warrior.js

const MAX_HP = 20;

const State = {
  last: {
    HP: MAX_HP,
    action: "none"
  }
};

const Utility = {
  walkForward: {
    scorer: (warrior) => warrior.feel().isEmpty() ? 0.5 : 0,
    do: (warrior) => warrior.walk()
  },
  walkBackward: {
    scorer: (warrior) => {
      const missingHP = (1 - warrior.health() / MAX_HP)
      return warrior.feel().isUnit() && missingHP >= 0.5 ? 1 : 0;
    },
    do: (warrior) => warrior.walk("backward")
  },
  attack : {
    scorer: (warrior) => warrior.feel().getUnit().isEnemy() ? 0.5 : 0,
    do : (warrior) => warrior.attack()
  },
  heal : {
    scorer: (warrior) => {
      const health = warrior.health();
      const facing = warrior.feel();

      // fak, healing isn't working
      if(State.last.action === "heal" && State.last.HP < health) {
        return 0;
      }

      if(health < MAX_HP && facing.isEmpty()) {
        return 0.6;
      }

      return 0;
    },
    do: (warrior) => warrior.rest()
  }
};

const utilitySorter = (a, b) => a.score > b.score ? -1 : 1;

class Player {
  playTurn(warrior) {
    this.consider(warrior);
  }

  consider(warrior) {
    const feel = warrior.feel();
    const scores = Object.keys(Utility).map((key) => Object.assign(
        { key, score: Utility[key].scorer(warrior) },
        Utility[key],
    ));

    scores.sort(utilitySorter);

    scores[0].do(warrior);
    State.last.hp = warrior.health();
    State.last.action = scores[0].key;
  }
}