import type {
  EthereumProvider,
  JsonRpcRequest,
  JsonRpcResponse,
} from "../../../../../../types/providers.js";
import type { RequestHandler } from "../../types.js";

import { HardhatError } from "@nomicfoundation/hardhat-errors";
import { isObject } from "@nomicfoundation/hardhat-utils/lang";

import { getRequestParams } from "../../../json-rpc.js";

/**
 * This class modifies JSON-RPC requests.
 * It checks if the request is related to transactions and ensures that the "from" field is populated with a sender account if it's missing.
 * If no account is available for sending transactions, it throws an error.
 * The class also provides a mechanism to retrieve the sender account, which must be implemented by subclasses.
 */
export abstract class SenderHandler implements RequestHandler {
  readonly #methods: ReadonlySet<string> = new Set([
    "eth_sendTransaction",
    "eth_call",
    "eth_estimateGas",
  ]);

  protected readonly provider: EthereumProvider;

  constructor(provider: EthereumProvider) {
    this.provider = provider;
  }

  public isSupportedMethod(jsonRpcRequest: JsonRpcRequest): boolean {
    return this.#methods.has(jsonRpcRequest.method);
  }

  public async handle(
    jsonRpcRequest: JsonRpcRequest,
  ): Promise<JsonRpcRequest | JsonRpcResponse> {
    if (!this.isSupportedMethod(jsonRpcRequest)) {
      return jsonRpcRequest;
    }

    const method = jsonRpcRequest.method;
    const params = getRequestParams(jsonRpcRequest);

    const [tx] = params;

    if (isObject(tx) && tx.from === undefined) {
      const senderAccount = await this.getSender();

      if (senderAccount !== undefined) {
        tx.from = senderAccount;
      } else if (method === "eth_sendTransaction") {
        throw new HardhatError(
          HardhatError.ERRORS.CORE.NETWORK.NO_REMOTE_ACCOUNT_AVAILABLE,
        );
      }
    }

    return jsonRpcRequest;
  }

  protected abstract getSender(): Promise<string | undefined>;
}