lib.rs

// 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.

//! # Contracts Pallet
//!
//! The Contracts module provides functionality for the runtime to deploy and execute WebAssembly
//! smart-contracts.
//!
//! - [`Config`]
//! - [`Call`]
//!
//! ## Overview
//!
//! This module extends accounts based on the [`frame_support::traits::fungible`] traits to have
//! smart-contract functionality. It can be used with other modules that implement accounts based on
//! the [`frame_support::traits::fungible`] traits. These "smart-contract accounts" have the ability
//! to instantiate smart-contracts and make calls to other contract and non-contract accounts.
//!
//! The smart-contract code is stored once, and later retrievable via its hash.
//! This means that multiple smart-contracts can be instantiated from the same hash, without
//! replicating the code each time.
//!
//! When a smart-contract is called, its associated code is retrieved via the code hash and gets
//! executed. This call can alter the storage entries of the smart-contract account, instantiate new
//! smart-contracts, or call other smart-contracts.
//!
//! Finally, when an account is reaped, its associated code and storage of the smart-contract
//! account will also be deleted.
//!
//! ### Weight
//!
//! Senders must specify a [`Weight`] limit with every call, as all instructions invoked by the
//! smart-contract require weight. Unused weight is refunded after the call, regardless of the
//! execution outcome.
//!
//! If the weight limit is reached, then all calls and state changes (including balance transfers)
//! are only reverted at the current call's contract level. For example, if contract A calls B and B
//! runs out of gas mid-call, then all of B's calls are reverted. Assuming correct error handling by
//! contract A, A's other calls and state changes still persist.
//!
//! ### Notable Scenarios
//!
//! Contract call failures are not always cascading. When failures occur in a sub-call, they do not
//! "bubble up", and the call will only revert at the specific contract level. For example, if
//! contract A calls contract B, and B fails, A can decide how to handle that failure, either
//! proceeding or reverting A's changes.
//!
//! ## Interface
//!
//! ### Dispatchable functions
//!
//! * [`Pallet::instantiate_with_code`] - Deploys a new contract from the supplied Wasm binary,
//! optionally transferring
//! some balance. This instantiates a new smart contract account with the supplied code and
//! calls its constructor to initialize the contract.
//! * [`Pallet::instantiate`] - The same as `instantiate_with_code` but instead of uploading new
//! code an existing `code_hash` is supplied.
//! * [`Pallet::call`] - Makes a call to an account, optionally transferring some balance.
//! * [`Pallet::upload_code`] - Uploads new code without instantiating a contract from it.
//! * [`Pallet::remove_code`] - Removes the stored code and refunds the deposit to its owner. Only
//!   allowed to code owner.
//! * [`Pallet::set_code`] - Changes the code of an existing contract. Only allowed to `Root`
//!   origin.
//! * [`Pallet::migrate`] - Runs migration steps of current multi-block migration in priority,
//!   before [`Hooks::on_idle`][frame_support::traits::Hooks::on_idle] activates.
//!
//! ## Usage
//!
//! * [`ink!`](https://use.ink) is language that enables writing Wasm-based smart contracts in plain
//!   Rust.

#![allow(rustdoc::private_intra_doc_links)]
#![cfg_attr(not(feature = "std"), no_std)]
#![cfg_attr(feature = "runtime-benchmarks", recursion_limit = "1024")]

mod address;
mod benchmarking;
mod exec;
mod gas;
mod schedule;
mod storage;
mod wasm;

pub mod chain_extension;
pub mod migration;
pub mod unsafe_debug;
pub mod weights;

#[cfg(test)]
mod tests;
use crate::{
	exec::{AccountIdOf, ErrorOrigin, ExecError, Executable, Key, Stack as ExecStack},
	gas::GasMeter,
	storage::{meter::Meter as StorageMeter, ContractInfo, DeletionQueueManager},
	wasm::{CodeInfo, WasmBlob},
};
use codec::{Codec, Decode, Encode, HasCompact, MaxEncodedLen};
use environmental::*;
use frame_support::{
	dispatch::{
		DispatchError, Dispatchable, GetDispatchInfo, Pays, PostDispatchInfo, RawOrigin,
		WithPostDispatchInfo,
	},
	ensure,
	error::BadOrigin,
	traits::{
		fungible::{Inspect, Mutate, MutateHold},
		ConstU32, Contains, Get, Randomness, Time,
	},
	weights::Weight,
	BoundedVec, RuntimeDebug, RuntimeDebugNoBound,
};
use frame_system::{ensure_signed, pallet_prelude::OriginFor, EventRecord, Pallet as System};
use pallet_contracts_primitives::{
	Code, CodeUploadResult, CodeUploadReturnValue, ContractAccessError, ContractExecResult,
	ContractInstantiateResult, ContractResult, ExecReturnValue, GetStorageResult,
	InstantiateReturnValue, StorageDeposit,
};
use scale_info::TypeInfo;
use smallvec::Array;
use sp_runtime::traits::{Convert, Hash, Saturating, StaticLookup, Zero};
use sp_std::{fmt::Debug, prelude::*};

pub use crate::{
	address::{AddressGenerator, DefaultAddressGenerator},
	exec::Frame,
	migration::{MigrateSequence, Migration, NoopMigration},
	pallet::*,
	schedule::{HostFnWeights, InstructionWeights, Limits, Schedule},
	wasm::Determinism,
};
pub use weights::WeightInfo;

#[cfg(doc)]
pub use crate::wasm::api_doc;

type CodeHash<T> = <T as frame_system::Config>::Hash;
type TrieId = BoundedVec<u8, ConstU32<128>>;
type BalanceOf<T> =
	<<T as Config>::Currency as Inspect<<T as frame_system::Config>::AccountId>>::Balance;
type CodeVec<T> = BoundedVec<u8, <T as Config>::MaxCodeLen>;
type AccountIdLookupOf<T> = <<T as frame_system::Config>::Lookup as StaticLookup>::Source;
type DebugBufferVec<T> = BoundedVec<u8, <T as Config>::MaxDebugBufferLen>;
type EventRecordOf<T> =
	EventRecord<<T as frame_system::Config>::RuntimeEvent, <T as frame_system::Config>::Hash>;

/// The old weight type.
///
/// This is a copy of the [`frame_support::weights::OldWeight`] type since the contracts pallet
/// needs to support it indefinitely.
type OldWeight = u64;

/// Used as a sentinel value when reading and writing contract memory.
///
/// It is usually used to signal `None` to a contract when only a primitive is allowed
/// and we don't want to go through encoding a full Rust type. Using `u32::Max` is a safe
/// sentinel because contracts are never allowed to use such a large amount of resources
/// that this value makes sense for a memory location or length.
const SENTINEL: u32 = u32::MAX;

/// The target that is used for the log output emitted by this crate.
///
/// Hence you can use this target to selectively increase the log level for this crate.
///
/// Example: `RUST_LOG=runtime::contracts=debug my_code --dev`
const LOG_TARGET: &str = "runtime::contracts";

#[frame_support::pallet]
pub mod pallet {
	use super::*;
	use frame_support::pallet_prelude::*;
	use frame_system::pallet_prelude::*;
	use sp_runtime::Perbill;

	/// The current storage version.
	pub(crate) const STORAGE_VERSION: StorageVersion = StorageVersion::new(14);

	#[pallet::pallet]
	#[pallet::storage_version(STORAGE_VERSION)]
	pub struct Pallet<T>(_);

	#[pallet::config]
	pub trait Config: frame_system::Config {
		/// The time implementation used to supply timestamps to contracts through `seal_now`.
		type Time: Time;

		/// The generator used to supply randomness to contracts through `seal_random`.
		///
		/// # Deprecated
		///
		/// Codes using the randomness functionality cannot be uploaded. Neither can contracts
		/// be instantiated from existing codes that use this deprecated functionality. It will
		/// be removed eventually. Hence for new `pallet-contracts` deployments it is okay
		/// to supply a dummy implementation for this type (because it is never used).
		type Randomness: Randomness<Self::Hash, BlockNumberFor<Self>>;

		/// The fungible in which fees are paid and contract balances are held.
		type Currency: Inspect<Self::AccountId>
			+ Mutate<Self::AccountId>
			+ MutateHold<Self::AccountId, Reason = Self::RuntimeHoldReason>;

		/// The overarching event type.
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;

		/// The overarching call type.
		type RuntimeCall: Dispatchable<RuntimeOrigin = Self::RuntimeOrigin, PostInfo = PostDispatchInfo>
			+ GetDispatchInfo
			+ codec::Decode
			+ IsType<<Self as frame_system::Config>::RuntimeCall>;

		/// Filter that is applied to calls dispatched by contracts.
		///
		/// Use this filter to control which dispatchables are callable by contracts.
		/// This is applied in **addition** to [`frame_system::Config::BaseCallFilter`].
		/// It is recommended to treat this as a whitelist.
		///
		/// # Stability
		///
		/// The runtime **must** make sure that all dispatchables that are callable by
		/// contracts remain stable. In addition [`Self::RuntimeCall`] itself must remain stable.
		/// This means that no existing variants are allowed to switch their positions.
		///
		/// # Note
		///
		/// Note that dispatchables that are called via contracts do not spawn their
		/// own wasm instance for each call (as opposed to when called via a transaction).
		/// Therefore please make sure to be restrictive about which dispatchables are allowed
		/// in order to not introduce a new DoS vector like memory allocation patterns that can
		/// be exploited to drive the runtime into a panic.
		type CallFilter: Contains<<Self as frame_system::Config>::RuntimeCall>;

		/// Used to answer contracts' queries regarding the current weight price. This is **not**
		/// used to calculate the actual fee and is only for informational purposes.
		type WeightPrice: Convert<Weight, BalanceOf<Self>>;

		/// Describes the weights of the dispatchables of this module and is also used to
		/// construct a default cost schedule.
		type WeightInfo: WeightInfo;

		/// Type that allows the runtime authors to add new host functions for a contract to call.
		type ChainExtension: chain_extension::ChainExtension<Self> + Default;

		/// Cost schedule and limits.
		#[pallet::constant]
		type Schedule: Get<Schedule<Self>>;

		/// The type of the call stack determines the maximum nesting depth of contract calls.
		///
		/// The allowed depth is `CallStack::size() + 1`.
		/// Therefore a size of `0` means that a contract cannot use call or instantiate.
		/// In other words only the origin called "root contract" is allowed to execute then.
		///
		/// This setting along with [`MaxCodeLen`](#associatedtype.MaxCodeLen) directly affects
		/// memory usage of your runtime.
		type CallStack: Array<Item = Frame<Self>>;

		/// The amount of balance a caller has to pay for each byte of storage.
		///
		/// # Note
		///
		/// Changing this value for an existing chain might need a storage migration.
		#[pallet::constant]
		type DepositPerByte: Get<BalanceOf<Self>>;

		/// Fallback value to limit the storage deposit if it's not being set by the caller.
		#[pallet::constant]
		type DefaultDepositLimit: Get<BalanceOf<Self>>;

		/// The amount of balance a caller has to pay for each storage item.
		///
		/// # Note
		///
		/// Changing this value for an existing chain might need a storage migration.
		#[pallet::constant]
		type DepositPerItem: Get<BalanceOf<Self>>;

		/// The percentage of the storage deposit that should be held for using a code hash.
		/// Instantiating a contract, or calling [`chain_extension::Ext::add_delegate_dependency`]
		/// protects the code from being removed. In order to prevent abuse these actions are
		/// protected with a percentage of the code deposit.
		#[pallet::constant]
		type CodeHashLockupDepositPercent: Get<Perbill>;

		/// The address generator used to generate the addresses of contracts.
		type AddressGenerator: AddressGenerator<Self>;

		/// The maximum length of a contract code in bytes.
		///
		/// The value should be chosen carefully taking into the account the overall memory limit
		/// your runtime has, as well as the [maximum allowed callstack
		/// depth](#associatedtype.CallStack). Look into the `integrity_test()` for some insights.
		#[pallet::constant]
		type MaxCodeLen: Get<u32>;

		/// The maximum allowable length in bytes for storage keys.
		#[pallet::constant]
		type MaxStorageKeyLen: Get<u32>;

		/// The maximum number of delegate_dependencies that a contract can lock with
		/// [`chain_extension::Ext::add_delegate_dependency`].
		#[pallet::constant]
		type MaxDelegateDependencies: Get<u32>;

		/// Make contract callable functions marked as `#[unstable]` available.
		///
		/// Contracts that use `#[unstable]` functions won't be able to be uploaded unless
		/// this is set to `true`. This is only meant for testnets and dev nodes in order to
		/// experiment with new features.
		///
		/// # Warning
		///
		/// Do **not** set to `true` on productions chains.
		#[pallet::constant]
		type UnsafeUnstableInterface: Get<bool>;

		/// The maximum length of the debug buffer in bytes.
		#[pallet::constant]
		type MaxDebugBufferLen: Get<u32>;

		/// Overarching hold reason.
		type RuntimeHoldReason: From<HoldReason>;

		/// The sequence of migration steps that will be applied during a migration.
		///
		/// # Examples
		/// ```
		/// use pallet_contracts::migration::{v10, v11};
		/// # struct Runtime {};
		/// # struct Currency {};
		/// type Migrations = (v10::Migration<Runtime, Currency>, v11::Migration<Runtime>);
		/// ```
		///
		/// If you have a single migration step, you can use a tuple with a single element:
		/// ```
		/// use pallet_contracts::migration::v10;
		/// # struct Runtime {};
		/// # struct Currency {};
		/// type Migrations = (v10::Migration<Runtime, Currency>,);
		/// ```
		type Migrations: MigrateSequence;

		/// Type that provides debug handling for the contract execution process.
		///
		/// # Warning
		///
		/// Do **not** use it in a production environment or for benchmarking purposes.
		#[cfg(feature = "unsafe-debug")]
		type Debug: unsafe_debug::UnsafeDebug<Self>;
	}

	#[pallet::hooks]
	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
		fn on_idle(_block: BlockNumberFor<T>, mut remaining_weight: Weight) -> Weight {
			use migration::MigrateResult::*;

			loop {
				let (result, weight) = Migration::<T>::migrate(remaining_weight);
				remaining_weight.saturating_reduce(weight);

				match result {
					// There is not enough weight to perform a migration, or make any progress, we
					// just return the remaining weight.
					NoMigrationPerformed | InProgress { steps_done: 0 } => return remaining_weight,
					// Migration is still in progress, we can start the next step.
					InProgress { .. } => continue,
					// Either no migration is in progress, or we are done with all migrations, we
					// can do some more other work with the remaining weight.
					Completed | NoMigrationInProgress => break,
				}
			}

			ContractInfo::<T>::process_deletion_queue_batch(remaining_weight)
				.saturating_add(T::WeightInfo::on_process_deletion_queue_batch())
		}

		fn integrity_test() {
			Migration::<T>::integrity_test();

			// Total runtime memory limit
			let max_runtime_mem: u32 = T::Schedule::get().limits.runtime_memory;
			// Memory limits for a single contract:
			// Value stack size: 1Mb per contract, default defined in wasmi
			const MAX_STACK_SIZE: u32 = 1024 * 1024;
			// Heap limit is normally 16 mempages of 64kb each = 1Mb per contract
			let max_heap_size = T::Schedule::get().limits.max_memory_size();
			// Max call depth is CallStack::size() + 1
			let max_call_depth = u32::try_from(T::CallStack::size().saturating_add(1))
				.expect("CallStack size is too big");

			// Check that given configured `MaxCodeLen`, runtime heap memory limit can't be broken.
			//
			// In worst case, the decoded Wasm contract code would be `x16` times larger than the
			// encoded one. This is because even a single-byte wasm instruction has 16-byte size in
			// wasmi. This gives us `MaxCodeLen*16` safety margin.
			//
			// Next, the pallet keeps the Wasm blob for each
			// contract, hence we add up `MaxCodeLen` to the safety margin.
			//
			// Finally, the inefficiencies of the freeing-bump allocator
			// being used in the client for the runtime memory allocations, could lead to possible
			// memory allocations for contract code grow up to `x4` times in some extreme cases,
			// which gives us total multiplier of `17*4` for `MaxCodeLen`.
			//
			// That being said, for every contract executed in runtime, at least `MaxCodeLen*17*4`
			// memory should be available. Note that maximum allowed heap memory and stack size per
			// each contract (stack frame) should also be counted.
			//
			// Finally, we allow 50% of the runtime memory to be utilized by the contracts call
			// stack, keeping the rest for other facilities, such as PoV, etc.
			//
			// This gives us the following formula:
			//
			// `(MaxCodeLen * 17 * 4 + MAX_STACK_SIZE + max_heap_size) * max_call_depth <
			// max_runtime_mem/2`
			//
			// Hence the upper limit for the `MaxCodeLen` can be defined as follows:
			let code_len_limit = max_runtime_mem
				.saturating_div(2)
				.saturating_div(max_call_depth)
				.saturating_sub(max_heap_size)
				.saturating_sub(MAX_STACK_SIZE)
				.saturating_div(17 * 4);

			assert!(
				T::MaxCodeLen::get() < code_len_limit,
				"Given `CallStack` height {:?}, `MaxCodeLen` should be set less than {:?} \
				 (current value is {:?}), to avoid possible runtime oom issues.",
				max_call_depth,
				code_len_limit,
				T::MaxCodeLen::get(),
			);

			// Debug buffer should at least be large enough to accommodate a simple error message
			const MIN_DEBUG_BUF_SIZE: u32 = 256;
			assert!(
				T::MaxDebugBufferLen::get() > MIN_DEBUG_BUF_SIZE,
				"Debug buffer should have minimum size of {} (current setting is {})",
				MIN_DEBUG_BUF_SIZE,
				T::MaxDebugBufferLen::get(),
			)
		}
	}

	#[pallet::call]
	impl<T: Config> Pallet<T>
	where
		<BalanceOf<T> as HasCompact>::Type: Clone + Eq + PartialEq + Debug + TypeInfo + Encode,
	{
		/// Deprecated version if [`Self::call`] for use in an in-storage `Call`.
		#[pallet::call_index(0)]
		#[pallet::weight(T::WeightInfo::call().saturating_add(<Pallet<T>>::compat_weight_limit(*gas_limit)))]
		#[allow(deprecated)]
		#[deprecated(note = "1D weight is used in this extrinsic, please migrate to `call`")]
		pub fn call_old_weight(
			origin: OriginFor<T>,
			dest: AccountIdLookupOf<T>,
			#[pallet::compact] value: BalanceOf<T>,
			#[pallet::compact] gas_limit: OldWeight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			data: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Self::call(
				origin,
				dest,
				value,
				<Pallet<T>>::compat_weight_limit(gas_limit),
				storage_deposit_limit,
				data,
			)
		}

		/// Deprecated version if [`Self::instantiate_with_code`] for use in an in-storage `Call`.
		#[pallet::call_index(1)]
		#[pallet::weight(
			T::WeightInfo::instantiate_with_code(code.len() as u32, data.len() as u32, salt.len() as u32)
			.saturating_add(<Pallet<T>>::compat_weight_limit(*gas_limit))
		)]
		#[allow(deprecated)]
		#[deprecated(
			note = "1D weight is used in this extrinsic, please migrate to `instantiate_with_code`"
		)]
		pub fn instantiate_with_code_old_weight(
			origin: OriginFor<T>,
			#[pallet::compact] value: BalanceOf<T>,
			#[pallet::compact] gas_limit: OldWeight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			code: Vec<u8>,
			data: Vec<u8>,
			salt: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Self::instantiate_with_code(
				origin,
				value,
				<Pallet<T>>::compat_weight_limit(gas_limit),
				storage_deposit_limit,
				code,
				data,
				salt,
			)
		}

		/// Deprecated version if [`Self::instantiate`] for use in an in-storage `Call`.
		#[pallet::call_index(2)]
		#[pallet::weight(
			T::WeightInfo::instantiate(data.len() as u32, salt.len() as u32).saturating_add(<Pallet<T>>::compat_weight_limit(*gas_limit))
		)]
		#[allow(deprecated)]
		#[deprecated(note = "1D weight is used in this extrinsic, please migrate to `instantiate`")]
		pub fn instantiate_old_weight(
			origin: OriginFor<T>,
			#[pallet::compact] value: BalanceOf<T>,
			#[pallet::compact] gas_limit: OldWeight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			code_hash: CodeHash<T>,
			data: Vec<u8>,
			salt: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Self::instantiate(
				origin,
				value,
				<Pallet<T>>::compat_weight_limit(gas_limit),
				storage_deposit_limit,
				code_hash,
				data,
				salt,
			)
		}

		/// Upload new `code` without instantiating a contract from it.
		///
		/// If the code does not already exist a deposit is reserved from the caller
		/// and unreserved only when [`Self::remove_code`] is called. The size of the reserve
		/// depends on the size of the supplied `code`.
		///
		/// If the code already exists in storage it will still return `Ok` and upgrades
		/// the in storage version to the current
		/// [`InstructionWeights::version`](InstructionWeights).
		///
		/// - `determinism`: If this is set to any other value but [`Determinism::Enforced`] then
		///   the only way to use this code is to delegate call into it from an offchain execution.
		///   Set to [`Determinism::Enforced`] if in doubt.
		///
		/// # Note
		///
		/// Anyone can instantiate a contract from any uploaded code and thus prevent its removal.
		/// To avoid this situation a constructor could employ access control so that it can
		/// only be instantiated by permissioned entities. The same is true when uploading
		/// through [`Self::instantiate_with_code`].
		#[pallet::call_index(3)]
		#[pallet::weight(T::WeightInfo::upload_code(code.len() as u32))]
		pub fn upload_code(
			origin: OriginFor<T>,
			code: Vec<u8>,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			determinism: Determinism,
		) -> DispatchResult {
			Migration::<T>::ensure_migrated()?;
			let origin = ensure_signed(origin)?;
			Self::bare_upload_code(origin, code, storage_deposit_limit.map(Into::into), determinism)
				.map(|_| ())
		}

		/// Remove the code stored under `code_hash` and refund the deposit to its owner.
		///
		/// A code can only be removed by its original uploader (its owner) and only if it is
		/// not used by any contract.
		#[pallet::call_index(4)]
		#[pallet::weight(T::WeightInfo::remove_code())]
		pub fn remove_code(
			origin: OriginFor<T>,
			code_hash: CodeHash<T>,
		) -> DispatchResultWithPostInfo {
			Migration::<T>::ensure_migrated()?;
			let origin = ensure_signed(origin)?;
			<WasmBlob<T>>::remove(&origin, code_hash)?;
			// we waive the fee because removing unused code is beneficial
			Ok(Pays::No.into())
		}

		/// Privileged function that changes the code of an existing contract.
		///
		/// This takes care of updating refcounts and all other necessary operations. Returns
		/// an error if either the `code_hash` or `dest` do not exist.
		///
		/// # Note
		///
		/// This does **not** change the address of the contract in question. This means
		/// that the contract address is no longer derived from its code hash after calling
		/// this dispatchable.
		#[pallet::call_index(5)]
		#[pallet::weight(T::WeightInfo::set_code())]
		pub fn set_code(
			origin: OriginFor<T>,
			dest: AccountIdLookupOf<T>,
			code_hash: CodeHash<T>,
		) -> DispatchResult {
			Migration::<T>::ensure_migrated()?;
			ensure_root(origin)?;
			let dest = T::Lookup::lookup(dest)?;
			<ContractInfoOf<T>>::try_mutate(&dest, |contract| {
				let contract = if let Some(contract) = contract {
					contract
				} else {
					return Err(<Error<T>>::ContractNotFound.into())
				};
				<WasmBlob<T>>::increment_refcount(code_hash)?;
				<WasmBlob<T>>::decrement_refcount(contract.code_hash);
				Self::deposit_event(
					vec![T::Hashing::hash_of(&dest), code_hash, contract.code_hash],
					Event::ContractCodeUpdated {
						contract: dest.clone(),
						new_code_hash: code_hash,
						old_code_hash: contract.code_hash,
					},
				);
				contract.code_hash = code_hash;
				Ok(())
			})
		}

		/// Makes a call to an account, optionally transferring some balance.
		///
		/// # Parameters
		///
		/// * `dest`: Address of the contract to call.
		/// * `value`: The balance to transfer from the `origin` to `dest`.
		/// * `gas_limit`: The gas limit enforced when executing the constructor.
		/// * `storage_deposit_limit`: The maximum amount of balance that can be charged from the
		///   caller to pay for the storage consumed.
		/// * `data`: The input data to pass to the contract.
		///
		/// * If the account is a smart-contract account, the associated code will be
		/// executed and any value will be transferred.
		/// * If the account is a regular account, any value will be transferred.
		/// * If no account exists and the call value is not less than `existential_deposit`,
		/// a regular account will be created and any value will be transferred.
		#[pallet::call_index(6)]
		#[pallet::weight(T::WeightInfo::call().saturating_add(*gas_limit))]
		pub fn call(
			origin: OriginFor<T>,
			dest: AccountIdLookupOf<T>,
			#[pallet::compact] value: BalanceOf<T>,
			gas_limit: Weight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			data: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Migration::<T>::ensure_migrated()?;
			let common = CommonInput {
				origin: Origin::from_runtime_origin(origin)?,
				value,
				data,
				gas_limit: gas_limit.into(),
				storage_deposit_limit: storage_deposit_limit.map(Into::into),
				debug_message: None,
			};
			let dest = T::Lookup::lookup(dest)?;
			let mut output =
				CallInput::<T> { dest, determinism: Determinism::Enforced }.run_guarded(common);
			if let Ok(retval) = &output.result {
				if retval.did_revert() {
					output.result = Err(<Error<T>>::ContractReverted.into());
				}
			}
			output.gas_meter.into_dispatch_result(output.result, T::WeightInfo::call())
		}

		/// Instantiates a new contract from the supplied `code` optionally transferring
		/// some balance.
		///
		/// This dispatchable has the same effect as calling [`Self::upload_code`] +
		/// [`Self::instantiate`]. Bundling them together provides efficiency gains. Please
		/// also check the documentation of [`Self::upload_code`].
		///
		/// # Parameters
		///
		/// * `value`: The balance to transfer from the `origin` to the newly created contract.
		/// * `gas_limit`: The gas limit enforced when executing the constructor.
		/// * `storage_deposit_limit`: The maximum amount of balance that can be charged/reserved
		///   from the caller to pay for the storage consumed.
		/// * `code`: The contract code to deploy in raw bytes.
		/// * `data`: The input data to pass to the contract constructor.
		/// * `salt`: Used for the address derivation. See [`Pallet::contract_address`].
		///
		/// Instantiation is executed as follows:
		///
		/// - The supplied `code` is deployed, and a `code_hash` is created for that code.
		/// - If the `code_hash` already exists on the chain the underlying `code` will be shared.
		/// - The destination address is computed based on the sender, code_hash and the salt.
		/// - The smart-contract account is created at the computed address.
		/// - The `value` is transferred to the new account.
		/// - The `deploy` function is executed in the context of the newly-created account.
		#[pallet::call_index(7)]
		#[pallet::weight(
			T::WeightInfo::instantiate_with_code(code.len() as u32, data.len() as u32, salt.len() as u32)
			.saturating_add(*gas_limit)
		)]
		pub fn instantiate_with_code(
			origin: OriginFor<T>,
			#[pallet::compact] value: BalanceOf<T>,
			gas_limit: Weight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			code: Vec<u8>,
			data: Vec<u8>,
			salt: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Migration::<T>::ensure_migrated()?;
			let origin = ensure_signed(origin)?;
			let code_len = code.len() as u32;

			let (module, upload_deposit) = Self::try_upload_code(
				origin.clone(),
				code,
				storage_deposit_limit.clone().map(Into::into),
				Determinism::Enforced,
				None,
			)?;

			// Reduces the storage deposit limit by the amount that was reserved for the upload.
			let storage_deposit_limit =
				storage_deposit_limit.map(|limit| limit.into().saturating_sub(upload_deposit));

			let data_len = data.len() as u32;
			let salt_len = salt.len() as u32;
			let common = CommonInput {
				origin: Origin::from_account_id(origin),
				value,
				data,
				gas_limit,
				storage_deposit_limit,
				debug_message: None,
			};

			let mut output =
				InstantiateInput::<T> { code: WasmCode::Wasm(module), salt }.run_guarded(common);
			if let Ok(retval) = &output.result {
				if retval.1.did_revert() {
					output.result = Err(<Error<T>>::ContractReverted.into());
				}
			}

			output.gas_meter.into_dispatch_result(
				output.result.map(|(_address, output)| output),
				T::WeightInfo::instantiate_with_code(code_len, data_len, salt_len),
			)
		}

		/// Instantiates a contract from a previously deployed wasm binary.
		///
		/// This function is identical to [`Self::instantiate_with_code`] but without the
		/// code deployment step. Instead, the `code_hash` of an on-chain deployed wasm binary
		/// must be supplied.
		#[pallet::call_index(8)]
		#[pallet::weight(
			T::WeightInfo::instantiate(data.len() as u32, salt.len() as u32).saturating_add(*gas_limit)
		)]
		pub fn instantiate(
			origin: OriginFor<T>,
			#[pallet::compact] value: BalanceOf<T>,
			gas_limit: Weight,
			storage_deposit_limit: Option<<BalanceOf<T> as codec::HasCompact>::Type>,
			code_hash: CodeHash<T>,
			data: Vec<u8>,
			salt: Vec<u8>,
		) -> DispatchResultWithPostInfo {
			Migration::<T>::ensure_migrated()?;
			let data_len = data.len() as u32;
			let salt_len = salt.len() as u32;
			let common = CommonInput {
				origin: Origin::from_runtime_origin(origin)?,
				value,
				data,
				gas_limit,
				storage_deposit_limit: storage_deposit_limit.map(Into::into),
				debug_message: None,
			};
			let mut output = InstantiateInput::<T> { code: WasmCode::CodeHash(code_hash), salt }
				.run_guarded(common);
			if let Ok(retval) = &output.result {
				if retval.1.did_revert() {
					output.result = Err(<Error<T>>::ContractReverted.into());
				}
			}
			output.gas_meter.into_dispatch_result(
				output.result.map(|(_address, output)| output),
				T::WeightInfo::instantiate(data_len, salt_len),
			)
		}

		/// When a migration is in progress, this dispatchable can be used to run migration steps.
		/// Calls that contribute to advancing the migration have their fees waived, as it's helpful
		/// for the chain. Note that while the migration is in progress, the pallet will also
		/// leverage the `on_idle` hooks to run migration steps.
		#[pallet::call_index(9)]
		#[pallet::weight(T::WeightInfo::migrate().saturating_add(*weight_limit))]
		pub fn migrate(origin: OriginFor<T>, weight_limit: Weight) -> DispatchResultWithPostInfo {
			use migration::MigrateResult::*;
			ensure_signed(origin)?;

			let weight_limit = weight_limit.saturating_add(T::WeightInfo::migrate());
			let (result, weight) = Migration::<T>::migrate(weight_limit);

			match result {
				Completed =>
					Ok(PostDispatchInfo { actual_weight: Some(weight), pays_fee: Pays::No }),
				InProgress { steps_done, .. } if steps_done > 0 =>
					Ok(PostDispatchInfo { actual_weight: Some(weight), pays_fee: Pays::No }),
				InProgress { .. } =>
					Ok(PostDispatchInfo { actual_weight: Some(weight), pays_fee: Pays::Yes }),
				NoMigrationInProgress | NoMigrationPerformed => {
					let err: DispatchError = <Error<T>>::NoMigrationPerformed.into();
					Err(err.with_weight(T::WeightInfo::migrate()))
				},
			}
		}
	}

	#[pallet::event]
	pub enum Event<T: Config> {
		/// Contract deployed by address at the specified address.
		Instantiated { deployer: T::AccountId, contract: T::AccountId },

		/// Contract has been removed.
		///
		/// # Note
		///
		/// The only way for a contract to be removed and emitting this event is by calling
		/// `seal_terminate`.
		Terminated {
			/// The contract that was terminated.
			contract: T::AccountId,
			/// The account that received the contracts remaining balance
			beneficiary: T::AccountId,
		},

		/// Code with the specified hash has been stored.
		CodeStored { code_hash: T::Hash, deposit_held: BalanceOf<T>, uploader: T::AccountId },

		/// A custom event emitted by the contract.
		ContractEmitted {
			/// The contract that emitted the event.
			contract: T::AccountId,
			/// Data supplied by the contract. Metadata generated during contract compilation
			/// is needed to decode it.
			data: Vec<u8>,
		},

		/// A code with the specified hash was removed.
		CodeRemoved { code_hash: T::Hash, deposit_released: BalanceOf<T>, remover: T::AccountId },

		/// A contract's code was updated.
		ContractCodeUpdated {
			/// The contract that has been updated.
			contract: T::AccountId,
			/// New code hash that was set for the contract.
			new_code_hash: T::Hash,
			/// Previous code hash of the contract.
			old_code_hash: T::Hash,
		},

		/// A contract was called either by a plain account or another contract.
		///
		/// # Note
		///
		/// Please keep in mind that like all events this is only emitted for successful
		/// calls. This is because on failure all storage changes including events are
		/// rolled back.
		Called {
			/// The caller of the `contract`.
			caller: Origin<T>,
			/// The contract that was called.
			contract: T::AccountId,
		},

		/// A contract delegate called a code hash.
		///
		/// # Note
		///
		/// Please keep in mind that like all events this is only emitted for successful
		/// calls. This is because on failure all storage changes including events are
		/// rolled back.
		DelegateCalled {
			/// The contract that performed the delegate call and hence in whose context
			/// the `code_hash` is executed.
			contract: T::AccountId,
			/// The code hash that was delegate called.
			code_hash: CodeHash<T>,
		},
	}

	#[pallet::error]
	pub enum Error<T> {
		/// Invalid schedule supplied, e.g. with zero weight of a basic operation.
		InvalidSchedule,
		/// Invalid combination of flags supplied to `seal_call` or `seal_delegate_call`.
		InvalidCallFlags,
		/// The executed contract exhausted its gas limit.
		OutOfGas,
		/// The output buffer supplied to a contract API call was too small.
		OutputBufferTooSmall,
		/// Performing the requested transfer failed. Probably because there isn't enough
		/// free balance in the sender's account.
		TransferFailed,
		/// Performing a call was denied because the calling depth reached the limit
		/// of what is specified in the schedule.
		MaxCallDepthReached,
		/// No contract was found at the specified address.
		ContractNotFound,
		/// The code supplied to `instantiate_with_code` exceeds the limit specified in the
		/// current schedule.
		CodeTooLarge,
		/// No code could be found at the supplied code hash.
		CodeNotFound,
		/// No code info could be found at the supplied code hash.
		CodeInfoNotFound,
		/// A buffer outside of sandbox memory was passed to a contract API function.
		OutOfBounds,
		/// Input passed to a contract API function failed to decode as expected type.
		DecodingFailed,
		/// Contract trapped during execution.
		ContractTrapped,
		/// The size defined in `T::MaxValueSize` was exceeded.
		ValueTooLarge,
		/// Termination of a contract is not allowed while the contract is already
		/// on the call stack. Can be triggered by `seal_terminate`.
		TerminatedWhileReentrant,
		/// `seal_call` forwarded this contracts input. It therefore is no longer available.
		InputForwarded,
		/// The subject passed to `seal_random` exceeds the limit.
		RandomSubjectTooLong,
		/// The amount of topics passed to `seal_deposit_events` exceeds the limit.
		TooManyTopics,
		/// The chain does not provide a chain extension. Calling the chain extension results
		/// in this error. Note that this usually  shouldn't happen as deploying such contracts
		/// is rejected.
		NoChainExtension,
		/// A contract with the same AccountId already exists.
		DuplicateContract,
		/// A contract self destructed in its constructor.
		///
		/// This can be triggered by a call to `seal_terminate`.
		TerminatedInConstructor,
		/// A call tried to invoke a contract that is flagged as non-reentrant.
		/// The only other cause is that a call from a contract into the runtime tried to call back
		/// into `pallet-contracts`. This would make the whole pallet reentrant with regard to
		/// contract code execution which is not supported.
		ReentranceDenied,
		/// Origin doesn't have enough balance to pay the required storage deposits.
		StorageDepositNotEnoughFunds,
		/// More storage was created than allowed by the storage deposit limit.
		StorageDepositLimitExhausted,
		/// Code removal was denied because the code is still in use by at least one contract.
		CodeInUse,
		/// The contract ran to completion but decided to revert its storage changes.
		/// Please note that this error is only returned from extrinsics. When called directly
		/// or via RPC an `Ok` will be returned. In this case the caller needs to inspect the flags
		/// to determine whether a reversion has taken place.
		ContractReverted,
		/// The contract's code was found to be invalid during validation.
		///
		/// The most likely cause of this is that an API was used which is not supported by the
		/// node. This happens if an older node is used with a new version of ink!. Try updating
		/// your node to the newest available version.
		///
		/// A more detailed error can be found on the node console if debug messages are enabled
		/// by supplying `-lruntime::contracts=debug`.
		CodeRejected,
		/// An indetermistic code was used in a context where this is not permitted.
		Indeterministic,
		/// A pending migration needs to complete before the extrinsic can be called.
		MigrationInProgress,
		/// Migrate dispatch call was attempted but no migration was performed.
		NoMigrationPerformed,
		/// The contract has reached its maximum number of delegate dependencies.
		MaxDelegateDependenciesReached,
		/// The dependency was not found in the contract's delegate dependencies.
		DelegateDependencyNotFound,
		/// The contract already depends on the given delegate dependency.
		DelegateDependencyAlreadyExists,
		/// Can not add a delegate dependency to the code hash of the contract itself.
		CannotAddSelfAsDelegateDependency,
	}

	/// A reason for the pallet contracts placing a hold on funds.
	#[pallet::composite_enum]
	pub enum HoldReason {
		/// The Pallet has reserved it for storing code on-chain.