# Summary

Adds new ability for contracts to perform some system functions:

• create new accounts (with possible code deploy and initialization)
• deploy new code (or redeploying code for upgrades)
• batched function calls
• transfer money
• stake
• delete key
• delete account

# Motivation

Contracts should have the ability to create new accounts, transfer money without calling code and stake. It will enable full functionality of contract-based accounts.

# Reference

We introduce additional promise APIs to support batched actions.

Firstly, we enable ability to create empty promises without any action. They act similarly to traditional promises, but don't contain function call action.

Secondly, we add API to append individual actions to promises. For example we can create a promise with a function_call first using promise_create and then attach a transfer action on top of this promise. So the transfer will only deposit tokens if the function call succeeds. Another example is how we create accounts now using batched actions. To create a new account, we create a transaction with the following actions: create_account, transfer, add_key. It creates a new account, deposit some funds on it and the adds a new key.

For more examples see NEP#8: https://github.com/nearprotocol/NEPs/pull/8/files?short_path=15b6752#diff-15b6752ec7d78e7b85b8c7de4a19cbd4

NOTE: The existing promise API is a special case of the batched promise API.

• Calling promise_batch_create and then promise_batch_action_function_call will produce the same promise as calling promise_create directly.
• Calling promise_batch_then and then promise_batch_action_function_call will produce the same promise as calling promise_then directly.

## Promises API​

promise_batch_create(account_id_len: u64, account_id_ptr: u64) -> u64

Creates a new promise towards given account_id without any actions attached to it.

###### Panics​
• If account_id_len + account_id_ptr points outside the memory of the guest or host, with MemoryAccessViolation.
###### Returns​
• Index of the new promise that uniquely identifies it within the current execution of the method.

promise_batch_then(promise_idx: u64, account_id_len: u64, account_id_ptr: u64) -> u64            

Attaches a new empty promise that is executed after promise pointed by promise_idx is complete.

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If account_id_len + account_id_ptr points outside the memory of the guest or host, with MemoryAccessViolation.
###### Returns​
• Index of the new promise that uniquely identifies it within the current execution of the method.

promise_batch_action_create_account(promise_idx: u64)

Appends CreateAccount action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R48

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.

promise_batch_action_deploy_contract(promise_idx: u64, code_len: u64, code_ptr: u64)

Appends DeployContract action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R49

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If code_len + code_ptr points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_function_call(promise_idx: u64,                                   method_name_len: u64,                                   method_name_ptr: u64,                                   arguments_len: u64,                                   arguments_ptr: u64,                                   amount_ptr: u64,                                   gas: u64)

Appends FunctionCall action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R50

NOTE: Calling promise_batch_create and then promise_batch_action_function_call will produce the same promise as calling promise_create directly.

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If account_id_len + account_id_ptr or method_name_len + method_name_ptr or arguments_len + arguments_ptr or amount_ptr + 16 points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_transfer(promise_idx: u64, amount_ptr: u64)

Appends Transfer action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R51

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If amount_ptr + 16 points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_stake(promise_idx: u64,                           amount_ptr: u64,                           public_key_len: u64,                           public_key_ptr: u64)

Appends Stake action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R52

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If the given public key is not a valid public key (e.g. wrong length) InvalidPublicKey.
• If amount_ptr + 16 or public_key_len + public_key_ptr points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_add_key_with_full_access(promise_idx: u64,                                              public_key_len: u64,                                              public_key_ptr: u64,                                              nonce: u64)

Appends AddKey action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R54 The access key will have FullAccess permission, details: [0005-access-keys.md#guide-level-explanation](click here)

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If the given public key is not a valid public key (e.g. wrong length) InvalidPublicKey.
• If public_key_len + public_key_ptr points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_add_key_with_function_call(promise_idx: u64,                                                public_key_len: u64,                                                public_key_ptr: u64,                                                nonce: u64,                                                allowance_ptr: u64,                                                receiver_id_len: u64,                                                receiver_id_ptr: u64,                                                method_names_len: u64,                                                method_names_ptr: u64)

Appends AddKey action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-156752ec7d78e7b85b8c7de4a19cbd4R54 The access key will have FunctionCall permission, details: [0005-access-keys.md#guide-level-explanation](click here)

• If the allowance value (not the pointer) is 0, the allowance is set to None (which means unlimited allowance). And positive value represents a Some(...) allowance.
• Given method_names is a utf-8 string with , used as a separator. The vm will split the given string into a vector of strings.
###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If the given public key is not a valid public key (e.g. wrong length) InvalidPublicKey.
• if method_names is not a valid utf-8 string, fails with BadUTF8.
• If public_key_len + public_key_ptr, allowance_ptr + 16, receiver_id_len + receiver_id_ptr or method_names_len + method_names_ptr points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_delete_key(promise_idx: u64,                                public_key_len: u64,                                public_key_ptr: u64)

Appends DeleteKey action to the batch of actions for the given promise pointed by promise_idx. Details for the action: https://github.com/nearprotocol/NEPs/pull/8/files#diff-15b6752ec7d78e7b85b8c7de4a19cbd4R55

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If the given public key is not a valid public key (e.g. wrong length) InvalidPublicKey.
• If public_key_len + public_key_ptr points outside the memory of the guest or host, with MemoryAccessViolation.

promise_batch_action_delete_account(promise_idx: u64,                                    beneficiary_id_len: u64,                                    beneficiary_id_ptr: u64)

Appends DeleteAccount action to the batch of actions for the given promise pointed by promise_idx. Action is used to delete an account. It can be performed on a newly created account, on your own account or an account with insufficient funds to pay rent. Takes beneficiary_id to indicate where to send the remaining funds.

###### Panics​
• If promise_idx does not correspond to an existing promise panics with InvalidPromiseIndex.
• If the promise pointed by the promise_idx is an ephemeral promise created by promise_and.
• If beneficiary_id_len + beneficiary_id_ptr points outside the memory of the guest or host, with MemoryAccessViolation.