'use strict';

const threshold = 0.5;


const move_forward = {
  size: 1,
  propose: (world, agent, head) => {
    if (head[0] > threshold) {
      const dx = { n: 0, e: 1, s: 0, w: -1 }[agent.flags.orientation];
      const dy = { n: -1, e: 0, s: 1, w: 0 }[agent.flags.orientation];
      return [{
        agent_changes: [{
          agent_id: agent.id,
          x: agent.x + dx,
          y: agent.y + dy,
        }],
      }];
    } else {
      return [];
    }
  },
};

const move_backward = {
  size: 1,
  propose: (world, agent, head) => {
    if (head[0] > threshold) {
      const dx = { n: 0, e: 1, s: 0, w: -1 }[agent.flags.orientation];
      const dy = { n: -1, e: 0, s: 1, w: 0 }[agent.flags.orientation];
      return [{
        agent_changes: [{
          agent_id: agent.id,
          x: agent.x - dx,
          y: agent.y - dy,
        }],
      }];
    } else {
      return [];
    }
  },
};


const turn_left = {
  size: 1,
  propose: (world, agent, head) => {
    if (head[0] > threshold) {
      const orientation = { n: 'w', e: 'n', s: 'e', w: 's' }[agent.flags.orientation];
      return [{
        agent_changes: [{
          agent_id: agent.id,
          flags: { orientation },
        }],
      }];
    } else {
      return [];
    }
  },
};


const turn_right = {
  size: 1,
  propose: (world, agent, head) => {
    if (head[0] > threshold) {
      const orientation = { n: 'e', e: 's', s: 'w', w: 'n' }[agent.flags.orientation];
      return [{
        agent_changes: [{
          agent_id: agent.id,
          flags: { orientation },
        }],
      }];
    } else {
      return [];
    }
  },
};


const place = {
  size: 1,
  propose: (world, agent, head) => {
    if (head[0] < threshold) { return []; }
    else {
      const dx = { n: 0, e: 1, s: 0, w: -1 }[agent.flags.orientation];
      const dy = { n: -1, e: 0, s: 1, w: 0 }[agent.flags.orientation];
      return [
        { lattice_changes: [{
          x: agent.x + dx, y: agent.y + dy,
          from: 'empty', to: 'mutable',
          flags: { emit: [1, 0, 0, 0, 0, 0, 0, 0] },
        }]}
      ];
    }
  },
};




export const actions = [
  move_forward, move_backward, turn_left, turn_right, place,
];