# @polkadot/extension

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A very simple scaffolding browser extension that injects a [@polkadot/api](https://github.com/polkadot-js/api) Signer into a page, along with any associated accounts, allowing for use by any dapp. This is an extensible POC implementation of a Polkadot/Substrate browser signer.

As it stands, it does one thing: it _only_ manages accounts and allows the signing of transactions with those accounts. It does not inject providers for use by dapps at this early point, nor does it perform wallet functions where it constructs and submits txs to the network.

# Running

Currently is not packaged since it is under heavy development. As such you need to build it yourself. To use -

1. Build via `yarn build` or `yarn watch`
2. Add the extension under `chrome://extensions/`
  - ensure you have the Development flag set
  - "Load unpacked" and point to `packages/extension/build`
  - if developing, after making changes - refresh the extension
3. When visiting `http://localhost:3000` or `https://polkadot.js.org/apps/` it will inject the extension (the manifest currently only lists these 2 endpoints)

Once added, you can create an account (via a generated seed) or import via an existing seed. The UI, when loaded, will show these accounts as `<account name> (extension)`

## Technical

The extension injects `injectedWeb3` into the global `window` object, exposing the following:

```js
window.injectedWeb3 = {
  // this is the name for this extension, there could be multiples injected,
  // each with their own keys
  'polkadot-js': {
    // same as above, just easier to manage having accessible here
    name: 'polkadot-js',
    // semver for the package
    version: '0.1.0',

    // this is called to enable the injection, and returns an injected
    // object containing the accounts, signer and provider interfaces
    // (or it will reject if not authorized)
    enable (originName: string): Promise<Injected>
  }
}
```

When there is more than one extension, each will populate an entry above, so from an extension implementation perspective, the structure should not be overridded. The injected interface, when returned via `enable`, contains the following -

```js
interface Injected {
  readonly accounts: Accounts;
  readonly signer: Signer;
  // not injected as of yet, subscriptable provider for polkadot-js injection
  // readonly provider: Provider
}

// exposes accounts
interface Accounts {
  get (): Promise<Array<{
    readonly address: string; // ss-58 encoded address
    readonly name?: string; // optional name for display
  }>>;
}

// a signer that communicates with the extension via sendMessage
interface Signer extends SignerInterface {
  // no specific signer extensions, exposes the `sign` interface for use by
  // the polkadot-js API
}
```

The app can use all or any of these, depending on needs. To instantiate the `@polkadot/api` with the provider (app does not have it's own) and the signer (allowing the extension to sign messages) can be done via -

```js
import { ApiPromise } from '@polkadot/api';

const { signer } = window.injectedWeb3;
const api = await Api.create({ signer });
```