From c8db7d6e68cfef7d83d318cbfe00f4e75461e27e Mon Sep 17 00:00:00 2001
From: Franco Colmenarez <info@francoacg.com>
Date: Sun, 2 Jul 2023 20:24:58 -0500
Subject: [PATCH] get_bg_modes function

---
 snes-core/src/cpu/bus.rs       |  16 ++---
 snes-core/src/ppu/registers.rs | 110 +++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+), 12 deletions(-)

diff --git a/snes-core/src/cpu/bus.rs b/snes-core/src/cpu/bus.rs
index 576714b..0ebb12f 100644
--- a/snes-core/src/cpu/bus.rs
+++ b/snes-core/src/cpu/bus.rs
@@ -111,21 +111,13 @@ mod bus_tests {
         assert_eq!(Bus::map_address(0xBF21FF), MemoryMap::PPU);
 
         assert_eq!(Bus::map_address(0x004200), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x0042FF), MemoryMap::CPU);
+        assert_eq!(Bus::map_address(0x00420F), MemoryMap::CPU);
         assert_eq!(Bus::map_address(0x3F4200), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x3F42FF), MemoryMap::CPU);
+        assert_eq!(Bus::map_address(0x3F420F), MemoryMap::CPU);
         assert_eq!(Bus::map_address(0x804200), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x8042FF), MemoryMap::CPU);
+        assert_eq!(Bus::map_address(0x80420F), MemoryMap::CPU);
         assert_eq!(Bus::map_address(0xBF4200), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0xBF42FF), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x004300), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x0043FF), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x3F4300), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x3F43FF), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x804300), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0x8043FF), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0xBF4300), MemoryMap::CPU);
-        assert_eq!(Bus::map_address(0xBF43FF), MemoryMap::CPU);
+        assert_eq!(Bus::map_address(0xBF420F), MemoryMap::CPU);
 
         assert_eq!(Bus::map_address(0x004016), MemoryMap::Joypad);
         assert_eq!(Bus::map_address(0x004017), MemoryMap::Joypad);
diff --git a/snes-core/src/ppu/registers.rs b/snes-core/src/ppu/registers.rs
index aac6fa9..b6dc176 100644
--- a/snes-core/src/ppu/registers.rs
+++ b/snes-core/src/ppu/registers.rs
@@ -103,6 +103,16 @@ impl BgSize {
     }
 }
 
+#[derive(Debug, PartialEq, Copy, Clone)]
+pub enum BgMode{
+    Color2BPP,
+    Color4BPP,
+    Color8BPP,
+    OffsetPerTile,
+    ExtBg,
+}
+
+
 #[derive(Debug, Copy, Clone)]
 pub enum Background {
     Bg1,
@@ -172,6 +182,61 @@ impl PPURegisters {
         }
     }
 
+    pub fn get_bg_modes(&self) -> (Option<BgMode>, Option<BgMode>, Option<BgMode>, Option<BgMode>) {
+        let byte = self.read(BGMODE);
+        match byte & 0b111 {
+            0 => (
+                Some(BgMode::Color2BPP),
+                Some(BgMode::Color2BPP),
+                Some(BgMode::Color2BPP),
+                Some(BgMode::Color2BPP),
+            ),
+            1 => (
+                Some(BgMode::Color4BPP),
+                Some(BgMode::Color4BPP),
+                Some(BgMode::Color2BPP),
+                None,
+            ),
+            2 => (
+                Some(BgMode::Color4BPP),
+                Some(BgMode::Color4BPP),
+                Some(BgMode::OffsetPerTile),
+                None,
+            ),
+            3 => (
+                Some(BgMode::Color8BPP),
+                Some(BgMode::Color4BPP),
+                None,
+                None,
+            ),
+            4 => (
+                Some(BgMode::Color8BPP),
+                Some(BgMode::Color2BPP),
+                Some(BgMode::OffsetPerTile),
+                None,
+            ),
+            5 => (
+                Some(BgMode::Color4BPP),
+                Some(BgMode::Color2BPP),
+                None,
+                None,
+            ),
+            6 => (
+                Some(BgMode::Color4BPP),
+                None,
+                Some(BgMode::OffsetPerTile),
+                None,
+            ),
+            7 => (
+                Some(BgMode::Color8BPP),
+                Some(BgMode::ExtBg),
+                None,
+                None,
+            ),
+            _ => unreachable!(),
+        }
+    }
+
     pub fn is_vblanking(&self) -> bool {
         if self.h_count >= 1 && self.h_count <= 224 {
             return false
@@ -201,6 +266,51 @@ mod ppu_registers_test {
         assert_eq!(registers.get_bg_size(Background::Bg1), BgSize::T32x64);
     }
 
+    #[test]
+    fn test_get_bg_modes() {
+        let mut registers = PPURegisters::new();
+        registers.write(BGMODE, 0);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color2BPP), Some(BgMode::Color2BPP), Some(BgMode::Color2BPP), Some(BgMode::Color2BPP)),
+        );
+        registers.write(BGMODE, 1);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color4BPP), Some(BgMode::Color4BPP), Some(BgMode::Color2BPP), None),
+        );
+        registers.write(BGMODE, 2);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color4BPP), Some(BgMode::Color4BPP), Some(BgMode::OffsetPerTile), None),
+        );
+        registers.write(BGMODE, 3);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color8BPP), Some(BgMode::Color4BPP), None, None),
+        );
+        registers.write(BGMODE, 4);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color8BPP), Some(BgMode::Color2BPP), Some(BgMode::OffsetPerTile), None),
+        );
+        registers.write(BGMODE, 5);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color4BPP), Some(BgMode::Color2BPP), None, None),
+        );
+        registers.write(BGMODE, 6);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color4BPP), None, Some(BgMode::OffsetPerTile), None),
+        );
+        registers.write(BGMODE, 7);
+        assert_eq!(
+            registers.get_bg_modes(),
+            (Some(BgMode::Color8BPP), Some(BgMode::ExtBg), None, None),
+        );
+    }
+
     #[test]
     fn test_is_vblanking() {
         let mut registers = PPURegisters::new();