"""
pdf_parser.py — Extract plain text from PDF, DOCX, and TXT files.
"""

import os
import logging
from io import BytesIO

logger = logging.getLogger(__name__)

PDF_MAX_PAGES = int(os.getenv("PDF_MAX_PAGES", "15"))


def extract_text_from_pdf(file_bytes: bytes) -> str:
    """Extract text from a PDF byte stream (up to PDF_MAX_PAGES pages)."""
    try:
        import PyPDF2
        reader = PyPDF2.PdfReader(BytesIO(file_bytes))
        pages = reader.pages[:PDF_MAX_PAGES]
        text = "\n".join(page.extract_text() or "" for page in pages)
        return text.strip()
    except Exception as exc:
        logger.error(f"[PDF] Extraction failed: {exc}")
        return ""


def extract_text_from_docx(file_bytes: bytes) -> str:
    """Extract text from a DOCX byte stream."""
    try:
        import docx
        from io import BytesIO as _BytesIO
        doc = docx.Document(_BytesIO(file_bytes))
        return "\n".join(para.text for para in doc.paragraphs).strip()
    except Exception as exc:
        logger.error(f"[DOCX] Extraction failed: {exc}")
        return ""


def extract_text(file_bytes: bytes, filename: str) -> str:
    """Dispatch extraction based on file extension."""
    ext = os.path.splitext(filename.lower())[1]
    if ext == ".pdf":
        return extract_text_from_pdf(file_bytes)
    elif ext in (".docx", ".doc"):
        return extract_text_from_docx(file_bytes)
    elif ext == ".txt":
        return file_bytes.decode("utf-8", errors="ignore").strip()
    else:
        raise ValueError(f"Unsupported file type: {ext}. Allowed: PDF, DOCX, TXT.")