Problem

This PR addresses the deposit issue with the AccountBalance storage type as outlined in #387. Currently, storage for each AccountBalance record created does not reserve the necessary deposit. Below are the cases where AccountBalance records are created or destroyed:

Related Functions

• do_mint: Creates an AccountBalance record for mint_to when a new collection item is minted.
• do_transfer: Transfers a collection item from the owner to the dest account. If the dest account does not have enough balance (including does not exist), an AccountBalance record is created. If the sender's AccountBalance becomes zero after the transfer, their AccountBalance record is removed.
• do_burn: Removes the AccountBalance of the owner, if they only have one item and that item is burned.
• do_mint_pre_signed: Calls do_mint.

Description for do_mint_pre_signed: This function allows minting a new item using a pre-signed message. The minting process is similar to the regular minting process, but it is performed by a pre-authorized account. The mint_to account receives the newly minted item. The minting process is configurable through the provided mint_data. The attributes, metadata, and price of the item are set according to the provided mint_data. The with_details_and_config closure is called to validate the provided collection_details and collection_config before minting the item.

• do_buy_item: Calls do_transfer to transfer an item from the seller to the buyer.
• do_claim_swap: Calls do_transfer twice—once to transfer from A to B, and then from B to A.

Solution

Refactor the AccountBalance storage value type to store a tuple (u32, AccountDepositOf<T>), representing:

• u32: Tracks the total number of items in the collection owned by the account.
• AccountDepositOf<T>: A tuple of (AccountId, DepositBalance)
  • AccountId: The depositor who reserves funds for creating the AccountBalance record.
  • DepositBalance: The amount reserved from the depositor for creating the AccountBalance record.

Reserve Logic

• do_mint:

  • Depositor = Collection owner.
  • If minting to a new mint_to account, the collection owner reserves the funds to create the AccountBalance record.
  • If the account already exists in AccountBalance, the value of AccountBalance is simply incremented.

• do_transfer:

  • Depositor = Provided depositor or the transferred collection item owner.
  • Decrements the AccountBalance of the sender and increments that of the recipient.
  • If transferring to a non-existing destination account (dest), the depositor or the collection item owner (if provided) reserves the funds to create the AccountBalance record.
  • If the destination account already exists, the account itself is responsible for reserving the funds for its AccountBalance record.

• do_buy_item: Call do_transfer with the caller as the buyer account.

• do_claim_swap:

  • Executes two do_transfer operations:
    1. From A to B: Call do_transfer with the depositor as the receive_item.owner
    2. From B to A: Call do_transfer with the caller as the send_item.owner

Unreserve Logic

• do_transfer:
  • Decrements the AccountBalance of the sender account.
  • If the sender's AccountBalance value reaches zero, the AccountBalance is removed, and the deposited funds are unreserved and returned to the depositor.
• do_burn:
  • Decrements the AccountBalance of the item owner.
  • If the owner's AccountBalance value reaches zero, the AccountBalance is removed, and the deposited funds are unreserved and returned to the depositor.