package modes

import (
	"fmt"
	"image/color"
	"math"
	"strconv"
	"strings"

	"github.com/hajimehoshi/ebiten/v2"

	"kidskeyboard/internal/ui"
)

type CalculatorMode struct {
	ctx      Context
	display  string
	acc      float64
	op       string
	newEntry bool
	err      bool
}

func NewCalculatorMode(ctx Context) *CalculatorMode {
	return &CalculatorMode{ctx: ctx, display: "0", newEntry: true}
}

func (m *CalculatorMode) Name() string { return "CTRL+F4 Calculator" }
func (m *CalculatorMode) OnEnter()     {}
func (m *CalculatorMode) OnLeave()     {}
func (m *CalculatorMode) Update()      {}

func (m *CalculatorMode) HandleInput() {
	handled := false
	valid := false
	chars := ebiten.AppendInputChars(nil)

	for _, r := range chars {
		handled = true
		if m.handleChar(r) {
			valid = true
		}
	}

	for _, key := range justPressedKeys() {
		switch {
		case key == ebiten.KeyDelete:
			handled = true
			m.clear()
			valid = true
		case key == ebiten.KeyBackspace:
			handled = true
			m.backspace()
			valid = true
		case key == ebiten.KeyEnter || key == ebiten.KeyNumpadEnter:
			handled = true
			m.equals()
			valid = true
		case isNumpadOperatorKey(key) && len(chars) == 0:
			handled = true
			m.operator(operatorForKey(key))
			valid = true
		default:
			if childKey(key) && len(chars) == 0 {
				handled = true
			}
		}
	}

	if valid {
		m.ctx.Audio.PlayBeep()
	} else if handled {
		m.ctx.Audio.PlayError()
	}
}

func (m *CalculatorMode) handleChar(r rune) bool {
	switch {
	case r >= '0' && r <= '9':
		m.digit(string(r))
		return true
	case r == '+' || r == '-' || r == '*' || r == '/':
		m.operator(string(r))
		return true
	case r == 'c' || r == 'C':
		m.clear()
		return true
	default:
		return false
	}
}

func (m *CalculatorMode) Draw(screen *ebiten.Image) {
	screen.Fill(color.Black)
	w, h := screen.Bounds().Dx(), screen.Bounds().Dy()
	ui.Text(screen, "CTRL+F4", 20, 20, color.White, 2)

	panelW := float32(min(float64(w)*0.78, 620))
	keySize := panelW / 4
	startX := (float32(w) - panelW) / 2
	startY := float32(h)/2 - keySize*1.9
	displayH := keySize * 0.72

	ui.Rect(screen, startX, startY-displayH-16, panelW, displayH, color.NRGBA{R: 20, G: 20, B: 20, A: 255})
	ui.RectOutline(screen, startX, startY-displayH-16, panelW, displayH, 2, color.White)
	scale := 4.0
	if len(m.display) > 12 {
		scale = 3
	}
	ui.CenteredText(screen, m.display, int(startX+panelW/2), int(startY-displayH/2-16), color.White, scale)

	keys := [][]string{
		{"7", "8", "9", "/"},
		{"4", "5", "6", "*"},
		{"1", "2", "3", "-"},
		{"C", "0", "=", "+"},
	}
	for r, row := range keys {
		for c, label := range row {
			x := startX + float32(c)*keySize
			y := startY + float32(r)*keySize
			ui.Rect(screen, x+4, y+4, keySize-8, keySize-8, color.NRGBA{R: 28, G: 28, B: 28, A: 255})
			ui.RectOutline(screen, x+4, y+4, keySize-8, keySize-8, 2, color.White)
			ui.CenteredText(screen, label, int(x+keySize/2), int(y+keySize/2), color.White, 4)
		}
	}
}

func (m *CalculatorMode) digit(d string) {
	if m.err || m.newEntry || m.display == "0" {
		m.display = d
		m.newEntry = false
		m.err = false
		return
	}
	if len(m.display) < 16 {
		m.display += d
	}
}

func (m *CalculatorMode) operator(op string) {
	if m.err {
		return
	}
	if m.op != "" && !m.newEntry {
		m.equals()
	}
	m.acc = m.value()
	m.op = op
	m.newEntry = true
}

func (m *CalculatorMode) equals() {
	if m.err || m.op == "" {
		m.newEntry = true
		return
	}
	right := m.value()
	var result float64
	switch m.op {
	case "+":
		result = m.acc + right
	case "-":
		result = m.acc - right
	case "*":
		result = m.acc * right
	case "/":
		if right == 0 {
			m.display = "DIV 0"
			m.err = true
			m.op = ""
			m.newEntry = true
			return
		}
		result = m.acc / right
	}
	m.display = formatNumber(result)
	m.acc = result
	m.op = ""
	m.newEntry = true
}

func (m *CalculatorMode) backspace() {
	if m.err || m.newEntry || len(m.display) <= 1 {
		m.display = "0"
		m.err = false
		m.newEntry = true
		return
	}
	m.display = m.display[:len(m.display)-1]
}

func (m *CalculatorMode) clear() {
	m.display = "0"
	m.acc = 0
	m.op = ""
	m.err = false
	m.newEntry = true
}

func (m *CalculatorMode) value() float64 {
	v, _ := strconv.ParseFloat(m.display, 64)
	return v
}

func formatNumber(v float64) string {
	if math.Abs(v-math.Round(v)) < 0.0000001 {
		return fmt.Sprintf("%.0f", v)
	}
	return strings.TrimRight(strings.TrimRight(fmt.Sprintf("%.6f", v), "0"), ".")
}

func isNumpadOperatorKey(key ebiten.Key) bool {
	switch key {
	case ebiten.KeyNumpadAdd, ebiten.KeyNumpadSubtract, ebiten.KeyNumpadMultiply, ebiten.KeyNumpadDivide:
		return true
	default:
		return false
	}
}

func operatorForKey(key ebiten.Key) string {
	switch key {
	case ebiten.KeyNumpadAdd:
		return "+"
	case ebiten.KeyNumpadSubtract:
		return "-"
	case ebiten.KeyNumpadMultiply:
		return "*"
	case ebiten.KeyNumpadDivide:
		return "/"
	default:
		return ""
	}
}