open FunctionRegistry_Core
open FunctionRegistry_Helpers

let nameSpace = "Danger"
let requiresNamespace = true

module NumberToNumber = {
  let make = (name, fn) =>
    FnDefinition.make(
      ~name,
      ~inputs=[FRTypeNumber],
      ~run=(_, inputs, _, _) => {
        inputs
        ->getOrError(0)
        ->E.R.bind(Prepare.oneNumber)
        ->E.R2.fmap(fn)
        ->E.R2.fmap(Wrappers.evNumber)
      },
      (),
    )
}

module TwoNumbersToNumber = {
  let make = (name, fn) =>
    FnDefinition.make(
      ~name,
      ~inputs=[FRTypeNumber, FRTypeNumber],
      ~run=(_, inputs, _, _) => {
        inputs->Prepare.ToValueTuple.twoNumbers->E.R2.fmap(fn)->E.R2.fmap(Wrappers.evNumber)
      },
      (),
    )
}

module ThreeNumbersToNumber = {
  let make = (name, fn) =>
    FnDefinition.make(
      ~name,
      ~inputs=[FRTypeNumber, FRTypeNumber, FRTypeNumber],
      ~run=(_, inputs, _, _) => {
        inputs->Prepare.ToValueTuple.threeNumbers->E.R2.fmap(fn)->E.R2.fmap(Wrappers.evNumber)
      },
      (),
    )
}

module FunctionToNumberZero = {
  let make = (name, fn) =>
    FnDefinition.make(
      ~name,
      ~inputs=[FRTypeLambda],
      ~run=(_, inputs, _, _) => {
        Ok(0.0)->E.R2.fmap(Wrappers.evNumber)
      },
      (),
    )
}

module Internals = {
  let factorial = Stdlib.Math.factorial
  let choose = ((n, k)) => factorial(n) /. (factorial(n -. k) *. factorial(k))
  let pow = (base, exp) => Js.Math.pow_float(~base, ~exp)
  let binomial = ((n, k, p)) => choose((n, k)) *. pow(p, k) *. pow(1.0 -. p, n -. k)
  let applyFunctionAtPoint = (aLambda, internalNumber: internalExpressionValue, environment , reducer): result<
    ReducerInterface_InternalExpressionValue.t,
    Reducer_ErrorValue.errorValue,
  > => {
    let x = internalNumber
    let result =  Reducer_Expression_Lambda.doLambdaCall(
      aLambda,
      list{x},
      environment,
      reducer,
    )
    result
  }

}

let library = [
  Function.make(
    ~name="laplace",
    ~nameSpace,
    ~requiresNamespace,
    ~output=EvtNumber,
    ~examples=[`Danger.laplace(1, 20)`],
    ~definitions=[
      TwoNumbersToNumber.make("laplace", ((successes, trials)) =>
        (successes +. 1.0) /. (trials +. 2.0)
      ),
    ],
    (),
  ),
  Function.make(
    ~name="factorial",
    ~nameSpace,
    ~requiresNamespace,
    ~output=EvtNumber,
    ~examples=[`Danger.factorial(20)`],
    ~definitions=[NumberToNumber.make("factorial", Internals.factorial)],
    (),
  ),
  Function.make(
    ~name="choose",
    ~nameSpace,
    ~requiresNamespace,
    ~output=EvtNumber,
    ~examples=[`Danger.choose(1, 20)`],
    ~definitions=[TwoNumbersToNumber.make("choose", Internals.choose)],
    (),
  ),
  Function.make(
    ~name="binomial",
    ~nameSpace,
    ~requiresNamespace,
    ~output=EvtNumber,
    ~examples=[`Danger.binomial(1, 20, 0.5)`],
    ~definitions=[ThreeNumbersToNumber.make("binomial", Internals.binomial)],
    (),
  ),
  Function.make(
    ~name="functionToZero",
    ~nameSpace,
    ~requiresNamespace,
    ~output=EvtNumber,
    ~examples=[`Danger.functionToZero({|x| x})`],
    ~definitions=[FunctionToNumberZero.make("functionToZero", x => x)],
    (),
  ),
  Function.make(
    ~name="applyFunctionAtPoint",
    ~nameSpace,
    ~output=EvtArray,
    ~requiresNamespace=false,
    ~examples=[`Danger.applyFunctionAtPoint({|x| x+1}, 1)`],
    ~definitions=[
      FnDefinition.make(
        ~name="applyFunctionAtPoint",
        ~inputs=[FRTypeLambda, FRTypeNumber],
        ~run=(inputs, _, env, reducer) =>
          switch inputs {
          | [IEvLambda(aLambda), point] =>
            Internals.applyFunctionAtPoint(aLambda, point, env, reducer)->E.R2.errMap(_ => "Error!")
          | _ => Error(impossibleError)
          },
        (),
      ),
    ],
    (),
  ),
]