import { Map, fromJS } from 'immutable';

 
 let Symbol = (window['Symbol'] !== undefined) ? window['Symbol'] : x => `_Symbol__${x}`;
 
 export const fireListeners = Symbol('fireListeners');
 
 const noOpTransform = val => val;
 
 export function lensTransformer(
     lens,
     getTransform = noOpTransform,
     setTransform = noOpTransform
 ) {
     return {
         get: () => getTransform(lens.get()),
         set: (val) => lens.set(setTransform(val)),
         withValue(cb) {
             return cb(this.get());
         },
 
     };
 }
 
 export function makeLens(key, self) {
     const createLens = (keyPath) => {
         return {
             get() {

                 let result = self._currentState.getIn(keyPath);

                 if (result && result.toJS !== undefined) {
                     result = result.toJS();
                 }
                 return result;
             },
             set(val) {

                 const oldState = self._currentState;

                 if (self._currentState.getIn(keyPath) === undefined) {

                     for (let x = 0; x < keyPath.length; x++) {
                         const subPath = keyPath.slice(0, x);

                         if (self._currentState.getIn(subPath) === undefined && self._currentState.hasIn(subPath)) {
                             self._currentState = self._currentState.setIn(subPath, Map());

                         }
                     }
                 }
 

                 self._currentState = self._currentState.setIn(keyPath, fromJS(val));
                 self[fireListeners](oldState, self._currentState);

             },
             lensFor(key) {
                 let subPath = key instanceof Array ? key : [key];
                 return createLens([...keyPath, ...subPath]);
             },
 

             withValue(cb, ...rest) {
                 return cb(this.get(), ...rest);

             },
 
             swap(cb) {
                 this.set(cb(this.get()));
                 return this.get();
             }
         };
     };
 
     return createLens(key instanceof Array ? key : [key]);

 }