package input

import "unicode"
import "git.tebibyte.media/sashakoshka/stone"

var selectedInput *Input

func SelectNone () {
	selectedInput = nil
}

type Input struct {
	cursor int
	text   []rune
	X, Y, Width int
	Obscure bool
	OnDone func ()
	OnCancel func ()
}

func (input *Input) HandleButton (button stone.Button, control, shift, alt bool) {
	switch button {
	case stone.KeyLeft:
		if control {
			input.cursor -= input.distanceToPreviousWordBound()
		} else if alt {
			input.cursorToBeginning()
		} else {
			input.cursor --
		}
		input.constrainCursor()
		
	case stone.KeyRight:
		if control {
			input.cursor += input.distanceToNextWordBound()
		} else if alt {
			input.cursorToEnd()
		} else {
			input.cursor ++
		}
		input.constrainCursor()
		
	case stone.KeyHome:
		input.cursorToBeginning()
		input.constrainCursor()
		
	case stone.KeyEnd:
		input.cursorToEnd()
		input.constrainCursor()
	
	case stone.KeyBackspace:
		if control {
			input.backspace(input.distanceToPreviousWordBound())
		} else if alt {
			input.backspace(input.cursor)
		} else {
			input.backspace(1)
		}
		input.constrainCursor()
	
	case stone.KeyDelete:
		if control {
			input.delete(input.distanceToNextWordBound())
		} else if alt {
			input.delete(len(input.text))
		} else {
			input.delete(1)
		}
		input.constrainCursor()

	case stone.KeyEnter:
		SelectNone()
		if input.OnDone != nil {
			input.OnDone()
		}

	case stone.KeyEscape:
		SelectNone()
		if input.OnCancel != nil {
			input.OnCancel()
		}
	
	default:
		if button.Printable() {
			input.text = append(input.text, 0)
			copy (
				input.text[input.cursor + 1:],
				input.text[input.cursor:])
			input.text[input.cursor] = rune(button)
			input.cursor ++
		}
	}

	return
}

func (input *Input) Draw (buffer stone.Buffer) {
	buffer.SetRune(input.X, input.Y, '[')
	buffer.SetRune(input.X + 1, input.Y, 0)
	buffer.SetRune(input.X + input.Width - 2, input.Y, 0)
	buffer.SetRune(input.X + input.Width - 1, input.Y, ']')

	actualWidth := input.Width - 4
	scroll := 0

	x := input.X + 2
	for index := 0; index < actualWidth; index ++ {
		character := input.charAtSafe(index + scroll)

		if input.Selected() && index == input.cursor {
			buffer.SetStyle(x, input.Y, stone.StyleUnderline)
		} else {
			buffer.SetStyle(x, input.Y, stone.StyleNormal)
		}

		if input.Obscure && character > 0 {
			buffer.SetRune(x, input.Y, '*')
		} else {
			buffer.SetRune(x, input.Y, character)
		}
		x ++
	}
}

func (input *Input) charAtSafe (index int) (character rune) {
	if index <  0               { return }
	if index >= len(input.text) { return }
	character = input.text[index]
	return
}

func (input *Input) constrainCursor () (constrained bool) {
	if input.cursor < 0 {
		input.cursorToBeginning()
		constrained = true
	} else if input.cursor > len(input.text) {
		input.cursorToEnd()
		constrained = true
	}

	return
}

func (input *Input) distanceToPreviousWordBound () (distance int) {
	index := input.cursor
	index    --
	distance ++
	
	for {
		if index < 0 { break }
		
		character := input.text[index]
		isWordChar :=
			unicode.IsLetter(character) ||
			unicode.IsDigit(character)
		if !isWordChar {
			distance --
			break
		}
		
		distance ++
		index --
	}

	if distance < 1 {
		distance ++
	}

	return
}

func (input *Input) distanceToNextWordBound () (distance int) {
	index := input.cursor
	
	for {
		if index >= len(input.text) { break }
		
		character := input.text[index]
		isWordChar :=
			unicode.IsLetter(character) ||
			unicode.IsDigit(character)
		if !isWordChar {
			break
		}
		
		distance ++
		index ++
	}

	if distance < 1 {
		distance ++
	}

	return
}

func (input *Input) backspace (amount int) {
	if input.cursor - amount < 0 {
		amount = input.cursor
	}
		
	copy (
		input.text[input.cursor - amount:],
		input.text[input.cursor:])
	input.text = input.text[:len(input.text) - amount]
	input.cursor -= amount
}

func (input *Input) delete (amount int) {
	if input.cursor + amount > len(input.text) {
		amount = len(input.text) - input.cursor
	}

	// TODO
	copy (
		input.text[input.cursor:],
		input.text[input.cursor + amount:])
	input.text = input.text[:len(input.text) - amount]
}

func (input *Input) cursorToBeginning () {
	input.cursor = 0
}

func (input *Input) cursorToEnd () {
	input.cursor = len(input.text)
}

func (input *Input) Reset () {
	input.SetText("")
}

func (input *Input) Text () (text string) {
	text = string(input.text)
	return
}

func (input *Input) SetText (text string) {
	input.text = []rune(text)
	input.cursorToEnd()
	return
}

func (input *Input) Selected () (selected bool) {
	selected = selectedInput == input
	return
}

func (input *Input) Select () () {
	selectedInput = input
	return
}

func Selected () (selected *Input) {
	selected = selectedInput
	return
}