package editor

import (
	"timshome.page/gilo/char"
	"timshome.page/gilo/editor/document"
	"timshome.page/gilo/internal/gilo"
	"timshome.page/gilo/terminal"
)

// ----------------------------------------------------------------------------
// !Constants representing input keys
// ----------------------------------------------------------------------------

const (
	keyUp       = "ARROW_UP"
	keyDown     = "ARROW_DOWN"
	keyLeft     = "ARROW_LEFT"
	keyRight    = "ARROW_RIGHT"
	keyPageUp   = "PAGE_UP"
	keyPageDown = "PAGE_DOWN"
	keyHome     = "HOME"
	keyEnd      = "END"
	keyDelete   = "DELETE"
)

/**
 * Determine what to do with an individual character of input
 */
func (e *Editor) processKeypressChar(ch rune) bool {
	switch ch {
	case char.Ctrl('q'):
		if e.doc.IsDirty() && e.quitTimes > 0 {
			e.SetStatusMessage("WARNING!!! File has unsaved changes. Press Ctrl-Q %d more times to quit.", e.quitTimes)
			e.quitTimes -= 1

			return true
		}

		// Clean up on exit
		terminal.Write(terminal.ClearScreen + terminal.ResetCursor)

		return false

	case char.Ctrl('s'):
		e.save()

	case char.Ctrl('f'):
		e.find()

	case char.Enter:
		e.doc.InsertNewline(e.cursor)
		e.cursor.Y += 1
		e.cursor.X = 0

	case char.Backspace, char.Ctrl('h'):
		e.delChar()

	case char.Esc, char.Ctrl('l'):
		// Modifier keys that return ANSI escape sequences
		str := parseEscapeSequence()

		// Don't swallow a character after ESC if it doesn't
		// start an ANSI escape sequence
		if len(str) == 1 {
			return e.processKeypressChar(rune(str[0]))
		}

		e.processKeypressStr(str)

	default:
		e.insertChar(ch)
	}

	// Clear the quit message and restart the
	// confirmation count if confirmation is not
	// completed
	if e.quitTimes != gilo.QuitTimes {
		e.quitTimes = gilo.QuitTimes
		e.SetStatusMessage("")
	}

	return true
}

/**
 * Determine what do do with a parsed ANSI escape sequence
 */
func (e *Editor) processKeypressStr(key string) {
	switch key {
	case keyUp,
		keyDown,
		keyLeft,
		keyRight,
		keyPageUp,
		keyPageDown,
		keyHome,
		keyEnd:

		e.moveCursor(key)

	case keyDelete:
		e.moveCursor(keyRight)
		e.delChar()
	}
}

func (e *Editor) moveCursor(key string) {
	var row *document.Row
	if e.cursor.Y >= e.doc.RowCount() {
		row = nil
	} else {
		row = e.doc.GetRow(e.cursor.Y)
	}

	switch key {
	case keyLeft:
		if e.cursor.X != 0 {
			e.cursor.X -= 1
		}

		// Move from beginning of current row to end of previous row
		if e.cursor.Y > 0 {
			e.cursor.Y -= 1
			e.cursor.X = e.doc.GetRow(e.cursor.Y).Size()
		}
	case keyRight:
		if row != nil && e.cursor.X < row.Size() {
			e.cursor.X += 1
		}

		// Move from end of current line to beginning of next line
		if row != nil && e.cursor.X == row.Size() && e.cursor.Y < e.doc.RowCount()-1 {
			e.cursor.Y += 1
			e.cursor.X = 0
		}
	case keyUp:
		if e.cursor.Y != 0 {
			e.cursor.Y -= 1
		}
	case keyDown:
		if e.cursor.Y < e.doc.RowCount() {
			e.cursor.Y += 1
		}
	case keyPageUp:
		if e.cursor.Y > e.screen.Rows {
			e.cursor.Y -= e.screen.Rows
		} else {
			e.cursor.Y = 0
		}

	case keyPageDown:
		if e.cursor.Y+e.screen.Rows > e.doc.RowCount() {
			e.cursor.Y += e.screen.Rows
		} else {
			e.cursor.Y = e.doc.RowCount() - 1
		}

	case keyHome:
		e.cursor.X = 0
	case keyEnd:
		if row != nil {
			e.cursor.X = row.Size()
		}
	}

	if e.cursor.Y < e.doc.RowCount() {
		row = e.doc.GetRow(e.cursor.Y)
		rowLen := row.Size()

		// Snap to the end of a shorter line from a longer one
		if e.cursor.X > rowLen {
			e.cursor.X = rowLen
		}
	}
}

// Convert the raw ANSI escape sequences to the type of key input
func parseEscapeSequence() string {
	// If we aren't starting an escape sequence,
	// return the character
	startChar, _ := terminal.ReadKey()
	if startChar != '[' && startChar != 'O' {
		return string(startChar)
	}

	// Read one or two characters after
	// \e[ or \eO, which is the end of the
	// handled escape sequences
	runes := [2]rune{'\000', '\000'}
	for i := 0; i < 2; i++ {
		ch, size := terminal.ReadKey()
		if size == 0 {
			return string(char.Esc)
		}
		runes[i] = ch

		if i == 0 && runes[0] >= 'A' && runes[0] <= 'Z' {
			return escSeqToKey([]rune{startChar, runes[0]})
		}

		// \e[*~
		if i == 1 && startChar == '[' && runes[1] == '~' {
			return escSeqToKey([]rune{startChar, runes[0], runes[1]})
		}
	}

	return string(char.Esc)
}

func escSeqToKey(seq []rune) string {
	// \eO*
	// \e[*
	if len(seq) == 2 {
		startChar, cmd := seq[0], seq[1]
		if startChar == 'O' {
			switch cmd {
			case 'H':
				return keyHome
			case 'F':
				return keyEnd
			}
		} else if startChar == '[' {
			switch cmd {
			case 'A':
				return keyUp
			case 'B':
				return keyDown
			case 'C':
				return keyRight
			case 'D':
				return keyLeft
			case 'H':
				return keyHome
			case 'F':
				return keyEnd
			}
		}
	} else if len(seq) == 3 { // \e[*~
		cmd := seq[1]
		switch cmd {
		case '1':
			return keyHome
		case '3':
			return keyDelete
		case '4':
			return keyEnd
		case '5':
			return keyPageUp
		case '6':
			return keyPageDown
		case '7':
			return keyHome
		case '8':
			return keyEnd
		}
	}

	return string(char.Esc)
}