From a5a18b917dbacda0524ab7800f16a582880d81fa Mon Sep 17 00:00:00 2001
From: Grzegorz Kucmierz <gkucmierz@gmail.com>
Date: Sat, 16 May 2020 19:15:56 +0200
Subject: [PATCH] Assembler interpreter (part II)

---
 assembler-interpreter-part-ii/index.js | 62 ++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 assembler-interpreter-part-ii/index.js

diff --git a/assembler-interpreter-part-ii/index.js b/assembler-interpreter-part-ii/index.js
new file mode 100644
index 0000000..de5af35
--- /dev/null
+++ b/assembler-interpreter-part-ii/index.js
@@ -0,0 +1,62 @@
+// https://www.codewars.com/kata/58e61f3d8ff24f774400002c/javascript
+
+function assemblerInterpreter(program) {
+  const lines = (program
+    .split(/\n/)
+    .map(line => line.replace(/;.*$/, '').trim())
+    .filter(line => line !== ''));
+  const parsed = [];
+  const labels = new Map();
+  let diff = 0;
+  for (i = 0; i < lines.length; ++i) {
+    const tokens = lines[i].split(/[,\s]+/);
+    const m = tokens[0].match(/(\w+)\:/);
+    if (m) {
+      labels.set(m[1], i-diff);
+      ++diff;
+    } else if (tokens[0] === 'msg') {
+      parsed[i-diff] = lines[i].match(/('[^']*')|[a-z0-9_]+/g);
+    } else {
+      parsed[i-diff] = tokens;
+    }
+  }
+  let ip = 0;
+  let cmp;
+  const res = [];
+  const stack = [];
+  const regs = new Map();
+  const constOrVal = n => ((+n) + '') === n ? +n : regs.get(n);
+  const jmpIf = (lbl, cond) => ip = cond ? labels.get(lbl) - 1 : ip;
+  const instr = {
+    mov: (a, b) => regs.set(a, constOrVal(b)),
+    inc: a => regs.set(a, regs.get(a) + 1),
+    dec: a => regs.set(a, regs.get(a) - 1),
+    add: (a, b) => regs.set(a, regs.get(a) + constOrVal(b)),
+    sub: (a, b) => regs.set(a, regs.get(a) - constOrVal(b)),
+    mul: (a, b) => regs.set(a, regs.get(a) * constOrVal(b)),
+    div: (a, b) => regs.set(a, regs.get(a) / constOrVal(b) | 0),
+    jmp: lbl => jmpIf(lbl, true),
+    cmp: (a, b) => cmp = Math.sign(constOrVal(a) - constOrVal(b)),
+    jne: lbl => jmpIf(lbl, cmp !== 0),
+    je: lbl => jmpIf(lbl, cmp === 0),
+    jge: lbl => jmpIf(lbl, cmp >= 0),
+    jg: lbl => jmpIf(lbl, cmp > 0),
+    jle: lbl => jmpIf(lbl, cmp <= 0),
+    jl: lbl => jmpIf(lbl, cmp < 0),
+    call: lbl => (stack.push(ip), jmpIf(lbl, true)),
+    ret: () => ip = stack.pop(),
+    msg: (...args) => res.push(args.map(arg => {
+      const m = arg.match(/^'(.*)'$/);
+      if (m) return m[1];
+      return constOrVal(arg);
+    }).join``)
+  };
+  let cntdwn = 1e6;
+  while (ip < parsed.length && --cntdwn > 0) {
+    const [cmd, ...args] = parsed[ip];
+    if (cmd === 'end') return res.join``;
+    instr[cmd](...args);
+    ++ip;
+  }
+  return -1;
+}