"""PDF content extraction for NSCT crawler.

Extracts text from PDF documents using pdfminer.six or pdfplumber
as fallback. Returns structured error markers when text extraction
is not possible.
"""

from __future__ import annotations

import io
import logging
from typing import BinaryIO

logger = logging.getLogger(__name__)

try:
    from pdfminer.high_level import extract_text as pdfminer_extract_text
    from pdfminer.layout import LAParams

    _HAS_PDFMINER = True
except ImportError:
    _HAS_PDFMINER = False
    pdfminer_extract_text = None  # type: ignore[assignment,misc]

try:
    import pdfplumber

    _HAS_PDFPLUMBER = True
except ImportError:
    _HAS_PDFPLUMBER = False
    pdfplumber = None  # type: ignore[assignment,misc]

try:
    from pdfminer.pdfinterp import PDFResourceManager, PDFPageInterpreter
    from pdfminer.pdfpage import PDFPage
    from pdfminer.converter import XMLConverter, TextConverter
    from pdfminer.layout import LAParams

    _HAS_PDFMINER_FULL = True
except ImportError:
    _HAS_PDFMINER_FULL = False
    PDFResourceManager = None  # type: ignore[assignment,misc]
    PDFPage = None  # type: ignore[assignment,misc]
    PDFPageInterpreter = None  # type: ignore[assignment,misc]
    XMLConverter = None  # type: ignore[assignment,misc]
    TextConverter = None  # type: ignore[assignment,misc]


def extract_pdf_from_bytes(pdf_bytes: bytes) -> str:
    """Extract text content from raw PDF bytes.

    Priority: pdfminer.six -> pdfplumber -> minimal fallback.

    Args:
        pdf_bytes: Raw PDF content.

    Returns:
        Extracted text content, or an error marker string if extraction fails.
    """
    if not pdf_bytes:
        return "pdf_extract_failed"

    content_types = "pdf_no_text"

    # --- Try pdfminer.six ---
    if _HAS_PDFMINER:
        try:
            stream = io.BytesIO(pdf_bytes)
            text = pdfminer_extract_text(
                stream,
                laparams=LAParams(
                    line_margin=0.5,
                    word_margin=0.1,
                    char_margin=2.0,
                    boxes_flow=0.5,
                ),
            )
            if text and text.strip():
                return text.strip()
        except Exception as exc:
            logger.debug("pdfminer extraction failed: %s", exc)

    # --- Try pdfplumber ---
    if _HAS_PDFPLUMBER:
        try:
            stream = io.BytesIO(pdf_bytes)
            with pdfplumber.open(stream) as pdf:
                parts: list[str] = []
                for page in pdf.pages:
                    page_text = page.extract_text()
                    if page_text:
                        parts.append(page_text)
                if parts:
                    text = "\n\n".join(parts)
                    return text.strip()
        except Exception as exc:
            logger.debug("pdfplumber extraction failed: %s", exc)

    return f"pdf_extract_failed"


def detect_pdf_content_type(pdf_bytes: bytes) -> str:
    """Detect the content type of PDF bytes.

    Args:
        pdf_bytes: Raw PDF content.

    Returns:
        Content type string.
    """
    if not pdf_bytes:
        return "unknown"

    # Check PDF magic bytes
    if pdf_bytes[:4] == b"%PDF":
        return "application/pdf"

    return "unknown"