This repository contains a decentralized futures contract implementation built with Ink! smart contracts.

Before toying with this code I would encourage you to to first go through the getting started section of Ink's website.

To build smart contract found in this repo you need to have cargo-contract installed.

cargo install cargo-contract --force

--force updates to the most recent cargo-contract version.

First, clone the repo. Next, navigate to the root of the directory (e.g. cd path_to_your_directory/ssal_commods) and run the following command:

cargo contract build

You should now have an optimized <contract-name>.wasm file, a metadata.json file and a <contract-name>.contract file in the target folder of your contract. The .contract file combines the Wasm and metadata into one file and can be used for instantiation.

To play with the contract you need to first install the substrate-contracts-node by following these instructions.

Next, you'll want to spin up the node running substrate-contracts-node. Once that's running you can access the Contracts UI. Follow these instructions.

Finally, deploy your contract to the UI by following this link.

Note: All of the token functionality came from the erc20 example from the ink-examples repo by paritytech. Here we'll only cover functions realted to commodity contract logic. I also wont cover all the read-only functions since they are self-explanatory.

create_contract takes as input:

• _price of type Balance: the price of the contract itself.
• _total of type Balance: the total price of the product being sold.
• _volume of type Grams: the weight, in grams, of the product being sold.
• _finality_block of type BlockNumber: the block after which the contract can be finalized.

The function then adds input data to the relevant mappings, increments the contract count, and adds the caller as the seller for the contract.

Returns InvalidBlockNumber if _finality_block is less than the current block number

buy_contract takes as input id, a ContractId specifying which contract the caller wants to buy.

The function transfers the amount designated by price from the caller's account to the seller's account and the amount designated by total from the caller's accont to the contract account. Then, it adds the caller's account to the buyer mapping using id as its key.

Returns ContractNotFound if the seller cannot be found for the given contract.

Returns ContractAlreadyBought if the contract already has a buyer listed.

Returns InsufficientBalance if the buyer does not have enough funds to cover both the contract price and total price of the product.

finalize takes as input id, a ContractId specifying which contract the caller wants to finalize. This function transfers the funds locked in the contract account to the seller's account.

The buyer calls this function when they have received their product. Only the buyer can call this function. This function can only be called at or after the finality block.

Returns ContractNotFound if there is no seller for the given contract.

Returns CannotFinalizeBeforeFinalityBlock if the caller attempts to finalize the contract before the finality block.

Returns OnlyBuyerCanFinalize if a caller other than the buyer for the given contract attempts to finalize. In theory, would return InsufficientBalance if the contract account does not have enough funds to pay the seller, but this should neveroccur.

Returns ContractAlreadyFinalized if the caller tries to finalize a contract that has already been finalized.

Returns ContractNotPurchased if the caller tries to finalize a contract that has not been purchased.

Run cargo test --features e2e-tests to run both unit and end-to-end tests. Otherwise, run cargo test for only unit tests.