from __future__ import annotations

import os
from dataclasses import dataclass
from functools import lru_cache


SCHEMA_VERSION = "v1"


def _env_int(name: str, default: int) -> int:
    try:
        return int(os.getenv(name, default))
    except Exception:
        return default


def _env_float(name: str, default: float) -> float:
    try:
        return float(os.getenv(name, default))
    except Exception:
        return default


@dataclass(frozen=True)
class DHTConfig:
    """Runtime configuration for the decentralized storage layer."""

    schema_version: str = SCHEMA_VERSION
    min_receipts: int = _env_int("DHT_MIN_RECEIPTS", 5)
    min_reachability_ratio: float = _env_float("DHT_MIN_REACHABILITY", 0.6)
    membership_ttl: int = _env_int("DHT_MEMBERSHIP_TTL", 600)
    replication_target: int = max(3, _env_int("DHT_REPLICATION_TARGET", 3))
    lease_ttl: int = _env_int("DHT_LEASE_TTL", 600)
    heartbeat_interval: int = _env_int("DHT_HEARTBEAT_INTERVAL", 60)
    heartbeat_miss_threshold: int = _env_int("DHT_HEARTBEAT_MISS_THRESHOLD", 3)
    rendezvous_base: str = os.getenv("DHT_RENDEZVOUS_HASH", "blake3")
    pow_difficulty: int = _env_int("DHT_POW_DIFFICULTY", 4)
    min_asn_diversity: int = _env_int("DHT_MIN_ASN", 3)
    min_ip_octet_diversity: int = _env_int("DHT_MIN_IP_OCTETS", 3)
    window_size: int = _env_int("DHT_METRIC_WINDOW_SEC", 3600)
    default_q: float = _env_float("DHT_MIN_Q", 0.6)
    seed_refresh_interval: int = _env_int("DHT_SEED_REFRESH_INTERVAL", 30)


@lru_cache
def load_config() -> DHTConfig:
    """Load configuration with process-wide memoisation."""

    return DHTConfig()


dht_config = load_config()