"""Configuration, loaded from environment variables."""

from __future__ import annotations

import os
from dataclasses import dataclass, field


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


def _list(name: str) -> list[str]:
    raw = os.environ.get(name, "")
    return [item.strip() for item in raw.split(",") if item.strip()]


def _require(name: str) -> str:
    value = os.environ.get(name, "").strip()
    if not value:
        raise RuntimeError(f"Missing required environment variable: {name}")
    return value


@dataclass(frozen=True)
class Settings:
    # --- BookStack ---
    bookstack_url: str
    bookstack_token_id: str
    bookstack_token_secret: str
    bookstack_verify_tls: bool = True
    request_timeout: float = 30.0

    # --- Behaviour ---
    read_only: bool = True
    allow_delete: bool = False
    max_content_chars: int = 40_000

    # --- Transport ---
    host: str = "0.0.0.0"
    port: int = 8080
    mcp_path: str = "/mcp"

    # --- Auth (client -> this MCP server) ---
    auth_mode: str = "none"  # none | token | github | github+token
    static_tokens: list[str] = field(default_factory=list)
    public_url: str = ""
    github_client_id: str = ""
    github_client_secret: str = ""
    allowed_hosts: list[str] = field(default_factory=list)

    # --- OIDC (your own IdP: Authentik, Keycloak, Authelia, Zitadel, ...) ---
    oidc_config_url: str = ""
    oidc_client_id: str = ""
    oidc_client_secret: str = ""
    oidc_verify_id_token: bool = False
    oidc_groups_claim: str = "groups"
    oidc_scopes: list[str] = field(default_factory=list)

    # --- Who may use the server (applies to both GitHub and OIDC) ---
    allowed_users: list[str] = field(default_factory=list)
    required_groups: list[str] = field(default_factory=list)

    @classmethod
    def from_env(cls) -> "Settings":
        auth_mode = os.environ.get("MCP_AUTH_MODE", "none").strip().lower()
        valid_modes = {
            "none", "token",
            "github", "github+token",
            "oidc", "oidc+token",
        }
        if auth_mode not in valid_modes:
            raise RuntimeError(
                f"MCP_AUTH_MODE must be one of {'|'.join(sorted(valid_modes))}, got {auth_mode!r}"
            )

        settings = cls(
            bookstack_url=_require("BOOKSTACK_URL").rstrip("/"),
            bookstack_token_id=_require("BOOKSTACK_TOKEN_ID"),
            bookstack_token_secret=_require("BOOKSTACK_TOKEN_SECRET"),
            bookstack_verify_tls=_bool("BOOKSTACK_VERIFY_TLS", True),
            request_timeout=float(os.environ.get("BOOKSTACK_TIMEOUT", "30")),
            read_only=_bool("BOOKSTACK_READ_ONLY", True),
            allow_delete=_bool("BOOKSTACK_ALLOW_DELETE", False),
            max_content_chars=int(os.environ.get("MCP_MAX_CONTENT_CHARS", "40000")),
            host=os.environ.get("MCP_HOST", "0.0.0.0"),
            port=int(os.environ.get("MCP_PORT", "8080")),
            mcp_path=os.environ.get("MCP_PATH", "/mcp"),
            auth_mode=auth_mode,
            static_tokens=_list("MCP_STATIC_TOKENS"),
            public_url=os.environ.get("MCP_PUBLIC_URL", "").rstrip("/"),
            github_client_id=os.environ.get("GITHUB_CLIENT_ID", ""),
            github_client_secret=os.environ.get("GITHUB_CLIENT_SECRET", ""),
            allowed_hosts=_list("MCP_ALLOWED_HOSTS"),
            oidc_config_url=os.environ.get("OIDC_CONFIG_URL", "").strip(),
            oidc_client_id=os.environ.get("OIDC_CLIENT_ID", ""),
            oidc_client_secret=os.environ.get("OIDC_CLIENT_SECRET", ""),
            oidc_verify_id_token=_bool("OIDC_VERIFY_ID_TOKEN", False),
            oidc_groups_claim=os.environ.get("OIDC_GROUPS_CLAIM", "groups"),
            oidc_scopes=_list("OIDC_SCOPES"),
            # GITHUB_ALLOWED_USERS is the old name, still honoured.
            allowed_users=[
                u.lower() for u in (_list("MCP_ALLOWED_USERS") or _list("GITHUB_ALLOWED_USERS"))
            ],
            required_groups=[g.lower() for g in _list("MCP_REQUIRED_GROUPS")],
        )
        settings.validate()
        return settings

    def validate(self) -> None:
        if "token" in self.auth_mode and not self.static_tokens:
            raise RuntimeError("MCP_AUTH_MODE includes 'token' but MCP_STATIC_TOKENS is empty")
        if "github" in self.auth_mode:
            if not (self.github_client_id and self.github_client_secret):
                raise RuntimeError(
                    "MCP_AUTH_MODE includes 'github' but GITHUB_CLIENT_ID / "
                    "GITHUB_CLIENT_SECRET are not set"
                )
        if "oidc" in self.auth_mode:
            if not self.oidc_config_url:
                raise RuntimeError(
                    "MCP_AUTH_MODE includes 'oidc' but OIDC_CONFIG_URL is not set. "
                    "This is your provider's discovery document, e.g. "
                    "https://auth.example.com/application/o/bookstack-mcp/.well-known/openid-configuration"
                )
            if not (self.oidc_client_id and self.oidc_client_secret):
                raise RuntimeError(
                    "MCP_AUTH_MODE includes 'oidc' but OIDC_CLIENT_ID / "
                    "OIDC_CLIENT_SECRET are not set"
                )
        if ("github" in self.auth_mode or "oidc" in self.auth_mode) and not self.public_url:
            raise RuntimeError(
                "MCP_PUBLIC_URL is required for OAuth (e.g. https://mcp.example.com)"
            )
        if not self.mcp_path.startswith("/"):
            raise RuntimeError("MCP_PATH must start with '/'")

    @property
    def api_base(self) -> str:
        return f"{self.bookstack_url}/api"