From 2902842fcc062552cf6ca50896b8c62a587df7ea Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Mon, 18 Apr 2022 17:26:11 -0400
Subject: [PATCH] Now the machine supports PEEK/POKE to RAM.

---
 src/buttons.js       | 36 ++++++++++++++++++++++++++++--------
 tests/basic_tests.js | 36 ++++++++++++++++++++++--------------
 2 files changed, 50 insertions(+), 22 deletions(-)

diff --git a/src/buttons.js b/src/buttons.js
index 6eb6a31..1640178 100644
--- a/src/buttons.js
+++ b/src/buttons.js
@@ -1,14 +1,13 @@
-
-
 export class ButtonMachine {
 
   constructor(code) {
     this.stack = [];
+    this.ram = new Array(64).fill(0);
     this.ip = 0;
     this.code = code;
-    this.max_clicks = 128;
+    this.max_clicks = 256;
     this.tick = 0;
-    this.registers = {};
+    this.registers = {'IX': 0};
     this.error = '';
     this.error_line = 0;
     this.halted = false;
@@ -29,7 +28,7 @@ export class ButtonMachine {
 
   /* Need to use a function because @babel/plugin-proposal-class-properties */
   static register_names() {
-    return ['AX', 'BX', 'CX', 'DX'];
+    return ['AX', 'BX', 'CX', 'DX', 'IX'];
   }
 
   static operations() {
@@ -160,6 +159,29 @@ export class ButtonMachine {
     this.next();
   }
 
+  op_PEEK(inc) {
+    let index = Math.abs(this.registers.IX) % this.ram.length;
+    this.stack.push(this.ram[index]);
+    if(inc) this.registers.IX = index + inc;
+    this.next();
+  }
+
+  op_POKE(inc) {
+    let index = Math.abs(this.registers.IX) % this.ram.length;
+    this.ram[index] = this.stack_top;
+    if(inc) this.registers.IX = index + inc;
+    this.next();
+  }
+
+  op_SWAP() {
+    if(!this.assert(this.stack.length >= 2, "Not enough elements on the stack to swap.")) return;
+
+    let [top, n] = [this.stack.pop(), this.stack.pop()];
+    this.stack.push(top);
+    this.stack.push(n);
+    this.next();
+  }
+
   get running() {
     return this.halted === false && this.tick < this.max_clicks && this.ip < this.code.length && this.cur_op !== undefined;
   }
@@ -192,6 +214,4 @@ export class ButtonMachine {
   }
 }
 
-export default {
-  ButtonMachine
-};
+export default { ButtonMachine };
diff --git a/tests/basic_tests.js b/tests/basic_tests.js
index fd2dae9..3b4a988 100644
--- a/tests/basic_tests.js
+++ b/tests/basic_tests.js
@@ -1,17 +1,25 @@
-import { ButtonMachine } from "../src/buttons.js";
+import { ButtonMachine } from '../src/buttons.js';
 
-const cpu = new ButtonMachine([
-  ["PUSH", 10],
-  ["PUSH", 1],
-  ["SUB"],
-  ["JZ", 5],
-  ["JUMP", 1],
-  ["PUSH", 100],
-  ["HALT"]
-]);
+let code = [
+  ['PUSH', -10], // start at -10
+  ['PUSH', 1],   // increment by 1
+  ['ADD'],
+  ['POKE', 1],   // put it in ram, IX++
+  ['JNZ', 1],    // the previous test fails so it jumps to loop again
+  ['STOR', 'IX'],
+  ['POP'],
+  ['PEEK', 1],
+  ['JNZ', 6],
+];
 
-cpu.run();
+let machine = new ButtonMachine(code);
 
-console.log("STACK TOP", cpu.stack_top);
-console.log("REGISTER", cpu.register_entries);
-console.log("STACK", cpu.stack);
+const ops = ButtonMachine.operations();
+const registers = ButtonMachine.register_names();
+
+machine.run();
+
+console.log("STACK TOP", machine.stack_top);
+console.log("REGISTER", machine.register_entries);
+console.log("STACK", machine.stack);
+console.log("RAM", machine.ram);