NEAR Non Fungible Token With Clone

Summary

Extended version of non-fungible tokens (NEP-171) that allows cloning tokens from existing ones.

Motivation

In Near blockchain there is a concept of storage cost, each byte added to a contract requires storage stake, the NEP-171 allows to mint NFTs but sometimes those NFTs are only duplicates with same metadata that still require to cover the storage stake.

Rationale and alternatives

NEAR's core Non-Fungible Token standard supports minting NFTs, when the metadata extension is enabled the an NFT can stores metadata. The NEP-171 allows to mint NFTs and set the metadata but there is no way to share/reuse the metadata between NFTs to reduce the storage stake. Prior art:

Non-Fungible Token standard (NEP-171)

Specification

Example Scenarios

https://github.com/near/near-sdk-rs/blob/master/near-contract-standards/src/non_fungible_token/metadata.rs#L27 Let's say we have a collecion of NFTs where some of those NFTs are only duplicates(copies) and we want to mint 1000 NFT that use the same metadata. The total size of the metadata is 1000 byte. The cost to store 1 Byte in a near account is 10^19 yocto NEAR/byte

Minting: To mint those 1000 NFTs we have to cover a total storage cost:

totalCost = 1000 copies * (1000 byte * 10^19 yocto NEAR/byte)
totalCost = 10 NEAR

Cloning Now, let's compare if we use the clone feature

totalCost = (1000 byte * 10^19 yocto NEAR/byte) + (1000 clones * (0))
totalCost = 0.01 NEAR

internal_clone_mint

Input

pub fn internal_clone_mint(
    &mut self,
    token_id: TokenId,
    clone_from_id: TokenId,
    token_owner_id: AccountId,
) -> Token;

The function accept as input a clone_from_id, as a result a new NFT is cloned and linked with a parent NFT using nft_clone_from_id