import os
import secrets
import warnings
from pathlib import Path
from typing import Annotated, Any, Literal, Self

from pydantic import (
    AnyUrl,
    BeforeValidator,
    EmailStr,
    HttpUrl,
    computed_field,
    model_validator,
)
from pydantic_settings import BaseSettings, SettingsConfigDict

#: Everything the engine keeps on disk, relative to :attr:`Settings.DATA_DIR`.
#: One setting to move the lot; each still overridable on its own, which is
#: what the container images do.
DERIVED_PATHS = {
    "FLOWS_DIR": "flows",
    "SECRETS_FILE": "secrets.enc",
    "ALERTS_FILE": "alerts.json",
    "PANELS_FILE": "panels.json",
    "OAUTH_PRIVATE_KEY_FILE": "oauth-key.pem",
    "CLOUD_CONFIG_FILE": "cloud.json",
}


def parse_cors(v: Any) -> list[str] | str:
    if isinstance(v, str) and not v.startswith("["):
        return [i.strip() for i in v.split(",") if i.strip()]
    elif isinstance(v, list | str):
        return v
    raise ValueError(v)


class Settings(BaseSettings):
    model_config = SettingsConfigDict(
        # The stack's own file, one level above ./backend/. An installed
        # `fluksio` has no such tree, so its CLI points this at the data
        # directory instead — and at nothing it might find in the cwd.
        env_file=os.environ.get("FLUKSIO_ENV_FILE", "../.env"),
        env_ignore_empty=True,
        extra="ignore",
    )
    API_V1_STR: str = "/api/v1"
    SECRET_KEY: str = secrets.token_urlsafe(32)
    # 60 minutes * 24 hours * 8 days = 8 days
    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 8
    FRONTEND_HOST: str = "http://localhost:5173"
    ENVIRONMENT: Literal["local", "staging", "production"] = "local"

    #: Everything this installation keeps: the database, the flow repository,
    #: secrets, artifacts and the user venv. The paths below derive from it
    #: unless they are set explicitly.
    DATA_DIR: Path = Path("flow-data")
    #: Any SQLAlchemy URL. The default puts SQLite in the data directory, which
    #: is what makes `fluksio serve` need no infrastructure at all.
    DATABASE_URL: str | None = None

    # Flows live on disk as a git repository; secrets stay outside it.
    FLOWS_DIR: Path = Path("flow-data/flows")
    SECRETS_FILE: Path = Path("flow-data/secrets.enc")
    # Which failures reach which channel. Beside the flows, not in them:
    # alerting is the deployment's concern, not any one flow's.
    ALERTS_FILE: Path = Path("flow-data/alerts.json")
    # Which dashboards each device shows. Beside the flows for the same reason
    # alerting is: where a screen hangs is the deployment's concern rather than
    # any one dashboard's.
    PANELS_FILE: Path = Path("flow-data/panels.json")
    # Which interpreter node code runs on. "auto" adopts the venv the engine
    # was installed into, when it was installed into one and there is no venv
    # of its own to lose — which is the `pip install fluksio` beside your own
    # packages case. "managed" always builds a separate one, which is what a
    # container wants. A path names an interpreter outright.
    NODE_VENV: str = "auto"
    # The MCP endpoint, and the OAuth server agents authenticate against. Off
    # until someone asks for it: it opens client registration to the network.
    MCP_ENABLED: bool = False
    # Unauthenticated test-only endpoints (user seeding). Requires an explicit
    # opt-in on top of ENVIRONMENT=local, so a deployment that merely kept the
    # default environment never exposes them.
    PRIVATE_API_ENABLED: bool = False
    DOMAIN: str = "localhost"
    OAUTH_PRIVATE_KEY_FILE: Path = Path("flow-data/oauth-key.pem")
    # Written only when someone enrols this installation with a portal.
    # Its absence is what keeps remote access off.
    CLOUD_CONFIG_FILE: Path = Path("flow-data/cloud.json")
    OAUTH_CODE_EXPIRE_SECONDS: int = 60
    # Short, because an agent's token is a bearer secret held by a program
    # rather than a person, and it can refresh unattended.
    MCP_TOKEN_EXPIRE_MINUTES: int = 60
    MCP_REFRESH_EXPIRE_DAYS: int = 30
    FLOW_MAX_WORKERS: int = 4
    # How long a python node may be silent before its worker is killed, unless
    # the node sets its own. 0, the default, disables it: a dead worker still
    # fails fast, and a slow one is left to finish. Set it where silence means
    # stuck rather than working.
    FLOW_NODE_TIMEOUT: float = 0.0
    # How long the engine's own metrics, events and run records are kept.
    OBS_RETENTION_DAYS: int = 30
    # Without a Redis host the engine keeps its state in memory.
    REDIS_HOST: str | None = None
    REDIS_PORT: int = 6379

    BACKEND_CORS_ORIGINS: Annotated[
        list[AnyUrl] | str, BeforeValidator(parse_cors)
    ] = []

    @model_validator(mode="before")
    @classmethod
    def _derive_data_paths(cls, data: Any) -> Any:
        """Put every stored thing under ``DATA_DIR`` unless it was named.

        ``setdefault``, so the container images keep their explicit ``/data``
        paths and a checkout keeps ``flow-data/``.
        """
        if not isinstance(data, dict):
            return data
        base = Path(str(data.get("DATA_DIR", "flow-data"))).expanduser()
        data["DATA_DIR"] = base
        for key, name in DERIVED_PATHS.items():
            data.setdefault(key, base / name)
        return data

    @computed_field  # type: ignore[prop-decorator]
    @property
    def oauth_issuer(self) -> str:
        """Who issues MCP tokens — this app, on its API host.

        Kept separate from the app's own URL because a hosted deployment can
        later point agents at a different issuer without the resource server
        changing: it validates whatever issuer it is configured to trust.
        """
        scheme = "http" if self.ENVIRONMENT == "local" else "https"
        return f"{scheme}://api.{self.DOMAIN}"

    @computed_field  # type: ignore[prop-decorator]
    @property
    def mcp_resource(self) -> str:
        """The resource an MCP token is issued for (RFC 8707)."""
        return f"{self.oauth_issuer}/mcp"

    @computed_field  # type: ignore[prop-decorator]
    @property
    def all_cors_origins(self) -> list[str]:
        return [str(origin).rstrip("/") for origin in self.BACKEND_CORS_ORIGINS] + [
            self.FRONTEND_HOST
        ]

    PROJECT_NAME: str = "Fluksio"
    SENTRY_DSN: HttpUrl | None = None

    @computed_field  # type: ignore[prop-decorator]
    @property
    def SQLALCHEMY_DATABASE_URI(self) -> str:
        """SQLite in the data directory, unless a URL says otherwise.

        One engine process owns this database — the same reason the image runs
        a single uvicorn worker — so a file beside the flows is the honest
        shape for it, and needs nothing running to be one.
        """
        if self.DATABASE_URL:
            return self.DATABASE_URL
        return f"sqlite:///{(self.DATA_DIR / 'fluksio.db').expanduser().resolve()}"

    SMTP_TLS: bool = True
    SMTP_SSL: bool = False
    SMTP_PORT: int = 587
    SMTP_HOST: str | None = None
    SMTP_USER: str | None = None
    SMTP_PASSWORD: str | None = None
    EMAILS_FROM_EMAIL: EmailStr | None = None
    EMAILS_FROM_NAME: str | None = None

    @model_validator(mode="after")
    def _set_default_emails_from(self) -> Self:
        if not self.EMAILS_FROM_NAME:
            self.EMAILS_FROM_NAME = self.PROJECT_NAME
        return self

    EMAIL_RESET_TOKEN_EXPIRE_HOURS: int = 48

    @computed_field  # type: ignore[prop-decorator]
    @property
    def emails_enabled(self) -> bool:
        return bool(self.SMTP_HOST and self.EMAILS_FROM_EMAIL)

    EMAIL_TEST_USER: EmailStr = "test@example.com"
    # Absent means "the CLI will make one on first run" — a pip install is not
    # asked for two environment variables before it can start.
    FIRST_SUPERUSER: EmailStr | None = None
    FIRST_SUPERUSER_PASSWORD: str | None = None

    def _check_default_secret(self, var_name: str, value: str | None) -> None:
        if value == "changethis":
            message = (
                f'The value of {var_name} is "changethis", '
                "for security, please change it, at least for deployments."
            )
            if self.ENVIRONMENT == "local":
                warnings.warn(message, stacklevel=1)
            else:
                raise ValueError(message)

    @model_validator(mode="after")
    def _enforce_non_default_secrets(self) -> Self:
        self._check_default_secret("SECRET_KEY", self.SECRET_KEY)
        self._check_default_secret(
            "FIRST_SUPERUSER_PASSWORD", self.FIRST_SUPERUSER_PASSWORD
        )

        return self


# No arguments and no required environment: a fresh install boots on the
# defaults above, into a data directory of its own.
settings = Settings()