From c4d22c44f1fb184eb31ed47b43e882ec6a0d0d00 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Wed, 26 Aug 2026 20:31:49 +0200
Subject: [PATCH] feat(core): wire emulator system bus and component
 integration

---
 src/GameBoy.Core/Emulator.cs | 109 +++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 src/GameBoy.Core/Emulator.cs

diff --git a/src/GameBoy.Core/Emulator.cs b/src/GameBoy.Core/Emulator.cs
new file mode 100644
index 0000000..e427ee7
--- /dev/null
+++ b/src/GameBoy.Core/Emulator.cs
@@ -0,0 +1,109 @@
+using GameBoy.Audio;
+using GameBoy.Cpu;
+using GameBoy.Input;
+using GameBoy.Memory;
+using GameBoy.Serial;
+using GameBoy.Timing;
+using GameBoy.Video;
+using CpuCore = GameBoy.Cpu.Cpu;
+using CartridgeInfo = GameBoy.Cartridge.Cartridge;
+
+namespace GameBoy
+{
+    public sealed partial class Emulator : ISystemBus
+    {
+        public const int ScreenWidth = Ppu.ScreenWidth;
+        public const int ScreenHeight = Ppu.ScreenHeight;
+
+        private const int CyclesPerFrame = 70224;
+
+        private readonly InterruptController interrupts = new InterruptController();
+        private readonly Ppu ppu;
+        private readonly Timer timer;
+        private readonly Joypad joypad;
+        private readonly SerialPort serial;
+        private readonly Apu apu;
+        private readonly Mmu mmu;
+        private readonly OamDma dma;
+        private readonly CpuCore cpu;
+
+        public CpuCore Cpu => cpu;
+        public Ppu Ppu => ppu;
+        public Joypad Joypad => joypad;
+        public CartridgeInfo Cartridge { get; }
+        public byte[] Framebuffer => ppu.Framebuffer;
+        public string SerialOutput => serial.Output;
+        public InterruptController Interrupts => interrupts;
+        public long TotalCycles { get; private set; }
+
+        public Emulator(byte[] rom)
+        {
+            Cartridge = new CartridgeInfo(rom);
+            ppu = new Ppu(interrupts);
+            timer = new Timer(interrupts);
+            joypad = new Joypad(interrupts);
+            serial = new SerialPort(interrupts);
+            apu = new Apu();
+            mmu = new Mmu(Cartridge, ppu, timer, joypad, serial, apu, interrupts);
+            dma = new OamDma(mmu, ppu);
+            mmu.Dma = dma;
+            cpu = new CpuCore(this);
+
+            cpu.ResetPostBoot();
+            InitPostBootIo();
+        }
+
+        private void InitPostBootIo()
+        {
+            ppu.WriteRegister(0xFF47, 0xFC);
+            ppu.WriteRegister(0xFF48, 0xFF);
+            ppu.WriteRegister(0xFF49, 0xFF);
+            ppu.WriteRegister(0xFF40, 0x91);
+        }
+
+        byte ISystemBus.Read(ushort address)
+        {
+            Tick4();
+            return mmu.Read(address);
+        }
+
+        void ISystemBus.Write(ushort address, byte value)
+        {
+            Tick4();
+            mmu.Write(address, value);
+        }
+
+        public void Tick4()
+        {
+            for (int i = 0; i < 4; i++)
+            {
+                timer.Step();
+                ppu.Step();
+                dma.Step();
+            }
+            apu.Step(4);
+            Cartridge.Step(4);
+            TotalCycles += 4;
+        }
+
+        public void StepInstruction()
+        {
+            cpu.Step();
+        }
+
+        public void RunFrame()
+        {
+            ppu.ConsumeFrame();
+            long deadline = TotalCycles + CyclesPerFrame * 2;
+            while (!ppu.FrameReady && TotalCycles < deadline)
+                cpu.Step();
+        }
+
+        public void RunCycles(long cycles)
+        {
+            long deadline = TotalCycles + cycles;
+            while (TotalCycles < deadline)
+                cpu.Step();
+        }
+    }
+}