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

// 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 crate::{
	storage::{self, unhashed, StorageAppend},
	Never,
};
use codec::{Decode, Encode, EncodeLike, FullCodec};

/// Generator for `StorageValue` used by `decl_storage`.
///
/// By default value is stored at:
/// ```nocompile
/// Twox128(module_prefix) ++ Twox128(storage_prefix)
/// ```
pub trait StorageValue<T: FullCodec> {
	/// The type that get/take returns.
	type Query;

	/// Module prefix. Used for generating final key.
	fn module_prefix() -> &'static [u8];

	/// Storage prefix. Used for generating final key.
	fn storage_prefix() -> &'static [u8];

	/// Convert an optional value retrieved from storage to the type queried.
	fn from_optional_value_to_query(v: Option<T>) -> Self::Query;

	/// Convert a query to an optional value into storage.
	fn from_query_to_optional_value(v: Self::Query) -> Option<T>;

	/// Generate the full key used in top storage.
	fn storage_value_final_key() -> [u8; 32] {
		crate::storage::storage_prefix(Self::module_prefix(), Self::storage_prefix())
	}
}

impl<T: FullCodec, G: StorageValue<T>> storage::StorageValue<T> for G {
	type Query = G::Query;

	fn hashed_key() -> [u8; 32] {
		Self::storage_value_final_key()
	}

	fn exists() -> bool {
		unhashed::exists(&Self::storage_value_final_key())
	}

	fn get() -> Self::Query {
		let value = unhashed::get(&Self::storage_value_final_key());
		G::from_optional_value_to_query(value)
	}

	fn try_get() -> Result<T, ()> {
		unhashed::get(&Self::storage_value_final_key()).ok_or(())
	}

	fn translate<O: Decode, F: FnOnce(Option<O>) -> Option<T>>(f: F) -> Result<Option<T>, ()> {
		let key = Self::storage_value_final_key();

		// attempt to get the length directly.
		let maybe_old = unhashed::get_raw(&key)
			.map(|old_data| O::decode(&mut &old_data[..]).map_err(|_| ()))
			.transpose()?;
		let maybe_new = f(maybe_old);
		if let Some(new) = maybe_new.as_ref() {
			new.using_encoded(|d| unhashed::put_raw(&key, d));
		} else {
			unhashed::kill(&key);
		}
		Ok(maybe_new)
	}

	fn put<Arg: EncodeLike<T>>(val: Arg) {
		unhashed::put(&Self::storage_value_final_key(), &val)
	}

	fn set(maybe_val: Self::Query) {
		if let Some(val) = G::from_query_to_optional_value(maybe_val) {
			unhashed::put(&Self::storage_value_final_key(), &val)
		} else {
			unhashed::kill(&Self::storage_value_final_key())
		}
	}

	fn kill() {
		unhashed::kill(&Self::storage_value_final_key())
	}

	fn mutate<R, F: FnOnce(&mut G::Query) -> R>(f: F) -> R {
		Self::try_mutate(|v| Ok::<R, Never>(f(v))).expect("`Never` can not be constructed; qed")
	}

	fn try_mutate<R, E, F: FnOnce(&mut G::Query) -> Result<R, E>>(f: F) -> Result<R, E> {
		let mut val = G::get();

		let ret = f(&mut val);
		if ret.is_ok() {
			match G::from_query_to_optional_value(val) {
				Some(ref val) => G::put(val),
				None => G::kill(),
			}
		}
		ret
	}

	fn mutate_exists<R, F>(f: F) -> R
	where
		F: FnOnce(&mut Option<T>) -> R,
	{
		Self::try_mutate_exists(|v| Ok::<R, Never>(f(v)))
			.expect("`Never` can not be constructed; qed")
	}

	fn try_mutate_exists<R, E, F>(f: F) -> Result<R, E>
	where
		F: FnOnce(&mut Option<T>) -> Result<R, E>,
	{
		let mut val = G::from_query_to_optional_value(Self::get());

		let ret = f(&mut val);
		if ret.is_ok() {
			match val {
				Some(ref val) => Self::put(val),
				None => Self::kill(),
			}
		}
		ret
	}

	fn take() -> G::Query {
		let key = Self::storage_value_final_key();
		let value = unhashed::get(&key);
		if value.is_some() {
			unhashed::kill(&key)
		}
		G::from_optional_value_to_query(value)
	}

	fn append<Item, EncodeLikeItem>(item: EncodeLikeItem)
	where
		Item: Encode,
		EncodeLikeItem: EncodeLike<Item>,
		T: StorageAppend<Item>,
	{
		let key = Self::storage_value_final_key();
		sp_io::storage::append(&key, item.encode());
	}
}