import { typedFnType } from "./function.js";
import { Type } from "../metacircular.js";
import { Int } from "../primitives/symbols.js";
import { DefaultMap } from "../util.js";
import { makeGeneric } from "../generics/generics.js";

const symbolList = Symbol('List');

const listTypeRegistry = new DefaultMap(elementType => ({
  symbol: symbolList,
  params: [elementType],
}));

// type constructor
export const lsType = elementType => listTypeRegistry.getdefault(elementType, true);

// 'normal' implementation
const emptyList = {l:[]};
const get = ls => i => ls.l[i];
const put = ls => i => elem => ({l: ls.l.with(Number(i), elem)});
// const push = ls => elem => ({l:ls.l.concat([elem])});

export const ModuleList = {l:[
  // Type -> Type
  ...typedFnType(lsType, fnType => fnType
    /* in  */ (Type)
    /* out */ (Type)
  ),

  // [a]
  {i: emptyList, t: makeGeneric(a => lsType(a))},

  // [a] -> Int -> a
  ...typedFnType(get, fnType => makeGeneric(a => fnType
    /* in  */ (lsType(a))
    /* out */ (fnType
      /* in  */ (Int)
      /* out */ (a)
  ))),

  // [a] -> Int -> a -> [a]
  ...typedFnType(put, fnType => makeGeneric(a => fnType
    /* in  */ (lsType(a))
    /* out */ (fnType
      /* in  */ (Int)
      /* out */ (fnType
        /* in  */ (a)
        /* out */ (lsType(a))
      )
  ))),
]};