Add Result type to scale

polkaj-scale-types/build.gradle

@@ -3,4 +3,5 @@ apply from: '../common_java_app.gradle'
 dependencies {
     api project(":polkaj-scale")
     api project(":polkaj-common-types")
+    testImplementation 'org.testng:testng:7.1.0'
 }

polkaj-scale-types/src/main/java/io/emeraldpay/polkaj/scaletypes/Result.java

@@ -0,0 +1,44 @@
+package io.emeraldpay.polkaj.scaletypes;
+
+
+public class Result<T, E> {
+
+    public enum ResultMode {
+        OK((byte) 0), ERR((byte) 1);
+        private byte value;
+
+        ResultMode(byte value) {
+            this.value = value;
+        }
+
+        public byte getValue() {
+            return this.value;
+        }
+    }
+
+    T ok;
+    E error;
+    ResultMode mode;
+
+    public Result(ResultMode mode, T ok, E error) {
+        this.mode = mode;
+        this.ok = ok;
+        this.error = error;
+    }
+
+    public boolean isOk() {
+        return mode == ResultMode.OK;
+    }
+
+    public boolean isError() {
+        return mode == ResultMode.ERR;
+    }
+
+    public T getOkValue() {
+        return ok;
+    }
+
+    public E getErrorValue() {
+        return error;
+    }
+}

polkaj-scale-types/src/main/java/io/emeraldpay/polkaj/scaletypes/ResultReader.java

@@ -0,0 +1,21 @@
+package io.emeraldpay.polkaj.scaletypes;
+
+import io.emeraldpay.polkaj.scale.ScaleCodecReader;
+import io.emeraldpay.polkaj.scale.ScaleReader;
+
+public class ResultReader<T, E> {
+    static final String unsupportedValueMessage = "Reading unsupported result mode value";
+
+    public Result<T, E> readResult(ScaleCodecReader reader, ScaleReader<T> okScaleReader, ScaleReader<E> errorScaleReader) {
+        byte mode = reader.readByte();
+        if (mode == Result.ResultMode.OK.getValue()) {
+            T ok = reader.read(okScaleReader);
+            return new Result(Result.ResultMode.OK, ok, null);
+        }
+        if (mode == Result.ResultMode.ERR.getValue()) {
+            E error = reader.read(errorScaleReader);
+            return new Result(Result.ResultMode.ERR, null, error);
+        }
+        throw new IllegalStateException(unsupportedValueMessage);
+    }
+}

polkaj-scale-types/src/main/java/io/emeraldpay/polkaj/scaletypes/ResultWriter.java

@@ -0,0 +1,18 @@
+package io.emeraldpay.polkaj.scaletypes;
+
+import io.emeraldpay.polkaj.scale.ScaleCodecWriter;
+import io.emeraldpay.polkaj.scale.ScaleWriter;
+
+import java.io.IOException;
+
+public class ResultWriter<T, E> {
+    public void writeResult(ScaleCodecWriter writer, ScaleWriter<T> okScaleWriter,
+                            ScaleWriter<E> errorScaleWriter, Result<T, E> result) throws IOException {
+        writer.writeByte(result.mode.getValue());
+        if (result.mode == Result.ResultMode.OK) {
+            writer.write(okScaleWriter, result.ok);
+            return;
+        }
+        writer.write(errorScaleWriter, result.error);
+    }
+}

polkaj-scale-types/src/test/java/io/emeraldpay/polkaj/scaletypes/EncodeDecodeResult.java

@@ -0,0 +1,34 @@
+package io.emeraldpay.polkaj.scaletypes;
+
+import io.emeraldpay.polkaj.scale.ScaleCodecReader;
+import io.emeraldpay.polkaj.scale.ScaleCodecWriter;
+import org.testng.annotations.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class EncodeDecodeResult {
+
+    @Test
+    public void EncodeDecodeResult() {
+        Result<Integer, Integer> dataToEncode = new Result<>(Result.ResultMode.OK, 10, 5);
+        ByteArrayOutputStream buf = new ByteArrayOutputStream();
+        try (ScaleCodecWriter writer = new ScaleCodecWriter(buf)) {
+            ResultWriter<Integer, Integer> resultWriter = new ResultWriter();
+            resultWriter.writeResult(writer, ScaleCodecWriter::writeCompact, ScaleCodecWriter::writeCompact, dataToEncode);
+
+            byte[] decodeBuf = buf.toByteArray();
+            ScaleCodecReader reader = new ScaleCodecReader(decodeBuf);
+            ResultReader<Integer, Integer> resultReader = new ResultReader<>();
+            Result<Integer, Integer> result = resultReader.readResult(reader, ScaleCodecReader::readCompactInt, ScaleCodecReader::readCompactInt);
+
+            assertEquals(dataToEncode.mode, result.mode);
+            assertEquals(dataToEncode.getOkValue(), result.getOkValue());
+            assertEquals(null, result.getErrorValue());
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}