You can find here the content of the workshop we did thanks to Encode and their Educate Series. To put a little bit of context for new comers, we based our work on the design of Collateral Debt Position stablecoins. The goal was to rebuild a vault with some collateral and debt and fetch the Bitcoin price to compute the collateral ratio. There should probably be a replay video on Encode's channel so you can check that out to fully understand what's going on.
The goal for you is to redo this canisters from scratch and make them work!
Here are the different steps:
Run: dfx new vault in your terminal. It will setup everything for you. Select Rust language for the backend. Add React for the frontend. Press enter (no selection). Then you should have a new vault repository that will be the base line for your work.
To check if everything is okay you can try to deploy the mock canisters by running dfx start --clean --background then dfx deploy. Then you can then click on both local http addresses and play with the canisters on your browser.
Once you have done that, you can start changing things a bit. Go to the lib.rs file and modify it with the content written in this repository as well as the vault_backend.did and cargo.toml files.
As you can see in the code, your vault_backend canister is calling another canister: let xrc_principal = Principal::from_text("bkyz2-fmaaa-aaaaa-qaaaq-cai").unwrap();.
This canister is the Exchange Rate Canister and it allows us to fetch the Bitcoin price. This canister has been developped by the Dfinity Foundation and you can download the .wasm and .did files here on the xrc folder. It is also available on their github: https://github.com/dfinity/exchange-rate-canister. Go to releases to have the .wasm file and find the .did file in the code. Then you can add both files on a new folder xrc right next to your vault_backend canister.
Next step is to declare this new canister by modifying your dfx.json file with the one written in this repository.
Okay, "theorically" you don't have to change your files now, you are good to go!
Run dfx start --clean on terminal, open a new one and run dfx deploy xrc wait a little bit and run dfx canister id xrc to check that it matches the principal written in the lib.rs file.
Happy? But it is software engineering so 99% chance it won't work.
One thing is that the exchange rate canister is not supposed to run locally like that. While running dfx start --clean you might have seen those messages: "Using the default definition for the 'local' shared network because /Users/username/.config/dfx/networks.json does not define it." or "Using the default definition for the 'local' shared network because /Users/username/.config/dfx/networks.json not found."
You need to specify the local network. Run touch /Users/username/.config/dfx/networks.json then nano /Users/username/.config/dfx/networks.json and add this to the file:
{ "local": { "bind": "127.0.0.1:8080", "type": "ephemeral", "replica": { "subnet_type": "system" } } }
Second thing is that the Exchange Rate Canister requires cycles to run properly so you have to add some cycles by running: dfx canister deposit-cycles 10_000_000_000_000 xrc.
Once this is done, you can run the following commands again:
dfx start --clean
dfx deploy xrc
dfx deploy vault_backend
And try to collect the collateral ratios!
In addition, you can dfx deploy vault_frontend to see all the vaults in the application.
You correctly fetched the Bitcoin Price but you might want to actually deal with ckBTC transaction?
You have to integrate the ckBTC_ledger canister from Dfinity's github:
.did: https://github.com/dfinity/ic/blob/master/rs/rosetta-api/icp_ledger/ledger.did
If you want to mint ckBTC and allow user to send their Bitcoin directly to your app go check the minter canister:
https://github.com/dfinity/ic/blob/4a3f022d4f7b0997ff5f02a0c384cb94715ecf2d/rs/bitcoin/ckbtc/minter/
But don't be too enthusiastic because their still is a lot of work to do! Good luck and have fun :)
Check out Roman Kashitsyn's blog https://mmapped.blog/posts. He is a former Dfinity Engineer and he know a lot of stuff when it comes to canister development. But I have to warn you, you will have to be quite focus if you want to understand something.