATAERR
    return returncode

entry_point = cliutil.make_entry_point(__name__, PROGNAME)

if __name__ == '__main__':
    exit(entry_point())