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HydroGiftCard

Implements the requirements outlined in create a Gift Card Ethereum Smart Contract leveraging the Hydro ecosystem.

Overview

HydroGiftCard is implemented as a Snowflake Resolver which uses the Resolver's allowance system to facilitate easier HYDRO token exchanges. The customer must deposit HYDRO into their snowflake and would then add HydroGiftCard as a resolver for their snowflake and allocate a sufficient allowance which they'll use to purchase GiftCards.

Vendors will specify Offers consisting of the gift card denominations that will be available to purchase (e.g. 100,000 HYDRO, 50,000 HYDRO, etc.). Vendors must have an identity registered in the Hydro ecosystem as their Offers are tied to their EIN.

Customers may buy a vendor's Offer for the exact amount of HYDRO which will be deducted from the HydroGiftCard resolver's allowance. The resulting GiftCard is tied to the customer's EIN and the vendor's EIN in a simple struct:

struct GiftCard {
  uint id;          // unique GiftCard identifier
  uint vendor;      // vendor's EIN
  uint customer;    // customer's/recipient's EIN
  uint balance;     // amount of HYDRO remaining
  uint vendorRedeemAllowed;   // amount authorized for the vendor to transfer
}

The funds are held in escrow in the HydroGiftCard smart contract until they are either redeemed or refunded.

The typical use case would have the customer then gift the GiftCard to another user. The recipient must have an identity and upon transfer would be entered as the new GiftCard.customer EIN. This transfer can only be authorized by the current GiftCard.customer via a signed permission statement from the customer's ClientRaindrop address.

The recipient can then redeem the GiftCard by spending it at the vendor. Redemption also requires a signed permission statement from the recipient's ClientRaindrop address. The authorized funds can only be transferred to the vendor.

The vendor's side of redeeming a GiftCard is demonstrated in the VendorSampleContract. Its receiveRedeemApproval() function is analagous to ERC-20's receiveApproval(). It allows the vendor's smart contract to trigger the funds transfer and then complete whatever business logic it needs to attend to.

A basic refund mechanism allows vendors to close out their GiftCards and transfer the remaining HYDRO balance out of escrow and back to the customer.

Deviations from the original requirements

  1. Gift cards not offered in limited quantities. I just couldn't see the business use case for this requirement. Why would a vendor sell the 50th gift card but decline to sell the 51st?

  2. Gift cards do not expire. In California and in other locales it is illegal for gift cards to expire.

  3. The refund mechanism was not part of the requirements, but unspent funds have to have a way to be returned from escrow, especially if the vendor is closing shop or exiting the Hydro ecosystem.

Testing With Truffle

  • This folder has a suite of tests created through Truffle.
  • To run these tests:
    • Clone this repo: git clone https://github.com/kdmukai/hydro-gift-card.git
    • Run npm install
    • Build dependencies with npm run build
    • Spin up a development blockchain: npm run chain
    • In another terminal tab, run the test suite: npm test