import React from 'react';
import * as gf from '../src/genfuns';
import * as m from './Model';

class Summary {
  constructor(wrapper = 'span') {
    this.wrapper = wrapper;
  }
}
class Detail { }

const total_receipt = items => items.reduce((acc, item) => acc + item.subtotal, 0);
const subtotal = items => items.reduce((acc, item) => acc + item.price, 0);
const total_tax = items => items.reduce((acc, item) => acc + item.tax, 0);

const display_money = amount => amount.toFixed(2);

const ItemLabel = ({ desc, amount, wrapper, ...restProps }) =>
  React.createElement(wrapper, restProps,
    [
      <span className="desc" key="0"> {desc}: </span>,
      <span className="price" key="1">{display_money(amount)}</span>
    ]
  );

export const Items = gf.defgeneric("Items", "animaltorender")
  .primary([gf.Shape("items", "view")], ({ items, view }) => Items(items, view))
  .primary([Array, Summary], (items, view) => (
    <>
      <ItemLabel desc="Subtotal" amount={subtotal(items)} wrapper={view.wrapper} />
      <ItemLabel desc="Tax" amount={total_tax(items)} wrapper={view.wrapper} />
      <ItemLabel desc="Total" amount={total_receipt(items)} wrapper={view.wrapper} />
    </>
  ))
  .primary([Array, Detail], items => (
    <ul>
      {items.map((a, idx) => <Item item={a} key={idx} />, items)}
      <Items items={items} view={new Summary('li')} />
    </ul>
  ))
  .fn;

export const Item = gf.defgeneric("Item", "itemtorender")
  .primary([gf.Shape("item")], ({ item }) => Item(item))
  .around([m.Item], function (_) {
    const [desc, price] = this.call_next_method();
    return <ItemLabel desc={desc} amount={price} wrapper='li' />;
  })
  .primary([m.NonFood], item => ["Non-food Item", item.price])
  .primary([m.NormalFood], item => ["Food", item.price])
  .primary([m.AlcoholicBeverage], item => ["Alcohol", item.price])
  .fn;

export const Receipt = ({items}) => (
  <div>
    <h1><Items {...{ items }} view={new Summary()} /></h1>
    <Items {...{ items }} view={new Detail()} />
  </div>
);