1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211

// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This file is part of Frontier.
//
// Copyright (c) 2022 Parity Technologies (UK) Ltd.
//
// This program 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.
//
// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

use ethereum_types::U256;
use jsonrpsee::core::RpcResult;
// Substrate
use sc_client_api::backend::{Backend, StorageProvider};
use sc_transaction_pool::ChainApi;
use sp_api::ProvideRuntimeApi;
use sp_blockchain::HeaderBackend;
use sp_runtime::traits::{Block as BlockT, UniqueSaturatedInto};
// Frontier
use fc_rpc_core::types::*;
use fp_rpc::EthereumRuntimeRPCApi;

use crate::{eth::Eth, frontier_backend_client, internal_err};

impl<B, C, P, CT, BE, A, CIDP, EC> Eth<B, C, P, CT, BE, A, CIDP, EC>
where
	B: BlockT,
	C: ProvideRuntimeApi<B>,
	C::Api: EthereumRuntimeRPCApi<B>,
	C: HeaderBackend<B> + StorageProvider<B, BE> + 'static,
	BE: Backend<B> + 'static,
	A: ChainApi<Block = B>,
{
	pub fn gas_price(&self) -> RpcResult<U256> {
		let block_hash = self.client.info().best_hash;

		self.client
			.runtime_api()
			.gas_price(block_hash)
			.map_err(|err| internal_err(format!("fetch runtime chain id failed: {:?}", err)))
	}

	pub async fn fee_history(
		&self,
		block_count: U256,
		newest_block: BlockNumberOrHash,
		reward_percentiles: Option<Vec<f64>>,
	) -> RpcResult<FeeHistory> {
		// The max supported range size is 1024 by spec.
		let range_limit = U256::from(1024);
		let block_count = if block_count > range_limit {
			range_limit.as_u64()
		} else {
			block_count.as_u64()
		};

		if let Some(id) = frontier_backend_client::native_block_id::<B, C>(
			self.client.as_ref(),
			self.backend.as_ref(),
			Some(newest_block),
		)
		.await?
		{
			let Ok(number) = self.client.expect_block_number_from_id(&id) else {
				return Err(internal_err(format!(
					"Failed to retrieve block number at {id}"
				)));
			};
			// Highest and lowest block number within the requested range.
			let highest = UniqueSaturatedInto::<u64>::unique_saturated_into(number);
			let lowest = highest.saturating_sub(block_count.saturating_sub(1));
			// Tip of the chain.
			let best_number =
				UniqueSaturatedInto::<u64>::unique_saturated_into(self.client.info().best_number);
			// Only support in-cache queries.
			if lowest < best_number.saturating_sub(self.fee_history_cache_limit) {
				return Err(internal_err("Block range out of bounds."));
			}
			if let Ok(fee_history_cache) = &self.fee_history_cache.lock() {
				let mut response = FeeHistory {
					oldest_block: U256::from(lowest),
					base_fee_per_gas: Vec::new(),
					gas_used_ratio: Vec::new(),
					reward: None,
				};
				let mut rewards = Vec::new();
				// Iterate over the requested block range.
				for n in lowest..highest + 1 {
					if let Some(block) = fee_history_cache.get(&n) {
						response.base_fee_per_gas.push(U256::from(block.base_fee));
						response.gas_used_ratio.push(block.gas_used_ratio);
						// If the request includes reward percentiles, get them from the cache.
						if let Some(ref requested_percentiles) = reward_percentiles {
							let mut block_rewards = Vec::new();
							// Resolution is half a point. I.e. 1.0,1.5
							let resolution_per_percentile: f64 = 2.0;
							// Get cached reward for each provided percentile.
							for p in requested_percentiles {
								// Find the cache index from the user percentile.
								let p = p.clamp(0.0, 100.0);
								let index = ((p.round() / 2f64) * 2f64) * resolution_per_percentile;
								// Get and push the reward.
								let reward = if let Some(r) = block.rewards.get(index as usize) {
									U256::from(*r)
								} else {
									U256::zero()
								};
								block_rewards.push(reward);
							}
							// Push block rewards.
							if !block_rewards.is_empty() {
								// Push block rewards.
								rewards.push(block_rewards);
							}
						}
					}
				}
				if rewards.len() > 0 {
					response.reward = Some(rewards);
				}
				// Calculate next base fee.
				if let (Some(last_gas_used), Some(last_fee_per_gas)) = (
					response.gas_used_ratio.last(),
					response.base_fee_per_gas.last(),
				) {
					let substrate_hash =
						self.client.expect_block_hash_from_id(&id).map_err(|_| {
							internal_err(format!("Expect block number from id: {}", id))
						})?;
					let schema =
						fc_storage::onchain_storage_schema(self.client.as_ref(), substrate_hash);
					let handler = self
						.overrides
						.schemas
						.get(&schema)
						.unwrap_or(&self.overrides.fallback);
					let default_elasticity = sp_runtime::Permill::from_parts(125_000);
					let elasticity = handler
						.elasticity(substrate_hash)
						.unwrap_or(default_elasticity)
						.deconstruct();
					let elasticity = elasticity as f64 / 1_000_000f64;
					let last_fee_per_gas =
						UniqueSaturatedInto::<u64>::unique_saturated_into(*last_fee_per_gas) as f64;
					if last_gas_used > &0.5 {
						// Increase base gas
						let increase = ((last_gas_used - 0.5) * 2f64) * elasticity;
						let new_base_fee =
							(last_fee_per_gas + (last_fee_per_gas * increase)) as u64;
						response.base_fee_per_gas.push(U256::from(new_base_fee));
					} else if last_gas_used < &0.5 {
						// Decrease base gas
						let increase = ((0.5 - last_gas_used) * 2f64) * elasticity;
						let new_base_fee =
							(last_fee_per_gas - (last_fee_per_gas * increase)) as u64;
						response.base_fee_per_gas.push(U256::from(new_base_fee));
					} else {
						// Same base gas
						response
							.base_fee_per_gas
							.push(U256::from(last_fee_per_gas as u64));
					}
				}
				return Ok(response);
			} else {
				return Err(internal_err("Failed to read fee history cache."));
			}
		}
		Err(internal_err(format!(
			"Failed to retrieve requested block {:?}.",
			newest_block
		)))
	}

	pub fn max_priority_fee_per_gas(&self) -> RpcResult<U256> {
		// https://github.com/ethereum/go-ethereum/blob/master/eth/ethconfig/config.go#L44-L51
		let at_percentile = 60;
		let block_count = 20;
		let index = (at_percentile * 2) as usize;

		let highest =
			UniqueSaturatedInto::<u64>::unique_saturated_into(self.client.info().best_number);
		let lowest = highest.saturating_sub(block_count - 1);

		// https://github.com/ethereum/go-ethereum/blob/master/eth/gasprice/gasprice.go#L149
		let mut rewards = Vec::new();
		if let Ok(fee_history_cache) = &self.fee_history_cache.lock() {
			for n in lowest..highest + 1 {
				if let Some(block) = fee_history_cache.get(&n) {
					let reward = if let Some(r) = block.rewards.get(index) {
						U256::from(*r)
					} else {
						U256::zero()
					};
					rewards.push(reward);
				}
			}
		} else {
			return Err(internal_err("Failed to read fee oracle cache."));
		}
		Ok(*rewards.iter().min().unwrap_or(&U256::zero()))
	}
}