const Extension = require('adopt').Extension

// Create an extension.
// An extension adds private methods to the types you specify.
// This extension adds a private toJson method to all Objects.
const jsonExt = Extension(Object) ({
  toJson(...args) {
    return JSON.stringify(this, ...args)
  }
})

const obj = {whee: 'this is fun'}

// You use brackets to call a private method, by
// looking it up in the extension.
//
// Like this:
console.log(obj [jsonExt.toJson] (null, 2))

// Prints:
//   {
//     "wheee": "this is fun"
//   }

const json = Extension(Object) ({
    // The default key is what you'll get if you use the extension itself
    // to look up a member in an Object.
    [Extension.defaultKey]: 'json',
    
    // Oh, also, getters and setters work fine.
    get json() { return JSON.stringify(this) },
    
    toJson(...args) { return JSON.stringify(this, ...args) }
})

const self = {
    brain: {thoughts: {distracting: 'many', curious: true}},
    heart: {isOpen: true}
}

// Isn't this nice?
console.log(self [json])

// And this still works.
console.log(self [json.toJson] (0, 2))

const sample = Extension(Array, String) ({
    _: require('lodash'),
    sample(...args) {
        return this._sample(this, ...args)
    }
})