#!/usr/bin/env python3
# SPDX-FileCopyrightText: 2022 James R. Barlow
# SPDX-License-Identifier: MPL-2.0

"""Validate a work order from API or command line."""

from __future__ import annotations

import logging
import os
import sys
from collections.abc import Sequence
from pathlib import Path
from shutil import copyfileobj

import pikepdf

from ocrmypdf._defaults import DEFAULT_ROTATE_PAGES_THRESHOLD
from ocrmypdf._exec import unpaper
from ocrmypdf._options import OcrOptions, ProcessingMode
from ocrmypdf._plugin_manager import OcrmypdfPluginManager
from ocrmypdf.exceptions import (
    BadArgsError,
    InputFileError,
    MissingDependencyError,
    OutputFileAccessError,
)
from ocrmypdf.helpers import (
    is_file_writable,
    running_in_docker,
    running_in_snap,
    safe_symlink,
)
from ocrmypdf.subprocess import check_external_program

log = logging.getLogger(__name__)


def check_platform() -> None:
    if sys.maxsize <= 2**32:  # pragma: no cover
        log.warning(
            "You are running OCRmyPDF in a 32-bit (x86) Python interpreter. "
            "This is not supported. 32-bit does not have enough address space "
            "to process large files. "
            "Please use a 64-bit (x86-64) version of Python."
        )


def check_options_languages(
    options: OcrOptions, ocr_engine_languages: list[str]
) -> None:
    # Check for blocked languages first, before checking if they're installed
    DENIED_LANGUAGES = {'equ', 'osd'}
    blocked = DENIED_LANGUAGES & set(options.languages)
    if blocked:
        raise BadArgsError(
            "The following languages are for Tesseract's internal use and "
            "should not be issued explicitly: "
            f"{', '.join(blocked)}\n"
            "Remove them from the -l/--language argument."
        )

    if not ocr_engine_languages:
        return

    missing_languages = set(options.languages) - set(ocr_engine_languages)
    if missing_languages:
        lang_text = '\n'.join(lang for lang in missing_languages)
        msg = (
            "OCR engine does not have language data for the following "
            "requested languages: \n"
            f"{lang_text}\n"
            "Please install the appropriate language data for your OCR engine.\n"
            "\n"
            "See the online documentation for instructions:\n"
            "    https://ocrmypdf.readthedocs.io/en/latest/languages.html\n"
            "\n"
            "Note: most languages are identified by a 3-letter ISO 639-2 Code.\n"
            "For example, English is 'eng', German is 'deu', and Spanish is 'spa'.\n"
            "Simplified Chinese is 'chi_sim' and Traditional Chinese is 'chi_tra'."
            "\n"
        )
        raise MissingDependencyError(msg)


def check_options_sidecar(options: OcrOptions) -> None:
    if options.sidecar == '\0':
        if options.output_file == '-':
            raise BadArgsError("--sidecar filename needed when output file is stdout.")
        elif options.output_file == os.devnull:
            raise BadArgsError(
                "--sidecar filename needed when output file is /dev/null or NUL."
            )
        options.sidecar = options.output_file + '.txt'
    if options.sidecar == options.input_file or options.sidecar == options.output_file:
        raise BadArgsError(
            "--sidecar file must be different from the input and output files"
        )


def check_options_preprocessing(options: OcrOptions) -> None:
    if options.clean_final:
        options.clean = True
    if options.unpaper_args and not options.clean:
        raise BadArgsError("--clean is required for --unpaper-args")
    if (
        options.rotate_pages_threshold != DEFAULT_ROTATE_PAGES_THRESHOLD
        and not options.rotate_pages
    ):
        raise BadArgsError("--rotate-pages is required for --rotate-pages-threshold")
    if options.clean:
        check_external_program(
            program='unpaper',
            package='unpaper',
            version_checker=unpaper.version,
            need_version='6.1',
            required_for="--clean, --clean-final",
        )


def check_options_strip(options: OcrOptions) -> None:
    """Reject options that cannot apply in strip mode.

    ``--mode strip`` removes the OCR text layer in place without rasterizing or
    running OCR, so image-processing and OCR-output options have no effect.
    """
    if options.mode != ProcessingMode.strip_text:
        return
    incompatible = {
        '--deskew': options.deskew,
        '--clean': options.clean,
        '--clean-final': options.clean_final,
        '--remove-background': options.remove_background,
        '--rotate-pages': options.rotate_pages,
        '--oversample': options.oversample,
        '--remove-vectors': options.remove_vectors,
        '--sidecar': options.sidecar,
    }
    used = sorted(name for name, value in incompatible.items() if value)
    if used:
        raise BadArgsError(
            "--mode strip removes the OCR text layer without rasterizing or "
            "running OCR, so these options have no effect and are not allowed: "
            f"{', '.join(used)}"
        )


def _check_plugin_invariant_options(options: OcrOptions) -> None:
    check_platform()
    check_options_strip(options)
    check_options_sidecar(options)
    check_options_preprocessing(options)


def _check_plugin_options(
    options: OcrOptions, plugin_manager: OcrmypdfPluginManager
) -> None:
    # First, let plugins check their external dependencies
    plugin_manager.check_options(options=options)

    # Then check OCR engine language support
    ocr_engine_languages = plugin_manager.get_ocr_engine(options=options).languages(
        options
    )
    check_options_languages(options, ocr_engine_languages)

    # Finally, run comprehensive validation using the coordinator
    from ocrmypdf._validation_coordinator import ValidationCoordinator

    coordinator = ValidationCoordinator(plugin_manager)
    coordinator.validate_all_options(options)


def check_options(options: OcrOptions, plugin_manager: OcrmypdfPluginManager) -> None:
    """Check options for validity and consistency.

    This function coordinates validation across the entire system:
    1. Core validation (platform, files, preprocessing)
    2. Plugin external dependency validation
    3. Plugin-specific validation (handled by plugin models)
    4. Cross-cutting validation (handled by validation coordinator)
    """
    _check_plugin_invariant_options(options)
    _check_plugin_options(options, plugin_manager)


def create_input_file(options: OcrOptions, work_folder: Path) -> tuple[Path, str]:
    if options.input_file == '-':
        # stdin
        log.info('reading file from standard input')
        target = work_folder / 'stdin'
        with open(target, 'wb') as stream_buffer:
            copyfileobj(sys.stdin.buffer, stream_buffer)
        return target, "stdin"
    elif hasattr(options.input_file, 'readable'):
        if not options.input_file.readable():
            raise InputFileError("Input file stream is not readable")
        log.info('reading file from input stream')
        target = work_folder / 'stream'
        with open(target, 'wb') as stream_buffer:
            copyfileobj(options.input_file, stream_buffer)
        return target, "stream"
    else:
        try:
            target = work_folder / 'origin'
            safe_symlink(options.input_file, target)
            return target, os.fspath(options.input_file)
        except FileNotFoundError as e:
            msg = f"File not found - {options.input_file}"
            if running_in_docker():  # pragma: no cover
                msg += (
                    "\nDocker cannot access your working directory unless you "
                    "explicitly share it with the Docker container and set up "
                    "permissions correctly.\n"
                    "You may find it easier to use stdin/stdout:"
                    "\n"
                    "\tdocker run -i --rm jbarlow83/ocrmypdf - - <input.pdf >output.pdf"
                    "\n"
                )
            elif running_in_snap():  # pragma: no cover
                msg += (
                    "\nSnap applications cannot access files outside of "
                    "your home directory unless you explicitly allow it. "
                    "You may find it easier to use stdin/stdout:"
                    "\n"
                    "\tsnap run ocrmypdf - - <input.pdf >output.pdf"
                    "\n"
                )
            raise InputFileError(msg) from e


def check_requested_output_file(options: OcrOptions) -> None:
    if options.output_file == '-':
        if sys.stdout.isatty():
            raise BadArgsError(
                "Output was set to stdout '-' but it looks like stdout "
                "is connected to a terminal.  Please redirect stdout to a "
                "file."
            )
    elif hasattr(options.output_file, 'writable'):
        if not options.output_file.writable():
            raise OutputFileAccessError("Output stream is not writable")
    elif not is_file_writable(options.output_file):
        raise OutputFileAccessError(
            f"Output file location ({options.output_file}) is not a writable file."
        )

    if (
        options.no_overwrite
        and not hasattr(options.output_file, 'writable')
        and options.output_file != '-'
        and Path(str(options.output_file)).exists()
    ):
        raise OutputFileAccessError(
            f"Output file already exists: {options.output_file}\n"
            "To overwrite it, omit the --no-overwrite / -n option."
        )


def report_output_file_size(
    options: OcrOptions,
    input_file: Path,
    output_file: Path,
    optimize_messages: Sequence[str] | None = None,
    file_overhead: int = 4000,
    page_overhead: int = 3000,
) -> None:
    if optimize_messages is None:
        optimize_messages = []
    try:
        output_size = Path(output_file).stat().st_size
        input_size = Path(input_file).stat().st_size
    except FileNotFoundError:
        return  # Outputting to stream or something
    with pikepdf.open(output_file) as p:
        # Overhead constants obtained by estimating amount of data added by OCR
        # PDF/A conversion, and possible XMP metadata addition, with compression
        reasonable_overhead = file_overhead + page_overhead * len(p.pages)
    ratio = output_size / input_size
    reasonable_ratio = output_size / (input_size + reasonable_overhead)
    if reasonable_ratio < 1.35 or input_size < 25000:
        return  # Seems fine

    reasons = []
    image_preproc = {
        'deskew',
        'clean_final',
        'remove_background',
        'oversample',
    }
    for arg in image_preproc:
        if getattr(options, arg, False):
            reasons.append(
                f"--{arg.replace('_', '-')} was issued, causing transcoding."
            )
    # Check force_ocr via the backward-compatible property
    if options.force_ocr:
        reasons.append("--force-ocr (or --mode force) was issued, causing transcoding.")

    reasons.extend(optimize_messages)

    if options.output_type.startswith('pdfa'):
        reasons.append("PDF/A conversion was enabled. (Try `--output-type pdf`.)")
    if options.plugins:
        reasons.append("Plugins were used.")

    if reasons:
        explanation = "Possible reasons for this include:\n" + '\n'.join(reasons) + "\n"
    else:
        explanation = "No reason for this increase is known.  Please report this issue."

    log.warning(
        f"The output file size is {ratio:.2f}× larger than the input file.\n"
        f"{explanation}"
    )