Gift wrapper - NFT Wrapper Contract

This module allows users to wrap fungible tokens into a single NFT, transfer it, and later unwrap it to retrieve the original tokens.

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Features

• Mint NFT: Create a new NFT with custom metadata (name, description, URL).
• Wrap Tokens: Deposit fungible tokens (of any type) into the NFT.
• Transfer NFT: NFTs can be transferred like any object on-chain.
• Unwrap Tokens: Redeem the original tokens from the NFT.
• Burn NFT: Delete the NFT object when it's no longer needed.

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Module: memest::vending_machine

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Data Structures

Nft

• Represents the wrapped NFT object.
• Fields:
  • id: UID
  • name: String
  • description: String
  • url: Url
  • balances: Bag (stores the wrapped tokens)

BalanceKey<phantom T>

• Key type to manage balances of each token inside the Bag.

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Events

Event	Description
NftCreatedEvent	Emitted when an NFT is minted.
WrapCoinEvent	Emitted when a token is wrapped into an NFT.
UnwrapCoinEvent	Emitted when a token is unwrapped from an NFT.
BurnNftEvent	Emitted when an NFT is burned.

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Errors

Code	Description
0 (ENftNotContainCoin)	Attempted to unwrap a token type that is not contained inside the NFT.

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Public Functions

mint_a_nft

public fun mint_a_nft(name: vector<u8>, description: vector<u8>, url: vector<u8>, ctx: &mut TxContext): Nft

• Mints a new NFT with provided metadata.
• Emits NftCreatedEvent.

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burn_nft

public fun burn_nft(nft: Nft, ctx: &mut TxContext)

• Burns (deletes) the NFT.
• Only works if there are no tokens wrapped inside.
• Emits BurnNftEvent.

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wrap_coin

public fun wrap_coin<C>(nft: &mut Nft, coin: Coin<C>, ctx: &mut TxContext)

• Wraps a fungible token Coin<C> into the NFT.
• If the token type already exists, increases the balance.
• Emits WrapCoinEvent.

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unwrap_coin

public fun unwrap_coin<C>(nft: &mut Nft, ctx: &mut TxContext): Coin<C>

• Unwraps a token of type C from the NFT.
• If the token is not found, it asserts and aborts with error code ENftNotContainCoin.
• Emits UnwrapCoinEvent.

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nft_name

#[test_only]
public fun nft_name(nft: &Nft): String

• Returns the name of the NFT.
• Used internally for testing.

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Security Notes

• Ownership: Only the owner of the NFT can unwrap tokens.
• Balance Handling: Each token type is safely stored and retrieved using type-safe keys (BalanceKey).
• Event Emission: Every important operation is logged as an event.
• Safe Burn: NFTs must have no remaining balances before they can be burned.

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Potential Future Enhancements

• Allow wrapping multiple token types at once.
• Add time-lock or vesting conditions for unwrapping.
• Implement wrapping/unwrapping service fees.

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