from __future__ import annotations

import os
from dataclasses import dataclass
from pathlib import Path

from dotenv import load_dotenv


PROJECT_ROOT = Path(__file__).resolve().parents[1]
DATA_DIR = PROJECT_ROOT / "data"
IMAGE_DIR = DATA_DIR / "images"
FAVORITES_DIR = DATA_DIR / "favorites"
METADATA_CSV = DATA_DIR / "metadata.csv"
DEFAULT_NAMESPACE = "image-retrieval-lab3"
DEFAULT_MODEL_NAME = "sentence-transformers/clip-ViT-B-32"
ALL_CATEGORIES_LABEL = "All"
FAVORITES_ZIP_PATH = FAVORITES_DIR / "favorites.zip"


class ConfigurationError(RuntimeError):
    """Raised when required runtime configuration is missing or invalid."""


@dataclass(frozen=True)
class Settings:
    project_root: Path
    image_dir: Path
    favorites_dir: Path
    metadata_csv: Path
    clip_model_name: str
    upstash_url: str | None
    upstash_token: str | None
    upstash_namespace: str

    def require_upstash(self) -> None:
        missing = []
        if not self.upstash_url:
            missing.append("UPSTASH_VECTOR_REST_URL")
        if not self.upstash_token:
            missing.append("UPSTASH_VECTOR_REST_TOKEN")
        if missing:
            joined = ", ".join(missing)
            raise ConfigurationError(
                f"Missing Upstash Vector configuration: {joined}. "
                "Copy .env.example to .env and fill in your Upstash REST URL and token."
            )


def load_settings() -> Settings:
    load_dotenv(PROJECT_ROOT / ".env")
    return Settings(
        project_root=PROJECT_ROOT,
        image_dir=IMAGE_DIR,
        favorites_dir=FAVORITES_DIR,
        metadata_csv=METADATA_CSV,
        clip_model_name=os.getenv("CLIP_MODEL_NAME", DEFAULT_MODEL_NAME),
        upstash_url=os.getenv("UPSTASH_VECTOR_REST_URL"),
        upstash_token=os.getenv("UPSTASH_VECTOR_REST_TOKEN"),
        upstash_namespace=os.getenv("UPSTASH_VECTOR_NAMESPACE", DEFAULT_NAMESPACE),
    )