from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path


@dataclass(frozen=True)
class PromptSet:
    system_prompt: str
    user_prompt: str


class PromptLoader:
    def __init__(self, prompts_dir: Path | None = None) -> None:
        default_dir = Path(__file__).resolve().parent.parent / "prompts"
        self._prompts_dir = prompts_dir or default_dir

    def load(self) -> PromptSet:
        system_prompt = self._read_text("system_prompt.txt")
        user_prompt = self._read_text("user_prompt.txt")
        return PromptSet(system_prompt=system_prompt, user_prompt=user_prompt)

    def _read_text(self, file_name: str) -> str:
        path = self._prompts_dir / file_name
        if not path.exists():
            raise FileNotFoundError(f"Prompt file not found: {path}")
        content = path.read_text(encoding="utf-8").strip()
        if not content:
            raise ValueError(f"Prompt file is empty: {path}")
        return content