import { Unit } from "../primitives/types.js";
import { unit } from "../primitives/unit.js";
import { constructorProduct, getLeft, getRight } from "./product.js";
import { fnType, prodType } from "./types.js";

function capitalizeFirstLetter(val) {
  return String(val).charAt(0).toUpperCase() + String(val).slice(1);
}

// [{l: "x", r: Double}, {l: "y", r: Double}] => (Double × (Double × Unit))
export const structType = fields => {
  if (fields.length === 0) {
    return Unit;
  }
  const [field, ...rest] = fields;
  const fieldType = getRight(field);
  return prodType(fieldType)(structType(rest));
};

export const makeConstructor = fields => {
  const internal = (nParams, ret) => {
    if (nParams === 0) {
      const result = ret(unit);
      return result;
    }
    return nextParam => {
      const wrappedName = 'wrapped_' + ret.name;
      const newRet = {
        [wrappedName]: inner => constructorProduct(nextParam)(ret(inner)),
      }[wrappedName];
      return internal(nParams-1, newRet);
    }
  };
  const id = x => x;
  return internal(fields.length, id);
};

export const makeConstructorType = type => fields => {
  if (fields.length === 0) {
    return type;
  }
  const [field, ...rest] = fields;
  const fieldType = getRight(field);
  return fnType(fieldType)(makeConstructorType(rest));
};

export const makeGetters = fields => {
  if (fields.length === 0) {
    return [];
  }
  const [field, ...rest] = fields;
  const fieldName = getLeft(field);
  const getterName = `get${capitalizeFirstLetter(fieldName)}`;
  return [
    { [getterName]: obj => getLeft(obj) }[getterName],
    ...makeGetters(rest).map(getter => ({[getter.name]: obj => getter(getRight(obj))}[getter.name])),
  ];
};

export const makeGettersTypes = type => fields => {
  return fields.map(field => {
    const fieldType = getRight(field);
    return fnType(type)(fieldType);
  });
};