// Copyright 2019-2021 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any
// person obtaining a copy of this software and associated
// documentation files (the "Software"), to deal in the
// Software without restriction, including without
// limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software
// is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice
// shall be included in all copies or substantial portions
// of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use std::io;
use std::time::Duration;

use jsonrpsee_types::{ErrorCode, ErrorObject, Id, InvalidRequest, Response, ResponsePayload};
use tokio::sync::mpsc;

use super::{DisconnectError, SendTimeoutError, SubscriptionMessage, TrySendError};

/// Bounded writer that allows writing at most `max_len` bytes.
///
/// ```
///    use std::io::Write;
///
///    use jsonrpsee_core::server::helpers::BoundedWriter;
///
///    let mut writer = BoundedWriter::new(10);
///    (&mut writer).write("hello".as_bytes()).unwrap();
///    assert_eq!(std::str::from_utf8(&writer.into_bytes()).unwrap(), "hello");
/// ```
#[derive(Debug, Clone)]
pub struct BoundedWriter {
	max_len: usize,
	buf: Vec<u8>,
}

impl BoundedWriter {
	/// Create a new bounded writer.
	pub fn new(max_len: usize) -> Self {
		Self { max_len, buf: Vec::with_capacity(128) }
	}

	/// Consume the writer and extract the written bytes.
	pub fn into_bytes(self) -> Vec<u8> {
		self.buf
	}
}

impl<'a> io::Write for &'a mut BoundedWriter {
	fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
		let len = self.buf.len() + buf.len();
		if self.max_len >= len {
			self.buf.extend_from_slice(buf);
			Ok(buf.len())
		} else {
			Err(io::Error::new(io::ErrorKind::OutOfMemory, "Memory capacity exceeded"))
		}
	}

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

/// Sink that is used to send back the result to the server for a specific method.
#[derive(Clone, Debug)]
pub struct MethodSink {
	/// Channel sender.
	tx: mpsc::Sender<String>,
	/// Max response size in bytes for a executed call.
	max_response_size: u32,
}

impl MethodSink {
	/// Create a new `MethodSink` with unlimited response size.
	pub fn new(tx: mpsc::Sender<String>) -> Self {
		MethodSink { tx, max_response_size: u32::MAX }
	}

	/// Create a new `MethodSink` with a limited response size.
	pub fn new_with_limit(tx: mpsc::Sender<String>, max_response_size: u32) -> Self {
		MethodSink { tx, max_response_size }
	}

	/// Returns whether this channel is closed without needing a context.
	pub fn is_closed(&self) -> bool {
		self.tx.is_closed()
	}

	/// Same as [`tokio::sync::mpsc::Sender::closed`].
	///
	/// # Cancel safety
	/// This method is cancel safe. Once the channel is closed,
	/// it stays closed forever and all future calls to closed will return immediately.
	pub async fn closed(&self) {
		self.tx.closed().await
	}

	/// Get the max response size.
	pub const fn max_response_size(&self) -> u32 {
		self.max_response_size
	}

	/// Attempts to send out the message immediately and fails if the underlying
	/// connection has been closed or if the message buffer is full.
	///
	/// Returns the message if the send fails such that either can be thrown away or re-sent later.
	pub fn try_send(&mut self, msg: String) -> Result<(), TrySendError> {
		self.tx.try_send(msg).map_err(Into::into)
	}

	/// Async send which will wait until there is space in channel buffer or that the subscription is disconnected.
	pub async fn send(&self, msg: String) -> Result<(), DisconnectError> {
		self.tx.send(msg).await.map_err(Into::into)
	}

	/// Send a JSON-RPC error to the client
	pub async fn send_error<'a>(&self, id: Id<'a>, err: ErrorObject<'a>) -> Result<(), DisconnectError> {
		let payload = ResponsePayload::<()>::error_borrowed(err);
		let json = serde_json::to_string(&Response::new(payload, id)).expect("valid JSON; qed");

		self.send(json).await
	}

	/// Similar to to `MethodSink::send` but only waits for a limited time.
	pub async fn send_timeout(&self, msg: String, timeout: Duration) -> Result<(), SendTimeoutError> {
		self.tx.send_timeout(msg, timeout).await.map_err(Into::into)
	}

	/// Waits for there to be space on the return channel.
	pub async fn has_capacity(&self) -> Result<(), DisconnectError> {
		match self.tx.reserve().await {
			// The permit is thrown away here because it's just
			// a way to ensure that the return buffer has space.
			Ok(_) => Ok(()),
			Err(_) => Err(DisconnectError(SubscriptionMessage::empty())),
		}
	}
}

/// Figure out if this is a sufficiently complete request that we can extract an [`Id`] out of, or just plain
/// unparseable garbage.
pub fn prepare_error(data: &[u8]) -> (Id<'_>, ErrorCode) {
	match serde_json::from_slice::<InvalidRequest>(data) {
		Ok(InvalidRequest { id }) => (id, ErrorCode::InvalidRequest),
		Err(_) => (Id::Null, ErrorCode::ParseError),
	}
}

#[cfg(test)]
mod tests {
	use crate::server::BoundedWriter;
	use jsonrpsee_types::{Id, Response, ResponsePayload};

	#[test]
	fn bounded_serializer_work() {
		let mut writer = BoundedWriter::new(100);
		let result = ResponsePayload::success(&"success");
		let rp = &Response::new(result, Id::Number(1));

		assert!(serde_json::to_writer(&mut writer, rp).is_ok());
		assert_eq!(String::from_utf8(writer.into_bytes()).unwrap(), r#"{"jsonrpc":"2.0","result":"success","id":1}"#);
	}

	#[test]
	fn bounded_serializer_cap_works() {
		let mut writer = BoundedWriter::new(100);
		// NOTE: `"` is part of the serialization so 101 characters.
		assert!(serde_json::to_writer(&mut writer, &"x".repeat(99)).is_err());
	}
}