Card Pay Protocol Contracts

The project hosts the contracts that comprise the Card Protocol. This includes the Prepaid Card Manager, Revenue Pool, SPEND token, and L2 Payment Token (e.g. DAI-CPXD).

About the Card Pay Protocol

The Card Pay Protocol is a set of contracts that are used to support commerce functions within the Cardstack ecosystem. This is includes fiat on-ramping, support for suppliers of prepaid cards via token bridging, the ability for merchants to sell digital goods and be paid by customers with prepaid cards.

The sequence diagram above depicts the flow of funds through the Card Protocol. The idea is starting from the left:

A Supplier bridges stable coin from Ethereum mainnet layer 1 into xDai layer 2 by sending stable coin to the token bridge.
The token bridge locks the layer 1 stable coin and mints a reciprocal layer 2 form of the locked token with the token suffix of "CPXD". So for example the DAI token would be minted as DAI.CPXD in layer 2. The token bridge will actually call into the Card Protocol to create a gnosis safe for the Supplier and place the newly minted layer 2 tokens in the gnosis safe for which the Supplier will be made an owner.
The Supplier will then use the funds from their gnosis safe to create a series of prepaid cards. The prepaid card is a gnosis safe that has 2 owners, where one owner is the Supplier and the other owner is the PrepaidCardManager contract. This safe requires 2 signatures in order to execute transactions, which means that the PrepaidCardManager contract needs to sign off on any transaction for the prepaid card gnosis safe.
Customers will go through a fiat on-ramp, whereby they exchange fiat currency for the ownership of a prepaid card created by the Supplier. As part of this purchase, the supplier will transfer ownership for one of the owners of the prepaid card gnosis safe to the customer (the PrepaidCardManager contract still retains its ownership of the prepaid card gnosis safe).
Meanwhile Merchants are registered into the Card Protocol, as part of the registration, a gnosis safe is created for the merchant. As a note, all the merchant addresses in the card protocol are assumed to be the address of the safe created for the merchant.
When a Customer is ready to purchase a product from a Merchant, the customer leverages a gnosis safe relay service function to call the PrepaidCardManager.send method, with a payMerchant action. This method will ultimately transfer the tokens used to pay a merchant into the RevenuePool contract.
At a later time, the Merchant can then withdraw the the funds held for them in the RevenuePool contract. This will be the layer 2 CPXD token.
At the merchant's choosing, they can bridge the layer 2 CPXD token back to layer 1. Because of the high gas fees in layer 1, likely the bridging back to layer 1 will only happen when the merchant has accrued enough layer 2 CPXD that it makes sense to offset the higher gas fees for bridging back to layer 1.

TokenManager

The TokenManager contract contains the list of CPXD tokens that are allowed to participate in the card protocol. Other contracts query the TokenManager contract to determine if a token being presented is an allowed token in the card protocol.

SupplierManager

The SupplierManager contract is used to register suppliers (entities that bring tokens into the card protocol) and provision gnosis safes for suppliers. The BridgeUtils contract uses the SupplierManager to get or create a safe for individuals that bridge tokens into the network in which the card protocol runs.

BridgeUtils

The BridgeUtils contract manages the point of interaction between the token bridge's home mediator contract and the Card Protocol. When the token bridge encounters an allowed stablecoin that it hasn't encountered before, it will create a new token contract in layer 2 for that token, as part of this, the token bridge will also inform the Card Protocol about the new token contract address, such that the Card Protocol can accept the new CPXD form of the stablecoin as payment for the creation of new prepaid cards, as well as, payments by customers to merchants. Additionally, as part of the token bridging process, the bridged tokens are placed in a gnosis safe that is owned by the Suppliers (the initiators of the token bridging process). This allows for easy gas-less (from the perspective of the users of the protocol) transactions. The gnosis safe as part of the token bridging process is actually created by the SupplierManager contract that the BridgeUtils contract refers to.

PrepaidCardManager

The PrepaidCardManager contract is responsible for creating the gnosis safes that are considered as Prepaid Cards. As part of this process, a gnosis safe is created when layer 2 CPXD tokens are sent to the PrepaidCardManager Contract (as part of the layer 2 CPXD token's ERC-677 onTokenTransfer() function). This gnosis safe represents a Prepaid Card.

There are two ways of creating prepaid cards when the tokens are sent to this contract:

When issuer and issuerSafe are provided in the onTokenTransfer data field, and the tokens are coming from a trusted caller (the PrepaidCardMarketV2 contract):

Prepaid cards will be created using the provided issuer as the issuer, and issuerSafe will be emitted as depot in the CreatePrepaidCard event

When issuer and issuerSafe are provided as zero addresses:

Prepaid cards will be created using the provided owner as the issuer

This safe is created with 2 owners:

The provided owner (case 1 explained above, i.e. the Customer), OR the sender of the transaction, i.e. the Supplier's gnosis safe (case 2)
The PrepaidCardManager contract itself.

As well as a threshold of 2 signatures in order to execute gnosis safe transactions. This approach means that the PrepaidCardManager contract needs to sign off on all transactions involving Prepaid Cards. As such the PrepaidCardManager contract allows Prepaid Cards to be able "send actions" by calling the send() function. The caller of the PrepaidCardManager.send() function (which is generally the txn sender of a gnosis safe relay server) specifies:

the "action" to send
the amount of §SPEND to send
a USD rate of the prepaid card's issuing token to use for the action
ABI encoded data as parameters for the "action" being sent
the prepaid card's EOA owner's signature to execute a gnosis tx for all the parameters specified above

The "send" message ultimately issues a gnosis safe tx to transfer the prepaid card's tokens to the ActionDispatcher contract with action and data, where the ActionDispatcher will dispatch the action to the appropriate contract to handle. As part of executing the gnosis transaction, a custom gas policy may be employed--this can be configured such that it is possible to specify on an action-by-action basis which token is used to pay for gas, and who is the gas recipient; such that it is possible to recoup the gas either out of the face value of the prepaid card or as a protocol fee that is charged to the recipient of the "action".

Examples of existing "actions" include:

splitting a prepaid card (using a prepaid card to fund the creation of more prepaid cards)
registering a merchant
paying a merchant
transferring a prepaid card.
registering a new reward program
provisioning a prepaid card to a customer

In the future prepaid cards will support actions that allow it to perform capabilities that will be expressed by rewards programs and the commerce protocol.

The PrepaidCardManager contract stores signers that are authorized to sign safe actions as a list of trusted contracts, configured as EIP-1271 signers. To reduce the contract size, we avoid adding them individually by using the setup function instead.

PrepaidCardMarket

The PrepaidCardMarket contract is responsible for provisioning already created prepaid card safes to customers. The intent is that Prepaid Card issuers can add their prepaid cards as inventory to this contract, thereby creating a SKU that represents the class of Prepaid Card which becomes available to provision to a customer. The act of adding a Prepaid Card to inventory means that the issuer of the Prepaid Card transfers their ownership of the Prepaid Card safe contract to the PrepaidCardMarket contract, such that the Prepaid Card safe has 2 contract owners: the PrepaidCardManager and the PrepaidCardMarket. Once a Prepaid Card is part of the inventory of the PrepaidCardMarket contract a "provisioner" role (which is a special EOA) is permitted to provision a Prepaid Card safe to a customer's EOA. This process entails leveraging an EIP-1271 contract signature to transfer ownership of the Prepaid Card safe from the PrepaidCardMarket contract to the specified customer EOA. Additionally the issuer of a Prepaid Card may also decide to remove Prepaid Cards from their inventory. This process also leverages EIP-1271 contract signatures to transfer ownership of the Prepaid Card safe from the PrepaidCardMarket contract back to the issuer that originally placed the Prepaid Card safe into their inventory.

A future update to this contract will provide the ability for EOAs to directly purchase Prepaid Card safes from the PrepaidCardMarket using native coin and/or CPXD tokens. In that future scenario we would leverage the "ask price" that can be set against a SKU to be able to purchase Prepaid Card safes directly. To support this eventual feature we have added the ability to set an "ask price" for SKUs in the inventory, however, capability to directly purchase a Prepaid Card from this contract is still TBD.

PrepaidCardMarketV2

The PrepaidCardMarketV2 market is responsible for provisioning prepaid cards without creating them beforehand. Once the issuer deposits their funds into the contract from their safe, their new balance will be saved and then they can continue to add SKUs and set the SKU asking price. It is then possible for them to call provisionPrepaidCard(customer, sku) on the contract, which will determine the price to create the prepaid card, create it by sending tokens to PrepaidCardManager (which will set the customer as the owner), and deduct the price to create the prepaid card from the issuer safe's balance recorded in the PrepaidCardMarketV2 contract.

ActionDispatcher

The ActionDispatcher receives actions that have been issued from the PrepaidCardManager.send() as gnosis safe transactions. The ActionDispatcher will confirm that the requested USD rate for the §SPEND amount falls within an acceptable range, and then will forward (via an ERC677 transferAndCall()) the action to the contract address that has been configured to handle the requested action.

PayMerchantHandler

The PayMerchantHandler is a contract that handles the payMerchant action. This contract will receive merchant payment dispatched from the ActionHandler. This contract will mint SPEND tokens into the safe of the merchant that is being paid, as well as, this contract will collect a protocol fee from the payment to the merchant (this is to offset the gas charges for the merchant payment as well as to pay for the protocol itself). This contract sends the protocol fee to a designated address that is used to collect protocol fees. After collecting the protocol fee, the remaining amount of CPXD tokens will then be sent to the RevenuePool contract where the merchant can claim their revenue.

RegisterMerchantHandler

The RegisterMerchantHandler is a contract that handles the registerMerchant action. This contract will receive merchant registration payments from the ActionHandler. This contract will call the MerchantManager contract to create a safe for the merchant, and send the collected registration payment to a designated address that is used to collect protocol fees.

SplitPrepaidCardHandler

The SplitPrepaidCardHandler is a contract that handles the split action. This contract will receive a payment from a prepaid card to create more prepaid cards (along with ABI encoded data that describes how to provision the new prepaid cards) from the ActionHandler. This contract will then transfer tokens directly to the PrepaidCardManager thereby creating new prepaid cards in the same manner that prepaid cards are created when tokens are transferred directly from a gnosis safe into the PrepaidCardManager. Note that for each prepaid card that is created via the PrepaidCardManager (regardless of where the tokens originate from) a gas fee is collected by the PrepaidCardManager contract to offset the cost of the gas used to create each prepaid card.

TransferPrepaidCardHandler

The TransferPrepaidCardHandler is a contract that handles the transfer action. This contract will receive a "transfer" action and an ABI encoded signature from the prepaid card's original EOA owner that authorizes the transfer of ownership from the ActionHandler. This contract will then call the PrepaidCardManager.transfer() function to perform a gnosis safe transfer of the prepaid card to the new EOA owner using the provided signature of the previous EOA owner of the prepaid card.

SetPrepaidCardInventoryHandler

The SetPrepaidCardInventoryHandler is a contract that handles the setPrepaidCardInventory action. This contract will receive a "setPrepaidCardInventory" action accompanied by ABI encoded fields that include the prepaid card to add to inventory, a signature from the prepaid card issuer to transfer the prepaid card safe to add to inventory to the PrepaidCardMarket contract, and the address of the PrepaidCardMarket contract. This contract will only permit unused Prepaid card safes to be added to inventory by the issuer of the Prepaid Card. This contract will then perform the gnosis safe transfer of the prepaid card to the PrepaidCardMarket contract using the provided signature, and then this contract will call the necessary functions to add the transferred prepaid card safe to the issuer's inventory in the PrepaidCardMarket contract.

RemovePrepaidCardInventoryHandler

The RemovePrepaidCardInventoryHandler is a contract that handles the removePrepaidCardInventory action. This contract will receive a "removePrepaidCardInventory" action accompanied by ABI encoded fields that include a list of prepaid card safe addresses to be removed from an issuer's inventory in the PrepaidCardMarket contract. This contract will iterate over the list of prepaid card safe addresses and leverage an EIP-1271 contract signature to transfer the prepaid card safes back to the issuer that originally added these prepaid card safes to the inventory, thereby removing these prepaid card safes from the PrepaidCardMarket contract inventory.

AddPrepaidCardSKUHandler

The AddPrepaidCardSKUHandler is a contract that handles the addPrepaidCardSKU action. This contract will receive a "addPrepaidCardSKU" action accompanied by ABI encoded fields that include the face value, customization DID, and the addresses of the issuing token, market and issuer's safe. It will then proceed to supply these params in the addSKU call to the PrepaidCardMarketV2 contract. Before the issuer can add SKUs, they first need to have some balance in the PrepaidCardMarketV2 contract.

SetPrepaidCardAskHandler

The SetPrepaidCardAskHandler is a contract that handles the setPrepaidCardAsk action. This contract will receive a "setPrepaidCardAsk" action accompanied by ABI encoded fields that include the SKU for prepaid card inventory and the ask price for a single item in the inventory in units of the issuing token for the prepaid card. Until an ask price is set for a SKU, the prepaid cards that are a part of the SKU cannot be provisioned. This is to prevent the scenario where prepaid cards could be purchased before a price is set when the TBD direct purchase functionality is added to the PrepaidCardMarket contract. Eventually when the TBD direct purchase functionality is added, the ask price will be used to charge EOAs that wish to purchase prepaid card inventory from the PrepaidCardMarket contract.

RegisterRewardProgramHandler

The RegisterRewardProgramHandler is a contract that handles the registerRewardProgram action. This contract will receive reward program registration payments from the ActionHandler. This contract will call the RewardManager to register the reward program and set a Reward Program Admin. This contract sends the protocol fee (rewardProgramRegistrationFeeInSpend) to a designated address that is used to collect protocol fees (for rewards). See reward glossary.

RegisterRewardeeHandler

The RegisterRewardeeHandler is a contract that handles the registerRewardee action. This contract will receive rewardee registration payments from the ActionHandler. This contract will call the RewardManager to register Rewardee under a reward program and create a reward safe for the rewardee. The prepaid card used for registerRewardee action will pay for the gas transaction cost in it's issuing token. See reward glossary.

LockRewardProgramHandler

The LockRewardProgramHandler is a contract that handles the lockRewardProgram action. This contract will call the RewardManager to update the lock state of the reward program, i.e. turn it on or off. The prepaid card used for lockRewardProgram will pay for the gas transaction cost in it's issuing token. See reward glossary.

UpdateRewardProgramAdminHandler

The UpdateRewardProgramAdminHandler is a contract that handles the updateRewardProgramAdmin action. This contract will call the RewardManager to update the Reward Program Admin that CAN control and manage the reward program. The prepaid card used for updateRewardProgramAdmin will pay for the gas transaction cost in it's issuing token. See reward glossary.

AddRewardRuleHandler

The AddRewardRuleHandler is a contract that handles the addRewardRule action. This contract will call the RewardManager to add a rule to a reward program. The prepaid card used for updateRewardProgramAdmin will pay for the transaction cost gas in it's issuing token. See reward glossary.

PayRewardTokensHandler

The PayRewardTokensHandler is a contract that handles the payRewardTokens action. This contract will send token transfers to fill up the RewardPool with reward tokens for a particular reward program. The prepaid card used for payRewardTokens will pay for the transaction cost gas in it's issuing token. See reward glossary.

Exchange

The Exchange is a contract that handles converting to and from §SPEND tokens from any other CPXD token, as well as getting the current USD rate for any of the CPXD tokens (which accompanies calls to PrepaidCardManager.send()). This contract is also responsible to determining if the USD rate that is being requested by PrepaidCardManager.send() calls falls within an allowable margin. We use the idea of a "rate lock" as part of the way in which callers call the PrepaidCardManager.send() function. The reason being is that these calls are normally issued from a gnosis relay server in 2 steps. The first step is to get an estimation of the transaction and then generate a signature, and the second step is to issue the transaction with the data from the transaction estimate along with the signature. In between those 2 steps the USD rate for the prepaid card's issuing token may have changed. To accommodate USD rate fluctuations the caller is allowed to specify the USD rate they used as part of the transaction estimation. This contract will then determine if that requested rate is actually allowable given the current USD rate and a configured "rate drift" percentage. If the requested rate falls outside of the "rate drift" percentage, then the transaction will be reverted. To accommodate the fact that we allow the caller to provide the USD rate to use, we have a pessimistic prepaid card face value calculation that we employ in PrepaidCardManager.faceValue() which uses the most pessimistic rate allowable given the "rate drift percentage" to calculate the prepaid card's face value after it's been used at least one time.

The Exchange contract assumes that all oracles use a uint 8 to represent their exchange rate, and in fact we assert this during conversion to ensure that the exchange rate logic converts correctly.

If an oracle changes their decimal precision from 8 bits, exchange will fail and transactions will revert, and this is expected behaviour. We only use oracles that have this level of precision to provide exchange rate data to the protocol.

MerchantManager

The MerchantManager contract is used to create gnosis safes for Merchants and establish mapping between the Merchant's EOA address and their safe address.

RevenuePool

The RevenuePool contract provides an escrow capability in the Card Protocol, where payments from Customers to Merchants are held in the RevenuePool contract, and Merchants can claim the proceeds of their sales by withdrawing tokens held by the RevenuePool on their behalf. The RevenuePool is configured as the recipient of ERC-677 tokens, and the PayMerchantHandler contract ultimately fashions a token transfer as part of paying a Merchant into the RevenuePool contract (with the Merchant's info in the call data of the token transfer).

SPEND

The SPEND token contract is a simple token contract that has mint and burn functions and whose tokens are not transferrable. The SPEND token can be thought of as a ticket that the Merchants receive as part of being paid by customers. These tokens are an accounting mechanism used to track the cumulative amount of payments that a Merchant has received from Customers.

IPriceOracle

In order to determine the amount of SPEND token to mint for Customer payments to *Merchants, we require a price oracle to convert the CPXD stable coin to USD. To support this we will leverage price oracles from both chainlink and DIA. Chainlink will provide stablecoin USD rates, and DIA will provide CARD USD rates. Chainlink and DIA use different interfaces for their onchain price feeds. In order to present a consolidated representation of various token prices we have created an IPriceOracle interface that represents the consolidated interface for all our price oracles, as well as we have a ChainlinkFeedAdapter and a DIAOracleAdapter contract that implements the IPriceOracle interface. These adapter contracts allow us to wrap the on-chain feeds from these two different token price sources into a consolidated interface that we can query from our Exchange contract. We also provide the token rates in units of ETH in order to support various web client needd.

RewardManager

Glossary for rewards within Cardpay:

Roles:

Rewardee: The EOA owner that receives reward tokens. A rewardee can be any participant within the cardpay ecosystem, such as Supplier, Merchant, Customer. For historical reasons, Payee used exchangeably with Rewardee.
Reward Program Admin: The EOA owner that is given authority to execute adminstrative functions for a Reward Program such as updateRewardProgramAdmin, lockRewardProgram.
Governance Admin: The EOA (represented as dao) that has the authority to removeRewardProgram.

Entities:

Reward Program: A program created to offer reward tokens Rewardees based on a rule. For example, Merchant might want to register a reward program to offer Card.cpxd tokens to Customers who spend > 100 SPEND in a week.
Reward Safe: Dual-owner safe owned by Rewardee and rewardManager. The safe is used to collect and store rewards. If a Rewardee doesn't have a Reward Safe, he needs to registerRewardee before the Rewardee can claim accrued rewards.
Tally: An offchain service that is responsible for computing rewards for a particular reward program; it determines how much reward token each Rewardee deserves.

The RewardManager is the main administrative contract that enables management of a Reward Programs. The RewardManager store corresponding states that are executed through a set of prepaid card actions:

registerRewardProgram
registerRewardee
addRewardRule
lockRewardProgram
updateRewardProgramAdmin

The RewardManager is responsible for creating gnosis safes that are known as Reward Safes. More importantly, the rewardManager host the EIP1271 signature callback that restrict the functions that a Reward Safe can execute. The two examples of this are:

withdrawFromRewardSafe: this function enables any ERC677 reward tokens to be transferred out of the Reward Safe after it has been claimed. The tokens transferred are used to pay for gas.
transferRewardSafe: this function enables the EOA-portion of the GnosisSafe ownership to be transferred. The transaction is gasless and considered as cost to the protocol fees collected during registerRewardee.

RewardPool

The RewardPool is a contract that stores inventory of the reward tokens(CPXD tokens) to be distributed to Rewardees for each Reward Program. The Reward Program Admin will refill the RewardPool with reward tokens for it's Reward Program when the balance gets low.

The RewardPool contract is also the interface in which Tally delivers rewards to a list of Rewardees. We use merkle trees as a way to verify how many tokens a Rewardee has claim to. For each rewardCycle (interval of blocks), Tally will write a root(a 32 byte hash) and store corresponding proofs(bytes) in offchain-storage. These proofs are used by the Rewardee to be verified against the roots and to claim reward tokens.

Prerequisites

The following prerequisites are required for this project:

NodeJS ver 14+
Yarn
jq (brew install jq)

Building

To build this project execute:

yarn install

Testing

To run all the tests execute:

yarn test

Or to run in parallel execute:

yarn test:parallel

The tests include a gas report which provides the min, max, and avg gas consumed for all the public functions in the contract based on the gas consumed while running tests, as well as, the gas required to deploy the contracts.

To generate the test coverage report execute:

yarn test:coverage

Solidity contracts has a maximum deployed bytecode size of 24KB. When a contract is larger than this, you'll receive out-of-gas errors when attempting to deploy it. In our tests we attempt a deploy of all our contracts to ensure they are deployable. Additionally you can generate a report of all the contract sizes to see if there are any contracts nearing or exceeding the max 24KB limit.

yarn test:size

Abis generated from this repository will be used inside the monorepo. To prepare the abis to be copied into the cardpay sdk here run the command below; a directory abi will be generated.

yarn write:abi

Deploying to private network

If you desire to test the protocol in an ad hoc manner in a private network (hardhat), then first start an RPC node in its own terminal window:

npx hardhat node

Switch to a different terminal window and then perform the following steps:

Compile the contracts if you have recently made changes (otherwise the most recently built contracts will be deployed):

yarn build:clean

The deploy and configure the protocol in the private network:

yarn deploy:hardhat

You can use the hardhat console to introspect the protocol:

npx hardhat --network localhost console --no-compile

Deployment

We use a provider that supports trezor hardware wallet signing for contract deployment. When deploying contracts make sure that your trezor hardware wallet is connectd to your computer's USB port.

Fund the Wallet

Determine the address that you are using to perform the deployment (usually we use the first address of the hardware wallet) and fund that wallet with enough native tokens (xDai tokens for the xDai network and SPOA for the Sokol network). There are faucets available here:

xDai Faucet: https://blockscout.com/xdai/mainnet/faucet
Sokol Faucet: https://blockscout.com/poa/sokol/faucet

Deploy Contract (first time deploy)

Staging: For a staging deploy, deploy to the Sokol network by entering the following command (specify environment variables that contain the optional configuration if there are values that you want to deploy with (like an already existing CPXD tokens or home bridge mediator address, etc):
```
yarn deploy:sokol
```
Production: For a production deploy, deploy to the xDai network by entering the following command (specify environment variables that contain the optional configuration if there are values that you want to deploy with (like an already existing CPXD tokens or home bridge mediator address, etc):
```
yarn deploy:xdai
```
Optional Configuration

As part of the contract deployment you may also provide the following environment variables to optionally configure the Card Protocol:
- GNOSIS_SAFE_MASTER_COPY This defaults to the v1.2.0 version of the Gnosis safe master copy address: 0x6851d6fdfafd08c0295c392436245e5bc78b0185
- GNOSIS_SAFE_FACTORY This defaults to the v1.1.1 version of the Gnosis safe factory address: 0x76E2cFc1F5Fa8F6a5b3fC4c8F4788F0116861F9B
- TALLY The address of the Tally contract which is responsible for withdrawing L2 tokens from the revenue pool on behalf of merchants when they wish to redeem their SPEND.
- BRIDGE_MEDIATOR This is the address of the layer 2 token bridge contract. This defaults to a zero address.
- MINIMUM_AMOUNT This is the minimum face value that a new prepaid card can be created with in units of SPEND. This defaults to 100 SPEND.
- MAXIMUM_AMOUNT This is the maximum face value that a new prepaid card can be created with in units of SPEND. This defaults to 10,000,000 SPEND.
- PAYABLE_TOKENS This is a comma separated list of bridged token addresses to pre-populate as tokens accepted by the Card Protocol
- GAS_FEE_RECEIVER This is the address of an entity that will receive gas fees as prepaid cards are created. Ideally this is the relay gas payer address.
- GAS_FEE_CARD_WEI This is the gas fee in units of CARD wei that is charged for the creation of each prepaid card.
- GAS_TOKEN This is the gas token used for paying merchants. This should be the address of the CARD.CPXD token, which is our gas token.
- RATE_DRIFT_PERCENTAGE This is the numerator of the percentage that represents the amount the requested USD rate is allowed to deviate from the actual rate when paying a merchant (where the actual rate comes from our configured oracle). The denominator for this fraction is 10⁸.
- MERCHANT_FEE_PERCENTAGE This is the numerator of the merchant fee percentage, where the denominator is 10⁸
- MERCHANT_REGISTRATION_FEE_IN_SPEND This is the registration fee that merchants must pay to register in SPEND tokens.
- MERCHANT_FEE_RECEIVER This is the address that will receive the merchant fees (presumably a gnosis safe on layer 2)
- REWARD_FEE_RECIEVER This is the address that will receive the reward registration fees (presumably a gnosis safe on layer 2)
- REWARD_PROGRAM_REGISTRATION_FEE_IN_SPEND This is the registration fee that rewardProgramAdmins must pay to register a reward program.
The contract addresses that are created are saved in a ./openzeppelin/addresses-{network}.json file.

As of 4/1/2021 the total native network cost to deploy is 0.1934 units (SPOA in sokol), where the block gas limit is 12499976.
Configure BridgeUtils If the BRIDGE_MEDIATOR environment variable was not supplied (because the layer 2 token bridge contracts have not yet been deployed), then deploy the layer 2 token bridge contracts, and then configure the BridgeUtils contract with the address of the layer 2 token bridge contract. Instructions to perform this are here.
Memorialize Contract State OpenZeppelin captures state information about the contracts that have been deployed. It uses this information to determine whether its safe to upgrade future versions of the contract based on changes that have been made as well where to update the contracts. It is OpenZeppelin's strong recommendation that this contract state be under source control. This means that after the initial deploy and after subsequent contract upgrades we need to commit and merge changes to the ./.openzeppelin folder. So make sure to git commit after any contract deploys and upgrades, as well as a git push to merge the commits back into the main branch so our representation of the state remains consistent.
Set up Gas Tokens After the Home Bridge Meditator has been setup to talk to the Card Protocol:
- bridge the tokens that will be used for gas (all the supported stable coins and the CARD token).
- Note the layer 2 *.CPXD address for each of the bridged tokens.
- Login to the relay service's admin interface: http://<relay_service_url>/admin
- Use the admin interface to add each of the stable coins and the CARD token as new tokens.
- Fill out the form for each token by providing the details for each token. Make sure to check the "gas" checkbox for each token, and save the settings.
Set up CARD Token Oracle for Relay Server After we have bridged our *.CPXD tokens and have addresses for our *.CPXD token, set up the "Cardpay" oracle in the relay server to provide CARD => DAI exchange rates.
- Login to the relay service's admin interface: http://<relay_service_url>/admin
- Use the admin interface to add a new price oracle:
  - The name of the price oracle should be: Cardpay
  - The configuration of the price oracle should be:
```
{
  "cardpay_price_oracle_addresses": {
    "CARD": "ADDRESS_OF_CARD_CPXD"
  }
}
```
- Use the admin interface to add a new price oracle ticker:
  - Select the "Cardpay" oracle in the Price Oracle drop down
  - Select the "CARD.CPXD" token in the Token drop down
  - Set the Ticker field to CARD/DAI
  - Leave the "Inverse" checkbox unchecked
  - Click on the "Save" button and you should see the live price for CARD token in units of DAI (it should be less than 1.0)
Configure Gas Token in PrepaidCardManager After we have bridged CARD.CPXD tokens and have an address for CARD, we need to set the CARD.CPXD as the gas token. This can be done by executing the PrepaidCardManager.setup() function with all the current values set as the parameters, plus the gas token set as the address for the CARD.CPXD token.
Fund Gas Tokens In order for the gnosis relay to airdrop the CARD.CPXD gas token on newly created prepaid card safes, we need to fund the relay txn funder with CARD.CPXD tokens. Bridge a significant amount of CARD tokens from layer 1 to layer 2, and then use the cardpay-sdk to transfer the layer 2 CARD.CPXD tokens from the depot safe that contains the bridge CARD.CPXD to the gnosis relayer txn funder's address. (curl https://<relay server>/api/v1/about/ to get this address).

Upgrading Contracts

We use the Open Zeppelin SDK to manage our upgradable contracts via hardhat scripts. Once a contract has been deployed we have the ability to change the logic in the contract while still retaining the contract state due to the way in which Open Zeppelin maintains proxy contracts and their corresponding implementations. There are a few limitations to be made aware of when updating a contract, which is outlined in the OZ documentation.. The OZ tools will check for any violations to the limitations as part of upgrading the contract and let you know if your changes to the contract are indeed upgradable changes. After you have made changes to the contract that you wish upgrade perform the following:

git pull (or fetch and merge if you prefer) the latest from the main git branch.
git commit your contract update changes (if they have not been committed already)
Run the deploy via yarn providing the network that you are deploying. Make sure to use environment variables documented above to retain all the current card protocol settings, such as the home bridge mediator address, the CPXD tokens, gas fee receiver, etc.
```
BRIDGE_MEDIATOR=<HOME BRIDGE ADDRESS> PAYABLE_TOKENS=<COMMA SEPARATED TOKEN ADDRESSES>, ... yarn deploy:<network>
```
git add ./openzeppelin to stage the updated contract state files.
git commit to commit the updated contract state files
Run the release script to tag a new version in github
```
./release.sh -n <NETWORK> -v <VERSION>
```
git push to merge the commits back into the main branch. These changes reflect the new contract upgrade state, and its very important that this state is shared with the team so it can remain consistent within our organization.

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README.md

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