Purpose of The Dapp

The dapp aims to issue short-term debt on chain with each token pegged to 10^-6 dollar and treat the xtz as the media for value exchange between usd and the debt token.

To know more details, please take a look at the spec on Flexible Loan System.

Contract Deployment

Tools: ide.ligolang.org + tezbridge + crontab

A few steps of manual work are required.

Deploy the contract and copy the contract address when it is done

Initialization Code on ligolang website, FYI


record [ owner = ("tz1NBWgCxEGy8U6UA4hRmemt3YmMXbPPe1YH" : address); 
         totalCredit = 0n; 
         totalSupply = 0n; 
         couponRate_inPerc = 9n; 
         creditorsMap = (map [] : map (address, counter)); 
         ledger = big_map [("tz1NBWgCxEGy8U6UA4hRmemt3YmMXbPPe1YH" : address) -> record [
            balance = 0n;
            allowances = (map [] : map (address , nat));
        ]];
 ]

Use entrypoint approve to allow the initialized contract to transfer tokens to creditors in future.

After step 1 & 2, the deployment part is done;

Backend Deployment

checkPoint in KT_ledger would be set to run for every 15 minutes to make sure expired record would be removed in time and the token would be released.

If you try to use the existing example currently on tezos.michshell.net, you can check up the faucet.json, That is the wallet of the owner of the debtor's (AKA. alice).

15 * * * * /Home/tezos/tezos-client transfer 0 from alice to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint checkPoint --burn-cap 1 >/var/log/tezos_update.log 2>&1

Webpage Usage

To boot the webpage: cd client and run npm run start.

Three functions have been built and put on the frontend for showcase.

"Debt ownership transfer" and "debt token withdrawal" have been released to the public users as transfer and burn buttons; "Token mint function" can be used when the token owner account is being connected to the tezbridge.

Spare the coarse design of the webpage as I know too little about frontend, especially javescript and react. Basically I'm mimicing the code mentioned in the reference section.

Limitations on the built part

Lots of errors and warnings under the hood cannot be addressed enough. If you are trying to run the app yourself, please open the browser dev console to make sure the process.
CORS policy needs to be overriden when making localhost test, here I would recommend chrome extension adds-on for temporary bypass. An alternative is to use a proxy to fetch value. Server side currently applies this method.
The safety of the contracts should be reinforced. Some of the entrypoint caller should be restricted to the debt owner or the contract owner only. The QC rules are not rigorous enough.
Insufficient amount of tezos would be collateralized corresponding to the amount of token, due to lack of QC rule.

Project Reference

The project is largely based on below materials. A lot more references have been used, however I cannot recall all of them accurately.

Thanks to the folks on tezos.stackexchange.com and ligolang discorder, and to the GOOGLE, of course.

Command line for copy and paste, FYI

#add creditor
./tezos-client transfer 0 from alice to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint addCreditor --arg '(Pair (Pair "tz1g4Kw2qhYELxeeHc2yiuLtPdovVckYNc6G" 50000000) (Pair 4 50001800))' --burn-cap 1

#modifyOwnership
./tezos-client transfer 3 from david to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint modifyOwnership --arg '(Pair (Pair "tz1VmUWL8DxseZnPTdhHQkkuk6nK55NVdKCG" "2020-06-21T00:39:07Z") 106)' --burn-cap 1

#checkPoint
./tezos-client transfer 0 from alice to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint checkPoint --burn-cap 1


#mint
./tezos-client transfer 100 from alice to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint mint --arg 100000000 --burn-cap 1

#approve
./tezos-client transfer 0 from alice to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint approve --arg '(Pair " KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB" 200000)' --burn-cap 1

#burn
./tezos-client transfer 0 from AHS_admin to KT1RWt6Qg94nu9EsiiFrXkd8JrqQ4j2FrCxB --entrypoint burn --arg '(Pair (Pair "XTZ" 166000000) 0)' --burn-cap 1