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Capi

Capi is a work in progress. The documentation may not reflect the current implementation. Expect a stable release and proper documentation in early 2023.

Capi is a framework for crafting interactions with Substrate chains. It consists of a development server and fluent API, which facilitates multichain interactions without compromising either performance or ease of use.

Installation

npm i capi
Deno Equivalent

import_map.json

{
  "imports": {
    "capi": "https://deno.land/x/capi/mod.ts"
  }
}

Configuration

Create a nets.ts and specify the chains with which you’d like to interact.

import { bins, net } from "capi"

const bin = bins({ polkadot: ["polkadot", "v0.9.38"] })

// The Polkadot relay chain
export const polkadot = net.ws({ url: "wss://rpc.polkadot.io/" })

// A Polkadot development network
export const polkadotDev = net.dev({
  bin: bin.polkadot,
  chain: "polkadot-dev",
})

Command Line Tool

In this documentation, we use Capi’s CLI via the alias “capi”, instead of via its full path:

./node_modules/.bin/capi
Deno Equivalent 
deno run -A https://deno.land/x/capi/main.ts

Codegen Chain-specific APIs

capi sync --package-json package.json
Deno Equivalent 
capi sync --import-map import_map.json

At a Glance

Retrieve the first 10 entries from a storage map of Polkadot.

import { polkadot } from "@capi/polkadot"

const accounts = await polkadot.System.Account.entries({ count: 10 }).run()

Development Networks

Let’s modify the usage above to target our configured devnet.

- import { polkadot } from "@capi/polkadot"
+ import { polkadotDev } from "@capi/polkadot-dev"

- const accounts = await polkadot.System.Account
+ const accounts = await polkadotDev.System.Account
    .entries({ count: 10 })
    .run()

To run code that depends on a devnet, use the serve command, followed by a “–” and your devnet-using command. In this case, we’ll run the script (main.js) with Node.JS.

capi serve -- node main.js

Other examples:

  • capi serve -- npm run start
  • capi serve -- deno run -A ./main.ts

Running Examples

Within a fresh clone of this repository…

deno task run examples/<example_file>

Rationale

In a likely future of specialized, interoperable chains, developers will need to make use of on-chain programs to satisfy varying use cases; the expertise required to interact with these on-chain programs is currently greater than that which should be expected of app developers. Does this mean that app developers must forgo integrating with this blossoming infrastructure? We think not; the open source community can use Capi to abstract over the atomics of the on-chain world. An interaction spanning several chains and dozens of methods can be described with a single Rune[^1].

As you read through this documentation, please consider use cases over which you might like to abstract; if you wish to add your use case to Capi’s standard library, please submit an issue.

Code of Conduct

Everyone interacting in this repo is expected to follow the code of conduct.

Contributing

Contributions are welcome and appreciated! Check out the contributing guide before you dive in.

License

Capi is Apache licensed.

[^1]: Rune is the unit of composition with which we model Capi programs.