from pathlib import Path

import fitz  # PyMuPDF
from loguru import logger

import config
import concurrent.futures


def is_pdf(filename: str) -> bool:
    return Path(filename).suffix.lower() == ".pdf"


def pdf_to_images(pdf_path: str, dpi: int = config.OCR_DPI,
                  max_pages: int = config.PDF_MAX_PAGES) -> list[Path]:
    pdf_path   = Path(pdf_path)
    output_dir = pdf_path.parent / pdf_path.stem
    output_dir.mkdir(exist_ok=True)

    ext          = config.PDF_IMAGE_FORMAT                     # "jpeg"
    page_indices = list(range(max_pages))

    # 이미 변환된 이미지가 모두 있으면 스킵
    cached = [output_dir / f"page_{i+1:03d}.{ext}" for i in page_indices]
    if all(p.exists() for p in cached):
        logger.debug(f"PDF 변환 캐시 사용: {pdf_path.name}")
        return cached

    pdf_path = Path(pdf_path)
    print(pdf_path.exists())
    print(pdf_path.stat().st_size)
    if not pdf_path.exists() or pdf_path.stat().st_size == 0:
        raise ValueError(f"유효하지 않은 PDF 파일입니다: {pdf_path.name}")

    matrix = fitz.Matrix(dpi / 72, dpi / 72)
    doc = fitz.open(str(pdf_path))

    img_paths = []
    for i in range(min(max_pages, len(doc))):
        img_path = output_dir / f"page_{i+1:03d}.{ext}"
        if img_path.exists():
            logger.debug(f"페이지 캐시 사용: {img_path.name}")
        else:
            pixmap = doc[i].get_pixmap(matrix=matrix, alpha=False)

            # 최대 너비 초과 시 비율 유지하며 축소
            if hasattr(config, 'PDF_MAX_WIDTH') and pixmap.width > config.PDF_MAX_WIDTH:
                scale = config.PDF_MAX_WIDTH / pixmap.width
                pixmap = doc[i].get_pixmap(matrix=fitz.Matrix(dpi / 72 * scale, dpi / 72 * scale), alpha=False)

            if ext in ("jpeg", "jpg"):
                pixmap.save(str(img_path), jpg_quality=config.PDF_JPEG_QUALITY)  # JPEG 저장
            else:
                pixmap.save(str(img_path))
            logger.debug(f"PDF 변환: {pdf_path.name} | 페이지 {i+1}")
        img_paths.append(img_path)

    doc.close()
    logger.info(f"PDF 변환 완료: {pdf_path.name} | {len(img_paths)}페이지 | {dpi}dpi {ext}")
    return img_paths


def pdf_to_images_batch(pdf_paths: list[str],
                        max_workers: int = config.OCR_MAX_WORKERS) -> dict[str, list[Path]]:
    """
    여러 PDF를 ThreadPoolExecutor로 병렬 변환
    반환: {pdf_path: [img_path, ...]}
    """
    results = {}

    def _convert(pdf_path: str):
        return pdf_path, pdf_to_images(pdf_path)

    with concurrent.futures.ThreadPoolExecutor(max_workers=max_workers) as executor:
        futures = {executor.submit(_convert, p): p for p in pdf_paths}
        for future in concurrent.futures.as_completed(futures):
            try:
                path, imgs = future.result()
                results[path] = imgs
            except Exception as e:
                path = futures[future]
                logger.error(f"PDF 변환 실패: {path} | {e}")
                results[path] = []

    return results