package tui

import (
	"github.com/rivo/uniseg"
	"zgo.at/termfo/keys"
	"strings"
)

type TextInput struct {
	id string
	linesBefore []string
	beforeCursor string
	selection string
	selectionBefore bool
	afterCursor string
	linesAfter []string
}

func (t *TextInput) Text() string {
	return t.beforeCursor + t.selection + t.afterCursor
}

func (t *TextInput) SetText(text string) {
	t.beforeCursor = ""
	t.afterCursor = text
}

func toGraphemes(s string) []string {
	g := uniseg.NewGraphemes(s)
	var result []string
	for g.Next() {
		result = append(result, g.Str())
	}
	return result
}

func splitRight(s string) (string, string) {
	if s == "" {
		return "", ""
	}
	gs := toGraphemes(s)
	return strings.Join(gs[:len(gs) - 1], ""), gs[len(gs) - 1]
}

func splitLeft(s string) (string, string) {
	if s == "" {
		return "", ""
	}
	cluster, rest, _, _ := uniseg.FirstGraphemeCluster([]byte(s), 0)
	return string(cluster), string(rest)
}

func (t *TextInput) Left(selection bool, word bool) {
	t.Deselect()
	var right string
	t.beforeCursor, right = splitRight(t.beforeCursor)
	t.afterCursor = right + t.afterCursor
}

func (t *TextInput) Right(selection bool, word bool) {
	t.Deselect()
	var left string
	left, t.afterCursor = splitLeft(t.afterCursor)
	t.beforeCursor += left
}

func (t *TextInput) Start(selection bool) {
	t.afterCursor = t.beforeCursor + t.afterCursor
	t.beforeCursor = ""
}

func (t *TextInput) End(selection bool) {
	t.beforeCursor = t.beforeCursor + t.afterCursor
	t.afterCursor = ""
}

func (t *TextInput) Selection() string {
	return t.selection
}

func (t *TextInput) Deselect() {
	if t.selectionBefore {
		t.beforeCursor += t.selection
	} else {
		t.afterCursor = t.selection + t.afterCursor
	}
	t.selection = ""
}

func (t *TextInput) Write(text string) {
	t.selection = ""
	t.beforeCursor += text
}

func (t *TextInput) Update(ev Event) (usedKeybind bool) {
	if Selected != t.id {
		return
	}
	if ev.TextInput != 0 {
		t.Write(string(ev.TextInput))
	}

	selection := ev.Key & keys.Shift != 0
	word := ev.Key & keys.Ctrl != 0
	switch ev.Key.WithoutMods() {
	case keys.Left:
		t.Left(selection, word)
	case keys.Right:
		t.Right(selection, word)
	case 'a':
		if ev.Key & keys.Ctrl != 0 {
			t.Start(selection)
		}
	case 'e':
		if ev.Key & keys.Ctrl != 0 {
			t.End(selection)
		}
	case keys.Backspace:
		if t.selection != "" {
			t.selection = ""
		} else {
			t.beforeCursor, _ = splitRight(t.beforeCursor)
		}
	default:
		return false
	}
	return true
}

func (t *TextInput) Show(id string) {
	t.id = id
	Push(id, Box {Width: Fill, Height: 4})//TextSize})
	Text(t.beforeCursor, nil)
	if t.selectionBefore {
		Text(t.selection, &Style {Bg: Blue, Fg: White, selected: true})
	}
	Cursor()
	if !t.selectionBefore {
		Text(t.selection, &Style {Bg: Blue, Fg: White, selected: true})
	}
	Text(t.afterCursor, nil)
	Pop()
}