Pixels Camp Challenge #2 - Factor-out redundancy

pixelscamp2016-challenge2-2.js

var c = (program = '') => {
  var register = undefined;
  var memory = [0];
  var memory_pointer = 0;
  var instruction_pointer = 0;
  var find_matching = (start, stop, direction) => {
      var level = 1;
      instruction_pointer += direction;
      while(level > 0 && instructions[instruction_pointer]) {
        instruction_pointer += direction;
        if (instructions[instruction_pointer] === start) level++;
        if (instructions[instruction_pointer] === stop) level--;
      }
  };
  var commands = {
    moo: () => {
      find_matching('moo', 'MOO', -1);
      instruction_pointer--;
    },
    mOo: () => {
      memory_pointer && memory_pointer--;
    },
    moO: () => {
      memory_pointer++;
      memory[memory_pointer] = memory[memory_pointer] || 0;
    },
    mOO: () => {
      var index = memory[memory_pointer];
      var instruction = tokens[index];
      if (instruction && index != 3) {
        commands[instruction]();
      } else {
        instructions = [];
      }
    },
    Moo: () => {
      if (memory[memory_pointer] === 0) {
        memory[memory_pointer] = input_char();
      } else {
        output_char(String.fromCharCode(memory[memory_pointer]));
      }
    },
    MOo: () => {
      memory[memory_pointer]--;
    },
    MoO: () => {
      memory[memory_pointer]++;
    },
    MOO: () => {
      if (memory[memory_pointer] === 0) {
        find_matching('MOO', 'moo', 1);
      }
    },
    OOO: () => {
      memory[memory_pointer] = 0;
    },
    MMM: () => {
      if(register === undefined) {
        register = memory[memory_pointer];
      } else {
        memory[memory_pointer] = register;
        register = undefined;
      }
    },
    OOM: () => {
      Array.from(memory[memory_pointer]+'').map(output_char);
    },  
    oom: () => {
      memory[memory_pointer] = input_char();
    }
  };
  var tokens = Object.keys(commands);
  var instructions = program.match(new RegExp(tokens.join('|'), 'g')) || [];

  while (instruction_pointer >= 0 && instruction_pointer < instructions.length) {
    var instruction = instructions[instruction_pointer];
    commands[instruction]();
    instruction_pointer++;
  }
};