package builtin

import (
	"math"

	"gitee.com/blizzard1413/dsl/function"
	"gitee.com/blizzard1413/dsl/types"
)

// RegisterMath 注册所有数学函数
func RegisterMath(registry function.Registry) error {
	mathFuncs := []struct {
		name string
		fn   func([]interface{}) (interface{}, error)
		sig  *function.Signature
	}{
		{"Math.abs", mathAbs, function.NewSignature([]types.Type{types.NewNumberType()}, types.NewNumberType())},
		{"Math.ceil", mathCeil, function.NewSignature([]types.Type{types.NewNumberType()}, types.NewNumberType())},
		{"Math.floor", mathFloor, function.NewSignature([]types.Type{types.NewNumberType()}, types.NewNumberType())},
		{"Math.round", mathRound, function.NewSignature([]types.Type{types.NewNumberType()}, types.NewNumberType())},
		{"Math.sqrt", mathSqrt, function.NewSignature([]types.Type{types.NewNumberType()}, types.NewNumberType())},
		{"Math.max", mathMax, function.NewVariadicSignature(1, types.NewNumberType())},
		{"Math.min", mathMin, function.NewVariadicSignature(1, types.NewNumberType())},
		{"Math.pow", mathPow, function.NewSignature([]types.Type{types.NewNumberType(), types.NewNumberType()}, types.NewNumberType())},
	}

	for _, mf := range mathFuncs {
		if err := registry.RegisterNative(mf.name, mf.sig, mf.fn); err != nil {
			return err
		}
	}

	return nil
}

// mathAbs 返回数字的绝对值
func mathAbs(args []interface{}) (interface{}, error) {
	x := toFloat64(args[0])
	return math.Abs(x), nil
}

// mathCeil 向上取整
func mathCeil(args []interface{}) (interface{}, error) {
	x := toFloat64(args[0])
	return math.Ceil(x), nil
}

// mathFloor 向下取整
func mathFloor(args []interface{}) (interface{}, error) {
	x := toFloat64(args[0])
	return math.Floor(x), nil
}

// mathRound 四舍五入
func mathRound(args []interface{}) (interface{}, error) {
	x := toFloat64(args[0])
	return math.Round(x), nil
}

// mathSqrt 平方根
func mathSqrt(args []interface{}) (interface{}, error) {
	x := toFloat64(args[0])
	return math.Sqrt(x), nil
}

// mathMax 返回最大值
func mathMax(args []interface{}) (interface{}, error) {
	if len(args) == 0 {
		return math.Inf(-1), nil
	}

	max := toFloat64(args[0])
	for i := 1; i < len(args); i++ {
		val := toFloat64(args[i])
		if val > max {
			max = val
		}
	}
	return max, nil
}

// mathMin 返回最小值
func mathMin(args []interface{}) (interface{}, error) {
	if len(args) == 0 {
		return math.Inf(1), nil
	}

	min := toFloat64(args[0])
	for i := 1; i < len(args); i++ {
		val := toFloat64(args[i])
		if val < min {
			min = val
		}
	}
	return min, nil
}

// mathPow 幂运算
func mathPow(args []interface{}) (interface{}, error) {
	base := toFloat64(args[0])
	exponent := toFloat64(args[1])
	return math.Pow(base, exponent), nil
}