"""Centralised configuration for the duplicate detector."""

from __future__ import annotations

import os
from dataclasses import dataclass
from decimal import Decimal
from typing import Tuple

from dotenv import load_dotenv

load_dotenv()



def _get_decimal(env_key: str, default: str) -> Decimal:
    raw_value = os.getenv(env_key, default)
    try:
        return Decimal(raw_value)
    except Exception as exc:  # pragma: no cover - defensive logging
        raise ValueError(f"Invalid decimal for {env_key}: {raw_value}") from exc


def _get_int(env_key: str, default: str) -> int:
    raw_value = os.getenv(env_key, default)
    try:
        return int(raw_value)
    except Exception as exc:  # pragma: no cover - defensive logging
        raise ValueError(f"Invalid int for {env_key}: {raw_value}") from exc


def _get_tuple(env_key: str, default: str) -> Tuple[str, ...]:
    raw_value = os.getenv(env_key, default)
    values = [value.strip() for value in raw_value.split(",") if value.strip()]
    if not values:
        raise ValueError(f"{env_key} must contain at least one value")
    return tuple(values)


@dataclass(frozen=True)
class Settings:
    mongo_uri: str = os.getenv("MONGO_URI")
    mongo_db: str = os.getenv("MONGO_DB", "expense")
    expense_collection: str = os.getenv("MONGO_EXPENSE_COLLECTION", "transactions")
    alias_collection: str = os.getenv("MONGO_ALIAS_COLLECTION", "merchant_aliases")
    suggestion_collection: str = os.getenv("MONGO_SUGGESTION_COLLECTION", "merge_suggestions")
    amount_tolerance_pct: Decimal = _get_decimal("AMOUNT_TOLERANCE_PCT", "1.0")
    time_tolerance_minutes: int = _get_int("TIME_TOLERANCE_MINUTES", "10")
    default_lookback_hours: int = _get_int("DEFAULT_LOOKBACK_HOURS", "48")
    service_name: str = os.getenv("SERVICE_NAME", "duplicate-detector")
    max_batch_size: int = _get_int("MAX_BATCH_SIZE", "5000")
    time_fields: Tuple[str, ...] = _get_tuple(
        "TIME_FIELDS",
        "date,expense_time,createdAt",
    )
    merchant_fields: Tuple[str, ...] = _get_tuple(
        "MERCHANT_FIELDS",
        "merchant,note,paymentType,type,to",
    )
    scheduler_interval_seconds: int = _get_int("SCHEDULER_INTERVAL_SECONDS", "60")


settings = Settings()