# © 2015 James R. Barlow: github.com/jbarlow83
#
# This file is part of OCRmyPDF.
#
# OCRmyPDF is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# OCRmyPDF 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.

# unpaper documentation:
# https://github.com/Flameeyes/unpaper/blob/master/doc/basic-concepts.md

"""Interface to unpaper executable"""

import os
import shlex
from functools import lru_cache
from subprocess import PIPE, STDOUT, CalledProcessError
from tempfile import TemporaryDirectory

from PIL import Image

from ..exceptions import MissingDependencyError, SubprocessOutputError
from . import get_version
from . import run as external_run


@lru_cache(maxsize=1)
def version():
    return get_version('unpaper')


def run(input_file, output_file, dpi, log, mode_args):
    args_unpaper = ['unpaper', '-v', '--dpi', str(dpi)] + mode_args

    SUFFIXES = {'1': '.pbm', 'L': '.pgm', 'RGB': '.ppm'}

    with TemporaryDirectory() as tmpdir, Image.open(input_file) as im:
        if im.mode not in SUFFIXES.keys():
            log.info("Converting image to other colorspace")
            try:
                if im.mode == 'P' and len(im.getcolors()) == 2:
                    im = im.convert(mode='1')
                else:
                    im = im.convert(mode='RGB')
            except IOError as e:
                im.close()
                raise MissingDependencyError(
                    "Could not convert image with type " + im.mode
                ) from e

        try:
            suffix = SUFFIXES[im.mode]
        except KeyError:
            raise MissingDependencyError(
                "Failed to convert image to a supported format."
            ) from e

        input_pnm = os.path.join(tmpdir, f'input{suffix}')
        output_pnm = os.path.join(tmpdir, f'output{suffix}')
        im.save(input_pnm, format='PPM')

        # To prevent any shenanigans from accepting arbitrary parameters in
        # --unpaper-args, we:
        # 1) run with cwd set to a tmpdir with only unpaper's files
        # 2) forbid the use of '/' in arguments, to prevent changing paths
        # 3) append absolute paths for the input and output file
        # This should ensure that a user cannot clobber some other file with
        # their unpaper arguments (whether intentionally or otherwise)
        args_unpaper.extend([input_pnm, output_pnm])
        try:
            proc = external_run(
                args_unpaper,
                check=True,
                close_fds=True,
                universal_newlines=True,
                stderr=STDOUT,
                cwd=tmpdir,
                stdout=PIPE,
            )
        except CalledProcessError as e:
            log.debug(e.output)
            raise e from e
        else:
            log.debug(proc.stdout)
            # unpaper sets dpi to 72; fix this
            try:
                with Image.open(output_pnm) as imout:
                    imout.save(output_file, dpi=(dpi, dpi))
            except (FileNotFoundError, OSError):
                raise SubprocessOutputError(
                    "unpaper: failed to produce the expected output file. "
                    + " Called with: "
                    + str(args_unpaper)
                ) from None


def validate_custom_args(args: str):
    unpaper_args = shlex.split(args)
    if any('/' in arg for arg in unpaper_args):
        raise ValueError('No filenames allowed in --unpaper-args')
    return unpaper_args


def clean(input_file, output_file, dpi, log, unpaper_args=None):
    default_args = [
        '--layout',
        'none',
        '--mask-scan-size',
        '100',  # don't blank out narrow columns
        '--no-border-align',  # don't align visible content to borders
        '--no-mask-center',  # don't center visible content within page
        '--no-grayfilter',  # don't remove light gray areas
        '--no-blackfilter',  # don't remove solid black areas
        '--no-deskew',  # don't deskew
    ]
    if not unpaper_args:
        unpaper_args = default_args
    run(input_file, output_file, dpi, log, unpaper_args)
