"""
TableExtractionTool — extracts DataFrames from files.
Falls back to LLM-based parsing for PDFs where heuristics fail.
Standalone image files are never processed for table extraction — they are
handled by extract_images() + images_to_chunks() instead.
"""
import logging
from pathlib import Path
from typing import List

logger = logging.getLogger(__name__)

_FALLBACK_EXTS = {".pdf"}


class TableExtractionTool:
    def __init__(self, llm_tool):
        self._llm = llm_tool

    def extract(self, filepath: str) -> List:
        """Extract DataFrames from filepath. Returns list of DataFrames (may be empty).
        Returns immediately for file types that cannot contain tables.
        """
        from utils.document_processor import extract_dataframes, has_tables
        if not has_tables(filepath):
            return []
        dfs = extract_dataframes(filepath)
        if not dfs and Path(filepath).suffix.lower() in _FALLBACK_EXTS:
            dfs = self._llm_extract(filepath)
        return dfs

    def _llm_extract(self, filepath: str) -> List:
        """LLM-based table extraction fallback for PDFs."""
        import io as _io
        import pandas as _pd
        from Prompts.table_prompts import LLM_TABLE_EXTRACT_PROMPT

        ocr_text = ""
        try:
            from pypdf import PdfReader
            reader = PdfReader(filepath)
            ocr_text = "\n".join(p.extract_text() or "" for p in reader.pages)
        except Exception as e:
            logger.warning(f"LLM table fallback OCR failed for '{filepath}': {e}")
            return []

        if not ocr_text.strip():
            return []

        prompt = LLM_TABLE_EXTRACT_PROMPT + ocr_text
        try:
            csv_text = self._llm.call([{"role": "user", "content": prompt}]).strip()
            if not csv_text or csv_text.startswith("NO_TABLE"):
                return []
            if csv_text.startswith("```"):
                csv_text = "\n".join(l for l in csv_text.splitlines() if not l.startswith("```"))
            df = _pd.read_csv(_io.StringIO(csv_text.strip()))
            return [df] if not df.empty else []
        except Exception as e:
            logger.warning(f"LLM table fallback parse failed for '{filepath}': {e}")
            return []