Supply Chain

In logistics, a supply chain is a system for tracking and delivering to an end consumer various items. As a rule, such systems can't work without a lot of paperwork and other layers of bureaucracy. All of this costs a lot of time and money and increases the likelihood of an accidental error or, worst of all, a fraud. With the help of smart contracts (programs) and blockchain technologies, it is possible to eliminate these problems by making a supply chain more efficient, reliable and transparent.

How to run

⚒️ Build programs

Upload Supply chain program requires build two auxiliary programs:

Build NFT contract as described in README.md
Build Sharded FT contract as described in README.md
Build Supply Chain program as described in README.md

🏗️ Upload programs

You can deploy a program using idea.gear-tech.io. In the network selector, choose Vara Network Testnet or Development (in this case, you should have a local node running).

*** Non-Fungible Token ***

Upload program nft.opt.wasm from /target/wasm32-unknown-unknown/release/
Upload metadata file meta.txt
Specify init payload and calculate gas!

info

Init payload:

name Str - NFT collection name
symbol Str - NFT collection symbol
base_uri Str - NFT collection base URI
royalties Option<Royalties> - Optional param to specify accounts to pay royalties

*** Sharded Fungible Token ***

Upload code ft_logic.opt.wasm from /target/wasm32-unknown-unknown/release/
Upload code ft_storage.opt.wasm from /target/wasm32-unknown-unknown/release/
Upload program ft_main.opt.wasm from /target/wasm32-unknown-unknown/release/
Upload metadata file meta.txt
Specify init payload and calculate gas!

info

InitFToken payload:

storage_code_hash (H256) - storage code ID
ft_logic_code_hash (H256) - logic code ID

*** Supply Chain ***

Upload code supply_chain.opt.wasm from /target/wasm32-unknown-unknown/release/

🖥️ Run UI

Install packages

yarn install

Configure .evn file. Specify network address and program ID like in the example below:

For proper application functioning, one needs to adjust an environment variable parameters. An example is available here.

REACT_APP_NODE_ADDRESS=wss://rpc-node.gear-tech.io
REACT_APP_CODE_ADDRESS=0x7141c1f9eb7c48063fc7d3a00e7ef157c4a95a83d656efaee910104d429b0de9

Run app

yarn start

Logic

Each newly produced item gets the NFT in Gear's context - Vara non-fungible token (VNFT) and its ID equals an ID of the item. Then, as an item moves along a supply chain, an item's NFT transfers between a supply chain program, item's producer, and future distributor, retailer and end consumer.
Anyone who knows an item's ID can get item info.
Sale, purchase, delivery is made in Vara fungible tokens (VFT).

Item info has the following struct:

supply-chain/io/src/lib.rs
pub struct ItemInfo {
    /// Item’s producer [`ActorId`].
    pub producer: ActorId,
    /// [`ActorId`] of an item’s current or past distributor (depends on item’s
    /// `state`). If it equals [`ActorId::zero()`], then it means that an item
    /// has never had a distributor.
    pub distributor: ActorId,
    /// [`ActorId`] of an item’s current or past retailer (depends on item’s
    /// `state`). If it equals [`ActorId::zero()`], then it means that an item
    /// has never had a retailer.
    pub retailer: ActorId,

    pub state: ItemState,
    /// An item’s price. If it equals 0, then, depending on item’s `state`, an
    /// item is sold for free or has never been put up for sale.
    pub price: u128,
    /// Milliseconds during which a current seller should deliver an item.
    pub delivery_time: u64,
}

And ItemState has the following struct and inner enums:

supply-chain/io/src/lib.rs
pub struct ItemState {
    pub state: ItemEventState,
    pub by: Role,
}

supply-chain/io/src/lib.rs
pub enum ItemEventState {
    #[default]
    Produced,
    Purchased,
    Received,
    Processed,
    Packaged,
    ForSale,
    Approved,
    Shipped,
}

supply-chain/io/src/lib.rs
pub enum Role {
    Producer,
    Distributor,
    Retailer,
    #[default]
    Consumer,
}

Item route

The item is produced with ProducerAction::Produce.
The item is put up for sale with ProducerAction::PutUpForSale.
The item is purchased with DistributorAction::Purchase.
The purchase is approved or not with ProducerAction::Approve. In the latter case, the item returns on the 2 step.
The item is shipped with ProducerAction::Ship.
The item is received with DistributorAction::Receive.
The item is processed with DistributorAction::Process.
The item is packaged with DistributorAction::Package.
The item is put up for sale with DistributorAction::PutUpForSale.
The item is purchased with RetailerAction::Purchase.
The purchase is approved or not with DistributorAction::Approve. In the latter case, the item returns on the 9 step.
The item is shipped with DistributorAction::Ship.
The item is received with RetailerAction::Receive.
The item is put up for sale with RetailerAction::PutUpForSale.
The item is purchased with ConsumerAction::Purchase.

The end!

Interface

Initialization

supply-chain/io/src/lib.rs
/// Initializes the Supply chain program.
///
/// # Requirements
/// - Each [`ActorId`] of `producers`, `distributors`, and `retailers` mustn't
/// equal [`ActorId::zero()`].
#[derive(Encode, Decode, Hash, TypeInfo, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Clone)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub struct Initialize {
    /// IDs of actors that'll have the right to interact with a supply chain on
    /// behalf of a producer.
    pub producers: Vec<ActorId>,
    /// IDs of actors that'll have the right to interact with a supply chain on
    /// behalf of a distributor.
    pub distributors: Vec<ActorId>,
    /// IDs of actors that'll have the right to interact with a supply chain on
    /// behalf of a retailer.
    pub retailers: Vec<ActorId>,

    /// A FT contract [`ActorId`].
    pub fungible_token: ActorId,
    /// An NFT contract [`ActorId`].
    pub non_fungible_token: ActorId,
}

Actions

supply-chain/io/src/lib.rs
/// Sends the program info about what it should do.
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub struct Action {
    pub action: InnerAction,
    pub kind: TransactionKind,
}

supply-chain/io/src/lib.rs
/// A part of [`Action`].
///
/// Determines how an action will be processed.
///
/// The program has a transaction caching mechanism for a continuation of
/// partially processed asynchronous actions. Most often, the reason of an
/// underprocession is the lack of gas.
///
/// Important notes:
/// - Only the last sent asynchronous action for
/// [`msg::source()`](gstd::msg::source) is cached.
/// - Non-asynchronous actions are never cached.
/// - There's no guarantee every underprocessed asynchronous action will be
/// cached. Use
/// [`is_action_cached()`](../supply_chain_state/metafns/fn.is_action_cached.html)
/// to check if some action is cached for some [`ActorId`].
/// - It's possible to send a retry action with a different payload, and it'll
/// continue with it because, for some action, not all payload is saved in the
/// cache (see [`CachedAction`]).
/// - The cache memory has a limit, so when it's reached every oldest cached
/// action is replaced with a new one.
#[derive(
    Default, Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash,
)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum TransactionKind {
    #[default]
    New,
    Retry,
}

supply-chain/io/src/lib.rs
/// A part of [`Action`].
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum InnerAction {
    Producer(ProducerAction),
    Distributor(DistributorAction),
    Retailer(RetailerAction),
    Consumer(ConsumerAction),
}

supply-chain/io/src/lib.rs
/// Actions for a producer.
///
/// Should be used inside [`InnerAction::Producer`].
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum ProducerAction {
    /// Produces one item and a corresponding NFT with given `token_metadata`.
    ///
    /// Transfers the created NFT for the item to a producer
    /// ([`msg::source()`]).
    ///
    /// # Requirements
    /// - [`msg::source()`] must be a producer in a supply chain.
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Produced`] & [`Role::Producer`].
    ///
    /// [`msg::source()`]: gstd::msg::source
    Produce { token_metadata: TokenMetadata },

    /// Puts a produced item up for sale to distributors for given `price` on
    /// behalf of a producer.
    ///
    /// Transfers an item's NFT to the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the producer of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Produced`] &
    /// [`Role::Producer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::ForSale`] & [`Role::Producer`].
    PutUpForSale { item_id: ItemId, price: u128 },

    /// Approves or not a distributor's purchase on behalf of a producer.
    ///
    /// If the purchase is approved, then item's [`ItemEventState`] changes to
    /// [`Approved`](ItemEventState::Approved) and, from that moment, an item
    /// can be shipped (by [`ProducerAction::Ship`]).
    ///
    /// If the purchase is **not** approved, then fungible tokens for it are
    /// refunded from the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)) to the item's
    /// distributor and item's [`ItemEventState`] changes back to
    /// [`ForSale`](ItemEventState::ForSale).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the producer of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Produced`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Approved`]/[`ItemEventState::ForSale`] &
    /// [`Role::Producer`].
    Approve {
        item_id: ItemId,
        /// Yes ([`true`]) or no ([`false`]).
        approve: bool,
    },

    /// Starts a shipping of a purchased item to a distributor on behalf of a
    /// producer.
    ///
    /// Starts the countdown for the delivery time specified for the item in
    /// [`DistributorAction::Purchase`].
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the producer of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Approved`] &
    /// [`Role::Producer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Shipped`] & [`Role::Producer`].
    Ship(ItemId),
}

supply-chain/io/src/lib.rs
/// Actions for a distributor.
///
/// Should be used inside [`InnerAction::Distributor`].
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum DistributorAction {
    /// Purchases an item from a producer on behalf of a distributor.
    ///
    /// Transfers fungible tokens for purchasing the item to the Supply chain
    /// contract ([`exec::program_id()`](gstd::exec::program_id)) until the item
    /// is received (by [`DistributorAction::Receive`]).
    ///
    /// **Note:** the item's producer must approve or not this purchase by
    /// [`ProducerAction::Approve`].
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be a distributor.
    /// - Item's [`ItemState`] must contain [`ItemEventState::ForSale`] &
    /// [`Role::Producer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Purchased`] & [`Role::Distributor`].
    Purchase {
        item_id: ItemId,
        /// Milliseconds during which the producer of an item should deliver it.
        /// A countdown starts after [`ProducerAction::Ship`] is executed.
        delivery_time: u64,
    },

    /// Receives a shipped item from a producer on behalf of a distributor.
    ///
    /// Depending on the time spent on a delivery, transfers fungible tokens for
    /// purchasing the item from the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)) to the item's producer
    /// or, as a penalty for being late, refunds a half or all of them to the
    /// item's distributor ([`msg::source()`]).
    ///
    /// Transfers an item's NFT to the distributor ([`msg::source()`]).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`] must be the distributor of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Shipped`] &
    /// [`Role::Producer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Received`] & [`Role::Distributor`].
    ///
    /// [`msg::source()`]: gstd::msg::source
    Receive(ItemId),

    /// Processes a received item on behalf of a distributor.
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the distributor of the
    /// item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Received`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Processed`] & [`Role::Distributor`].
    Process(ItemId),

    /// Packages a processed item on behalf of a distributor.
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the distributor of the
    /// item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Processed`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Packaged`] & [`Role::Distributor`].
    Package(ItemId),

    /// Puts a packaged item up for sale to retailers for given `price` on
    /// behalf of a distributor.
    ///
    /// Transfers an item's NFT to the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the distributor of the
    /// item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Packaged`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::ForSale`] & [`Role::Distributor`].
    PutUpForSale { item_id: ItemId, price: u128 },

    /// Approves or not a retailer's purchase on behalf of a distributor.
    ///
    /// If the purchase is approved, then item's [`ItemEventState`] changes to
    /// [`Approved`](ItemEventState::Approved) and, from that moment, an item
    /// can be shipped (by [`DistributorAction::Ship`]).
    ///
    /// If the purchase is **not** approved, then fungible tokens for it are
    /// refunded from the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)) to the item's retailer
    /// and item's [`ItemEventState`] changes back to
    /// [`ForSale`](ItemEventState::ForSale).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the distributor of the
    /// item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Purchased`] &
    /// [`Role::Retailer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Approved`]/[`ItemEventState::ForSale`] &
    /// [`Role::Distributor`].
    Approve {
        item_id: ItemId,
        /// Yes ([`true`]) or no ([`false`]).
        approve: bool,
    },

    /// Starts a shipping of a purchased item to a retailer on behalf of a
    /// distributor.
    ///
    /// Starts the countdown for the delivery time specified for the item in
    /// [`RetailerAction::Purchase`].
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the distributor of the
    /// item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Approved`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Shipped`] & [`Role::Distributor`].
    Ship(ItemId),
}

supply-chain/io/src/lib.rs
/// Actions for a retailer.
///
/// Should be used inside [`InnerAction::Retailer`].
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum RetailerAction {
    /// Purchases an item from a distributor on behalf of a retailer.
    ///
    /// Transfers fungible tokens for purchasing the item to the Supply chain
    /// contract ([`exec::program_id()`](gstd::exec::program_id)) until the item
    /// is received (by [`RetailerAction::Receive`]).
    ///
    /// **Note:** the item's distributor must approve or not this purchase by
    /// [`DistributorAction::Approve`].
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be a retailer.
    /// - Item's [`ItemState`] must contain [`ItemEventState::ForSale`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Purchased`] & [`Role::Retailer`].
    Purchase {
        item_id: ItemId,
        /// Milliseconds during which the distributor of an item should deliver
        /// it. A countdown starts after [`DistributorAction::Ship`] is
        /// executed.
        delivery_time: u64,
    },

    /// Receives a shipped item from a distributor on behalf of a retailer.
    ///
    /// Depending on the time spent on a delivery, transfers fungible tokens for
    /// purchasing the item from the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)) to the item's
    /// distributor or, as a penalty for being late, refunds a half or all of
    /// them to the item's retailer ([`msg::source()`]).
    ///
    /// Transfers an item's NFT to the retailer ([`msg::source()`]).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`] must be the retailer of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Shipped`] &
    /// [`Role::Distributor`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Received`] & [`Role::Retailer`].
    ///
    /// [`msg::source()`]: gstd::msg::source
    Receive(ItemId),

    /// Puts a received item up for sale to consumers for given `price` on
    /// behalf of a retailer.
    ///
    /// Transfers an item's NFT to the Supply chain program
    /// ([`exec::program_id()`](gstd::exec::program_id)).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - [`msg::source()`](gstd::msg::source) must be the retailer of the item.
    /// - Item's [`ItemState`] must contain [`ItemEventState::Received`] &
    /// [`Role::Retailer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::ForSale`] & [`Role::Retailer`].
    PutUpForSale { item_id: ItemId, price: u128 },
}

supply-chain/io/src/lib.rs
/// Actions for a consumer.
///
/// Should be used inside [`InnerAction::Consumer`].
#[derive(Encode, Decode, TypeInfo, Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub enum ConsumerAction {
    /// Purchases an item from a retailer.
    ///
    /// Transfers fungible tokens for purchasing the item to its retailer.
    ///
    /// Transfers an item's NFT to the consumer
    /// ([`msg::source()`](gstd::msg::source)).
    ///
    /// # Requirements
    /// - The item must exist in a supply chain.
    /// - Item's [`ItemState`] must contain [`ItemEventState::ForSale`] &
    /// [`Role::Retailer`].
    ///
    /// On success, replies with [`Event`] where [`ItemState`] contains
    /// [`ItemEventState::Purchased`] & [`Role::Consumer`].
    Purchase(ItemId),
}

Program metadata and state

Metadata interface description:

supply-chain/io/src/lib.rs
pub struct ContractMetadata;

impl Metadata for ContractMetadata {
    type Init = InOut<Initialize, Result<(), Error>>;
    type Handle = InOut<Action, Result<Event, Error>>;
    type Reply = ();
    type Others = ();
    type Signal = ();
    type State = Out<State>;
}

To display the full program state information, the state() function is used:

supply-chain/src/lib.rs
#[no_mangle]
extern fn state() {
    let state: State = generate_state();
    msg::reply(state, 0).expect("Failed to encode or reply with `State` from `state()`");
}

To display only necessary certain values from the state, you need to write a separate crate. In this crate, specify functions that will return the desired values from the State struct. For example - supply-chain/state:

supply-chain/state/src/lib.rs
#[gmeta::metawasm]
pub mod metafns {
    pub type State = supply_chain_io::State;

    pub fn item_info(state: State, item_id: ItemId) -> Option<ItemInfo> {
        state
            .items
            .into_iter()
            .find_map(|(some_item_id, item_info)| (some_item_id == item_id).then_some(item_info))
    }

    pub fn participants(state: State) -> Participants {
        Participants {
            producers: state.producers,
            distributors: state.distributors,
            retailers: state.retailers,
        }
    }

    pub fn roles(state: State, actor: ActorId) -> Vec<Role> {
        let mut roles = vec![Role::Consumer];

        if state.producers.contains(&actor) {
            roles.push(Role::Producer);
        }
        if state.distributors.contains(&actor) {
            roles.push(Role::Distributor);
        }
        if state.retailers.contains(&actor) {
            roles.push(Role::Retailer);
        }

        roles
    }

    pub fn existing_items(state: State) -> Vec<(ItemId, ItemInfo)> {
        state.items
    }

    pub fn fungible_token(state: State) -> ActorId {
        state.fungible_token
    }

    pub fn non_fungible_token(state: State) -> ActorId {
        state.non_fungible_token
    }

    pub fn is_action_cached(state: State, actor: ActorId, action: InnerAction) -> bool {
        if let Some(action) = action.into() {
            state.cached_actions.contains(&(actor, action))
        } else {
            false
        }
    }
}

Source code

The source code of this example of a supply chain program and an implementation of its testing is available on GitHub. They can be used as is or modified to suit your own scenarios.

For more details about testing programs written on Vara, refer to the Program Testing article.

Supply Chain

How to run​

⚒️ Build programs​

🏗️ Upload programs​

🖥️ Run UI​

Logic​

Item route​

Interface​

Initialization​

Actions​

Program metadata and state​

Source code​