From bc56fca299f6320f36fb1be83c1bdff2f4a06452 Mon Sep 17 00:00:00 2001
From: Denis Nutiu <denis.nutiu@gmail.com>
Date: Wed, 4 Dec 2024 22:34:19 +0200
Subject: [PATCH] implement Jump, SetRegister, AddValueToRegister

---
 src/emulator.rs    | 22 ++++++++++++++++++----
 src/instruction.rs | 41 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/src/emulator.rs b/src/emulator.rs
index c904803..bc61e26 100644
--- a/src/emulator.rs
+++ b/src/emulator.rs
@@ -2,7 +2,7 @@ use crate::display::Display;
 use crate::instruction::{Instruction, ProcessorInstruction};
 use crate::stack::Stack;
 use anyhow::anyhow;
-use log::{debug, info, warn};
+use log::{debug, info, trace, warn};
 use std::fs::File;
 use std::io::Read;
 use std::path::Path;
@@ -98,12 +98,17 @@ where
 
     /// Emulation loop executes the fetch -> decode -> execute pipeline
     fn emulation_loop<T>(&mut self) -> Result<(), anyhow::Error> {
+        let mut last_program_counter = self.program_counter;
         loop {
             // fetch instruction
             let instruction = self.fetch_instruction()?;
             self.program_counter += 2;
 
-            debug!("PC={} {:04x}", self.program_counter, instruction);
+            if last_program_counter != self.program_counter {
+                debug!("PC={} {:04x}", self.program_counter, instruction);
+            }
+            last_program_counter = self.program_counter;
+
 
             // decode & execute
             self.execute_instruction(instruction)?;
@@ -114,11 +119,20 @@ where
     fn execute_instruction(&mut self, instruction: Instruction) -> Result<(), anyhow::Error> {
         match instruction.processor_instruction() {
             ProcessorInstruction::ClearScreen => {
-                info!("clear display");
+                trace!("Clear display");
                 self.display.clear()
             }
             ProcessorInstruction::Jump(address) => {
-                todo!("implement jump")
+                trace!("Jump to address {:04x}", address);
+                self.program_counter = address
+            }
+            ProcessorInstruction::SetRegister(register, data) => {
+                trace!("Set register {} to data {:04x}", register, data);
+                self.registers[register] = data
+            }
+            ProcessorInstruction::AddValueToRegister(register, data) => {
+                trace!("Add to register {} data {:04x}", register, data);
+                self.registers[register] += data
             }
             ProcessorInstruction::UnknownInstruction => {
                 warn!("Unknown instruction: {:04x}, skipping.", instruction);
diff --git a/src/instruction.rs b/src/instruction.rs
index bcf0c6e..32f2af1 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -1,5 +1,17 @@
 use std::fmt;
 use std::fmt::{Display, Formatter, LowerHex};
+use log::info;
+/*
+Although every instruction will have a first nibble that tells you what kind of instruction it is,
+the rest of the nibbles will have different meanings. To differentiate these meanings,
+we usually call them different things, but all of them can be any hexadecimal number from 0 to F:
+
+    X: The second nibble. Used to look up one of the 16 registers (VX) from V0 through VF.
+    Y: The third nibble. Also used to look up one of the 16 registers (VY) from V0 through VF.
+    N: The fourth nibble. A 4-bit number.
+    NN: The second byte (third and fourth nibbles). An 8-bit immediate number.
+    NNN: The second, third and fourth nibbles. A 12-bit immediate memory address.
+ */
 
 #[derive(Debug, Clone, Copy)]
 pub enum ProcessorInstruction {
@@ -7,6 +19,10 @@ pub enum ProcessorInstruction {
     ClearScreen,
     /// Jumps to a given address
     Jump(u16),
+    /// Sets the register in the first argument to the given value
+    SetRegister(usize, u8),
+    /// Adds the value to the register
+    AddValueToRegister(usize, u8),
     UnknownInstruction
 }
 
@@ -44,7 +60,17 @@ impl Instruction {
             }
             // Jump
             0x1000..=0x1FFF => {
-                ProcessorInstruction::Jump(data & 0xFFF)
+                // 1NNN
+                ProcessorInstruction::Jump(Self::grab_inner_data(data))
+            }
+            // Set Register
+            0x6000..=0x6FFF => {
+                // 6XNN
+                ProcessorInstruction::SetRegister(Self::grab_first_nibble(data), Self::grab_last_byte(data))
+            }
+            0x7000..0x7FFF => {
+                // 7XNN
+                ProcessorInstruction::AddValueToRegister(Self::grab_first_nibble(data), Self::grab_last_byte(data))
             }
             // Unknown instruction
             _ => {
@@ -53,7 +79,20 @@ impl Instruction {
         }
     }
 
+    /// Grabs the inner data from the data, ignores the opcode.
+    fn grab_inner_data(data: u16) -> u16 {
+        data & 0x0FFF
+    }
 
+    /// Grabs the last byte from the data.
+    fn grab_last_byte(data: u16) -> u8 {
+        (data & 0x00FF) as u8
+    }
+
+    /// Grabs the first nibble from the data.
+    fn grab_first_nibble(data: u16) -> usize {
+        ((data & 0x0F00) >> 8) as usize
+    }
 }
 
 impl Display for Instruction {