# Substrate API Sidecar

Small service intended to run next to Substrate, exposing a limited set of endpoints over HTTP with meaningful responses.

### Installation

```
yarn
```

### Running

```
yarn start
```

### Available paths

+ `/block` fetch latest finalized block details.

+ `/block/NUMBER` fetch block details at block height `NUMBER`.

+ `/balance/ADDRESS` fetch balances for `ADDRESS` at latest finalized block.

+ `/balance/ADDRESS/NUMBER` fetch balances for `ADDRESS` at block height `NUMBER`.

+ `/payout/ADDRESS` fetch payout info for `ADDRESS` at latest finalized block.

+ `/payout/ADDRESS/NUMBER` fetch payout info for `ADDRESS` at block height `NUMBER`.

+ `/metadata` fetch chain metadata at latest finalized block.

+ `/metadata/NUMBER` fetch chain metadata at block height `NUMBER`.

+ `/tx/` submit a signed transaction, excepts a string with hex-encoded signed transaction in a json POST body:
    ```
    curl localhost:8080/tx/ -X POST --data '{"tx": "0x..."}' -H 'Content-Type: application/json'
    ```
    Expected result is a json with transaction hash:
    ```
    {
        "hash": "..."
    }
    ```

### Configuration

Following ENV variables can be set:

+ `BIND_HOST`: address on which the server will be listening, defaults to `127.0.0.1`.
+ `BIND_PORT`: port on which the server will be listening, defaults to `8080`.
+ `NODE_WS_URL`: WebSocket URL to which the RPC proxy will attempt to connect to, defaults to `ws://127.0.0.1:9944`.

### Chain compatibility

Sidecar should be compatible with any [Substrate](https://substrate.dev/) based chain, given constraints:

+ The chain ought to use FRAME and the `balances` pallet.
+ The chain is being finalized (by running `grandpa`).
+ If the chain is running on custom Node binaries, the JSON-RPC API should be backwards compatible with the default Substrate Node.