"""Config loading for the m2-market CLI (docs/config.md, contracts/cli.md)."""

from __future__ import annotations

import os
import tomllib
from dataclasses import dataclass
from pathlib import Path

DEFAULT_CONFIG_PATH = Path.home() / ".m2-market" / "config.toml"

REQUIRED_KEYS = (
    "operator_id",
    "tenant",
    "ledger_url",
    "ledger_api_key",
    "memory_api_url",
    "memory_api_key",
    "forgejo_url",
    "forgejo_token",
)


class ConfigError(Exception):
    """Raised when config.toml is missing, unreadable, or invalid."""


@dataclass
class Config:
    operator_id: str
    tenant: str
    ledger_url: str
    ledger_api_key: str
    memory_api_url: str
    memory_api_key: str
    forgejo_url: str
    forgejo_token: str
    apply_adapter: str = "local"


def config_path() -> Path:
    """Resolve the config.toml path, honoring the M2_MARKET_CONFIG override."""
    override = os.environ.get("M2_MARKET_CONFIG")
    return Path(override).expanduser() if override else DEFAULT_CONFIG_PATH


def load_config(path: Path | None = None) -> Config:
    """Load and validate ~/.m2-market/config.toml, raising ConfigError on failure."""
    path = path or config_path()

    if not path.is_file():
        raise ConfigError(
            f"config not found: {path} (set M2_MARKET_CONFIG or see docs/config.md)"
        )

    try:
        with path.open("rb") as f:
            data = tomllib.load(f)
    except tomllib.TOMLDecodeError as exc:
        raise ConfigError(f"invalid TOML in {path}: {exc}") from exc
    except OSError as exc:
        raise ConfigError(f"cannot read {path}: {exc}") from exc

    missing = [key for key in REQUIRED_KEYS if not data.get(key)]
    if missing:
        raise ConfigError(
            f"{path} missing required key(s): {', '.join(missing)} (see docs/config.md)"
        )

    kwargs = {key: data[key] for key in REQUIRED_KEYS}
    kwargs["apply_adapter"] = data.get("apply_adapter", "local")

    return Config(**kwargs)