from __future__ import annotations

import os
from dataclasses import dataclass
from pathlib import Path


@dataclass(frozen=True)
class ConnectionSettings:
    host: str
    port: int
    user: str
    password: str
    login_prompt: str
    exit_command: str


@dataclass(frozen=True)
class ToolSettings:
    tool_mode: bool
    tool_spec: str
    sideload_specs: list[str]


def load_env_file(path: str = ".env") -> None:
    """Populate ``os.environ`` with key/value pairs from a dotenv file."""
    env_path = Path(path)
    if not env_path.exists():
        return
    for line in env_path.read_text().splitlines():
        stripped = line.strip()
        if not stripped or stripped.startswith("#"):
            continue
        if "=" not in stripped:
            continue
        key, value = stripped.split("=", 1)
        key = key.strip()
        value = value.strip().strip('"').strip("'")
        if key and key not in os.environ:
            os.environ[key] = value


def require_env(key: str) -> str:
    value = os.environ.get(key)
    if value is None:
        raise RuntimeError(f"Missing required environment variable: {key}")
    return value


def parse_bool(raw: str) -> bool:
    return raw.strip().lower() in {"1", "true", "yes", "on"}


def parse_port(raw: str) -> int:
    try:
        return int(raw)
    except ValueError as exc:
        raise RuntimeError("MISTLE_PORT must be an integer") from exc


def parse_csv(raw: str) -> list[str]:
    return [value.strip() for value in raw.split(",") if value.strip()]


def read_connection_settings() -> ConnectionSettings:
    host = require_env("MISTLE_HOST")
    port = parse_port(require_env("MISTLE_PORT"))
    user = os.environ.get("MISTLE_USER", "")
    password = os.environ.get("MISTLE_PASSWORD", "")
    login_prompt = os.environ.get("MISTLE_LOGIN_PROMPT", "")
    exit_command = os.environ.get("MISTLE_EXIT_COMMAND", "")
    return ConnectionSettings(
        host=host,
        port=port,
        user=user,
        password=password,
        login_prompt=login_prompt,
        exit_command=exit_command,
    )


def read_tool_settings() -> ToolSettings:
    tool_mode = parse_bool(os.environ.get("MISTLE_TOOL_MODE", ""))
    tool_spec = os.environ.get("MISTLE_TOOL", "")
    sideload_specs = parse_csv(os.environ.get("MISTLE_SIDELOAD_TOOL", ""))
    return ToolSettings(
        tool_mode=tool_mode,
        tool_spec=tool_spec,
        sideload_specs=sideload_specs,
    )