// 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 crate::server::rpc_module::MethodSink;
use futures_channel::mpsc;
use futures_util::stream::StreamExt;
use jsonrpsee_types::error::{CallError, Error};
use jsonrpsee_types::to_json_raw_value;
use jsonrpsee_types::v2::error::{OVERSIZED_RESPONSE_CODE, OVERSIZED_RESPONSE_MSG};
use jsonrpsee_types::v2::{
	error::{CALL_EXECUTION_FAILED_CODE, UNKNOWN_ERROR_CODE},
	ErrorCode, ErrorObject, Id, InvalidRequest, Response, RpcError, TwoPointZero,
};
use serde::Serialize;

use std::io;

/// Bounded writer that allows writing at most `max_len` bytes.
///
/// ```
///    use jsonrpsee_utils::server::helpers::BoundedWriter;
///    use std::io::Write;
///
///    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)]
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(())
	}
}

/// Helper for sending JSON-RPC responses to the client
pub fn send_response(id: Id, tx: &MethodSink, result: impl Serialize, max_response_size: u32) {
	let mut writer = BoundedWriter::new(max_response_size as usize);

	let json = match serde_json::to_writer(&mut writer, &Response { jsonrpc: TwoPointZero, id: id.clone(), result }) {
		Ok(_) => {
			// Safety - serde_json does not emit invalid UTF-8.
			unsafe { String::from_utf8_unchecked(writer.into_bytes()) }
		}
		Err(err) => {
			tracing::error!("Error serializing response: {:?}", err);

			if err.is_io() {
				let data = to_json_raw_value(&format!("Exceeded max limit {}", max_response_size)).ok();
				let err = ErrorObject {
					code: ErrorCode::ServerError(OVERSIZED_RESPONSE_CODE),
					message: OVERSIZED_RESPONSE_MSG.into(),
					data: data.as_deref(),
				};
				return send_error(id, tx, err);
			} else {
				return send_error(id, tx, ErrorCode::InternalError.into());
			}
		}
	};

	if let Err(err) = tx.unbounded_send(json) {
		tracing::error!("Error sending response to the client: {:?}", err)
	}
}

/// Helper for sending JSON-RPC errors to the client
pub fn send_error(id: Id, tx: &MethodSink, error: ErrorObject) {
	let json = match serde_json::to_string(&RpcError { jsonrpc: TwoPointZero, error, id }) {
		Ok(json) => json,
		Err(err) => {
			tracing::error!("Error serializing error message: {:?}", err);

			return;
		}
	};

	if let Err(err) = tx.unbounded_send(json) {
		tracing::error!("Could not send error response to the client: {:?}", err)
	}
}

/// Helper for sending the general purpose `Error` as a JSON-RPC errors to the client
pub fn send_call_error(id: Id, tx: &MethodSink, err: Error) {
	let (code, message, data) = match err {
		Error::Call(CallError::InvalidParams(e)) => (ErrorCode::InvalidParams, e.to_string(), None),
		Error::Call(CallError::Failed(e)) => (ErrorCode::ServerError(CALL_EXECUTION_FAILED_CODE), e.to_string(), None),
		Error::Call(CallError::Custom { code, message, data }) => (code.into(), message, data),
		// This should normally not happen because the most common use case is to
		// return `Error::Call` in `register_async_method`.
		e => (ErrorCode::ServerError(UNKNOWN_ERROR_CODE), e.to_string(), None),
	};

	let err = ErrorObject { code, message: message.into(), data: data.as_deref() };

	send_error(id, tx, err)
}

/// 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),
	}
}

/// Read all the results of all method calls in a batch request from the ['Stream']. Format the result into a single
/// `String` appropriately wrapped in `[`/`]`.
pub async fn collect_batch_response(rx: mpsc::UnboundedReceiver<String>) -> String {
	let mut buf = String::with_capacity(2048);
	buf.push('[');
	let mut buf = rx
		.fold(buf, |mut acc, response| async move {
			acc.push_str(&response);
			acc.push(',');
			acc
		})
		.await;
	// Remove trailing comma
	buf.pop();
	buf.push(']');
	buf
}

#[cfg(test)]
mod tests {
	use super::{BoundedWriter, Id, Response, TwoPointZero};

	#[test]
	fn bounded_serializer_work() {
		let mut writer = BoundedWriter::new(100);
		let result = "success";

		assert!(
			serde_json::to_writer(&mut writer, &Response { jsonrpc: TwoPointZero, id: Id::Number(1), result }).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());
	}
}