// 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.

//! Shared HTTP utilities.

use crate::BoxError;
use bytes::{Buf, Bytes};
use http_body::Frame;
use http_body_util::{BodyExt, Limited};
use std::{
	pin::Pin,
	task::{Context, Poll},
};

/// HTTP request type.
pub type Request<T = Body> = http::Request<T>;
/// HTTP response type.
pub type Response<T = Body> = http::Response<T>;

/// Default HTTP body used by jsonrpsee.
#[derive(Debug, Default)]
pub struct Body(http_body_util::combinators::UnsyncBoxBody<Bytes, BoxError>);

impl Body {
	/// Create an empty body.
	pub fn empty() -> Self {
		Self::default()
	}

	/// Create a new body.
	pub fn new<B>(body: B) -> Self
	where
		B: http_body::Body<Data = Bytes> + Send + 'static,
		B::Data: Send + 'static,
		B::Error: Into<BoxError>,
	{
		Self(body.map_err(|e| e.into()).boxed_unsync())
	}
}

impl From<String> for Body {
	fn from(s: String) -> Self {
		let body = http_body_util::Full::from(s);
		Self::new(body)
	}
}

impl From<&'static str> for Body {
	fn from(s: &'static str) -> Self {
		let body = http_body_util::Full::from(s);
		Self::new(body)
	}
}

impl From<Vec<u8>> for Body {
	fn from(bytes: Vec<u8>) -> Self {
		let body = http_body_util::Full::from(bytes);
		Self::new(body)
	}
}

impl http_body::Body for Body {
	type Data = Bytes;
	type Error = BoxError;

	#[inline]
	fn poll_frame(
		mut self: Pin<&mut Self>,
		cx: &mut Context<'_>,
	) -> Poll<Option<Result<Frame<Self::Data>, Self::Error>>> {
		Pin::new(&mut self.0).poll_frame(cx)
	}

	#[inline]
	fn size_hint(&self) -> http_body::SizeHint {
		self.0.size_hint()
	}

	#[inline]
	fn is_end_stream(&self) -> bool {
		self.0.is_end_stream()
	}
}

/// Represents error that can when reading with a HTTP body.
#[derive(Debug, thiserror::Error)]
pub enum HttpError {
	/// The HTTP message was too large.
	#[error("The HTTP message was too big")]
	TooLarge,
	/// Malformed request
	#[error("Malformed request")]
	Malformed,
	/// Represents error that can happen when dealing with HTTP streams.
	#[error("{0}")]
	Stream(#[from] BoxError),
}

/// Read data from a HTTP body and return the data if it is valid JSON and within the allowed size range.
///
/// Returns `Ok((bytes, single))` if the body was in valid size range; and a bool indicating whether the JSON-RPC
/// request is a single or a batch.
/// Returns `Err` if the body was too large or the body couldn't be read.
pub async fn read_body<B>(headers: &http::HeaderMap, body: B, max_body_size: u32) -> Result<(Vec<u8>, bool), HttpError>
where
	B: http_body::Body<Data = Bytes> + Send + 'static,
	B::Data: Send,
	B::Error: Into<BoxError>,
{
	// NOTE(niklasad1): Values bigger than `u32::MAX` will be turned into zero here. This is unlikely to occur in
	// practice and in that case we fallback to allocating in the while-loop below instead of pre-allocating.
	let body_size = read_header_content_length(headers).unwrap_or(0);

	if body_size > max_body_size {
		return Err(HttpError::TooLarge);
	}

	futures_util::pin_mut!(body);

	// Allocate up to 16KB initially.
	let mut received_data = Vec::with_capacity(std::cmp::min(body_size as usize, 16 * 1024));
	let mut limited_body = Limited::new(body, max_body_size as usize);

	let mut is_single = None;

	while let Some(frame_or_err) = limited_body.frame().await {
		let frame = frame_or_err.map_err(HttpError::Stream)?;
		let Some(data) = frame.data_ref() else {
			continue;
		};

		// If it's the first chunk, trim the whitespaces to determine whether it's valid JSON-RPC call.
		if received_data.is_empty() {
			let first_non_whitespace =
				data.chunk().iter().enumerate().take(128).find(|(_, byte)| !byte.is_ascii_whitespace());

			let skip = match first_non_whitespace {
				Some((idx, b'{')) => {
					is_single = Some(true);
					idx
				}
				Some((idx, b'[')) => {
					is_single = Some(false);
					idx
				}
				_ => return Err(HttpError::Malformed),
			};

			// ignore whitespace as these doesn't matter just makes the JSON decoding slower.
			received_data.extend_from_slice(&data.chunk()[skip..]);
		} else {
			received_data.extend_from_slice(data.chunk());
		}
	}

	match is_single {
		Some(single) if !received_data.is_empty() => {
			tracing::trace!(
				target: "jsonrpsee-http",
				"HTTP response body: {}",
				std::str::from_utf8(&received_data).unwrap_or("Invalid UTF-8 data")
			);
			Ok((received_data, single))
		}
		_ => Err(HttpError::Malformed),
	}
}

/// Read the `Content-Length` HTTP Header. Must fit into a `u32`; returns `None` otherwise.
///
/// NOTE: There's no specific hard limit on `Content_length` in HTTP specification.
/// Thus this method might reject valid `content_length`
fn read_header_content_length(headers: &http::header::HeaderMap) -> Option<u32> {
	let length = read_header_value(headers, http::header::CONTENT_LENGTH)?;
	// HTTP Content-Length indicates number of bytes in decimal.
	length.parse::<u32>().ok()
}

/// Returns a string value when there is exactly one value for the given header.
pub fn read_header_value(headers: &http::header::HeaderMap, header_name: http::header::HeaderName) -> Option<&str> {
	let mut values = headers.get_all(header_name).iter();
	let val = values.next()?;
	if values.next().is_none() {
		val.to_str().ok()
	} else {
		None
	}
}

/// Returns an iterator of all values for a given a header name
pub fn read_header_values<'a>(
	headers: &'a http::header::HeaderMap,
	header_name: &str,
) -> http::header::GetAll<'a, http::header::HeaderValue> {
	headers.get_all(header_name)
}

#[cfg(test)]
mod tests {
	use super::{read_body, read_header_content_length, HttpError};
	use http_body_util::BodyExt;

	type Body = http_body_util::Full<bytes::Bytes>;

	#[tokio::test]
	async fn body_to_bytes_size_limit_works() {
		let headers = http::header::HeaderMap::new();
		let full_body = Body::from(vec![0; 128]);
		let body = full_body.map_err(|e| HttpError::Stream(e.into()));
		assert!(read_body(&headers, body, 127).await.is_err());
	}

	#[test]
	fn read_content_length_works() {
		let mut headers = http::header::HeaderMap::new();
		headers.insert(http::header::CONTENT_LENGTH, "177".parse().unwrap());
		assert_eq!(read_header_content_length(&headers), Some(177));

		headers.append(http::header::CONTENT_LENGTH, "999".parse().unwrap());
		assert_eq!(read_header_content_length(&headers), None);
	}

	#[test]
	fn read_content_length_too_big_value() {
		let mut headers = http::header::HeaderMap::new();
		headers.insert(http::header::CONTENT_LENGTH, "18446744073709551616".parse().unwrap());
		assert_eq!(read_header_content_length(&headers), None);
	}
}