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
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
// This file is part of Substrate.

// Copyright (C) 2019-2022 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.

//! Substrate runtime api
//!
//! The Substrate runtime api is the interface between the node and the runtime. There isn't a fixed
//! set of runtime apis, instead it is up to the user to declare and implement these runtime apis.
//! The declaration of a runtime api is normally done outside of a runtime, while the implementation
//! of it has to be done in the runtime. We provide the [`decl_runtime_apis!`] macro for declaring
//! a runtime api and the [`impl_runtime_apis!`] for implementing them. The macro docs provide more
//! information on how to use them and what kind of attributes we support.
//!
//! It is required that each runtime implements at least the [`Core`] runtime api. This runtime api
//! provides all the core functions that Substrate expects from a runtime.
//!
//! # Versioning
//!
//! Runtime apis support versioning. Each runtime api itself has a version attached. It is also
//! supported to change function signatures or names in a non-breaking way. For more information on
//! versioning check the [`decl_runtime_apis!`] macro.
//!
//! All runtime apis and their versions are returned as part of the [`RuntimeVersion`]. This can be
//! used to check which runtime api version is currently provided by the on-chain runtime.
//!
//! # Testing
//!
//! For testing we provide the [`mock_impl_runtime_apis!`] macro that lets you implement a runtime
//! api for a mocked object to use it in tests.
//!
//! # Logging
//!
//! Substrate supports logging from the runtime in native and in wasm. For that purpose it provides
//! the [`RuntimeLogger`](sp_runtime::runtime_logger::RuntimeLogger). This runtime logger is
//! automatically enabled for each call into the runtime through the runtime api. As logging
//! introduces extra code that isn't actually required for the logic of your runtime and also
//! increases the final wasm blob size, it is recommended to disable the logging for on-chain
//! wasm blobs. This can be done by enabling the `disable-logging` feature of this crate. Be aware
//! that this feature instructs `log` and `tracing` to disable logging at compile time by setting
//! the `max_level_off` feature for these crates. So, you should not enable this feature for a
//! native build as otherwise the node will not output any log messages.
//!
//! # How does it work?
//!
//! Each runtime api is declared as a trait with functions. When compiled to WASM, each implemented
//! runtime api function is exported as a function with the following naming scheme
//! `${TRAIT_NAME}_${FUNCTION_NAME}`. Such a function has the following signature
//! `(ptr: *u8, length: u32) -> u64`. It takes a pointer to an `u8` array and its length as an
//! argument. This `u8` array is expected to be the SCALE encoded parameters of the function as
//! defined in the trait. The return value is an `u64` that represents `length << 32 | pointer` of
//! an `u8` array. This return value `u8` array contains the SCALE encoded return value as defined
//! by the trait function. The macros take care to encode the parameters and to decode the return
//! value.

#![cfg_attr(not(feature = "std"), no_std)]

// Make doc tests happy
extern crate self as sp_api;

#[doc(hidden)]
pub use codec::{self, Decode, DecodeLimit, Encode};
#[doc(hidden)]
#[cfg(feature = "std")]
pub use hash_db::Hasher;
#[doc(hidden)]
#[cfg(not(feature = "std"))]
pub use sp_core::to_substrate_wasm_fn_return_value;
use sp_core::OpaqueMetadata;
#[doc(hidden)]
pub use sp_core::{offchain, ExecutionContext};
#[doc(hidden)]
#[cfg(feature = "std")]
pub use sp_runtime::StateVersion;
#[doc(hidden)]
pub use sp_runtime::{
	generic::BlockId,
	traits::{
		Block as BlockT, GetNodeBlockType, GetRuntimeBlockType, Hash as HashT, HashFor,
		Header as HeaderT, NumberFor,
	},
	transaction_validity::TransactionValidity,
	RuntimeString, TransactionOutcome,
};
#[doc(hidden)]
#[cfg(feature = "std")]
pub use sp_state_machine::{
	backend::AsTrieBackend, Backend as StateBackend, InMemoryBackend, OverlayedChanges,
	StorageProof, TrieBackend, TrieBackendBuilder,
};
#[doc(hidden)]
pub use sp_std::{mem, slice};
#[doc(hidden)]
pub use sp_version::{create_apis_vec, ApiId, ApisVec, RuntimeVersion};
#[cfg(feature = "std")]
use std::cell::RefCell;

/// Maximum nesting level for extrinsics.
pub const MAX_EXTRINSIC_DEPTH: u32 = 256;

/// Declares given traits as runtime apis.
///
/// The macro will create two declarations, one for using on the client side and one for using
/// on the runtime side. The declaration for the runtime side is hidden in its own module.
/// The client side declaration gets two extra parameters per function,
/// `&self` and `at: &BlockId<Block>`. The runtime side declaration will match the given trait
/// declaration. Besides one exception, the macro adds an extra generic parameter `Block:
/// BlockT` to the client side and the runtime side. This generic parameter is usable by the
/// user.
///
/// For implementing these macros you should use the
/// [`impl_runtime_apis!`] macro.
///
/// # Example
///
/// ```rust
/// sp_api::decl_runtime_apis! {
///     /// Declare the api trait.
///     pub trait Balance {
///         /// Get the balance.
///         fn get_balance() -> u64;
///         /// Set the balance.
///         fn set_balance(val: u64);
///     }
///
///     /// You can declare multiple api traits in one macro call.
///     /// In one module you can call the macro at maximum one time.
///     pub trait BlockBuilder {
///         /// The macro adds an explicit `Block: BlockT` generic parameter for you.
///         /// You can use this generic parameter as you would defined it manually.
///         fn build_block() -> Block;
///     }
/// }
///
/// # fn main() {}
/// ```
///
/// # Runtime api trait versioning
///
/// To support versioning of the traits, the macro supports the attribute `#[api_version(1)]`.
/// The attribute supports any `u32` as version. By default, each trait is at version `1`, if
/// no version is provided. We also support changing the signature of a method. This signature
/// change is highlighted with the `#[changed_in(2)]` attribute above a method. A method that
/// is tagged with this attribute is callable by the name `METHOD_before_version_VERSION`. This
/// method will only support calling into wasm, trying to call into native will fail (change
/// the spec version!). Such a method also does not need to be implemented in the runtime. It
/// is required that there exist the "default" of the method without the `#[changed_in(_)]`
/// attribute, this method will be used to call the current default implementation.
///
/// ```rust
/// sp_api::decl_runtime_apis! {
///     /// Declare the api trait.
///     #[api_version(2)]
///     pub trait Balance {
///         /// Get the balance.
///         fn get_balance() -> u64;
///         /// Set balance.
///         fn set_balance(val: u64);
///         /// Set balance, old version.
///         ///
///         /// Is callable by `set_balance_before_version_2`.
///         #[changed_in(2)]
///         fn set_balance(val: u16);
///         /// In version 2, we added this new function.
///         fn increase_balance(val: u64);
///     }
/// }
///
/// # fn main() {}
/// ```
///
/// To check if a given runtime implements a runtime api trait, the `RuntimeVersion` has the
/// function `has_api<A>()`. Also the `ApiExt` provides a function `has_api<A>(at: &BlockId)`
/// to check if the runtime at the given block id implements the requested runtime api trait.
///
/// # Declaring multiple api versions
///
/// Optionally multiple versions of the same api can be declared. This is useful for
/// development purposes. For example you want to have a testing version of the api which is
/// available only on a testnet. You can define one stable and one development version. This
/// can be done like this:
/// ```rust
/// sp_api::decl_runtime_apis! {
///     /// Declare the api trait.
/// 	#[api_version(2)]
///     pub trait Balance {
///         /// Get the balance.
///         fn get_balance() -> u64;
///         /// Set the balance.
///         fn set_balance(val: u64);
///         /// Transfer the balance to another user id
///         #[api_version(3)]
///         fn transfer_balance(uid: u64);
///     }
/// }
///
/// # fn main() {}
/// ```
/// The example above defines two api versions - 2 and 3. Version 2 contains `get_balance` and
/// `set_balance`. Version 3 additionally contains `transfer_balance`, which is not available
/// in version 2. Version 2 in this case is considered the default/base version of the api.
/// More than two versions can be defined this way. For example:
/// ```rust
/// sp_api::decl_runtime_apis! {
///     /// Declare the api trait.
///     #[api_version(2)]
///     pub trait Balance {
///         /// Get the balance.
///         fn get_balance() -> u64;
///         /// Set the balance.
///         fn set_balance(val: u64);
///         /// Transfer the balance to another user id
///         #[api_version(3)]
///         fn transfer_balance(uid: u64);
///         /// Clears the balance
///         #[api_version(4)]
///         fn clear_balance();
///     }
/// }
///
/// # fn main() {}
/// ```
/// Note that the latest version (4 in our example above) always contains all methods from all
/// the versions before.
pub use sp_api_proc_macro::decl_runtime_apis;

/// Tags given trait implementations as runtime apis.
///
/// All traits given to this macro, need to be declared with the
/// [`decl_runtime_apis!`](macro.decl_runtime_apis.html) macro. The implementation of the trait
/// should follow the declaration given to the
/// [`decl_runtime_apis!`](macro.decl_runtime_apis.html) macro, besides the `Block` type that
/// is required as first generic parameter for each runtime api trait. When implementing a
/// runtime api trait, it is required that the trait is referenced by a path, e.g. `impl
/// my_trait::MyTrait for Runtime`. The macro will use this path to access the declaration of
/// the trait for the runtime side.
///
/// The macro also generates the api implementations for the client side and provides it
/// through the `RuntimeApi` type. The `RuntimeApi` is hidden behind a `feature` called `std`.
///
/// To expose version information about all implemented api traits, the constant
/// `RUNTIME_API_VERSIONS` is generated. This constant should be used to instantiate the `apis`
/// field of `RuntimeVersion`.
///
/// # Example
///
/// ```rust
/// use sp_version::create_runtime_str;
/// #
/// # use sp_runtime::traits::{GetNodeBlockType, Block as BlockT};
/// # use sp_test_primitives::Block;
/// #
/// # /// The declaration of the `Runtime` type and the implementation of the `GetNodeBlockType`
/// # /// trait are done by the `construct_runtime!` macro in a real runtime.
/// # pub struct Runtime {}
/// # impl GetNodeBlockType for Runtime {
/// #     type NodeBlock = Block;
/// # }
/// #
/// # sp_api::decl_runtime_apis! {
/// #     /// Declare the api trait.
/// #     pub trait Balance {
/// #         /// Get the balance.
/// #         fn get_balance() -> u64;
/// #         /// Set the balance.
/// #         fn set_balance(val: u64);
/// #     }
/// #     pub trait BlockBuilder {
/// #        fn build_block() -> Block;
/// #     }
/// # }
///
/// /// All runtime api implementations need to be done in one call of the macro!
/// sp_api::impl_runtime_apis! {
/// #   impl sp_api::Core<Block> for Runtime {
/// #       fn version() -> sp_version::RuntimeVersion {
/// #           unimplemented!()
/// #       }
/// #       fn execute_block(_block: Block) {}
/// #       fn initialize_block(_header: &<Block as BlockT>::Header) {}
/// #   }
///
///     impl self::Balance<Block> for Runtime {
///         fn get_balance() -> u64 {
///             1
///         }
///         fn set_balance(_bal: u64) {
///             // Store the balance
///         }
///     }
///
///     impl self::BlockBuilder<Block> for Runtime {
///         fn build_block() -> Block {
///              unimplemented!("Please implement me!")
///         }
///     }
/// }
///
/// /// Runtime version. This needs to be declared for each runtime.
/// pub const VERSION: sp_version::RuntimeVersion = sp_version::RuntimeVersion {
///     spec_name: create_runtime_str!("node"),
///     impl_name: create_runtime_str!("test-node"),
///     authoring_version: 1,
///     spec_version: 1,
///     impl_version: 0,
///     // Here we are exposing the runtime api versions.
///     apis: RUNTIME_API_VERSIONS,
///     transaction_version: 1,
///     state_version: 1,
/// };
///
/// # fn main() {}
/// ```
///
/// # Implementing specific api version
///
/// If `decl_runtime_apis!` declares multiple versions for an api `impl_runtime_apis!`
/// should specify which version it implements by adding `api_version` attribute to the
/// `impl` block. If omitted - the base/default version is implemented. Here is an example:
/// ```ignore
/// sp_api::impl_runtime_apis! {
///     #[api_version(3)]
///     impl self::Balance<Block> for Runtime {
///          // implementation
///     }
/// }
/// ```
/// In this case `Balance` api version 3 is being implemented for `Runtime`. The `impl` block
/// must contain all methods declared in version 3 and below.
pub use sp_api_proc_macro::impl_runtime_apis;

/// Mocks given trait implementations as runtime apis.
///
/// Accepts similar syntax as [`impl_runtime_apis!`] and generates
/// simplified mock implementations of the given runtime apis. The difference in syntax is that
/// the trait does not need to be referenced by a qualified path, methods accept the `&self`
/// parameter and the error type can be specified as associated type. If no error type is
/// specified [`String`] is used as error type.
///
/// Besides implementing the given traits, the [`Core`](sp_api::Core) and
/// [`ApiExt`](sp_api::ApiExt) are implemented automatically.
///
/// # Example
///
/// ```rust
/// # use sp_runtime::traits::Block as BlockT;
/// # use sp_test_primitives::Block;
/// #
/// # sp_api::decl_runtime_apis! {
/// #     /// Declare the api trait.
/// #     pub trait Balance {
/// #         /// Get the balance.
/// #         fn get_balance() -> u64;
/// #         /// Set the balance.
/// #         fn set_balance(val: u64);
/// #     }
/// #     pub trait BlockBuilder {
/// #        fn build_block() -> Block;
/// #     }
/// # }
/// struct MockApi {
///     balance: u64,
/// }
///
/// /// All runtime api mock implementations need to be done in one call of the macro!
/// sp_api::mock_impl_runtime_apis! {
///     impl Balance<Block> for MockApi {
///         /// Here we take the `&self` to access the instance.
///         fn get_balance(&self) -> u64 {
///             self.balance
///         }
///         fn set_balance(_bal: u64) {
///             // Store the balance
///         }
///     }
///
///     impl BlockBuilder<Block> for MockApi {
///         fn build_block() -> Block {
///              unimplemented!("Not Required in tests")
///         }
///     }
/// }
///
/// # fn main() {}
/// ```
///
/// # `advanced` attribute
///
/// This attribute can be placed above individual function in the mock implementation to
/// request more control over the function declaration. From the client side each runtime api
/// function is called with the `at` parameter that is a [`BlockId`](sp_api::BlockId). When
/// using the `advanced` attribute, the macro expects that the first parameter of the function
/// is this `at` parameter. Besides that the macro also doesn't do the automatic return value
/// rewrite, which means that full return value must be specified. The full return value is
/// constructed like [`Result`]`<<ReturnValue>, Error>` while `ReturnValue` being the return
/// value that is specified in the trait declaration.
///
/// ## Example
/// ```rust
/// # use sp_runtime::{traits::Block as BlockT, generic::BlockId};
/// # use sp_test_primitives::Block;
/// # use codec;
/// #
/// # sp_api::decl_runtime_apis! {
/// #     /// Declare the api trait.
/// #     pub trait Balance {
/// #         /// Get the balance.
/// #         fn get_balance() -> u64;
/// #         /// Set the balance.
/// #         fn set_balance(val: u64);
/// #     }
/// # }
/// struct MockApi {
///     balance: u64,
/// }
///
/// sp_api::mock_impl_runtime_apis! {
///     impl Balance<Block> for MockApi {
///         #[advanced]
///         fn get_balance(&self, at: &BlockId<Block>) -> Result<u64, sp_api::ApiError> {
///             println!("Being called at: {}", at);
///
///             Ok(self.balance.into())
///         }
///         #[advanced]
///         fn set_balance(at: &BlockId<Block>, val: u64) -> Result<(), sp_api::ApiError> {
///             if let BlockId::Number(1) = at {
///                 println!("Being called to set balance to: {}", val);
///             }
///
///             Ok(().into())
///         }
///     }
/// }
///
/// # fn main() {}
/// ```
pub use sp_api_proc_macro::mock_impl_runtime_apis;

/// A type that records all accessed trie nodes and generates a proof out of it.
#[cfg(feature = "std")]
pub type ProofRecorder<B> = sp_trie::recorder::Recorder<HashFor<B>>;

/// A type that is used as cache for the storage transactions.
#[cfg(feature = "std")]
pub type StorageTransactionCache<Block, Backend> = sp_state_machine::StorageTransactionCache<
	<Backend as StateBackend<HashFor<Block>>>::Transaction,
	HashFor<Block>,
>;

#[cfg(feature = "std")]
pub type StorageChanges<SBackend, Block> = sp_state_machine::StorageChanges<
	<SBackend as StateBackend<HashFor<Block>>>::Transaction,
	HashFor<Block>,
>;

/// Extract the state backend type for a type that implements `ProvideRuntimeApi`.
#[cfg(feature = "std")]
pub type StateBackendFor<P, Block> =
	<<P as ProvideRuntimeApi<Block>>::Api as ApiExt<Block>>::StateBackend;

/// Extract the state backend transaction type for a type that implements `ProvideRuntimeApi`.
#[cfg(feature = "std")]
pub type TransactionFor<P, Block> =
	<StateBackendFor<P, Block> as StateBackend<HashFor<Block>>>::Transaction;

/// Something that can be constructed to a runtime api.
#[cfg(feature = "std")]
pub trait ConstructRuntimeApi<Block: BlockT, C: CallApiAt<Block>> {
	/// The actual runtime api that will be constructed.
	type RuntimeApi: ApiExt<Block>;

	/// Construct an instance of the runtime api.
	fn construct_runtime_api(call: &C) -> ApiRef<Self::RuntimeApi>;
}

/// Init the [`RuntimeLogger`](sp_runtime::runtime_logger::RuntimeLogger).
pub fn init_runtime_logger() {
	#[cfg(not(feature = "disable-logging"))]
	sp_runtime::runtime_logger::RuntimeLogger::init();
}

/// An error describing which API call failed.
#[cfg(feature = "std")]
#[derive(Debug, thiserror::Error)]
pub enum ApiError {
	#[error("Failed to decode return value of {function}")]
	FailedToDecodeReturnValue {
		function: &'static str,
		#[source]
		error: codec::Error,
	},
	#[error("Failed to convert return value from runtime to node of {function}")]
	FailedToConvertReturnValue {
		function: &'static str,
		#[source]
		error: codec::Error,
	},
	#[error("Failed to convert parameter `{parameter}` from node to runtime of {function}")]
	FailedToConvertParameter {
		function: &'static str,
		parameter: &'static str,
		#[source]
		error: codec::Error,
	},
	#[error("The given `StateBackend` isn't a `TrieBackend`.")]
	StateBackendIsNotTrie,
	#[error(transparent)]
	Application(#[from] Box<dyn std::error::Error + Send + Sync>),
	#[error("Api called for an unknown Block: {0}")]
	UnknownBlock(String),
}

/// Extends the runtime api implementation with some common functionality.
#[cfg(feature = "std")]
pub trait ApiExt<Block: BlockT> {
	/// The state backend that is used to store the block states.
	type StateBackend: StateBackend<HashFor<Block>>;

	/// Execute the given closure inside a new transaction.
	///
	/// Depending on the outcome of the closure, the transaction is committed or rolled-back.
	///
	/// The internal result of the closure is returned afterwards.
	fn execute_in_transaction<F: FnOnce(&Self) -> TransactionOutcome<R>, R>(&self, call: F) -> R
	where
		Self: Sized;

	/// Checks if the given api is implemented and versions match.
	fn has_api<A: RuntimeApiInfo + ?Sized>(&self, at: &BlockId<Block>) -> Result<bool, ApiError>
	where
		Self: Sized;

	/// Check if the given api is implemented and the version passes a predicate.
	fn has_api_with<A: RuntimeApiInfo + ?Sized, P: Fn(u32) -> bool>(
		&self,
		at: &BlockId<Block>,
		pred: P,
	) -> Result<bool, ApiError>
	where
		Self: Sized;

	/// Returns the version of the given api.
	fn api_version<A: RuntimeApiInfo + ?Sized>(
		&self,
		at: &BlockId<Block>,
	) -> Result<Option<u32>, ApiError>
	where
		Self: Sized;

	/// Start recording all accessed trie nodes for generating proofs.
	fn record_proof(&mut self);

	/// Extract the recorded proof.
	///
	/// This stops the proof recording.
	///
	/// If `record_proof` was not called before, this will return `None`.
	fn extract_proof(&mut self) -> Option<StorageProof>;

	/// Returns the current active proof recorder.
	fn proof_recorder(&self) -> Option<ProofRecorder<Block>>;

	/// Convert the api object into the storage changes that were done while executing runtime
	/// api functions.
	///
	/// After executing this function, all collected changes are reset.
	fn into_storage_changes(
		&self,
		backend: &Self::StateBackend,
		parent_hash: Block::Hash,
	) -> Result<StorageChanges<Self::StateBackend, Block>, String>
	where
		Self: Sized;
}

/// Parameters for [`CallApiAt::call_api_at`].
#[cfg(feature = "std")]
pub struct CallApiAtParams<'a, Block: BlockT, Backend: StateBackend<HashFor<Block>>> {
	/// The block id that determines the state that should be setup when calling the function.
	pub at: &'a BlockId<Block>,
	/// The name of the function that should be called.
	pub function: &'static str,
	/// The encoded arguments of the function.
	pub arguments: Vec<u8>,
	/// The overlayed changes that are on top of the state.
	pub overlayed_changes: &'a RefCell<OverlayedChanges>,
	/// The cache for storage transactions.
	pub storage_transaction_cache: &'a RefCell<StorageTransactionCache<Block, Backend>>,
	/// The context this function is executed in.
	pub context: ExecutionContext,
	/// The optional proof recorder for recording storage accesses.
	pub recorder: &'a Option<ProofRecorder<Block>>,
}

/// Something that can call into the an api at a given block.
#[cfg(feature = "std")]
pub trait CallApiAt<Block: BlockT> {
	/// The state backend that is used to store the block states.
	type StateBackend: StateBackend<HashFor<Block>> + AsTrieBackend<HashFor<Block>>;

	/// Calls the given api function with the given encoded arguments at the given block and returns
	/// the encoded result.
	fn call_api_at(
		&self,
		params: CallApiAtParams<Block, Self::StateBackend>,
	) -> Result<Vec<u8>, ApiError>;

	/// Returns the runtime version at the given block.
	fn runtime_version_at(&self, at: &BlockId<Block>) -> Result<RuntimeVersion, ApiError>;

	/// Get the state `at` the given block.
	fn state_at(&self, at: Block::Hash) -> Result<Self::StateBackend, ApiError>;
}

/// Auxiliary wrapper that holds an api instance and binds it to the given lifetime.
#[cfg(feature = "std")]
pub struct ApiRef<'a, T>(T, std::marker::PhantomData<&'a ()>);

#[cfg(feature = "std")]
impl<'a, T> From<T> for ApiRef<'a, T> {
	fn from(api: T) -> Self {
		ApiRef(api, Default::default())
	}
}

#[cfg(feature = "std")]
impl<'a, T> std::ops::Deref for ApiRef<'a, T> {
	type Target = T;

	fn deref(&self) -> &Self::Target {
		&self.0
	}
}

#[cfg(feature = "std")]
impl<'a, T> std::ops::DerefMut for ApiRef<'a, T> {
	fn deref_mut(&mut self) -> &mut T {
		&mut self.0
	}
}

/// Something that provides a runtime api.
#[cfg(feature = "std")]
pub trait ProvideRuntimeApi<Block: BlockT> {
	/// The concrete type that provides the api.
	type Api: ApiExt<Block>;

	/// Returns the runtime api.
	/// The returned instance will keep track of modifications to the storage. Any successful
	/// call to an api function, will `commit` its changes to an internal buffer. Otherwise,
	/// the modifications will be `discarded`. The modifications will not be applied to the
	/// storage, even on a `commit`.
	fn runtime_api(&self) -> ApiRef<Self::Api>;
}

/// Something that provides information about a runtime api.
#[cfg(feature = "std")]
pub trait RuntimeApiInfo {
	/// The identifier of the runtime api.
	const ID: [u8; 8];
	/// The version of the runtime api.
	const VERSION: u32;
}

/// The number of bytes required to encode a [`RuntimeApiInfo`].
///
/// 8 bytes for `ID` and 4 bytes for a version.
pub const RUNTIME_API_INFO_SIZE: usize = 12;

/// Crude and simple way to serialize the `RuntimeApiInfo` into a bunch of bytes.
pub const fn serialize_runtime_api_info(id: [u8; 8], version: u32) -> [u8; RUNTIME_API_INFO_SIZE] {
	let version = version.to_le_bytes();

	let mut r = [0; RUNTIME_API_INFO_SIZE];
	r[0] = id[0];
	r[1] = id[1];
	r[2] = id[2];
	r[3] = id[3];
	r[4] = id[4];
	r[5] = id[5];
	r[6] = id[6];
	r[7] = id[7];

	r[8] = version[0];
	r[9] = version[1];
	r[10] = version[2];
	r[11] = version[3];
	r
}

/// Deserialize the runtime API info serialized by [`serialize_runtime_api_info`].
pub fn deserialize_runtime_api_info(bytes: [u8; RUNTIME_API_INFO_SIZE]) -> ([u8; 8], u32) {
	let id: [u8; 8] = bytes[0..8]
		.try_into()
		.expect("the source slice size is equal to the dest array length; qed");

	let version = u32::from_le_bytes(
		bytes[8..12]
			.try_into()
			.expect("the source slice size is equal to the array length; qed"),
	);

	(id, version)
}

decl_runtime_apis! {
	/// The `Core` runtime api that every Substrate runtime needs to implement.
	#[core_trait]
	#[api_version(4)]
	pub trait Core {
		/// Returns the version of the runtime.
		fn version() -> RuntimeVersion;
		/// Execute the given block.
		fn execute_block(block: Block);
		/// Initialize a block with the given header.
		#[renamed("initialise_block", 2)]
		fn initialize_block(header: &<Block as BlockT>::Header);
	}

	/// The `Metadata` api trait that returns metadata for the runtime.
	pub trait Metadata {
		/// Returns the metadata of a runtime.
		fn metadata() -> OpaqueMetadata;
	}
}