use std::fmt::Debug;

use serde::{Deserialize, Serialize};

/// A definition of a custom API. The `Request` associated type is what a

/// connected client can send. The `Response` associated type is what your API

/// is expecetd to send from the server to the client. The `Dispatcher` is the

/// type that will handle the custom API requests.

///

/// This feature is powered by [`actionable`] through these derives:

///

/// * [`Action`](crate::permissions::Action) (trait and derive macro)

/// * [`Actionable`](crate::permissions::Actionable) (derive macro)

pub trait CustomApi: Debug + Send + Sync + 'static {

    /// The type that represents an API request. This type is what clients will send to the server.

    type Request: Serialize + for<'de> Deserialize<'de> + Send + Sync + Debug;

    /// The type that represents an API response. This type will be sent to clients from the server.

    type Response: Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + Debug;

    /// The error type that this Api instance can return.

    type Error: CustomApiError;

}

impl CustomApi for () {

    type Request = ();

    type Response = ();

    type Error = Infallible;

}

/// An Error type that can be used in within a [`CustomApi`] definition.

///

/// The reason `std::convert::Infallible` can't be used is because `CustomApi`

/// errors must be able to be serialized across a network connection. While a

/// value will never be present when this is Infallible, the associated type

/// still must be declared as Serializable.

#[error("an unreachable error")]

pub enum Infallible {}

/// An error that can be used within a [`CustomApi`] definition.

pub trait CustomApiError:

    std::fmt::Display + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + Debug

{

}

impl<T> CustomApiError for T where

    T: std::fmt::Display + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + Debug

{

}

/// The result of executing a custom API call.

pub type CustomApiResult<Api> = Result<<Api as CustomApi>::Response, <Api as CustomApi>::Error>;