import {behaviorItemFromJSON, createContext} from '@avocado/behavior';
import {compose} from '@avocado/core';
import {StateProperty, Trait} from '@avocado/entity';

const decorate = compose(
  StateProperty('life', {
    track: true,
  }),
  StateProperty('maxLife', {
    track: true,
  }),
);

export class Alive extends decorate(Trait) {

  static defaultParams() {
    return {
      deathActions: {
        type: 'actions',
        traversals: [
          {
            type: 'traversal',
            steps: [
              {
                type: 'key',
                key: 'entity',
              },
              {
                type: 'key',
                key: 'transition',
              },
              {
                type: 'invoke',
                args: [
                  {
                    type: 'literal',
                    value: {
                      opacity: 0,
                      visibleScaleX: .3,
                      visibleScaleY: 3,
                    },
                  },
                  {
                    type: 'literal',
                    value: 0.2,
                  },
                ],
              },
            ],
          },
        ],
      },
      // By default, die when life <= 0.
      deathCondition: {
        type: 'condition',
        operator: '<=',
        operands: [
          {
            type: 'traversal',
            steps: [
              {
                type: 'key',
                key: 'entity',
              },
              {
                type: 'key',
                key: 'life',
              },
            ],
          },
          {
            type: 'literal',
            value: 0,
          },
        ],
      },
    };
  }

  static defaultState() {
    return {
      life: 100,
      maxLife: 100,
    };
  }

  initialize() {
    this._context = createContext();
    this._context.add('entity', this.entity);
    const actionsJSON = this.params.get('deathActions').toJS();
    this._deathActions = behaviorItemFromJSON(actionsJSON);
    const conditionJSON = this.params.get('deathCondition').toJS();
    this._deathCondition = behaviorItemFromJSON(conditionJSON);
    this._isDying = false;
  }

  listeners() {
    return {

      tookDamage: (damage) => {
        this.entity.life -= damage.amount;
        // Clamp health between 0 and max.
        this.entity.life = Math.min(
          Math.max(0, this.entity.life),
          this.entity.maxLife
        );
      },

    }
  }

  methods() {
    return {

      die: () => {
        this._isDying = true;
        this.entity.emit('dying');
        this._deathActions.on('actionsFinished', () => {
          this.entity.destroy();
        });
      },

    };
  }

  tick(elapsed) {
    if (this._isDying) {
      this._deathActions.tick(this._context, elapsed);
    }
    else {
      if (this._deathCondition.check(this._context)) {
        // It's a good day to die.
        this.entity.die();
      }
    }
  }

}