Solidity Function Builder class prototype - builder pattern and method chaining style applied

FunctionBuilder.java

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import javax.validation.constraints.Max;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.PositiveOrZero;
import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Address;
import org.web3j.abi.datatypes.Bool;
import org.web3j.abi.datatypes.DynamicBytes;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Int;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.datatypes.Uint;
import org.web3j.abi.datatypes.Utf8String;
import org.web3j.abi.datatypes.primitive.Byte;

/**
 *
 * Note that all Solidity type names are lower case only. For all the types
 * refer <a href=
 * 'https://solidity.readthedocs.io/en/v0.5.3/abi-spec.html#types'>contract ABI
 * specification</a>
 *
 * Note that this class is <b>NOT</b> thread-safe and so is expected to be
 * instanciated inside function.
 *
 * @author Sangmoon Oh
 *
 * @see <a href='https://solidity.readthedocs.io/en/v0.5.15/abi-spec.html#types'>Contract ABI Specification / Types</a>
 */
@NotThreadSafe
public class FunctionBuilder{

  // Referenced materials
  // - https://docs.web3j.io/transactions/#transacting-with-a-smart-contract
  // -
  // https://docs.web3j.io/transactions/#querying-the-state-of-a-smart-contract
  // -https://kauri.io/interacting-with-an-ethereum-smart-contract-in-jav/14dc434d11ef4ee18bf7d57f079e246e/a

  private String name = null;

  final private List<Type> inputParams = new ArrayList<>();

  final private List<TypeReference<?>> outputParamTypes = new ArrayList<>();

  /**
   * Set the name of function to call
   *
   * @param name
   *          the function name
   * @return current builder instance
   * @throws IllegalArgumentException
   *           when {@code name} is {@code null}, empty or blank
   */
  public FunctionBuilder setName(@NotBlank final String name){

    if(name == null || name.trim().length() == 0){
      throw new IllegalArgumentException("The function name is not expected to be null, empty or blank.");
    }

    this.name = name;
    return this;
  }

  /**
   * Build {@code Function} instance using current name, input parameters and
   * output parameter types.
   *
   * @return {@code Function} instance
   * @throws IllegalStateException
   *           when function name is not specified.
   *
   * @see org.web3j.abi.datatypes.Function
   */
  public Function build(){

    final String name = this.name;
    if(name == null || name.trim().length() == 0){
      throw new IllegalArgumentException("Function name should be specified.");
    }

    final List<Type> input =
        (this.inputParams.size() == 0) ? Collections.emptyList(): this.inputParams;
    final List<TypeReference<?>> outputTypes =
        (this.outputParamTypes.size() == 0) ? Collections.emptyList(): this.outputParamTypes;

    return new Function(this.name, input, outputTypes);
  }

  /**
   * Returns ABI encoded function using current function name, input parameters
   * and output parameter types
   *
   * @return ABI encoded function
   * @throws IllegalStateException
   *           when function name is not specified.
   *
   * @see org.web3j.abi.FunctionEncoder#encode(Function)
   */
  public String buildAndEncode(){

    return FunctionEncoder.encode(this.build());

  }

  // Methods for input parameters

  /**
   * Append {@code uint<M>} ABI type input parameter.
   *
   * Bit size(M) is supposed be specified as a 1st parameter.
   *
   * @param n
   *          bit size of the type: should be multiples of 8 between 1 and 256
   * @param value
   *          the value for the parameter which should be in proper range
   *          according to the bit size.
   * @return current builder instance
   * @throws IllegalArgumentException
   *
   * @see org.web3j.abi.datatypes.generated
   * @see #addUintInputParam(int, long)
   */
  public FunctionBuilder addUintInputParam(@Min(8) @Max(256) final int n,
      @Nonnull @PositiveOrZero final BigInteger value){

    if(n < 1 || n > 256 || n % 8 != 0){
      throw new IllegalArgumentException("The bit size('n') should be one of 8, 16, 24, 32, ..., 256 (multiple of 8 between 1 and 256)");
    }

    try{
      final Uint param = Class.forName("org.web3j.abi.datatypes.generated.Uint" + n)
          .asSubclass(Uint.class)
          .getConstructor(BigInteger.class)
          .newInstance(value);

      this.inputParams.add(param);
      return this;
    } catch(RuntimeException ex){
      throw ex;
    } catch(Throwable ex){
      throw new RuntimeException(ex);
    }
  }

  /**
   * @see #addUintInputParam(int, BigInteger)
   */
  public FunctionBuilder addUintInputParam(@Min(8) @Max(256) final int n,
        @PositiveOrZero final long value){
    return this.addUintInputParam(n, BigInteger.valueOf(value));
  }

  /**
   * Append {@code uint} ABI type (which is synonyms for {@code uint256}) input parameter
   *
   * @param value
   * @return current builder instance
   * @throws IllegalArgumentException
   *
   * @see org.web3j.abi.datatypes.Uint
   * @see #addUintInputParam(long)
   */
  public FunctionBuilder addUintInputParam(@Nonnull @PositiveOrZero final BigInteger value){

    if(value == null || value.compareTo(BigInteger.ZERO) < 0){
      throw new IllegalArgumentException("The value should be equal to or larger than zero.");
    }

    // @TODO Uint256 or Uint ?
    this.inputParams.add(new Uint(value));
    return this;
  }

  /**
   * Append {@code uint} ABI type (which is synonyms for {@code uint256}) input parameter
   *
   * @param value
   * @return current builder instance
   * @throws IllegalArgumentException
   *
   * @see org.web3j.abi.datatypes.Uint
   * @see #addUintInputParam(BigInteger)
   */
  public FunctionBuilder addUintInputParam(@PositiveOrZero final long value){
    return this.addUintInputParam(BigInteger.valueOf(value));
  }


  /**
   * Append {@code int<M>} ABI type input parameter.
   *
   * Bit size({@code M}) is supposed be specified as a 1st parameter.
   *
   * @param n
   *          bit size of the type: should be multiples of 8 between 1 and 256
   * @param value
   *          the value for the parameter which should be in proper range
   *          according to the bit size.
   * @return current builder instance
   * @throws IllegalArgumentException
   *
   * @see org.web3j.abi.datatypes.generated
   * @see #addIntInputParam(int, long)
   */
  public FunctionBuilder addIntInputParam(@Min(8) @Max(256) final int n,
      @Nonnull final BigInteger value){

    if(n < 1 || n > 256 || n % 8 != 0){
      throw new IllegalArgumentException("The bit size('n') should be one of 8, 16, 24, 32, ..., 256 (multiple of 8 between 1 and 256)");
    }

    try{
      final Int param = Class.forName("org.web3j.abi.datatypes.generated.Int" + n)
          .asSubclass(Int.class)
          .getConstructor(BigInteger.class)
          .newInstance(value);

      this.inputParams.add(param);
      return this;
    } catch(RuntimeException ex){
      throw ex;
    } catch(Throwable ex){
      throw new RuntimeException(ex);
    }
  }

  /**
   * @see #addIntInputParam(int, BigInteger)
   */
  public FunctionBuilder addIntInputParam(@Min(8) @Max(256) final int n, final long value){
    return this.addIntInputParam(n, BigInteger.valueOf(value));
  }

  /**
   * Append {@code int} ABI type (which is synonyms for {@code int256}) input parameter
   *
   * @param value
   * @return current builder instance
   *
   * @see #addInputParam(long)
   * @see org.web3j.abi.datatypes.Int
   */
  public FunctionBuilder addIntInputParam(@Nonnull final BigInteger value){

    this.inputParams.add(new Int(value));
    return this;
  }

  /**
   * Append {@code int} ABI type (which is synonyms for {@code int256}) input parameter
   *
   * @param value
   * @return current builder instance
   *
   * @see #addIntInputParam(BigInteger)
   * @see org.web3j.abi.datatypes.Int
   */
  public FunctionBuilder addIntInputParam(final long value){
    return this.addIntInputParam(BigInteger.valueOf(value));
  }

  /**
   * Append {@code address} ABI type input parameter.
   *
   * The {@code value} is expected to be hex string that starts with prefix '0x'.
   *
   * @param value
   *          the hex string starting with '0x' for the address
   * @return current builder instance
   * @thows IllegalArgumentException when {@code value} doesn't start with '0x'
   *        or doesn't have length between 3 and 42
   *
   * @see org.web3j.abi.datatypes.Address
   */
  public FunctionBuilder addAddressInputParam(@NotBlank @Pattern(regexp = "0x[0-9a-fA-F]{1,40}") final String value){

    if(value == null || !value.startsWith("0x")){
      throw new IllegalArgumentException("The address value is expected to start with '0x'.");
    }
    // @TODO more validations

    this.inputParams.add(new Address(value));
    return this;
  }


  /**
   * Append {@code bool} ABI type input parameter
   *
   * @param value
   * @return current builder instance
   *
   * @see org.web3j.abi.datatypes.Bool
   */
  public FunctionBuilder addBoolInputParam(final boolean value){

    this.inputParams.add(new Bool(value));
    return this;
  }


  /**
   * Append {@code byte} Solidity type (which is synonym for {@code bytes1}) input parameter
   *
   * @param value
   * @return current builder instance
   *
   * @see org.web3j.abi.datatypes.primitive.Byte
   */
  public FunctionBuilder addByteInputParam(final byte value){

    this.inputParams.add(new Byte(value));
    return this;
  }


  /**
   * Append {@code bytes<M>} ABI type (fixed-sized byte array) input parameter.
   *
   * @param n
   * @param value
   * @return current builder instance
   *
   * @see org.web3j.abi.datatypes.generated
   */
  public FunctionBuilder addBytesInputParam(@Min(1) @Max(32) final int n, final byte[] value) {
    //@TODO

    return this;

  }

  /**
   * Append {@code bytes} ABI type (dynamic sized byte sequence) input parameter
   *
   * @param value
   *          {@code byte[]} Java type value for the parameter
   * @return current builder instance
   *
   * @see org.web3j.abi.datatypes.DynamicBytes
   */
  public FunctionBuilder addBytesInputParam(@Nullable final byte[] value){

    this.inputParams.add(new DynamicBytes(value));
    return this;
  }


  /**
   * Append {@code string} ABI type input parameter.
   *
   * @param value
   *          parameter value, which can be {@code null}
   * @return current builder instance
   *
   * @see org.web3j.abi.datatypes.Utf8String
   */
  public FunctionBuilder addStringInputParam(@Nullable final String value){

    this.inputParams.add(new Utf8String(value));
    return this;
  }


  // @TODO Methods for array type input parameters

  // Methods for output parameter types

  /**
   * Append {@code uint<M>} ABI type output parameter
   *
   * @param n bit size of the type: should be multiples of 8 between 1 and 256
   * @return current builder instance
   * @throws IllegalArgumentException
   *
   */
  public FunctionBuilder addUintOutputParamType(@Min(8) @Max(256) final int n){

    if(n < 1 || n > 256 || n % 8 != 0){
      throw new IllegalArgumentException("The bit size('n') should be one of 8, 16, 24, 32, ..., 256 (multiple of 8 between 1 and 256)");
    }

    try{
      final Class<? extends Uint> clazz = Class.forName("org.web3j.abi.datatypes.generated.Uint" + n).asSubclass(Uint.class);
      this.outputParamTypes.add(TypeReference.create(clazz));

      return this;
    } catch(RuntimeException ex){
      throw ex;
    } catch(Throwable ex){
      throw new RuntimeException(ex);
    }
  }

  /**
   * Append {@code uint} ABI type output parameter.
   *
   * @return
   */
  public FunctionBuilder addUintOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Uint>(){});
    return this;
  }

  /**
   * Append {@code int<M>} ABI type output parameter.
   *
   * @param n bit size of the type: should be multiples of 8 between 1 and 256
   * @return
   * @throws IllegalArgumentException
   */
  public FunctionBuilder addIntOutputParamType(@Min(8) @Max(256) final int n){

    if(n < 1 || n > 256 || n % 8 != 0){
      throw new IllegalArgumentException("The bit size('n') should be one of 8, 16, 24, 32, ..., 256 (multiple of 8 between 1 and 256)");
    }

    try{
      final Class<? extends Int> clazz = Class.forName("org.web3j.abi.datatypes.generated.Int" + n).asSubclass(Int.class);
      this.outputParamTypes.add(TypeReference.create(clazz));

      return this;
    } catch(RuntimeException ex){
      throw ex;
    } catch(Throwable ex){
      throw new RuntimeException(ex);
    }
  }

  public FunctionBuilder addIntOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Int>(){});
    return this;
  }

  public FunctionBuilder addAddressOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Address>(){});
    return this;
  }

  public FunctionBuilder addBoolOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Bool>(){});
    return this;
  }

  public FunctionBuilder addByteOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Byte>(){});
    return this;
  }

  public FunctionBuilder addBytesOutputParamType(@Min(1) @Max(32) final int n){

    // @TODO
    return this;
  }

  public FunctionBuilder addBytesOutputParamType(){

    this.outputParamTypes.add(new TypeReference<DynamicBytes>(){});
    return this;
  }

  public FunctionBuilder addStringOutputParamType(){

    this.outputParamTypes.add(new TypeReference<Utf8String>(){});
    return this;
  }

  // @TODO Methods for array type output parameters

}