ec.js

import R from 'ramda';

function newId(){
  let d = new Date().getTime();
  let uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    const r = (d + Math.random()*16)%16 | 0;
    d = Math.floor(d/16);
    return (c=='x' ? r : (r&0x3|0x8)).toString(16);
  });
  return uuid;
}

export const newWorld = () => ({});

export const newEntity = () => ({});

export const addEntity = R.curry( function( world, entity ){
  const id = newId();
  world[ id ] = entity;
  entity._id = id;
  return entity;
});

export const removeEntity = R.curry( function( world, entity ){
  delete world[ entity._id ];
  return entity;
});

export const getEntityById = R.curry( function( world, id ){
  return world[ id ];
});

export const lookupEntityId = R.curry( function( world, entity ){
  for( let id in world ){
    if( world[ id ] === entity ){
      return id;
    }
  }
});

export const createComponent = function( componentType, componentData ){
  const component = new componentType( componentData );
  return component;
};

export const addComponent = R.curry( function( entity, component ){
  entity[ component.name ] = component;
  return component;
});

export const removeComponent = R.curry( function( entity, component ){
  delete entity[ component.name ];
  return component;
});

export const getEntities = R.curry(function( world, ...components ){
  return R.filter( hasKeys( components ), R.values( world ) );
});

export const getEntityList = R.curry( function( world ){
  return R.values( world );
});

const hasKeys = R.curry( function( keys, object ){
  const objectKeys = R.keys( object );
  return R.all( function( keyName ){
    if( keyName.charAt( 0 ) === '!' ){
      return ( object[ keyName.slice(1,keyName.length) ] === undefined );
    }
    else{
      return ( object[ keyName ] !== undefined );
    }
  }, keys );
});

export const defineComponent = function( componentTemplate ){
  const componentType = function( data ){
    const initializer = componentTemplate.init.bind( this );
    initializer( data );
  };
  componentType.prototype.name = componentTemplate.name;
  return componentType;
};

export const world = function( entities ){

  return {
    addEntity: addEntity( entities ),
    removeEntity: removeEntity( entities ),
    getEntities: ( ...args ) => getEntities( entities, ...args ),
    get: () => entities,
    clone: () => R.clone( entities ),
    getEntityById: getEntityById( entities ),
    lookupEntityId: lookupEntityId( entities ),
  };
};