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
// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use codec::{Decode, Encode};
use hash_db::{HashDB, Hasher};
use scale_info::TypeInfo;
use sp_std::{
	collections::btree_set::BTreeSet,
	iter::{DoubleEndedIterator, IntoIterator},
	vec::Vec,
};
// Note that `LayoutV1` usage here (proof compaction) is compatible
// with `LayoutV0`.
use crate::LayoutV1 as Layout;

/// A proof that some set of key-value pairs are included in the storage trie. The proof contains
/// the storage values so that the partial storage backend can be reconstructed by a verifier that
/// does not already have access to the key-value pairs.
///
/// The proof consists of the set of serialized nodes in the storage trie accessed when looking up
/// the keys covered by the proof. Verifying the proof requires constructing the partial trie from
/// the serialized nodes and performing the key lookups.
#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode, TypeInfo)]
pub struct StorageProof {
	trie_nodes: BTreeSet<Vec<u8>>,
}

impl StorageProof {
	/// Constructs a storage proof from a subset of encoded trie nodes in a storage backend.
	pub fn new(trie_nodes: impl IntoIterator<Item = Vec<u8>>) -> Self {
		StorageProof { trie_nodes: BTreeSet::from_iter(trie_nodes) }
	}

	/// Returns a new empty proof.
	///
	/// An empty proof is capable of only proving trivial statements (ie. that an empty set of
	/// key-value pairs exist in storage).
	pub fn empty() -> Self {
		StorageProof { trie_nodes: BTreeSet::new() }
	}

	/// Returns whether this is an empty proof.
	pub fn is_empty(&self) -> bool {
		self.trie_nodes.is_empty()
	}

	/// Convert into an iterator over encoded trie nodes in lexicographical order constructed
	/// from the proof.
	pub fn into_iter_nodes(self) -> impl Sized + DoubleEndedIterator<Item = Vec<u8>> {
		self.trie_nodes.into_iter()
	}

	/// Create an iterator over encoded trie nodes in lexicographical order constructed
	/// from the proof.
	pub fn iter_nodes(&self) -> impl Sized + DoubleEndedIterator<Item = &Vec<u8>> {
		self.trie_nodes.iter()
	}

	/// Convert into plain node vector.
	pub fn into_nodes(self) -> BTreeSet<Vec<u8>> {
		self.trie_nodes
	}

	/// Creates a [`MemoryDB`](crate::MemoryDB) from `Self`.
	pub fn into_memory_db<H: Hasher>(self) -> crate::MemoryDB<H> {
		self.into()
	}

	/// Creates a [`MemoryDB`](crate::MemoryDB) from `Self` reference.
	pub fn to_memory_db<H: Hasher>(&self) -> crate::MemoryDB<H> {
		self.into()
	}

	/// Merges multiple storage proofs covering potentially different sets of keys into one proof
	/// covering all keys. The merged proof output may be smaller than the aggregate size of the
	/// input proofs due to deduplication of trie nodes.
	pub fn merge(proofs: impl IntoIterator<Item = Self>) -> Self {
		let trie_nodes = proofs
			.into_iter()
			.flat_map(|proof| proof.into_iter_nodes())
			.collect::<BTreeSet<_>>()
			.into_iter()
			.collect();

		Self { trie_nodes }
	}

	/// Encode as a compact proof with default trie layout.
	pub fn into_compact_proof<H: Hasher>(
		self,
		root: H::Out,
	) -> Result<CompactProof, crate::CompactProofError<H::Out, crate::Error<H::Out>>> {
		let db = self.into_memory_db();
		crate::encode_compact::<Layout<H>, crate::MemoryDB<H>>(&db, &root)
	}

	/// Encode as a compact proof with default trie layout.
	pub fn to_compact_proof<H: Hasher>(
		&self,
		root: H::Out,
	) -> Result<CompactProof, crate::CompactProofError<H::Out, crate::Error<H::Out>>> {
		let db = self.to_memory_db();
		crate::encode_compact::<Layout<H>, crate::MemoryDB<H>>(&db, &root)
	}

	/// Returns the estimated encoded size of the compact proof.
	///
	/// Running this operation is a slow operation (build the whole compact proof) and should only
	/// be in non sensitive path.
	///
	/// Return `None` on error.
	pub fn encoded_compact_size<H: Hasher>(self, root: H::Out) -> Option<usize> {
		let compact_proof = self.into_compact_proof::<H>(root);
		compact_proof.ok().map(|p| p.encoded_size())
	}
}

impl<H: Hasher> From<StorageProof> for crate::MemoryDB<H> {
	fn from(proof: StorageProof) -> Self {
		From::from(&proof)
	}
}

impl<H: Hasher> From<&StorageProof> for crate::MemoryDB<H> {
	fn from(proof: &StorageProof) -> Self {
		let mut db = crate::MemoryDB::default();
		proof.iter_nodes().for_each(|n| {
			db.insert(crate::EMPTY_PREFIX, &n);
		});
		db
	}
}

/// Storage proof in compact form.
#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode, TypeInfo)]
pub struct CompactProof {
	pub encoded_nodes: Vec<Vec<u8>>,
}

impl CompactProof {
	/// Return an iterator on the compact encoded nodes.
	pub fn iter_compact_encoded_nodes(&self) -> impl Iterator<Item = &[u8]> {
		self.encoded_nodes.iter().map(Vec::as_slice)
	}

	/// Decode to a full storage_proof.
	pub fn to_storage_proof<H: Hasher>(
		&self,
		expected_root: Option<&H::Out>,
	) -> Result<(StorageProof, H::Out), crate::CompactProofError<H::Out, crate::Error<H::Out>>> {
		let mut db = crate::MemoryDB::<H>::new(&[]);
		let root = crate::decode_compact::<Layout<H>, _, _>(
			&mut db,
			self.iter_compact_encoded_nodes(),
			expected_root,
		)?;
		Ok((
			StorageProof::new(db.drain().into_iter().filter_map(|kv| {
				if (kv.1).1 > 0 {
					Some((kv.1).0)
				} else {
					None
				}
			})),
			root,
		))
	}

	/// Convert self into a [`MemoryDB`](crate::MemoryDB).
	///
	/// `expected_root` is the expected root of this compact proof.
	///
	/// Returns the memory db and the root of the trie.
	pub fn to_memory_db<H: Hasher>(
		&self,
		expected_root: Option<&H::Out>,
	) -> Result<(crate::MemoryDB<H>, H::Out), crate::CompactProofError<H::Out, crate::Error<H::Out>>>
	{
		let mut db = crate::MemoryDB::<H>::new(&[]);
		let root = crate::decode_compact::<Layout<H>, _, _>(
			&mut db,
			self.iter_compact_encoded_nodes(),
			expected_root,
		)?;

		Ok((db, root))
	}
}