"""
ocr.py — OCR helper for Teacher AI v3.
Uses PaddleOCR (already in requirements.txt) to extract text from images.
"""

import logging
from pathlib import Path

logger = logging.getLogger(__name__)

# Lazy-load so startup is fast; PaddleOCR downloads models on first use.
_ocr_engine = None


def _get_engine():
    global _ocr_engine
    if _ocr_engine is None:
        try:
            from paddleocr import PaddleOCR
            # use_angle_cls=True handles rotated text; lang="en" for English.
            # Set show_log=False to silence PaddlePaddle verbose output.
            _ocr_engine = PaddleOCR(use_angle_cls=True, lang="en", show_log=False)
            logger.info("PaddleOCR engine initialised.")
        except ImportError as exc:
            raise RuntimeError(
                "paddleocr is not installed. Add 'paddleocr' to requirements.txt."
            ) from exc
    return _ocr_engine


def extract_text(image_path: str) -> str:
    """
    Extract text from *image_path* and return it as a single string.

    Raises
    ------
    FileNotFoundError
        If *image_path* does not exist.
    ValueError
        If PaddleOCR returns no results at all.
    """
    path = Path(image_path)
    if not path.exists():
        raise FileNotFoundError(f"Image not found: {image_path}")

    engine = _get_engine()
    result = engine.ocr(str(path), cls=True)

    if not result or result == [None]:
        raise ValueError("OCR returned no results for the provided image.")

    lines = []
    for page in result:
        if page is None:
            continue
        for item in page:
            # item = [[box], [text, confidence]]
            try:
                text, confidence = item[1]
                if confidence >= 0.5:          # discard low-confidence fragments
                    lines.append(text.strip())
            except (IndexError, TypeError):
                continue

    return "\n".join(lines)