From 95b769d227028087edb721954d16264811dc2b0d Mon Sep 17 00:00:00 2001
From: Denis Nutiu <denis.nutiu@gmail.com>
Date: Wed, 4 Dec 2024 00:07:33 +0200
Subject: [PATCH] decode instruction using pattern matching

---
 src/emulator.rs    | 19 ++++++-------------
 src/instruction.rs | 40 ++++++++++++++++++++++++++++++++++++++--
 2 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/src/emulator.rs b/src/emulator.rs
index d71ca42..c904803 100644
--- a/src/emulator.rs
+++ b/src/emulator.rs
@@ -1,5 +1,5 @@
 use crate::display::Display;
-use crate::instruction::Instruction;
+use crate::instruction::{Instruction, ProcessorInstruction};
 use crate::stack::Stack;
 use anyhow::anyhow;
 use log::{debug, info, warn};
@@ -112,18 +112,15 @@ where
     }
 
     fn execute_instruction(&mut self, instruction: Instruction) -> Result<(), anyhow::Error> {
-        match instruction.raw() {
-            // Clear Display
-            0x00E0 => {
+        match instruction.processor_instruction() {
+            ProcessorInstruction::ClearScreen => {
                 info!("clear display");
                 self.display.clear()
             }
-            // Jump
-            0x1000..=0x1FFF => {
-                info!("jump to {}", instruction);
+            ProcessorInstruction::Jump(address) => {
+                todo!("implement jump")
             }
-            // Unknown instruction
-            _ => {
+            ProcessorInstruction::UnknownInstruction => {
                 warn!("Unknown instruction: {:04x}, skipping.", instruction);
             }
         }
@@ -142,10 +139,6 @@ where
         ]))
     }
 
-    fn decode_instruction(&mut self, _instruction: Instruction) -> Result<(), anyhow::Error> {
-        todo!("must implement");
-    }
-
     /// Loads the ROM found at the rom path in the emulator's RAM memory.
     fn load_rom<T>(&mut self, rom_file: T) -> Result<(), anyhow::Error>
     where
diff --git a/src/instruction.rs b/src/instruction.rs
index 9993145..bcf0c6e 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -1,23 +1,59 @@
 use std::fmt;
 use std::fmt::{Display, Formatter, LowerHex};
 
+#[derive(Debug, Clone, Copy)]
+pub enum ProcessorInstruction {
+    /// Clears the screen
+    ClearScreen,
+    /// Jumps to a given address
+    Jump(u16),
+    UnknownInstruction
+}
+
 #[derive(Debug)]
 pub struct Instruction {
     data: u16,
+    processor_instruction: ProcessorInstruction
 }
 
 impl Instruction {
     /// Creates a new instruction instance.
     pub(crate) fn new(data: [u8; 2]) -> Self {
+        let data = (data[0] as u16) << 8u8 | (data[1] as u16);
         Instruction {
-            data: (data[0] as u16) << 8u8 | (data[1] as u16),
+            data,
+            processor_instruction: Instruction::decode_instruction(data),
         }
     }
-
     /// raw returns the raw instruction data.
     pub fn raw(&self) -> u16 {
         self.data
     }
+
+    /// Returns the processor instruction.
+    pub fn processor_instruction(&self) -> ProcessorInstruction {
+        self.processor_instruction
+    }
+
+    /// Decodes the raw instruction data into a processor instruction.
+    fn decode_instruction(data: u16) -> ProcessorInstruction {
+        match data {
+            // Clear Display
+            0x00E0 => {
+                ProcessorInstruction::ClearScreen
+            }
+            // Jump
+            0x1000..=0x1FFF => {
+                ProcessorInstruction::Jump(data & 0xFFF)
+            }
+            // Unknown instruction
+            _ => {
+                ProcessorInstruction::UnknownInstruction
+            }
+        }
+    }
+
+
 }
 
 impl Display for Instruction {