//! Crate ruma_api contains core types used to define the requests and responses for each endpoint
//! in the various [Matrix](https://matrix.org) API specifications.
//! These types can be shared by client and server code for all Matrix APIs.
//!
//! When implementing a new Matrix API, each endpoint has a type that implements `Endpoint`, plus
//! the necessary associated types.
//! An implementation of `Endpoint` contains all the information about the HTTP method, the path and
//! input parameters for requests, and the structure of a successful response.
//! Such types can then be used by client code to make requests, and by server code to fulfill
//! those requests.

#![deny(missing_debug_implementations)]
#![deny(missing_docs)]
#![feature(try_from)]

extern crate futures;
extern crate http;
#[cfg(test)] extern crate ruma_identifiers;
#[cfg(test)] extern crate serde;
#[cfg(test)] #[macro_use] extern crate serde_derive;
extern crate serde_json;
extern crate serde_urlencoded;

use std::convert::TryInto;
use std::io;

use futures::future::FutureFrom;
use http::{Method, Request, Response, StatusCode};

/// A Matrix API endpoint.
pub trait Endpoint<T, U> {
    /// Data needed to make a request to the endpoint.
    type Request: TryInto<Request<T>, Error = Error>;
    /// Data returned from the endpoint.
    type Response: FutureFrom<Response<U>, Error = Error>;

    /// Metadata about the endpoint.
    const METADATA: Metadata;
}

/// An error when converting an `Endpoint::Request` to a `http::Request` or a `http::Response` to
/// an `Endpoint::Response`.
#[derive(Debug)]
pub enum Error {
    /// An HTTP error.
    Http(http::Error),
    /// A I/O error.
    Io(io::Error),
    /// A Serde JSON error.
    SerdeJson(serde_json::Error),
    /// A Serde URL encoding error.
    SerdeUrlEncoded(serde_urlencoded::ser::Error),
    /// An HTTP status code indicating error.
    StatusCode(StatusCode),
}

impl From<http::Error> for Error {
    fn from(error: http::Error) -> Self {
        Error::Http(error)
    }
}

impl From<io::Error> for Error {
    fn from(error: io::Error) -> Self {
        Error::Io(error)
    }
}

impl From<serde_json::Error> for Error {
    fn from(error: serde_json::Error) -> Self {
        Error::SerdeJson(error)
    }
}

impl From<serde_urlencoded::ser::Error> for Error {
    fn from(error: serde_urlencoded::ser::Error) -> Self {
        Error::SerdeUrlEncoded(error)
    }
}

/// Metadata about an API endpoint.
#[derive(Clone, Debug)]
pub struct Metadata {
    /// A human-readable description of the endpoint.
    pub description: &'static str,
    /// The HTTP method used by this endpoint.
    pub method: Method,
    /// A unique identifier for this endpoint.
    pub name: &'static str,
    /// The path of this endpoint's URL, with variable names where path parameters should be filled
    /// in during a request.
    pub path: &'static str,
    /// Whether or not this endpoint is rate limited by the server.
    pub rate_limited: bool,
    /// Whether or not the server requires an authenticated user for this endpoint.
    pub requires_authentication: bool,
}

#[cfg(test)]
mod tests {
    /// PUT /_matrix/client/r0/directory/room/:room_alias
    pub mod create {
        use std::convert::TryFrom;

        use futures::future::{FutureFrom, FutureResult, err, ok};
        use http::method::PUT;
        use http::{Request as HttpRequest, Response as HttpResponse};
        use ruma_identifiers::{RoomAliasId, RoomId};
        use serde_json;

        use super::super::{Endpoint as ApiEndpoint, Error, Metadata};

        #[derive(Debug)]
        pub struct Endpoint;

        impl ApiEndpoint<Vec<u8>, Vec<u8>> for Endpoint {
            type Request = Request;
            type Response = Response;

            const METADATA: Metadata = Metadata {
                description: "Add an alias to a room.",
                method: PUT,
                name: "create_alias",
                path: "/_matrix/client/r0/directory/room/:room_alias",
                rate_limited: false,
                requires_authentication: true,
            };

        }

        /// A request to create a new room alias.
        #[derive(Debug)]
        pub struct Request {
            pub room_id: RoomId, // body
            pub room_alias: RoomAliasId, // path
        }

        #[derive(Debug, Serialize)]
        struct RequestBody {
            room_id: RoomId,
        }

        impl TryFrom<Request> for HttpRequest<Vec<u8>> {
            type Error = Error;

            fn try_from(request: Request) -> Result<HttpRequest<Vec<u8>>, Self::Error> {
                let metadata = Endpoint::METADATA;

                let path = metadata.path
                    .to_string()
                    .replace(":room_alias", &request.room_alias.to_string());

                let request_body = RequestBody {
                    room_id: request.room_id,
                };

                let http_request = HttpRequest::builder()
                    .method(metadata.method)
                    .uri(path.as_ref())
                    .body(serde_json::to_vec(&request_body).map_err(Error::from)?)?;

                Ok(http_request)
            }
        }

        /// The response to a request to create a new room alias.
        pub struct Response;

        impl FutureFrom<HttpResponse<Vec<u8>>> for Response {
            type Future = FutureResult<Self, Self::Error>;
            type Error = Error;

            fn future_from(http_response: HttpResponse<Vec<u8>>) -> FutureResult<Self, Self::Error> {
                if http_response.status().is_success() {
                    ok(Response)
                } else {
                    err(Error::StatusCode(http_response.status().clone()))
                }
            }
        }
    }
}