import { getInst, getType } from "../primitives/dynamic.js";
import { symbolBool, symbolBottom, symbolByte, symbolChar, symbolDouble, symbolDynamic, symbolInt, symbolUUID, symbolType, symbolUnit, symbolOrdering } from "../primitives/primitive_types.js";
import { UNBOUND_SYMBOLS } from "../primitives/typevars.js";
import { symbolDictIterator } from "../structures/dict.types.js";
import { symbolSetIterator } from "../structures/set.types.js";
import { symbolDict, symbolFunction, symbolList, symbolProduct, symbolSet, symbolSum } from "../structures/type_constructors.js";
import { prettyT } from "../util/pretty.js";
import { compareBools, compareDoubles, compareInts, compareOrderings, compareStrings, compareSymbols, compareUnits } from "./primitives.js";
import { compareDictIterators, compareDicts, compareFunctions, compareLists, compareProducts, compareSetIterators, compareSets, compareSums } from "./structures.js";
import { compareTypes } from "./type.js";

export const compareDynamic = x => y =>
  compareTypes(getType(x))(getType(y))
    || makeCompareFn(getType(x))(getInst(x))(getInst(y));

// const cannotCompareTypeVarInstances = _ => _ => { throw new Error("Cannot compare instance of type variables"); }


const cannotCompareTypeVarInstances = _ => _ => 0;

const typeSymbolToCmp = new Map([
  [symbolInt     , compareInts     ],
  [symbolBool    , compareBools    ],
  [symbolDouble  , compareDoubles  ],
  [symbolByte    , compareDoubles  ],
  [symbolChar    , compareStrings  ],
  [symbolUnit    , compareUnits    ],
  [symbolBottom  , _ => _ => { throw new Error("Bottom!"); }],
  [symbolUUID    , compareSymbols  ],
  // [SymbolGenericType, ?] TODO
  [symbolType    , compareTypes    ],
  [symbolDynamic , compareDynamic  ],
  [symbolOrdering, compareOrderings],

  // these functions take extra comparison callbacks:
  [symbolFunction    , compareFunctions    ],
  [symbolSum         , compareSums         ],
  [symbolProduct     , compareProducts     ],
  [symbolList        , compareLists        ],
  [symbolSet         , compareSets         ],
  [symbolDict        , compareDicts        ],
  [symbolSetIterator , compareSetIterators ],
  [symbolDictIterator, compareDictIterators],

  // even though we cannot compare typevar instances,
  // we still need to give a function or shit will break
  // types that contain typevars are never instantiated,
  // EXCEPT:
  //   - generic functions (but for function comparison we don't look at the in/out types)
  //   - empty list, empty set, empty dict are all generic, but for each type there is only one empty element, so it never needs to be compared to another one
  ...UNBOUND_SYMBOLS.map(uuid => [uuid, cannotCompareTypeVarInstances]),
]);

export const makeCompareFn = type => {
  return type.params.reduce(
    (acc, cur) => acc(makeCompareFn(cur(type))),
    typeSymbolToCmp.get(type.symbol)
    || (() => { throw new Error(`don't know how to compare instances of '${prettyT(type)}'`); })()
  );
};