Writing Data Oracles in JavaScript

# macOS/Linux example
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash
nvm install --lts
nvm use --lts

mkdir my_project
cd my_project

npm install -g @bytecodealliance/componentize-js

package newton:provider@0.1.0;

interface http {
    record http-request {
        url: string,
        method: string,
        headers: list<tuple<string, string>>,
        body: option<list<u8>>,
    }

    record http-response {
        status: u16,
        headers: list<tuple<string, string>>,
        body: list<u8>,
    }

    fetch: func(request: http-request) -> result<http-response, string>;
}

world newton-provider {
    import http;
    export run: func(input: string) -> result<string, string>;
}

// Import the WIT import exactly like the ComponentizeJS usage pattern:
// e.g. import { log } from 'local:hello/logger' in their docs.
// Here our package is newton:provider and interface is http.
import { fetch as httpFetch } from "newton:provider/http@0.1.0";

// WIT: export run: func(input: string) -> result<string, string>
// We return a JSON string on success AND on "errors"
// (i.e., we don't surface WIT Err<string> — we encode error info in JSON)
export function run(input) {
  const req = JSON.parse(input);

  // Fetch ETH price from CoinGecko
  const response = httpFetch({
    url: "https://api.coingecko.com/api/v3/simple/price?ids=ethereum&vs_currencies=usd",
    method: "GET",
    headers: [],
    body: null,
  });

  if (response.tag === "err") {
    return JSON.stringify({ error: response.val });
  }

  const body = new TextDecoder().decode(new Uint8Array(response.val.body));
  const data = JSON.parse(body);

  return JSON.stringify({
    eth_price_usd: data.ethereum.usd,
    timestamp: Date.now(),
  });
}

componentize-js --wit newton-provider.wit -o policy.wasm app.js -d stdio random clocks http fetch-event

my_project/
├─ policy.wasm
├─ newton-provider.wit
└─ app.js

import { componentize } from "@bytecodealliance/componentize-js";
import { readFile, writeFile } from "node:fs/promises";

const { component, imports } = await componentize({
  sourcePath: "./app.js", // your JS file
  witPath: "./newton-provider.wit", // WIT file path
  worldName: "newton-provider", // the world in your WIT
});

await writeFile("policy.wasm", component);
console.log("guest imports:", imports);

node componentize.mjs

newton-cli --chain-id 11155111 policy-data simulate \
  --wasm-file policy.wasm \
  --input-json '{"inquiry_id": "inq_xRZrQFKg7rqZ5UZGLhnvb2ympshE"}'