from __future__ import annotations

import os
from dataclasses import dataclass


def _env_bool(name: str, default: bool) -> bool:
    raw = os.getenv(name)
    if raw is None:
        return default
    return raw.strip().lower() in {"1", "true", "yes", "on"}


def _env_set(name: str) -> frozenset[str]:
    return frozenset(value.strip() for value in os.getenv(name, "").split(",") if value.strip())


@dataclass(frozen=True, slots=True)
class RuntimeSettings:
    environment: str = "development"
    backend: str = "memory"
    allow_ephemeral: bool = True
    api_host: str = "127.0.0.1"
    api_port: int = 8010
    api_base: str = "http://127.0.0.1:8010"
    mcp_host: str = "127.0.0.1"
    mcp_port: int = 8011
    mcp_transport: str = "http"
    database_url: str | None = None
    api_token: str | None = None
    v2_groups: frozenset[str] = frozenset()
    v2_write_groups: frozenset[str] = frozenset()
    legacy_write_groups: frozenset[str] = frozenset()
    legacy_health: bool = False

    def __post_init__(self) -> None:
        overlap = self.v2_write_groups & self.legacy_write_groups
        if overlap:
            joined = ", ".join(sorted(overlap))
            raise ValueError(f"hub-core and Core Hub write groups overlap: {joined}")
        unknown = self.v2_write_groups - self.v2_groups
        if unknown:
            joined = ", ".join(sorted(unknown))
            raise ValueError(f"hub-core write groups are not enabled: {joined}")

    @classmethod
    def from_env(cls) -> RuntimeSettings:
        environment = os.getenv("HUB_CORE_ENV", "development")
        default_ephemeral = environment in {"development", "test"}
        api_host = os.getenv("HUB_CORE_API_HOST", "127.0.0.1")
        api_port = int(os.getenv("HUB_CORE_API_PORT", "8010"))
        return cls(
            environment=environment,
            backend=os.getenv("HUB_CORE_BACKEND", "memory"),
            allow_ephemeral=_env_bool("HUB_CORE_ALLOW_EPHEMERAL", default_ephemeral),
            api_host=api_host,
            api_port=api_port,
            api_base=os.getenv("HUB_CORE_API_BASE", f"http://127.0.0.1:{api_port}"),
            mcp_host=os.getenv("HUB_CORE_MCP_HOST", "127.0.0.1"),
            mcp_port=int(os.getenv("HUB_CORE_MCP_PORT", "8011")),
            mcp_transport=os.getenv("HUB_CORE_MCP_TRANSPORT", "http"),
            database_url=os.getenv("HUB_CORE_DATABASE_URL") or os.getenv("DATABASE_URL"),
            api_token=os.getenv("HUB_CORE_API_TOKEN") or os.getenv("CORE_HUB_API_TOKEN"),
            v2_groups=_env_set("HUB_CORE_V2_GROUPS"),
            v2_write_groups=_env_set("HUB_CORE_V2_WRITE_GROUPS"),
            legacy_write_groups=_env_set("CORE_HUB_V2_WRITE_GROUPS"),
            legacy_health=_env_bool("HUB_CORE_LEGACY_HEALTH", False),
        )

    def readiness_checks(self, store_backend: str) -> dict[str, str]:
        ephemeral_allowed = store_backend != "memory" or self.allow_ephemeral
        return {
            "environment": self.environment,
            "configured_backend": self.backend,
            "active_backend": store_backend,
            "ephemeral_backend": "allowed" if ephemeral_allowed else "not_allowed",
            "contract": "helixforge.hub-extension/0.1.0",
            "v2_groups": ",".join(sorted(self.v2_groups)) or "none",
            "v2_write_groups": ",".join(sorted(self.v2_write_groups)) or "none",
            "legacy_write_groups": ",".join(sorted(self.legacy_write_groups)) or "none",
        }

    def is_ready(self, store_backend: str) -> bool:
        return self.backend == store_backend and (
            store_backend != "memory" or self.allow_ephemeral
        )