import Core from '../core';

//https://github.com/airportyh/protomorphism

class Protocol{

constructor(spec){

this.registry = new Map();

this.fallback = null;

for (let funName in spec){

this[funName] = createFun(funName).bind(this);

}

function createFun(funName){

return function(...args) {

let thing = args[0];

let fun = null;

if(Number.isInteger(thing) && this.hasImplementation(Core.Integer)){

fun = this.registry.get(Core.Integer)[funName];

}else if(typeof thing === "number" && !Number.isInteger(thing) && this.hasImplementation(Core.Float)){

fun = this.registry.get(Core.Float)[funName];

}else if(typeof thing === "string" && this.hasImplementation(Core.BitString)){

fun = this.registry.get(Core.BitString)[funName];

}else if(this.hasImplementation(thing)){

fun = this.registry.get(thing.constructor)[funName];

}else if(this.fallback){

fun = this.fallback[funName];

}

if(fun != null){

let retval = fun.apply(this, args);

return retval;

}

throw new Error("No implementation found for " + thing);

};

}

}

implementation(type, implementation){

if(type === null){

this.fallback = implementation;

}else{

this.registry.set(type, implementation);

}

}

hasImplementation(thing) {

if (thing === Core.Integer || thing === Core.Float || Core.BitString){

return this.registry.has(thing);

}

return this.registry.has(thing.constructor);

}

}

export default Protocol;