from __future__ import annotations

from pathlib import Path
from typing import Iterable


ALLOWED_LAYOUT_TYPES = {"title_slide", "content_slide", "split_slide"}


def validate_file_extension(filename: str, allowed_extensions: Iterable[str]) -> None:
    if not any(filename.lower().endswith(ext.lower()) for ext in allowed_extensions):
        raise ValueError(
            f"Invalid file extension: {filename}. Allowed extensions are: {list(allowed_extensions)}"
        )


def validate_template(template_path: str | Path) -> Path:
    if not template_path:
        raise ValueError("Template path cannot be empty.")

    path = Path(template_path)
    if not path.exists() or not path.is_file():
        raise ValueError(f"Template file does not exist: {path}")

    validate_file_extension(path.name, [".pptx"])
    return path


def validate_slide_content(slide_content: dict) -> None:
    if not isinstance(slide_content, dict):
        raise ValueError("Invalid slide content: Expected a dictionary.")

    title = slide_content.get("title", "")
    bullets = slide_content.get("bullets", [])
    layout_type = slide_content.get("layout_type", "content_slide")

    if not isinstance(title, str) or not title.strip():
        raise ValueError("Each slide must include a non-empty 'title' string.")

    if not isinstance(bullets, list) or not all(isinstance(item, str) for item in bullets):
        raise ValueError("Each slide must include 'bullets' as a list of strings.")

    if layout_type not in ALLOWED_LAYOUT_TYPES:
        raise ValueError(
            f"Invalid layout_type '{layout_type}'. Expected one of {sorted(ALLOWED_LAYOUT_TYPES)}."
        )


def validate_slides(slides: list[dict]) -> bool:
    if not isinstance(slides, list):
        raise ValueError("Generated slide data must be a list.")

    for slide in slides:
        validate_slide_content(slide)

    return True