package com.loomcom.symon;

import com.loomcom.symon.devices.Memory;
import com.loomcom.symon.exceptions.MemoryAccessException;

import junit.framework.TestCase;

public class CpuZeroPageYModeTest extends TestCase {

    protected Cpu    cpu;
    protected Bus    bus;
    protected Memory mem;

    protected void setUp() throws Exception {
        this.cpu = new Cpu();
        this.bus = new Bus(0x0000, 0xffff);
        this.mem = new Memory(0x0000, 0xffff);
        bus.addCpu(cpu);
        bus.addDevice(mem);

        // Load the reset vector.
        bus.write(0xfffc, Bus.DEFAULT_LOAD_ADDRESS & 0x00ff);
        bus.write(0xfffd, (Bus.DEFAULT_LOAD_ADDRESS & 0xff00) >>> 8);

        cpu.reset();
        // Assert initial state
        assertEquals(0, cpu.getAccumulator());
        assertEquals(0, cpu.getXRegister());
        assertEquals(0, cpu.getYRegister());
        assertEquals(0x200, cpu.getProgramCounter());
        assertEquals(0xff, cpu.getStackPointer());
        assertEquals(0x24, cpu.getProcessorStatus());
    }

    /*
    * The following opcodes are tested for correctness in this file:
    *
    * STX - $96
    * LDX - $b6
    *
    */

    /* STX - Store X Register - $96 */

    public void test_STX() throws MemoryAccessException {
        cpu.setYRegister(0x30);
        cpu.setXRegister(0x00);
        bus.loadProgram(0x96, 0x10);  // STX $10,Y
        cpu.step();
        assertEquals(0x00, bus.read(0x40, true));
        // Should have no effect on flags.
        assertFalse(cpu.getZeroFlag());
        assertFalse(cpu.getNegativeFlag());

        cpu.reset();
        cpu.setYRegister(0x30);
        cpu.setXRegister(0x0f);
        bus.loadProgram(0x96, 0x10);  // STX $10,Y
        cpu.step();
        assertEquals(0x0f, bus.read(0x40, true));
        assertFalse(cpu.getZeroFlag());
        assertFalse(cpu.getNegativeFlag());

        cpu.reset();
        cpu.setYRegister(0x30);
        cpu.setXRegister(0x80);
        bus.loadProgram(0x96, 0x10);  // STX $10,Y
        cpu.step();
        assertEquals(0x80, bus.read(0x40, true));
        assertFalse(cpu.getZeroFlag());
        assertFalse(cpu.getNegativeFlag());
    }

    /* LDX - Load X Register - $b6 */

    public void test_LDX() throws MemoryAccessException {
        bus.write(0x40, 0x00);
        bus.write(0x41, 0x0f);
        bus.write(0x42, 0x80);

        bus.loadProgram(0xb6, 0x10,
                        0xb6, 0x11,
                        0xb6, 0x12);

        cpu.setYRegister(0x30);

        cpu.step();
        assertEquals(0x00, cpu.getXRegister());
        assertTrue(cpu.getZeroFlag());
        assertFalse(cpu.getNegativeFlag());

        cpu.step();
        assertEquals(0x0f, cpu.getXRegister());
        assertFalse(cpu.getZeroFlag());
        assertFalse(cpu.getNegativeFlag());

        cpu.step();
        assertEquals(0x80, cpu.getXRegister());
        assertFalse(cpu.getZeroFlag());
        assertTrue(cpu.getNegativeFlag());
    }

}