otterscan/src/useChainInfo.ts

import { createContext, useContext } from "react";
import useSWRImmutable from "swr/immutable";
import { chainInfoURL } from "./url";
import { OtterscanRuntime } from "./useRuntime";

export type ChainInfo = {
  network: string | undefined;
  faucets: string[];
  nativeCurrency: {
    name: string;
    symbol: string;
    decimals: number;
  };
};

export const defaultChainInfo: ChainInfo = {
  network: undefined,
  faucets: [],
  nativeCurrency: {
    name: "Ether",
    symbol: "ETH",
    decimals: 18,
  },
};

export const ChainInfoContext = createContext<ChainInfo | undefined>(undefined);

const chainInfoFetcher = async (assetsURLPrefix: string, chainId: number) => {
  const url = chainInfoURL(assetsURLPrefix, chainId);
  const res = await fetch(url);
  if (!res.ok) {
    return defaultChainInfo;
  }

  const info: ChainInfo = await res.json();
  return info;
};

export const useChainInfoFromMetadataFile = (
  runtime: OtterscanRuntime | undefined
): ChainInfo | undefined => {
  const assetsURLPrefix = runtime?.config?.assetsURLPrefix;
  const chainId = runtime?.provider?.network.chainId;

  const { data, error } = useSWRImmutable(
    assetsURLPrefix !== undefined && chainId !== undefined
      ? [assetsURLPrefix, chainId]
      : null,
    chainInfoFetcher
  );
  if (error) {
    return defaultChainInfo;
  }
  return data;
};

export const useChainInfo = (): ChainInfo => {
  const chainInfo = useContext(ChainInfoContext);
  if (chainInfo === undefined) {
    throw new Error("no chain info");
  }
  return chainInfo;
};