From ece218d3cec9abf815096a0fdd21853e71820ebc Mon Sep 17 00:00:00 2001
From: Isaac Marovitz <isaacryu@icloud.com>
Date: Fri, 15 Dec 2023 00:18:52 -0500
Subject: [PATCH] MBC2

---
 src/mbc/mbc2.rs | 62 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/mbc/mod.rs  |  3 ++-
 src/mmu.rs      |  2 ++
 3 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 src/mbc/mbc2.rs

diff --git a/src/mbc/mbc2.rs b/src/mbc/mbc2.rs
new file mode 100644
index 0000000..76a2131
--- /dev/null
+++ b/src/mbc/mbc2.rs
@@ -0,0 +1,62 @@
+use crate::mbc::mode::MBC;
+use crate::memory::Memory;
+
+pub struct MBC2 {
+    rom: Vec<u8>,
+    ram: Vec<u8>,
+    ram_enabled: bool,
+    rom_bank: usize
+}
+
+impl Memory for MBC2 {
+    fn read(&self, a: u16) -> u8 {
+        match a {
+            0x0000..=0x3FFF => self.rom[a as usize],
+            0x4000..=0x7FFF => self.rom[a as usize + self.rom_bank * 0x4000 - 0x4000],
+            0xA000..=0xA1FF => {
+                if self.ram_enabled {
+                    self.ram[(a - 0xA000) as usize]
+                } else {
+                    0x00
+                }
+            }
+            _ => panic!("Read to unsupported MBC2 address ({:#06x})!", a),
+        }
+    }
+
+    fn write(&mut self, a: u16, v: u8) {
+        let v = v & 0x0F;
+        match a {
+            0x0000..=0x1FFF => {
+                if a & 0x0100 == 0 {
+                    self.ram_enabled = v == 0x0A;
+                }
+            },
+            0x2000..=0x3FFF => {
+                if a & 0x0100 != 0 {
+                    self.rom_bank = v as usize;
+                }
+            },
+            0xA000..=0xA1FF => {
+                if self.ram_enabled {
+                    self.ram[(a - 0xa000) as usize] = v
+                }
+            }
+            _ => panic!("Write to unsupported MBC2 address ({:#06x})!", a),
+        }
+    }
+}
+
+impl MBC for MBC2 { }
+
+impl MBC2 {
+    pub fn new(rom: Vec<u8>) -> Self {
+        Self {
+            rom,
+            ram: vec![0x00; 512],
+            ram_enabled: false,
+            rom_bank: 1
+        }
+    }
+}
+
diff --git a/src/mbc/mod.rs b/src/mbc/mod.rs
index dfc7870..b996342 100644
--- a/src/mbc/mod.rs
+++ b/src/mbc/mod.rs
@@ -2,4 +2,5 @@ pub mod mode;
 pub mod rom_only;
 pub mod mbc1;
 pub mod mbc3;
-pub mod mbc5;
\ No newline at end of file
+pub mod mbc5;
+pub mod mbc2;
\ No newline at end of file
diff --git a/src/mmu.rs b/src/mmu.rs
index a100050..870e69a 100644
--- a/src/mmu.rs
+++ b/src/mmu.rs
@@ -2,6 +2,7 @@ use bitflags::bitflags;
 use crate::mbc::mode::{MBC, MBCMode};
 use crate::mbc::rom_only::ROMOnly;
 use crate::mbc::mbc1::MBC1;
+use crate::mbc::mbc2::MBC2;
 use crate::mbc::mbc3::MBC3;
 use crate::mbc::mbc5::MBC5;
 use crate::memory::Memory;
@@ -38,6 +39,7 @@ impl MMU {
         let mbc: Box<dyn MBC> = match mbc_mode {
             MBCMode::RomOnly => Box::new(ROMOnly::new(rom)),
             MBCMode::MBC1 => Box::new(MBC1::new(rom)),
+            MBCMode::MBC2 => Box::new(MBC2::new(rom)),
             MBCMode::MBC3 => Box::new(MBC3::new(rom)),
             MBCMode::MBC5 => Box::new(MBC5::new(rom)),
             v => panic!("Unsupported MBC type! {:}", v)