import { unit } from "../primitives/unit.js";
import { capitalizeFirstLetter } from "../util/util.js";

export const makeConstructor = fieldNames => {
  const internal = (fieldNames, ret) => {
    if (fieldNames.length === 0) {
      const result = ret(unit);
      return result;
    }
    return nextParam => {
      const [fieldName, ...rest] = fieldNames;
      const wrappedName = 'ctor_' + fieldName;
      const newRet = {
        [wrappedName]: inner => ({[fieldName]: nextParam, ...ret(inner)}),
      }[wrappedName];
      return internal(rest, newRet);
    }
  };
  const id = x => x;
  return internal(fieldNames, id);
};

export const makeGetters = fieldNames => {
  return fieldNames.map(fieldName => {
    const getterName = `get${capitalizeFirstLetter(fieldName)}`;
    return {
      [getterName]: obj => obj[fieldName],
    }[getterName];
  })
};

export const makeStructCompareFn = compares => {
  return a => b => {
    for (const {l: fieldName, r: getCompareFn} of compares) {
      const cmp = getCompareFn()(a[fieldName])(b[fieldName]);
      if (cmp !== 0) return cmp;
    }
    return 0;
  }
}