/*
 * SimpleAssetDemo implements a simple chaincode to manage an asset
 */
public class SimpleAssetDemo extends ChaincodeBase {
   /*
    * Init is called during chaincode instantiation to initialize any data.
    */
    @Override
   public Response init(ChaincodeStub stub) {
   }
   /*
    * Invoke is called per transaction on the chaincode. Each transaction is
    * either a 'get' or a 'set' on the asset created by Init function. The 'set'
    * method may create a new asset by specifying a new key-value pair.
    */
    @Override
   public Response invoke(ChaincodeStub stub) {
   }

   public static void main(String[] args) {
        new SimpleAssetDemo().start(args);
   }
}

/*
 * The init function is used to initialize two key-value pairs. The user-provided input parameters are KEY1_NAME, VALUE1, 
 * KEY2_NAME, VALUE2 
 */
@Override
public Response init(ChaincodeStub stub) {
    try {
        _logger.info("Init java simple chaincode");
        List<String> args = stub.getParameters();
        if (args.size() != 4) {
            newErrorResponse("Incorrect number of arguments. Expecting 4");
        }
        // Initialize the chaincode
        String account1Key = args.get(0);
        int account1Value = Integer.parseInt(args.get(1));
        String account2Key = args.get(2);
        int account2Value = Integer.parseInt(args.get(3));

        _logger.info(String.format("account %s, value = %s; account %s, value %s", account1Key, account1Value, account2Key, account2Value));
        stub.putStringState(account1Key, args.get(1));
        stub.putStringState(account2Key, args.get(3));

        return newSuccessResponse();
    } catch (Throwable e) {
        return newErrorResponse(e);
    }
}

// The invoke function subdivides the user-called function into several sub-functions, including invoke, delete, and query.
@Override
public Response invoke(ChaincodeStub stub) {
    try {
        _logger.info("Invoke java simple chaincode");
        String func = stub.getFunction();
        List<String> params = stub.getParameters();
        if (func.equals("invoke")) {
            return invoke(stub, params);
        }
        if (func.equals("delete")) {
            return delete(stub, params);
        }
        if (func.equals("query")) {
            return query(stub, params);
        }
        return newErrorResponse("Invalid invoke function name. Expecting one of: [\\"invoke\\", \\"delete\\", \\"query\\"]");
    } catch (Throwable e) {
        return newErrorResponse(e);
    }
}

// The invoke function realizes the transfer of values between two keys. The input includes KEY1_NAME, KEY2_NAME, and VALUE.
private Response invoke(ChaincodeStub stub, List<String> args) {
    if (args.size() != 3) {
        return newErrorResponse("Incorrect number of arguments. Expecting 3");
    }
    String accountFromKey = args.get(0);
    String accountToKey = args.get(1);

    String accountFromValueStr = stub.getStringState(accountFromKey);
    if (accountFromValueStr == null) {
        return newErrorResponse(String.format("Entity %s not found", accountFromKey));
    }
    int accountFromValue = Integer.parseInt(accountFromValueStr);

    String accountToValueStr = stub.getStringState(accountToKey);
    if (accountToValueStr == null) {
        return newErrorResponse(String.format("Entity %s not found", accountToKey));
    }
    int accountToValue = Integer.parseInt(accountToValueStr);

    int amount = Integer.parseInt(args.get(2));

    if (amount > accountFromValue) {
        return newErrorResponse(String.format("not enough money in account %s", accountFromKey));
    }

    accountFromValue -= amount;
    accountToValue += amount;

    _logger.info(String.format("new value of A: %s", accountFromValue));
    _logger.info(String.format("new value of B: %s", accountToValue));

    stub.putStringState(accountFromKey, Integer.toString(accountFromValue));
    stub.putStringState(accountToKey, Integer.toString(accountToValue));

    _logger.info("Transfer complete");

    return newSuccessResponse("invoke finished successfully", ByteString.copyFrom(accountFromKey + ": " + accountFromValue + " " + accountToKey + ": " + accountToValue, UTF_8).toByteArray());
}

// The delete function is used to delete the specified key from the ledger. The input is KEY_NAME.
private Response delete(ChaincodeStub stub, List<String> args) {
    if (args.size() != 1) {
        return newErrorResponse("Incorrect number of arguments. Expecting 1");
    }
    String key = args.get(0);
    // Delete the key from the state in ledger
    stub.delState(key);
    return newSuccessResponse();
}

// query mainly retrieves the corresponding value of a KEY. the input is KEY_NAME. 
 private Response query(ChaincodeStub stub, List<String> args) { 
 if (args.size() != 1) { 
 return newErrorResponse("Incorrect number of arguments. Expecting NAME of the person to query"); 
 } 
 String KEY = args.get(0); 
 // byte[] stateBytes 
 String val = stub.getStringState(KEY); 
 if (val == null) { 
 return newErrorResponse(String.format("Error: state for %s is null", KEY)); 
 } 
 _logger.info(String.format("query Response: NAME: %s, Amount: %s ", KEY, val)); 
 return newSuccessResponse(val, ByteString.copyFrom(val, UTF_8).toByteArray()); 
}