package tui

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

type TextInput struct {
	id string
	beforeCursor string
	selection string
	selectionBefore bool
	afterCursor string
	Private bool
}

var selectedStyle = Style {Bg: Blue, Fg: White, selected: true}

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

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

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, word bool) (string, string) {
	if s == "" {
		return "", ""
	}
	gs := toGraphemes(s)
	if !word {
		return strings.Join(gs[:len(gs) - 1], ""), gs[len(gs) - 1]
	} else {
		i := len(gs)
		for unicode.IsSpace([]rune(gs[i - 1])[0]) {
			i--
			if i < 0 {
				return "", s
			}
		}
		for !unicode.IsSpace([]rune(gs[i - 1])[0]) {
			i--
			if i < 1 {
				break
			}
		}
		return strings.Join(gs[:i], ""), strings.Join(gs[i:], "")
	}
}

func splitLeft(s string, word bool) (string, string) {
	if s == "" {
		return "", ""
	}
	gs := toGraphemes(s)
	if !word {
		return gs[0], strings.Join(gs[1:], "")
	} else {
		i := 0
		for unicode.IsSpace([]rune(gs[i])[0]) {
			i++
			if i >= len(gs) {
				return "", s
			}
		}
		for !unicode.IsSpace([]rune(gs[i])[0]) {
			i++
			if i >= len(gs) {
				break
			}
		}
		return strings.Join(gs[:i], ""), strings.Join(gs[i:], "")
	}
}

func (t *TextInput) Left(selection bool, word bool) {
	if !selection {
		t.Deselect()
	}
	if selection && t.selection == "" {
		t.selectionBefore = false
	}
	var right string
	if selection && t.selectionBefore {
		t.selection, right = splitRight(t.selection, word)
	} else {
		t.beforeCursor, right = splitRight(t.beforeCursor, word)
	}
	if !selection || t.selectionBefore {
		t.afterCursor = right + t.afterCursor
	} else {
		t.selection = right + t.selection
	}
}

func (t *TextInput) Right(selection bool, word bool) {
	if !selection {
		t.Deselect()
	}
	if selection && t.selection == "" {
		t.selectionBefore = true
	}
	var left string
	if selection && !t.selectionBefore {
		left, t.selection = splitLeft(t.selection, word)
	} else {
		left, t.afterCursor = splitLeft(t.afterCursor, word)
	}
	if !selection || !t.selectionBefore {
		t.beforeCursor += left
	} else {
		t.selection += left
	}
}

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

func (t *TextInput) End(selection bool) {
	if !selection {
		t.Deselect()
	}
	if selection {
		t.selection = t.selection + t.afterCursor
		t.selectionBefore = true
	} else {
		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) IsEmpty() bool {
	return t.beforeCursor == "" && t.selection == "" && t.afterCursor == ""
}

func (t *TextInput) Update(ev Event) (usedKeybind bool) {
	if Selected != t.id {
		t.Deselect()
		return
	}
	if ev.TextInput != 0 {
		t.Write(string(ev.TextInput))
	}
	if ev.Key == keys.Tab {
		t.Write("\t")
	}

	selection := ev.Key & keys.Shift != 0
	word := ev.Key & keys.Ctrl != 0
	if ev.Key & keys.Alt != 0 {
		selection = true
		word = true
	}
	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 | keys.Alt) != 0 {
			t.Start(selection)
		}
	case 'e':
		if ev.Key & (keys.Ctrl | keys.Alt) != 0 {
			t.End(selection)
		}
	case 'h':
		if ev.Key & keys.Ctrl == 0 {
			break
		}
		word = false
		fallthrough
	case keys.Backspace:
		if t.selection != "" {
			t.selection = ""
		} else {
			t.beforeCursor, _ = splitRight(t.beforeCursor, word)
		}
	case 'j':
		if ev.Key & keys.Ctrl != 0 {
			t.Write("\n")
		}
	default:
		return false
	}
	return true
}

func (t *TextInput) showText(text string, style *Style) {
	if !t.Private {
		Text(text, style)
	} else {
		Text(strings.Repeat("*", len([]rune(text))), style)
	}
}

func (t *TextInput) Show(id string) {
	t.id = id
	Push(id, Box {Width: Fill, Height: TextSize})
	t.showText(t.beforeCursor, nil)
	if t.selectionBefore {
		t.showText(t.selection, &selectedStyle)
	}
	if t.selection == "" {
		Cursor()
	}
	if !t.selectionBefore {
		t.showText(t.selection, &selectedStyle)
	}
	t.showText(t.afterCursor, nil)
	Pop()
}