package niri

import (
	"encoding/json"
	"fmt"
	"regexp"
	"strconv"
)

type PositionChange struct {
	SetFixed    Option[int] `json:"SetFixed,omitempty"`
	AdjustFixed Option[int] `json:"AdjustFixed,omitempty"`
}

func (m PositionChange) String() string {
	data, _ := json.MarshalIndent(m, "", "\t")
	return string(data)
}

func PositionSetFixed(position int) PositionChange {
	return PositionChange{SetFixed: &position}
}

func PositionAdjustFixed(position int) PositionChange {
	return PositionChange{AdjustFixed: &position}
}

const positionPatternString = `^(\+|-)?(\d+?)$`
const positionPatternGroupAdjust = 1
const positionPatternGroupIntValue = 2

var positionPattern = regexp.MustCompile(positionPatternString)

func ParsePosition(str string) (PositionChange, error) {
	matches := positionPattern.FindStringSubmatch(str)
	if matches == nil {
		return PositionChange{}, fmt.Errorf("invalid position spec '%s'. Expected pattern: %s", str, positionPatternString)
	}

	adjust := matches[positionPatternGroupAdjust] != ""
	negative := matches[positionPatternGroupAdjust] == "-"

	factor := 1
	if negative {
		factor = -1
	}

	intValue, err := strconv.ParseInt(matches[positionPatternGroupIntValue], 10, 64)
	if err != nil {
		return PositionChange{}, fmt.Errorf("invalid position spec '%s'. Expected pattern: %s", str, positionPatternString)
	}

	switch true {
	case adjust:
		return PositionAdjustFixed(int(intValue) * factor), nil
	case !adjust:
		return PositionSetFixed(int(intValue) * factor), nil
	default:
		return PositionChange{}, fmt.Errorf("invalid position spec '%s'. Expected pattern: %s", str, positionPatternString)
	}
}