//! A subset of JSON-RPC types used by the Language Server Protocol.

pub use self::error::{Error, ErrorCode};
pub use crate::generated_impl::ServerRequest;

pub(crate) use self::pending::{ClientRequests, ServerRequests};

use std::borrow::Cow;
use std::fmt::{self, Debug, Display, Formatter};

use lsp_types::notification::Notification;
use lsp_types::request::Request;
use lsp_types::NumberOrString;
use serde::de::{self, Deserializer};
use serde::ser::Serializer;
use serde::{Deserialize, Serialize};
use serde_json::Value;

mod error;
mod pending;

/// A specialized [`Result`] error type for JSON-RPC handlers.
///
/// [`Result`]: enum@std::result::Result
pub type Result<T> = std::result::Result<T, Error>;

/// A unique ID used to correlate requests and responses together.
#[derive(Clone, Debug, Eq, Hash, PartialEq, Deserialize, Serialize)]
#[serde(untagged)]
pub enum Id {
    /// Numeric ID.
    Number(i64),
    /// String ID.
    String(String),
    /// Null ID.
    ///
    /// While `null` is considered a valid request ID by the JSON-RPC 2.0 specification, its use is
    /// _strongly_ discouraged because the specification also uses a `null` value to indicate an
    /// unknown ID in the [`Response`] object.
    Null,
}

impl Default for Id {
    fn default() -> Self {
        Id::Null
    }
}

impl Display for Id {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match self {
            Id::Number(id) => Display::fmt(id, f),
            Id::String(id) => Debug::fmt(id, f),
            Id::Null => f.write_str("null"),
        }
    }
}

impl From<NumberOrString> for Id {
    fn from(num_or_str: NumberOrString) -> Self {
        match num_or_str {
            NumberOrString::Number(num) => Id::Number(num as i64),
            NumberOrString::String(s) => Id::String(s),
        }
    }
}

/// A successful or failed JSON-RPC response.
#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
pub struct Response {
    jsonrpc: Version,
    #[serde(flatten)]
    kind: ResponseKind,
    id: Id,
}

impl Response {
    /// Creates a new successful response from a request ID and `Error` object.
    #[inline]
    pub const fn ok(id: Id, result: Value) -> Self {
        Response {
            jsonrpc: Version,
            kind: ResponseKind::Ok { result },
            id,
        }
    }

    /// Creates a new error response from a request ID and `Error` object.
    #[inline]
    pub const fn error(id: Id, error: Error) -> Self {
        Response {
            jsonrpc: Version,
            kind: ResponseKind::Err { error },
            id,
        }
    }

    /// Creates a new response from a request ID and either an `Ok(Value)` or `Err(Error)` body.
    #[inline]
    pub fn from_parts(id: Id, body: Result<Value>) -> Self {
        match body {
            Ok(result) => Response::ok(id, result),
            Err(error) => Response::error(id, error),
        }
    }

    /// Splits the response into a request ID paired with either an `Ok(Value)` or `Err(Error)` to
    /// signify whether the response is a success or failure.
    #[inline]
    pub fn into_parts(self) -> (Id, Result<Value>) {
        match self.kind {
            ResponseKind::Ok { result } => (self.id, Ok(result)),
            ResponseKind::Err { error } => (self.id, Err(error)),
        }
    }

    /// Returns the corresponding request ID, if known.
    #[inline]
    pub fn id(&self) -> &Id {
        &self.id
    }
}

#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
#[serde(deny_unknown_fields)]
#[serde(untagged)]
enum ResponseKind {
    Ok { result: Value },
    Err { error: Error },
}

/// An incoming JSON-RPC message.
#[derive(Clone, Debug, PartialEq, Deserialize)]
#[cfg_attr(test, derive(Serialize))]
#[serde(untagged)]
pub enum Incoming {
    /// Response to a server-to-client request.
    Response(Response),
    /// Request intended for the language server.
    Request(ServerRequest),
}

/// A server-to-client LSP request.
#[derive(Clone, Debug, PartialEq, Serialize)]
#[cfg_attr(test, derive(Deserialize))]
pub struct ClientRequest {
    jsonrpc: Version,
    method: Cow<'static, str>,
    #[serde(flatten)]
    kind: ClientMethod,
}

impl ClientRequest {
    /// Constructs a JSON-RPC request from its corresponding LSP type.
    pub(crate) fn request<R: Request>(id: u32, params: R::Params) -> Self {
        // Since `R::Params` come from the `lsp-types` crate and validity is enforced via the
        // `Request` trait, the `unwrap()` call below should never fail.
        ClientRequest {
            jsonrpc: Version,
            method: R::METHOD.into(),
            kind: ClientMethod::Request {
                params: serde_json::to_value(params).unwrap(),
                id: Id::Number(id as i64),
            },
        }
    }

    /// Constructs a JSON-RPC notification from its corresponding LSP type.
    pub(crate) fn notification<N: Notification>(params: N::Params) -> Self {
        // Since `N::Params` comes from the `lsp-types` crate and validity is enforced via the
        // `Notification` trait, the `unwrap()` call below should never fail.
        ClientRequest {
            jsonrpc: Version,
            method: N::METHOD.into(),
            kind: ClientMethod::Notification {
                params: serde_json::to_value(params).unwrap(),
            },
        }
    }
}

impl Display for ClientRequest {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = WriterFormatter { inner: f };
        serde_json::to_writer(&mut w, self).map_err(|_| fmt::Error)
    }
}

#[derive(Clone, Debug, PartialEq, Serialize)]
#[cfg_attr(test, derive(Deserialize))]
#[serde(untagged)]
enum ClientMethod {
    Request { params: Value, id: Id },
    Notification { params: Value },
}

/// An outgoing JSON-RPC message.
#[derive(Clone, Debug, PartialEq, Serialize)]
#[cfg_attr(test, derive(Deserialize))]
#[serde(untagged)]
pub enum Outgoing {
    /// Response to a client-to-server request.
    Response(Response),
    /// Request intended for the language client.
    Request(ClientRequest),
}

impl Display for Outgoing {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = WriterFormatter { inner: f };
        serde_json::to_writer(&mut w, self).map_err(|_| fmt::Error)
    }
}

struct WriterFormatter<'a, 'b: 'a> {
    inner: &'a mut Formatter<'b>,
}

impl<'a, 'b> std::io::Write for WriterFormatter<'a, 'b> {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        fn io_error<E>(_: E) -> std::io::Error {
            // Error value does not matter because fmt::Display impl below just
            // maps it to fmt::Error
            std::io::Error::new(std::io::ErrorKind::Other, "fmt error")
        }
        let s = std::str::from_utf8(buf).map_err(io_error)?;
        self.inner.write_str(s).map_err(io_error)?;
        Ok(buf.len())
    }

    fn flush(&mut self) -> std::io::Result<()> {
        Ok(())
    }
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub(crate) struct Version;

impl<'de> Deserialize<'de> for Version {
    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        match Cow::<'de, str>::deserialize(deserializer)?.as_ref() {
            "2.0" => Ok(Version),
            _ => Err(de::Error::custom("expected JSON-RPC version \"2.0\"")),
        }
    }
}

impl Serialize for Version {
    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        "2.0".serialize(serializer)
    }
}

/// Error response returned for every request received before the server is initialized.
///
/// See [here](https://microsoft.github.io/language-server-protocol/specification#initialize)
/// for reference.
pub(crate) fn not_initialized_error() -> Error {
    Error {
        code: ErrorCode::ServerError(-32002),
        message: "Server not initialized".to_string(),
        data: None,
    }
}

#[cfg(test)]
mod tests {
    use serde_json::json;

    use super::*;

    #[test]
    fn incoming_from_str_or_value() {
        let v = json!({"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{}},"id":0});
        let from_str: Incoming = serde_json::from_str(&v.to_string()).unwrap();
        let from_value: Incoming = serde_json::from_value(v).unwrap();
        assert_eq!(from_str, from_value);
    }

    #[test]
    fn outgoing_from_str_or_value() {
        let v = json!({"jsonrpc":"2.0","result":{},"id":1});
        let from_str: Outgoing = serde_json::from_str(&v.to_string()).unwrap();
        let from_value: Outgoing = serde_json::from_value(v).unwrap();
        assert_eq!(from_str, from_value);
    }

    #[test]
    fn parses_incoming_message() {
        let server_request =
            json!({"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{}},"id":0});
        let incoming = serde_json::from_value(server_request).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));

        let server_notif = json!({"jsonrpc":"2.0","method":"initialized","params":{}});
        let incoming = serde_json::from_value(server_notif).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));

        let client_request = json!({"jsonrpc":"2.0","id":0,"result":[null]});
        let incoming = serde_json::from_value(client_request).unwrap();
        assert!(matches!(incoming, Incoming::Response(_)));
    }

    #[test]
    fn parses_outgoing_message() {
        let client_request = json!({"jsonrpc":"2.0","method":"workspace/configuration","params":{"scopeUri":null,"section":"foo"},"id":0});
        let outgoing = serde_json::from_value(client_request).unwrap();
        assert!(matches!(outgoing, Outgoing::Request(_)));

        let client_notif = json!({"jsonrpc":"2.0","method":"window/logMessage","params":{"message":"foo","type":0}});
        let outgoing = serde_json::from_value(client_notif).unwrap();
        assert!(matches!(outgoing, Outgoing::Request(_)));

        let server_response = json!({"jsonrpc":"2.0","id":0,"result":[null]});
        let outgoing = serde_json::from_value(server_response).unwrap();
        assert!(matches!(outgoing, Outgoing::Response(_)));
    }

    #[test]
    fn parses_invalid_server_request() {
        let unknown_method = json!({"jsonrpc":"2.0","method":"foo"});
        let incoming = serde_json::from_value(unknown_method).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));

        let unknown_method_with_id = json!({"jsonrpc":"2.0","method":"foo","id":0});
        let incoming = serde_json::from_value(unknown_method_with_id).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));

        let missing_method = json!({"jsonrpc":"2.0"});
        let incoming = serde_json::from_value(missing_method).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));

        let missing_method_with_id = json!({"jsonrpc":"2.0","id":0});
        let incoming = serde_json::from_value(missing_method_with_id).unwrap();
        assert!(matches!(incoming, Incoming::Request(_)));
    }

    #[test]
    fn accepts_null_request_id() {
        let request_id: Id = serde_json::from_value(json!(null)).unwrap();
        assert_eq!(request_id, Id::Null);
    }

    #[test]
    fn accepts_negative_integer_request_id() {
        let request_id: Id = serde_json::from_value(json!(-1)).unwrap();
        assert_eq!(request_id, Id::Number(-1));
    }
}