feat(2020-day-08): run an entire brogram, breaking on infinite loop

Author: developher-net

2020/day-08/runProgram.js

@@ -1,4 +1,4 @@
-const log = []
+let log = []
 log[0] = [1]
 log[1] = [2, 8]
 log[2] = [3]
@@ -7,7 +7,7 @@ log[4] = [7]
 log[6] = [4]
 log[7] = [5]
 
-const program = [
+let program = [
   'nop +0',
   'acc +1',
   'jmp +4',
@@ -21,6 +21,7 @@ const program = [
 
 let accumulator = 0
 let position = 1
+let breaker = false
 
 /**
  * API of commands this language supports
@@ -61,9 +62,27 @@ const execInstruction = (inst, instKey = 0, evKey = 0) => {
   // Support jumping by passing back next
   position = api[cmd](instKey, arg)
   logEvent({ instKey, evKey })
+  // break out when reaching an infinite loop
+  if (log[instKey].length > 1) {
+    breaker = true
+  }
   return position
 }
 
+const run = (insts) => {
+  program = insts
+  accumulator = 0
+  position = 0
+  log = []
+  let evKey = 0
+
+  // eslint-disable-next-line no-unmodified-loop-condition
+  while (breaker === false) {
+    evKey++
+    execInstruction(program[position], position, evKey)
+  }
+}
+
 const formatLogRow = (command, idx, program) => {
   let countStr
   if (!log[idx]) {
@@ -111,7 +130,7 @@ const logEvent = ({ instKey, evKey }) => {
 }
 
 module.exports = {
-  run: console.log('run'),
+  run,
   getAccumulator: () => accumulator,
   getPosition: () => position,
   execInstruction,

2020/day-08/runProgram.test.js

@@ -2,6 +2,17 @@
 const { expect } = require('chai')
 const { run, getPosition, getAccumulator, execInstruction, parseCommand, logEvent, displayLog } = require('./runProgram')
 
+const exampleProgram = [
+  'nop +0',
+  'acc +1',
+  'jmp +4',
+  'acc +3',
+  'jmp -3',
+  'acc -99',
+  'acc +1',
+  'jmp -4',
+  'acc +6'
+]
 const exampleLog = `
 nop +0  | 1
 acc +1  | 2, 8(!)
@@ -15,12 +26,6 @@ acc +6  | `
 
 describe('--- Day 8: Handheld Halting ---', () => {
   describe('Part 1', () => {
-    xdescribe('run()', () => {
-      it('executes the steps of a given program', () => {
-        run()
-        expect(false).to.equal(true)
-      })
-    })
     describe('execInstruction()', () => {
       it('executes a specified command', () => {
         expect(getPosition()).to.equal(1)
@@ -84,5 +89,14 @@ describe('--- Day 8: Handheld Halting ---', () => {
         )
       })
     })
+    describe('run()', () => {
+      it('executes the steps of a given program', () => {
+        run(exampleProgram)
+        // stops at infinite loop
+        expect(getPosition()).to.equal(2)
+        expect(getAccumulator()).to.equal(6)
+        expect(displayLog()).to.equal(exampleLog)
+      })
+    })
   })
 })