package io.trygvis.btree;

import org.junit.Test;

import java.nio.ByteBuffer;
import java.util.Iterator;

import static io.trygvis.btree.HeapPage.*;
import static org.junit.Assert.*;

public class HeapPageTest {

    int pageSize = 128;

    @Test
    public void testBasic() {
        ByteBuffer buffer = ByteBuffer.allocate(pageSize);

        HeapPage page = HeapPage.blankHeapPage(buffer);
        assertEquals(pageSize - headerSize, page.bytesFree());

        int itemCount = 6;
        byte[] object = new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf};

        for (int i = 0; i < itemCount; i++) {
            page.append(object);
            assertEquals("i=" + i, pageSize - headerSize - (object.length + itemSize) * (i + 1), page.bytesFree());
        }

        try {
            page.append(object);
            fail("Expected PageOverflowException");
        } catch (PageOverflowException e) {
            assertEquals(pageSize - headerSize - itemCount * (object.length + itemSize), e.bytesFree);
            assertEquals(object.length, e.bytesRequested);
        }

        {
            ByteBuffer expectedBuffer = ByteBuffer.allocate(pageSize);
            int position = pageSize - itemCount * (object.length + itemSize);
            expectedBuffer.putInt(position);
            expectedBuffer.position(position);
            for (int i = 0; i < itemCount; i++) {
                expectedBuffer.put(object);
                expectedBuffer.putInt(object.length);
            }
            assertEquals(pageSize, expectedBuffer.position());

            byte[] expectedArray = expectedBuffer.array();
            byte[] actualArray = buffer.array();
            assertArrayEquals(expectedArray, actualArray);
        }

        {
            Iterator<ByteBuffer> it = page.bufferIterator().iterator();
            for (int i = 0; i < itemCount; i++) {
                assertTrue(it.hasNext());
                ByteBuffer bb = it.next();
                assertArrayEquals(object, toArray(bb));
            }
            assertFalse(it.hasNext());
        }
    }

    private byte[] toArray(ByteBuffer bb) {
        byte[] bytes = new byte[bb.limit()];
        bb.get(bytes);
        return bytes;
    }
}