package subex

import (
	"main/walk"
	"errors"
)

func binopAdd(values []walk.Value) ([]walk.Value, error) {
	if len(values) != 2 {
		return nil, errors.New("Tried to sum a weird number of values")
	}

	lhs, lhsIsNumber := values[0].(walk.NumberValue)
	if !lhsIsNumber {
		return nil, errors.New("Tried to sum a lhs that is not a number")
	}

	rhs, rhsIsNumber := values[1].(walk.NumberValue)
	if !rhsIsNumber {
		return nil, errors.New("Tried to sum a rhs that is not a number")
	}

	return []walk.Value{walk.NumberValue(float64(lhs) + float64(rhs))}, nil
}

func binopMultiply(values []walk.Value) ([]walk.Value, error) {
	if len(values) != 2 {
		return nil, errors.New("Tried to multiply a weird number of values")
	}

	lhs, lhsIsNumber := values[0].(walk.NumberValue)
	if !lhsIsNumber {
		return nil, errors.New("Tried to multiply a lhs that is not a number")
	}

	rhs, rhsIsNumber := values[1].(walk.NumberValue)
	if !rhsIsNumber {
		return nil, errors.New("Tried to multiply a rhs that is not a number")
	}

	return []walk.Value{walk.NumberValue(float64(lhs) * float64(rhs))}, nil
}

func binopDivide(values []walk.Value) ([]walk.Value, error) {
	if len(values) != 2 {
		return nil, errors.New("Tried to divide a weird number of values")
	}

	lhs, lhsIsNumber := values[0].(walk.NumberValue)
	if !lhsIsNumber {
		return nil, errors.New("Tried to divide a lhs that is not a number")
	}

	rhs, rhsIsNumber := values[1].(walk.NumberValue)
	if !rhsIsNumber {
		return nil, errors.New("Tried to divide a rhs that is not a number")
	}

	return []walk.Value{walk.NumberValue(float64(lhs) / float64(rhs))}, nil
}

func arithmeticSum(values []walk.Value) ([]walk.Value, error) {
	var total float64 = 0
	for _, value := range values {
		n, isNumber := value.(walk.NumberValue)
		if !isNumber {
			return nil, errors.New("Tried to sum non-number value")
		}
		total += float64(n)
	}

	return []walk.Value{walk.NumberValue(total)}, nil
}

func arithmeticProduct(values []walk.Value) ([]walk.Value, error) {
	var product float64 = 0
	for _, value := range values {
		n, isNumber := value.(walk.NumberValue)
		if !isNumber {
			return nil, errors.New("Tried to sum non-number value")
		}
		product *= float64(n)
	}

	return []walk.Value{walk.NumberValue(product)}, nil
}