import static org.testng.Assert.assertEquals;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import static java.nio.charset.StandardCharsets.UTF_8;

import org.testng.annotations.Test;

/* @test
 * @summary Test creating a String from a bytebuffer
 * @run testng StringByteBufferConversions 
 */
public class StringByteBufferConversions {

    @Test(expectedExceptions = NullPointerException.class)
    public void nullByteBufferShouldThrowException() {
        // given
        ByteBuffer buffer = null;

        // when
        new String(buffer, 0, 1, UTF_8);
    }

    @Test(expectedExceptions = StringIndexOutOfBoundsException.class)
    public void undersizedByteBufferShouldThrowException() {
        // given
        ByteBuffer buffer = ByteBuffer.allocateDirect(5);

        // when
        new String(buffer, 0, 10, UTF_8);
    }
    
    @Test(expectedExceptions = NullPointerException.class)
    public void nullCharsetShouldThrowException() {
        // given
        ByteBuffer buffer = ByteBuffer.allocateDirect(20);

        // when
        new String(buffer, 0, 10, null);
    }
    
    @Test
    public void heapByteBuffersCanBeConvertedToStrings() {
        // given
        String expected = "Hello World";
        ByteBuffer buffer = ByteBuffer.wrap(expected.getBytes(UTF_8));

        // when
        String str = new String(buffer, 0, buffer.capacity(), UTF_8);

        // then
        assertEquals(str, expected);
    }
    
    @Test
    public void directByteBuffersCanBeConvertedToStrings() {
        // given
        String expected = "Hello World";
        byte[] bytes = expected.getBytes(UTF_8);
        ByteBuffer buffer = ByteBuffer.allocateDirect(bytes.length)
                                      .put(bytes, 0, bytes.length);

        buffer.position(0);

        // when
        String str = new String(buffer, 0, buffer.capacity(), UTF_8);

        // then
        assertEquals(str, expected);
    }
    
    @Test
    public void chunksOfByteBuffersCanBeConvertedToStrings() {
        // given
        String expected = "Hello World";
        byte[] bytes = expected.getBytes(UTF_8);
        int offset = 5;
        int length = offset + bytes.length + 5;
        ByteBuffer buffer = ByteBuffer.allocateDirect(length);
        buffer.position(offset);
        buffer.put(bytes, 0, bytes.length);
        buffer.position(0);

        // when
        String str = new String(buffer, offset, bytes.length, UTF_8);

        // then
        assertEquals(str, expected);
    }
    
    @Test(expectedExceptions = NullPointerException.class)
    public void getBytesThrowsExceptionWithNullBuffer() {
        "".getBytes((ByteBuffer)null, 0, UTF_8);
    }

    @Test(expectedExceptions = NullPointerException.class)
    public void getBytesThrowsExceptionWithNullByteArray() {
        "".getBytes((byte[])null, 0, UTF_8);
    }
    
    @Test(expectedExceptions = NullPointerException.class)
    public void getBytesThrowsExceptionWithNullCharset() {
        byte[] bytes = new byte[16];
        "".getBytes(bytes, 0, null);
    }

    @Test
    public void shouldEncodeStringsOntoByteArrays() {
        byte[] bytes = new byte[11];
        int written = "Hello World".getBytes(bytes, 0, UTF_8);
        assertEquals(written, 11);

        assertEquals(new String(bytes, UTF_8), "Hello World");
    }

    @Test
    public void shouldEncodeStringsOntoByteBuffer() {
        ByteBuffer bytes = ByteBuffer.allocateDirect(12);
        int written = "Hello World".getBytes(bytes, 0, UTF_8);
        assertEquals(written, 11);

        assertEquals(new String(bytes, 0, written, UTF_8), "Hello World");
    }

    @Test
    public void shouldEncodeStringsOntoChunkOfByteArray() {
        byte[] bytes = new byte[20];
        final int offset = 5;
        int written = "Hello World".getBytes(bytes, offset, UTF_8);
        assertEquals(written, 11);

        assertEquals(new String(bytes, offset, written, UTF_8), "Hello World");
    }
    
    @Test
    public void shouldEncodeStringsOntoChunkOfByteBuffer() {
        ByteBuffer bytes = ByteBuffer.allocateDirect(20);
        final int offset = 5;
        int written = "Hello World".getBytes(bytes, offset, UTF_8);
        assertEquals(written, 11);

        assertEquals(new String(bytes, offset, written, UTF_8), "Hello World");
    }

}