"""Docling parser.

Uses docling library for advanced document parsing with layout detection,
table structure recognition, and unified document representation.

Supports: PDF, DOCX, PPTX, XLSX, HTML, XHTML, CSV, Markdown, AsciiDoc,
images (PNG, JPEG, TIFF, BMP, WEBP), WebVTT, and specialized XML formats.
"""
import importlib.util
import logging
import os
import tempfile
import zipfile
from pathlib import Path
from typing import Dict, List, Optional, Union

from application.parser.file.base_parser import BaseParser, DocumentParseError
from application.utils import truncate_to_line_boundary

logger = logging.getLogger(__name__)


# Per-stage batch size for docling's threaded pipeline; 1 holds the
# concurrent working set to a single page (see _apply_pipeline_caps).
_PIPELINE_BATCH_SIZE = 1


def _apply_pipeline_caps(pipeline_options) -> None:
    """Cap docling's threaded-pipeline queue depth and batch sizes in place.

    hasattr-guarded so docling builds without these knobs are unaffected.
    """
    from application.core.settings import settings

    caps = {
        "queue_max_size": max(1, settings.DOCLING_PIPELINE_QUEUE_MAX_SIZE),
        "layout_batch_size": _PIPELINE_BATCH_SIZE,
        "table_batch_size": _PIPELINE_BATCH_SIZE,
        "ocr_batch_size": _PIPELINE_BATCH_SIZE,
    }
    for name, value in caps.items():
        if hasattr(pipeline_options, name):
            setattr(pipeline_options, name, value)


def _tabular_content_size(file: Path) -> int:
    """Effective content size of a tabular file, in bytes.

    Docling's memory scales with cell count, and for XLSX the cell count is
    hidden by zip compression — a 2 MB xlsx can hold ~850k cells. So for the
    zip-based ``.xlsx`` the measure is the inner-uncompressed size (read from
    the central directory without decompressing); for plain-text CSV the
    on-disk size already reflects the content.

    Args:
        file: Path to the tabular file.

    Returns:
        Content size in bytes, or -1 when it can't be determined.
    """
    path = Path(file)
    try:
        if path.suffix.lower() == ".xlsx":
            with zipfile.ZipFile(path) as zf:
                return sum(info.file_size for info in zf.infolist())
        return path.stat().st_size
    except (OSError, zipfile.BadZipFile):
        try:
            return path.stat().st_size
        except OSError:
            return -1


def _exceeds_tabular_gate(file: Path) -> bool:
    """Whether a tabular file is too large (by content) to hand to docling.

    Docling materializes a ``TableCell`` model per cell, so tabular memory
    scales with cell count, not on-disk bytes (~11 KB of RSS per 4-cell CSV
    row — an 88 MB CSV needs ~26 GB). Oversized CSV/XLSX files are routed to
    the lightweight parsers in ``tabular_parser`` instead.

    Args:
        file: Path to the tabular file about to be parsed.

    Returns:
        True when the file's content exceeds ``DOCLING_TABULAR_MAX_BYTES``
        (and the gate is enabled), False otherwise or when size is unknown.
    """
    from application.core.settings import settings

    max_bytes = settings.DOCLING_TABULAR_MAX_BYTES
    if max_bytes <= 0:
        return False
    return _tabular_content_size(file) > max_bytes


def _capped_markup_copy(file: Path) -> Optional[str]:
    """Head-truncate an oversized markup file to a temp copy for docling.

    HTML/VTT have no lightweight full-content parser to fall back to (unlike
    CSV/XLSX), so element-dense markup is bounded by parsing only the first
    ``DOCLING_MARKUP_MAX_BYTES`` — enough context for retrieval, and docling's
    lenient HTML/VTT backends handle a truncated tail. Cuts on a line boundary
    when one is reasonably close to the limit.

    Args:
        file: Path to the markup file about to be parsed.

    Returns:
        Path to a temp copy the caller must delete, or None when the file is
        within the limit / the gate is disabled / the size can't be read.
    """
    from application.core.settings import settings

    max_bytes = settings.DOCLING_MARKUP_MAX_BYTES
    if max_bytes <= 0:
        return None
    try:
        if Path(file).stat().st_size <= max_bytes:
            return None
        with open(file, "rb") as src:
            head = src.read(max_bytes)
    except OSError:
        return None
    head = truncate_to_line_boundary(head)
    with tempfile.NamedTemporaryFile(
        delete=False, suffix=Path(file).suffix
    ) as tmp:
        tmp.write(head)
    return tmp.name


def _parse_markup_bounded(
    parser: "DoclingParser", file: Path, errors: str
) -> Union[str, List[str]]:
    """Run ``parser`` on ``file``, first truncating it if it is oversized markup."""
    capped = _capped_markup_copy(file)
    if capped is None:
        return DoclingParser.parse_file(parser, file, errors)
    logger.warning(
        f"Markup {Path(file).name} exceeds DOCLING_MARKUP_MAX_BYTES; "
        "parsing a head-truncated copy to bound memory"
    )
    try:
        return DoclingParser.parse_file(parser, Path(capped), errors)
    finally:
        try:
            os.unlink(capped)
        except OSError:
            pass


class DoclingParser(BaseParser):
    """Parser using docling for advanced document processing.

    Docling provides:
    - Advanced PDF layout analysis
    - Table structure recognition
    - Reading order detection
    - OCR for scanned documents (supports RapidOCR)
    - Unified DoclingDocument format
    - Export to Markdown

    Uses hybrid OCR approach by default:
    - Text regions: Direct PDF text extraction (fast)
    - Bitmap/image regions: OCR only these areas (smart)
    """

    def __init__(
        self,
        ocr_enabled: bool = True,
        table_structure: bool = True,
        export_format: str = "markdown",
        use_rapidocr: bool = True,
        ocr_languages: Optional[List[str]] = None,
        force_full_page_ocr: bool = False,
    ):
        """Initialize DoclingParser.

        Args:
            ocr_enabled: Enable OCR for bitmap/image regions in documents
            table_structure: Enable table structure recognition
            export_format: Output format ('markdown', 'text', 'html')
            use_rapidocr: Use RapidOCR engine (default True, works well in Docker)
            ocr_languages: List of OCR languages (default: ['english'])
            force_full_page_ocr: Force OCR on entire page (False = smart hybrid OCR)
        """
        super().__init__()
        self.ocr_enabled = ocr_enabled
        self.table_structure = table_structure
        self.export_format = export_format
        self.use_rapidocr = use_rapidocr
        self.ocr_languages = ocr_languages or ["english"]
        self.force_full_page_ocr = force_full_page_ocr
        self._converter = None

    def _create_converter(self):
        """Create a docling converter with hybrid OCR configuration.

        Uses smart OCR approach:
        - When ocr_enabled=True and force_full_page_ocr=False (default):
          Layout model detects text vs bitmap regions, OCR only runs on bitmaps
        - When ocr_enabled=True and force_full_page_ocr=True:
          OCR runs on entire page (for scanned documents/images)
        - When ocr_enabled=False:
          No OCR, only native text extraction

        Returns:
            DocumentConverter instance
        """
        from docling.document_converter import (
            DocumentConverter,
            ImageFormatOption,
            InputFormat,
            PdfFormatOption,
        )
        from docling.datamodel.pipeline_options import PdfPipelineOptions

        pipeline_options = PdfPipelineOptions(
            do_ocr=self.ocr_enabled,
            do_table_structure=self.table_structure,
        )
        _apply_pipeline_caps(pipeline_options)

        if self.ocr_enabled:
            ocr_options = self._get_ocr_options()
            if ocr_options is not None:
                pipeline_options.ocr_options = ocr_options

        return DocumentConverter(
            format_options={
                InputFormat.PDF: PdfFormatOption(
                    pipeline_options=pipeline_options,
                ),
                InputFormat.IMAGE: ImageFormatOption(
                    pipeline_options=pipeline_options,
                ),
            }
        )

    def _init_parser(self) -> Dict:
        """Initialize the docling converter with hybrid OCR."""
        logger.info("Initializing DoclingParser...")
        logger.info(f"  ocr_enabled={self.ocr_enabled}")
        logger.info(f"  force_full_page_ocr={self.force_full_page_ocr}")
        logger.info(f"  use_rapidocr={self.use_rapidocr}")

        if importlib.util.find_spec("docling.document_converter") is None:
            raise ImportError(
                "docling is required for DoclingParser. "
                "Install it with: pip install docling"
            )

        # Create converter with hybrid OCR (smart: text direct, bitmaps OCR'd)
        self._converter = self._create_converter()

        logger.info("DoclingParser initialized successfully")
        return {
            "ocr_enabled": self.ocr_enabled,
            "table_structure": self.table_structure,
            "export_format": self.export_format,
            "use_rapidocr": self.use_rapidocr,
            "ocr_languages": self.ocr_languages,
            "force_full_page_ocr": self.force_full_page_ocr,
        }

    def _get_ocr_options(self):
        """Get OCR options based on configuration.

        Returns RapidOcrOptions if use_rapidocr is True and available,
        otherwise returns None to use docling defaults.
        """
        if not self.use_rapidocr:
            return None

        try:
            from docling.datamodel.pipeline_options import RapidOcrOptions

            return RapidOcrOptions(
                lang=self.ocr_languages,
                force_full_page_ocr=self.force_full_page_ocr,
            )
        except ImportError as e:
            logger.warning(f"Failed to import RapidOcrOptions: {e}")
            return None
        except Exception as e:
            logger.error(f"Error creating RapidOcrOptions: {e}")
            return None

    def _export_content(self, document) -> str:
        """Export document content in the configured format.

        Handles edge case where text is nested under picture elements (e.g., OCR'd
        images). If the standard export returns minimal content but document.texts
        contains extracted text, falls back to direct text extraction.
        """
        if self.export_format == "markdown":
            content = document.export_to_markdown()
        elif self.export_format == "html":
            content = document.export_to_html()
        else:
            content = document.export_to_text()

        # Handle case where text is nested under pictures (common with OCR'd images)
        # Standard exports may return just "<!-- image -->" while actual text exists
        stripped_content = content.strip()
        is_minimal = len(stripped_content) < 50 or stripped_content == "<!-- image -->"

        if is_minimal and hasattr(document, "texts") and document.texts:
            # Extract text directly from document.texts
            extracted_texts = [t.text for t in document.texts if t.text]
            if extracted_texts:
                logger.info(
                    f"Standard export minimal ({len(stripped_content)} chars), "
                    f"extracting {len(extracted_texts)} texts directly"
                )
                return "\n\n".join(extracted_texts)

        return content

    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, List[str]]:
        """Parse file using docling with hybrid OCR.

        Uses smart OCR approach where the layout model detects text vs bitmap
        regions. Text is extracted directly, bitmaps are OCR'd only when needed.

        Args:
            file: Path to the file to parse
            errors: Error handling mode (ignored, docling handles internally)

        Returns:
            Parsed document content as markdown string
        """
        logger.info(f"parse_file called for: {file}")

        if self._converter is None:
            self._init_parser()

        try:
            logger.info(f"Converting file with hybrid OCR: {file}")
            result = self._converter.convert(str(file))
            content = self._export_content(result.document)
            logger.info(f"Parse complete, content length: {len(content)} chars")

            return content

        except Exception as e:
            logger.error(f"Error parsing file with docling: {e}", exc_info=True)
            # ``errors`` governs *decoding* leniency, not whether a total
            # conversion failure may be substituted for the document. Returning
            # the message here (the old ``errors == "ignore"`` branch) made the
            # caller store the traceback as the file's text and report the
            # upload successful — the model then read the error as the document.
            raise DocumentParseError(
                f"Failed to parse {Path(file).name} with docling: {e}"
            ) from e


class DoclingPDFParser(DoclingParser):
    """Docling-based PDF parser with advanced features and RapidOCR support.

    Uses hybrid OCR approach by default:
    - Text regions: Direct PDF text extraction (fast)
    - Bitmap/image regions: OCR only these areas (smart)

    Set force_full_page_ocr=True only for fully scanned documents.
    """

    def __init__(
        self,
        ocr_enabled: bool = True,
        table_structure: bool = True,
        use_rapidocr: bool = True,
        ocr_languages: Optional[List[str]] = None,
        force_full_page_ocr: bool = False,
    ):
        super().__init__(
            ocr_enabled=ocr_enabled,
            table_structure=table_structure,
            export_format="markdown",
            use_rapidocr=use_rapidocr,
            ocr_languages=ocr_languages,
            force_full_page_ocr=force_full_page_ocr,
        )


class DoclingDocxParser(DoclingParser):
    """Docling-based DOCX parser."""

    def __init__(self):
        super().__init__(export_format="markdown")


class DoclingPPTXParser(DoclingParser):
    """Docling-based PPTX parser."""

    def __init__(self):
        super().__init__(export_format="markdown")


class DoclingXLSXParser(DoclingParser):
    """Docling-based XLSX parser with table structure."""

    def __init__(self):
        super().__init__(table_structure=True, export_format="markdown")

    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, List[str]]:
        """Parse an XLSX file, delegating oversized files to ``ExcelParser``."""
        if _exceeds_tabular_gate(file):
            logger.warning(
                f"XLSX {file.name} exceeds DOCLING_TABULAR_MAX_BYTES; "
                "using lightweight Excel parser instead of docling"
            )
            from application.parser.file.tabular_parser import ExcelParser

            return ExcelParser().parse_file(file, errors)
        return super().parse_file(file, errors)


class DoclingHTMLParser(DoclingParser):
    """Docling-based HTML parser."""

    def __init__(self):
        super().__init__(export_format="markdown")

    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, List[str]]:
        """Parse HTML, truncating oversized element-dense markup first."""
        return _parse_markup_bounded(self, file, errors)


class DoclingImageParser(DoclingParser):
    """Docling-based image parser with OCR and RapidOCR support.

    For images, force_full_page_ocr=True is used since images are entirely
    visual and require full OCR to extract any text.
    """

    def __init__(
        self,
        ocr_enabled: bool = True,
        use_rapidocr: bool = True,
        ocr_languages: Optional[List[str]] = None,
        force_full_page_ocr: bool = True,
    ):
        super().__init__(
            ocr_enabled=ocr_enabled,
            export_format="markdown",
            use_rapidocr=use_rapidocr,
            ocr_languages=ocr_languages,
            force_full_page_ocr=force_full_page_ocr,
        )


class DoclingCSVParser(DoclingParser):
    """Docling-based CSV parser."""

    def __init__(self):
        super().__init__(table_structure=True, export_format="markdown")

    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, List[str]]:
        """Parse a CSV file, delegating oversized files to the plain ``CSVParser``."""
        if _exceeds_tabular_gate(file):
            logger.warning(
                f"CSV {file.name} exceeds DOCLING_TABULAR_MAX_BYTES; "
                "using plain CSV parser instead of docling"
            )
            from application.parser.file.tabular_parser import CSVParser

            return CSVParser().parse_file(file, errors)
        return super().parse_file(file, errors)


class DoclingMarkdownParser(DoclingParser):
    """Docling-based Markdown parser."""

    def __init__(self):
        super().__init__(export_format="markdown")


class DoclingAsciiDocParser(DoclingParser):
    """Docling-based AsciiDoc parser."""

    def __init__(self):
        super().__init__(export_format="markdown")


class DoclingVTTParser(DoclingParser):
    """Docling-based WebVTT (video text tracks) parser."""

    def __init__(self):
        super().__init__(export_format="markdown")

    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, List[str]]:
        """Parse WebVTT, truncating oversized cue-dense tracks first."""
        return _parse_markup_bounded(self, file, errors)


class DoclingXMLParser(DoclingParser):
    """Docling-based XML parser (USPTO, JATS)."""

    def __init__(self):
        super().__init__(export_format="markdown")