// Copyright 2019-2020 Parity Technologies (UK) Ltd.
// This file is part of Parity Bridges Common.

// Parity Bridges Common is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Bridges Common is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.

//! Primitives for sending and receiving Substrate <-> Substrate messages.

#![cfg_attr(not(feature = "std"), no_std)]
// RuntimeApi generated functions
#![allow(clippy::too_many_arguments)]
// Generated by `DecodeLimit::decode_with_depth_limit`
#![allow(clippy::unnecessary_mut_passed)]

use codec::{Decode, Encode};
use sp_api::decl_runtime_apis;

/// Lane identifier.
pub type LaneId = [u8; 4];

/// Message nonce. Valid messages will never have 0 nonce.
pub type MessageNonce = u64;

/// Message key (unique message identifier) as it is stored in the storage.
#[derive(Encode, Decode, Clone)]
pub struct MessageKey {
	/// ID of the message lane.
	pub lane_id: LaneId,
	/// Message nonce.
	pub nonce: MessageNonce,
}

/// Message as it is stored in the storage.
#[derive(Encode, Decode, Clone)]
pub struct Message<Payload> {
	/// Message key.
	pub key: MessageKey,
	/// Message payload.
	pub payload: Payload,
}

/// Message processing result.
pub enum MessageResult<Payload> {
	/// Message has been processed and should not be queued.
	Processed,
	/// Message has NOT been processed and should be queued for processing later.
	NotProcessed(Message<Payload>),
}

/// Called when inbound message is received.
pub trait OnMessageReceived<Payload> {
	/// Called when inbound message is received.
	///
	/// It is up to the implementers of this trait to determine whether the message
	/// is invalid (i.e. improperly encoded, has too large weight, ...) or not. And,
	/// if message is invalid, then it should be dropped immediately (by returning
	/// `MessageResult::Processed`), or it'll block the lane forever.
	fn on_message_received(&mut self, message: Message<Payload>) -> MessageResult<Payload>;
}

/// Inbound lane data.
#[derive(Encode, Decode, Clone)]
pub struct InboundLaneData {
	/// Nonce of oldest message that we haven't processed yet. May point to not-yet-received message if
	/// lane is currently empty.
	pub oldest_unprocessed_nonce: MessageNonce,
	/// Nonce of latest message that we have received from bridged chain.
	pub latest_received_nonce: MessageNonce,
}

impl Default for InboundLaneData {
	fn default() -> Self {
		InboundLaneData {
			// it is 1 because we're processing everything in [oldest_unprocessed_nonce; latest_received_nonce]
			oldest_unprocessed_nonce: 1,
			latest_received_nonce: 0,
		}
	}
}

/// Outbound lane data.
#[derive(Encode, Decode, Clone)]
pub struct OutboundLaneData {
	/// Nonce of oldest message that we haven't yet pruned. May point to not-yet-generated message if
	/// all sent messages are already pruned.
	pub oldest_unpruned_nonce: MessageNonce,
	/// Nonce of latest message, received by bridged chain.
	pub latest_received_nonce: MessageNonce,
	/// Nonce of latest message, processed by bridged chain.
	pub latest_processed_nonce: MessageNonce,
	/// Nonce of latest message, generated by us.
	pub latest_generated_nonce: MessageNonce,
}

impl Default for OutboundLaneData {
	fn default() -> Self {
		OutboundLaneData {
			// it is 1 because we're pruning everything in [oldest_unpruned_nonce; latest_received_nonce]
			oldest_unpruned_nonce: 1,
			latest_received_nonce: 0,
			latest_processed_nonce: 0,
			latest_generated_nonce: 0,
		}
	}
}

decl_runtime_apis! {
	/// Outbound message lane API.
	pub trait OutboundLaneApi<Payload: Decode> {
		/// Returns nonce of the latest message, received by bridged chain.
		fn latest_received_nonce(lane: LaneId) -> MessageNonce;
		/// Returns nonce of the latest message, processed by bridged chain.
		fn latest_processed_nonce(lane: LaneId) -> MessageNonce;
		/// Returns nonce of the latest message, generated by given lane.
		fn latest_generated_nonce(lane: LaneId) -> MessageNonce;
	}

	/// Inbound message lane API.
	pub trait InboundLaneApi {
		/// Returns nonce of the latest message, received by given lane.
		fn latest_received_nonce(lane: LaneId) -> MessageNonce;
		/// Returns nonce of the latest message, processed by given lane.
		fn latest_processed_nonce(lane: LaneId) -> MessageNonce;
	}
}