import { pretty } from "../util/pretty.js";
import { inspect } from "node:util";

// UUID -> Computation<a> -> Slot<a>
const newSlot = uuid => computation => ({
  overwrites: uuid,
  computation,
  // depth: 1,
  // [inspect.custom]: (depth, options, inspect) => options.stylize(`newSlot(${inspect(uuid)})(${inspect(computation)})`, 'special'),
});

// a -> Computation<a>
const newValue = val => ({
  kind: "value",
  out: val,
  // [inspect.custom]: (depth, options, inspect) => options.stylize(`newValue(${val})`, 'special'),
});

// Slot<a> -> Computation<a>
const read = slot => ({
  kind: "transformation",
  in: slot,
  fn: `${x => x}`,
  out: slot.computation.out,
  // [inspect.custom]: (depth, options, inspect) => options.stylize(`read(${inspect(slot)})`, 'special'),
});

// Computation<a> -> Computation<a -> b> -> Computation<b>
const transform = input => fn => {
  const output = fn.out(input.out);
  if (input.kind === "value") {
    // our input had no read dependency, thus likewise our output does not:
    return {
      kind: "value",
      out: output,
    };
  }
  else {
    return {
      kind: "transformation",
      in: input.in,
      fn,
      out: output,
    };
  }
};



const price = newSlot(Symbol('price'))(newValue(5));
const tax   = newSlot(Symbol('tax'))(newValue(1));

const total =
  transform(read(price))(
    transform(read(tax))(
      newValue(tax => price => price + tax)));

console.log(pretty({total,}));



const getReadDependencies = computation => new Set([
  ...(computation.kind === "value" ? [] : [computation.in, ...getReadDependencies(computation.fn)]),
]);

console.log("getReadDependencies(total):", getReadDependencies(total));