from __future__ import annotations

from pathlib import Path
from typing import Callable

import fitz
import pytesseract
from PIL import Image


def get_total_pages(pdf_path: Path) -> int:
    """Return total number of pages in a PDF file."""
    with fitz.open(pdf_path) as document:
        return document.page_count


def ocr_pdf_range(
    pdf_path: Path,
    start_page: int,
    end_page: int,
    *,
    lang: str,
    dpi: int,
    rotate: int = 0,
    on_progress: Callable[[int, int, int], None] | None = None,
) -> list[tuple[int, str]]:
    """Run OCR for the selected inclusive page range and return extracted text."""
    scale = dpi / 72.0
    matrix = fitz.Matrix(scale, scale)
    total_in_range = end_page - start_page + 1
    results: list[tuple[int, str]] = []

    with fitz.open(pdf_path) as document:
        for index, page_number in enumerate(range(start_page, end_page + 1), start=1):
            if on_progress is not None:
                on_progress(index, total_in_range, page_number)

            page = document.load_page(page_number - 1)
            pixmap = page.get_pixmap(matrix=matrix, alpha=False)
            image = Image.frombytes(
                "RGB",
                (pixmap.width, pixmap.height),
                pixmap.samples,
            )
            try:
                if rotate:
                    rotated_image = image.rotate(-rotate, expand=True)
                else:
                    rotated_image = image

                text = pytesseract.image_to_string(rotated_image, lang=lang)
            except Exception as exc:
                raise RuntimeError(f"OCR failed on page {page_number}") from exc
            finally:
                if rotate:
                    rotated_image.close()
                image.close()

            results.append((page_number, text))

    return results