/**
 * helpers for testing equivalence of two implementations, one of them on bigints
 */
import { test, Random } from '../testing/property.js';
import { Provable } from '../provable/provable.js';
import { deepEqual } from 'node:assert/strict';
import { Bool, Field } from '../provable/wrapped.js';
import { AnyTuple, Tuple } from '../util/types.js';
import { provable } from '../provable/types/provable-derivers.js';
import { assert } from '../provable/gadgets/common.js';
import { synchronousRunners } from '../provable/core/provable-context.js';

export {
  equivalent,
  equivalentProvable,
  equivalentAsync,
  oneOf,
  throwError,
  handleErrors,
  deepEqual as defaultAssertEqual,
  id,
};
export {
  spec,
  field,
  fieldWithRng,
  bigintField,
  bool,
  boolean,
  unit,
  array,
  record,
  map,
  onlyIf,
  fromRandom,
  first,
  second,
  constant,
};
export { Spec, ToSpec, FromSpec, SpecFromFunctions, ProvableSpec, First, Second };

// TODO get rid of this top-level await by making `test` support async functions
let { runAndCheckSync } = await synchronousRunners();

// a `Spec` tells us how to compare two functions

type FromSpec<In1, In2> = {
  // `rng` creates random inputs to the first function
  rng: Random<In1>;

  // `there` converts to inputs to the second function
  there: (x: In1) => In2;

  // `provable` tells us how to create witnesses, to test provable code
  // note: we only allow the second function to be provable;
  // the second because it's more natural to have non-provable types as random generator output
  provable?: Provable<In2, any>;
};

type ToSpec<Out1, Out2> = {
  // `back` converts outputs of the second function back to match the first function
  back: (x: Out2) => Out1;

  // `assertEqual` to compare outputs against each other; defaults to `deepEqual`
  assertEqual?: (x: Out1, y: Out1, message: string) => void;
};

type Spec<T1, T2> = FromSpec<T1, T2> & ToSpec<T1, T2>;

type ProvableSpec<T1, T2> = Spec<T1, T2> & { provable: Provable<T2, any> };

type FuncSpec<In1 extends Tuple<any>, Out1, In2 extends Tuple<any>, Out2> = {
  from: {
    [k in keyof In1]: k extends keyof In2 ? FromSpec<In1[k], In2[k]> : never;
  };
  to: ToSpec<Out1, Out2>;
};

type AnyTupleFunction = (...args: AnyTuple) => any;

type SpecFromFunctions<F1 extends AnyTupleFunction, F2 extends AnyTupleFunction> = FuncSpec<
  Parameters<F1>,
  ReturnType<F1>,
  Parameters<F2>,
  ReturnType<F2>
>;

function id<T>(x: T) {
  return x;
}

// unions of specs, to cleanly model function parameters that are unions of types

type FromSpecUnion<T1, T2> = {
  _isUnion: true;
  specs: Tuple<FromSpec<T1, T2>>;
  rng: Random<[number, T1]>;
};

type OrUnion<T1, T2> = FromSpec<T1, T2> | FromSpecUnion<T1, T2>;

type Union<T> = T[keyof T & number];

function oneOf<In extends Tuple<FromSpec<any, any>>>(
  ...specs: In
): FromSpecUnion<Union<Params1<In>>, Union<Params2<In>>> {
  // the randomly generated value from a union keeps track of which spec it came from
  let rng = Random.oneOf(
    ...specs.map((spec, i) => Random.map(spec.rng, (x) => [i, x] as [number, any]))
  );
  return { _isUnion: true, specs, rng };
}

function toUnion<T1, T2>(spec: OrUnion<T1, T2>): FromSpecUnion<T1, T2> {
  let specAny = spec as any;
  return specAny._isUnion ? specAny : oneOf(specAny);
}

// equivalence tester

function equivalent<In extends Tuple<FromSpec<any, any>>, Out extends ToSpec<any, any>>({
  from,
  to,
  verbose,
}: {
  from: In;
  to: Out;
  verbose?: boolean;
}) {
  return function run(
    f1: (...args: Params1<In>) => First<Out>,
    f2: (...args: Params2<In>) => Second<Out>,
    label = 'expect equal results'
  ) {
    let generators = from.map((spec) => spec.rng);
    let assertEqual = to.assertEqual ?? deepEqual;
    let start = performance.now();
    let nRuns = test(...(generators as any[]), (...args) => {
      args.pop();
      let inputs = args as Params1<In>;
      handleErrors(
        () => f1(...inputs),
        () => to.back(f2(...(inputs.map((x, i) => from[i].there(x)) as Params2<In>))),
        (x, y) => assertEqual(x, y, label),
        label
      );
    });

    if (verbose) {
      let ms = (performance.now() - start).toFixed(1);
      let runs = nRuns.toString().padStart(2, ' ');
      console.log(`${label.padEnd(20, ' ')}    success on ${runs} runs in ${ms}ms.`);
    }
  };
}

// async equivalence

function equivalentAsync<In extends Tuple<FromSpec<any, any>>, Out extends ToSpec<any, any>>(
  { from, to }: { from: In; to: Out },
  { runs = 1 } = {}
) {
  return async function run(
    f1: (...args: Params1<In>) => Promise<First<Out>> | First<Out>,
    f2: (...args: Params2<In>) => Promise<Second<Out>> | Second<Out>,
    label = 'expect equal results'
  ) {
    let generators = from.map((spec) => spec.rng);
    let assertEqual = to.assertEqual ?? deepEqual;

    let nexts = generators.map((g) => g.create());

    for (let i = 0; i < runs; i++) {
      let args = nexts.map((next) => next());
      let inputs = args as Params1<In>;
      try {
        await handleErrorsAsync(
          () => f1(...inputs),
          async () => to.back(await f2(...(inputs.map((x, i) => from[i].there(x)) as Params2<In>))),
          (x, y) => assertEqual(x, y, label),
          label
        );
      } catch (err) {
        console.log(...inputs);
        throw err;
      }
    }
  };
}

// equivalence tester for provable code

function isProvable(spec: FromSpecUnion<any, any>) {
  return spec.specs.some((spec) => spec.provable);
}

function equivalentProvable<In extends Tuple<OrUnion<any, any>>, Out extends ToSpec<any, any>>({
  from: fromRaw,
  to,
  verbose,
}: {
  from: In;
  to: Out;
  verbose?: boolean;
}) {
  let fromUnions = fromRaw.map(toUnion);
  assert(fromUnions.some(isProvable), 'equivalentProvable: no provable input');

  return function run(
    f1: (...args: Params1<In>) => First<Out>,
    f2: (...args: Params2<In>) => Second<Out>,
    label = 'expect equal results'
  ) {
    let generators = fromUnions.map((spec) => spec.rng);
    let assertEqual = to.assertEqual ?? deepEqual;

    let start = performance.now();
    let nRuns = test.custom({ minRuns: 5 })(...generators, (...args) => {
      args.pop();

      // figure out which spec to use for each argument
      let from = (args as [number, unknown][]).map(([j], i) => fromUnions[i].specs[j]);
      let inputs = (args as [number, unknown][]).map(([, x]) => x) as Params1<In>;
      let inputs2 = inputs.map((x, i) => from[i].there(x)) as Params2<In>;

      // outside provable code
      handleErrors(
        () => f1(...inputs),
        () => f2(...inputs2),
        (x, y) => assertEqual(x, to.back(y), label),
        label
      );

      // inside provable code
      runAndCheckSync(() => {
        let inputWitnesses = inputs2.map((x, i) => {
          let provable = from[i].provable;
          return provable !== undefined ? Provable.witness(provable, () => x) : x;
        }) as Params2<In>;
        handleErrors(
          () => f1(...inputs),
          () => f2(...inputWitnesses),
          (x, y) => Provable.asProver(() => assertEqual(x, to.back(y), label)),
          label
        );
      });
    });
    if (verbose) {
      let ms = (performance.now() - start).toFixed(1);
      let runs = nRuns.toString().padStart(2, ' ');
      console.log(`${label.padEnd(20, ' ')}    success on ${runs} runs in ${ms}ms.`);
    }
  };
}

// creating specs

function spec<T, S>(spec: {
  rng: Random<T>;
  there: (x: T) => S;
  back: (x: S) => T;
  assertEqual?: (x: T, y: T, message: string) => void;
  provable: Provable<S>;
}): ProvableSpec<T, S>;
function spec<T, S>(spec: {
  rng: Random<T>;
  there: (x: T) => S;
  back: (x: S) => T;
  assertEqual?: (x: T, y: T, message: string) => void;
}): Spec<T, S>;
function spec<T>(spec: {
  rng: Random<T>;
  provable: Provable<T>;
  assertEqual?: (x: T, y: T, message: string) => void;
}): ProvableSpec<T, T>;
function spec<T>(spec: {
  rng: Random<T>;
  assertEqual?: (x: T, y: T, message: string) => void;
}): Spec<T, T>;
function spec<T, S>(spec: {
  rng: Random<T>;
  there?: (x: T) => S;
  back?: (x: S) => T;
  assertEqual?: (x: T, y: T, message: string) => void;
  provable?: Provable<S>;
}): Spec<T, S> {
  return {
    rng: spec.rng,
    there: spec.there ?? (id as any),
    back: spec.back ?? (id as any),
    assertEqual: spec.assertEqual,
    provable: spec.provable,
  };
}

// some useful specs

let unit: ToSpec<void, void> = { back: id, assertEqual() {} };

let field: ProvableSpec<bigint, Field> = {
  rng: Random.field,
  there: Field,
  back: (x) => x.toBigInt(),
  provable: Field,
};

let bigintField: Spec<bigint, bigint> = {
  rng: Random.field,
  there: id,
  back: id,
};

let bool: ProvableSpec<boolean, Bool> = {
  rng: Random.boolean,
  there: Bool,
  back: (x) => x.toBoolean(),
  provable: Bool,
};
let boolean: Spec<boolean, boolean> = fromRandom(Random.boolean);

function fieldWithRng(rng: Random<bigint>): ProvableSpec<bigint, Field> {
  return { ...field, rng };
}

// spec combinators

function array<T, S>(spec: ProvableSpec<T, S>, n: number): ProvableSpec<T[], S[]>;
function array<T, S>(spec: Spec<T, S>, n: Random<number> | number): Spec<T[], S[]>;
function array<T, S>(spec: Spec<T, S>, n: Random<number> | number): Spec<T[], S[]> {
  return {
    rng: Random.array(spec.rng, n),
    there: (x) => x.map(spec.there),
    back: (x) => x.map(spec.back),
    provable: typeof n === 'number' && spec.provable ? Provable.Array(spec.provable, n) : undefined,
  };
}

function record<Specs extends { [k in string]: Spec<any, any> }>(
  specs: Specs
): Spec<{ [k in keyof Specs]: First<Specs[k]> }, { [k in keyof Specs]: Second<Specs[k]> }> {
  let isProvable = Object.values(specs).every((spec) => spec.provable);
  return {
    rng: Random.record(mapObject(specs, (spec) => spec.rng)) as any,
    there: (x) => mapObject(specs, (spec, k) => spec.there(x[k])) as any,
    back: (x) => mapObject(specs, (spec, k) => spec.back(x[k])) as any,
    provable: isProvable ? provable(mapObject(specs, (spec) => spec.provable) as any) : undefined,
  };
}

function map<T1, T2, S1, S2>(
  { from, to }: { from: ProvableSpec<T1, T2>; to: ProvableSpec<S1, S2> },
  there: (t: T1) => S1
): ProvableSpec<S1, S2>;
function map<T1, T2, S1, S2>(
  { from, to }: { from: FromSpec<T1, T2>; to: Spec<S1, S2> },
  there: (t: T1) => S1
): Spec<S1, S2>;
function map<T1, T2, S1, S2>(
  { from, to }: { from: FromSpec<T1, T2>; to: Spec<S1, S2> },
  there: (t: T1) => S1
): Spec<S1, S2> {
  return { ...to, rng: Random.map(from.rng, there) };
}

function onlyIf<T, S>(spec: Spec<T, S>, onlyIf: (t: T) => boolean): Spec<T, S> {
  return { ...spec, rng: Random.reject(spec.rng, (x) => !onlyIf(x)) };
}

function mapObject<K extends string, T, S>(
  t: { [k in K]: T },
  map: (t: T, k: K) => S
): { [k in K]: S } {
  return Object.fromEntries(Object.entries<T>(t).map(([k, v]) => [k, map(v, k as K)])) as any;
}

function fromRandom<T>(rng: Random<T>): Spec<T, T> {
  return { rng, there: id, back: id };
}

function first<T, S>(spec: Spec<T, S>): Spec<T, T> {
  return { rng: spec.rng, there: id, back: id };
}
function second<T, S>(spec: Spec<T, S>): Spec<S, S> {
  return {
    rng: Random.map(spec.rng, spec.there),
    there: id,
    back: id,
    provable: spec.provable,
  };
}

function constant<T, S>(spec: Spec<T, S>, value: T): Spec<T, S> {
  return { ...spec, rng: Random.constant(value) };
}

// helper to ensure two functions throw equivalent errors

function handleErrors<T, S, R>(
  op1: () => T,
  op2: () => S,
  useResults?: (a: T, b: S) => R,
  label?: string
): R | undefined {
  let result1: T, result2: S;
  let error1: Error | undefined;
  let error2: Error | undefined;
  try {
    result1 = op1();
  } catch (err) {
    error1 = err as Error;
  }
  try {
    result2 = op2();
  } catch (err) {
    error2 = err as Error;
  }
  if (!!error1 !== !!error2) {
    error1 && console.log(error1);
    error2 && console.log(error2);
  }
  let message = `${(label && `${label}: `) || ''}equivalent errors`;
  deepEqual(!!error1, !!error2, message);
  if (!(error1 || error2) && useResults !== undefined) {
    return useResults(result1!, result2!);
  }
}

async function handleErrorsAsync<T, S, R>(
  op1: () => T,
  op2: () => S,
  useResults?: (a: Awaited<T>, b: Awaited<S>) => R,
  label?: string
): Promise<R | undefined> {
  let result1: Awaited<T>, result2: Awaited<S>;
  let error1: Error | undefined;
  let error2: Error | undefined;
  try {
    result1 = await op1();
  } catch (err) {
    error1 = err as Error;
  }
  try {
    result2 = await op2();
  } catch (err) {
    error2 = err as Error;
  }
  if (!!error1 !== !!error2) {
    error1 && console.log(error1);
    error2 && console.log(error2);
  }
  let message = `${(label && `${label}: `) || ''}equivalent errors`;
  deepEqual(!!error1, !!error2, message);
  if (!(error1 || error2) && useResults !== undefined) {
    return useResults(result1!, result2!);
  }
}

function throwError(message?: string): any {
  throw Error(message);
}

// infer input types from specs

type Param1<In extends OrUnion<any, any>> = In extends {
  there: (x: infer In) => any;
}
  ? In
  : In extends FromSpecUnion<infer T1, any>
  ? T1
  : never;
type Param2<In extends OrUnion<any, any>> = In extends {
  there: (x: any) => infer In;
}
  ? In
  : In extends FromSpecUnion<any, infer T2>
  ? T2
  : never;

type Params1<Ins extends Tuple<OrUnion<any, any>>> = {
  [k in keyof Ins]: Param1<Ins[k]>;
};
type Params2<Ins extends Tuple<OrUnion<any, any>>> = {
  [k in keyof Ins]: Param2<Ins[k]>;
};

type First<Out extends ToSpec<any, any>> = Out extends ToSpec<infer Out1, any> ? Out1 : never;
type Second<Out extends ToSpec<any, any>> = Out extends ToSpec<any, infer Out2> ? Out2 : never;