// funcs-math.go
package expr

import (
	"fmt"
	"io"
)

func checkNumberParamExpected(funcName string, paramValue any, paramPos int) (err error) {
	if !(isNumber(paramValue) || isList(paramValue)) {
		err = fmt.Errorf("%s(): param nr %d has wrong type %T, number expected", funcName, paramPos+1, paramValue)
	}
	return
}

func doAdd(ctx ExprContext, name string, it Iterator) (result any, err error) {
	var sumAsFloat = false
	var floatSum float64 = 0.0
	var intSum int64 = 0
	var v any

	for v, err = it.Next(); err == nil; v, err = it.Next() {
		if err = checkNumberParamExpected(name, v, it.Index()); err != nil {
			break
		}

		if array, ok := v.([]any); ok {
			if v, err = doAdd(ctx, name, NewFlatArrayIterator(array)); err != nil {
				break
			}
		}

		if !sumAsFloat && isFloat(v) {
			sumAsFloat = true
			floatSum = float64(intSum)
		}
		if sumAsFloat {
			floatSum += numAsFloat(v)
		} else {
			iv, _ := v.(int64)
			intSum += iv
		}
	}
	if err == nil || err == io.EOF {
		err = nil
		if sumAsFloat {
			result = floatSum
		} else {
			result = intSum
		}
	}
	return
}

func addFunc(ctx ExprContext, name string, args []any) (result any, err error) {
	result, err = doAdd(ctx, name, NewFlatArrayIterator(args))
	return
}

func doMul(ctx ExprContext, name string, it Iterator) (result any, err error) {
	var mulAsFloat = false
	var floatProd float64 = 1.0
	var intProd int64 = 1
	var v any

	for v, err = it.Next(); err == nil; v, err = it.Next() {
		if err = checkNumberParamExpected(name, v, it.Index()); err != nil {
			break
		}

		if array, ok := v.([]any); ok {
			if v, err = doAdd(ctx, name, NewFlatArrayIterator(array)); err != nil {
				break
			}
		}

		if !mulAsFloat && isFloat(v) {
			mulAsFloat = true
			floatProd = float64(intProd)
		}
		if mulAsFloat {
			floatProd *= numAsFloat(v)
		} else {
			iv, _ := v.(int64)
			intProd *= iv
		}
	}
	if err == nil || err == io.EOF {
		err = nil
		if mulAsFloat {
			result = floatProd
		} else {
			result = intProd
		}
	}
	return
}

func mulFunc(ctx ExprContext, name string, args []any) (result any, err error) {
	result, err = doMul(ctx, name, NewFlatArrayIterator(args))
	return
}

func ImportMathFuncs(ctx ExprContext) {
	ctx.RegisterFunc("add", &simpleFunctor{f: addFunc}, 0, -1)
	ctx.RegisterFunc("mul", &simpleFunctor{f: mulFunc}, 0, -1)
}