from __future__ import annotations

from pathlib import Path
from typing import Iterable, List, Optional

from pypdf import PdfReader, PdfWriter


def merge_pdfs(pdf_paths: Iterable[str | Path], out_pdf_path: str | Path) -> dict:
    out_pdf_path = Path(out_pdf_path)
    out_pdf_path.parent.mkdir(parents=True, exist_ok=True)

    writer = PdfWriter()

    merged: List[str] = []
    skipped: List[str] = []

    for p in pdf_paths:
        path = Path(p)
        try:
            reader = PdfReader(str(path))
            # просто добавляем страницы подряд
            for page in reader.pages:
                writer.add_page(page)
            merged.append(str(path))
        except Exception:
            skipped.append(str(path))

    if merged:
        with out_pdf_path.open("wb") as f:
            writer.write(f)

    return {
        "out_pdf": str(out_pdf_path),
        "merged_count": len(merged),
        "skipped_count": len(skipped),
        "merged_files": merged,
        "skipped_files": skipped,
    }


def merge_all_pdfs_in_dir(files_dir: str | Path, out_pdf_path: str | Path) -> dict:
    files_dir = Path(files_dir)
    pdfs = sorted(files_dir.rglob("*.pdf")) + sorted(files_dir.rglob("*.PDF"))
    return merge_pdfs(pdfs, out_pdf_path)