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

// Copyright (C) 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/>.

//! Logic for optimizing GRANDPA Finality Proofs.

use crate::justification::{
	verification::{Error, JustificationVerifier, PrecommitError},
	GrandpaJustification,
};

use crate::justification::verification::{
	IterationFlow, JustificationVerificationContext, SignedPrecommit,
};
use sp_consensus_grandpa::AuthorityId;
use sp_runtime::traits::Header as HeaderT;
use sp_std::{collections::btree_set::BTreeSet, prelude::*};

// Verification callbacks for justification optimization.
struct JustificationOptimizer<Header: HeaderT> {
	votes: BTreeSet<AuthorityId>,

	extra_precommits: Vec<usize>,
	duplicate_votes_ancestries_idxs: Vec<usize>,
	redundant_votes_ancestries: BTreeSet<Header::Hash>,
}

impl<Header: HeaderT> JustificationOptimizer<Header> {
	fn optimize(self, justification: &mut GrandpaJustification<Header>) {
		for invalid_precommit_idx in self.extra_precommits.into_iter().rev() {
			justification.commit.precommits.remove(invalid_precommit_idx);
		}
		if !self.duplicate_votes_ancestries_idxs.is_empty() {
			for idx in self.duplicate_votes_ancestries_idxs.iter().rev() {
				justification.votes_ancestries.swap_remove(*idx);
			}
		}
		if !self.redundant_votes_ancestries.is_empty() {
			justification
				.votes_ancestries
				.retain(|header| !self.redundant_votes_ancestries.contains(&header.hash()))
		}
	}
}

impl<Header: HeaderT> JustificationVerifier<Header> for JustificationOptimizer<Header> {
	fn process_duplicate_votes_ancestries(
		&mut self,
		duplicate_votes_ancestries: Vec<usize>,
	) -> Result<(), Error> {
		self.duplicate_votes_ancestries_idxs = duplicate_votes_ancestries.to_vec();
		Ok(())
	}

	fn process_redundant_vote(
		&mut self,
		precommit_idx: usize,
	) -> Result<IterationFlow, PrecommitError> {
		self.extra_precommits.push(precommit_idx);
		Ok(IterationFlow::Skip)
	}

	fn process_known_authority_vote(
		&mut self,
		precommit_idx: usize,
		signed: &SignedPrecommit<Header>,
	) -> Result<IterationFlow, PrecommitError> {
		// Skip duplicate votes
		if self.votes.contains(&signed.id) {
			self.extra_precommits.push(precommit_idx);
			return Ok(IterationFlow::Skip)
		}

		Ok(IterationFlow::Run)
	}

	fn process_unknown_authority_vote(
		&mut self,
		precommit_idx: usize,
	) -> Result<(), PrecommitError> {
		self.extra_precommits.push(precommit_idx);
		Ok(())
	}

	fn process_unrelated_ancestry_vote(
		&mut self,
		precommit_idx: usize,
	) -> Result<IterationFlow, PrecommitError> {
		self.extra_precommits.push(precommit_idx);
		Ok(IterationFlow::Skip)
	}

	fn process_invalid_signature_vote(
		&mut self,
		precommit_idx: usize,
	) -> Result<(), PrecommitError> {
		self.extra_precommits.push(precommit_idx);
		Ok(())
	}

	fn process_valid_vote(&mut self, signed: &SignedPrecommit<Header>) {
		self.votes.insert(signed.id.clone());
	}

	fn process_redundant_votes_ancestries(
		&mut self,
		redundant_votes_ancestries: BTreeSet<Header::Hash>,
	) -> Result<(), Error> {
		self.redundant_votes_ancestries = redundant_votes_ancestries;
		Ok(())
	}
}

/// Verify and optimize given justification by removing unknown and duplicate votes.
pub fn verify_and_optimize_justification<Header: HeaderT>(
	finalized_target: (Header::Hash, Header::Number),
	context: &JustificationVerificationContext,
	justification: &mut GrandpaJustification<Header>,
) -> Result<(), Error> {
	let mut optimizer = JustificationOptimizer {
		votes: BTreeSet::new(),
		extra_precommits: vec![],
		duplicate_votes_ancestries_idxs: vec![],
		redundant_votes_ancestries: Default::default(),
	};
	optimizer.verify_justification(finalized_target, context, justification)?;
	optimizer.optimize(justification);

	Ok(())
}