// +build !windows

package termbox

import (
	"fmt"
	"os"
	"os/signal"
	"runtime"
	"syscall"
	"time"

	"github.com/mattn/go-runewidth"
)

// public API

// Initializes termbox library. This function should be called before any other functions.
// After successful initialization, the library must be finalized using 'Close' function.
//
// Example usage:
//      err := termbox.Init()
//      if err != nil {
//              panic(err)
//      }
//      defer termbox.Close()
func Init() error {
	if IsInit {
		return nil
	}

	var err error

	if runtime.GOOS == "openbsd" || runtime.GOOS == "freebsd" {
		out, err = os.OpenFile("/dev/tty", os.O_RDWR, 0)
		if err != nil {
			return err
		}
		in = int(out.Fd())
	} else {
		out, err = os.OpenFile("/dev/tty", os.O_WRONLY, 0)
		if err != nil {
			return err
		}
		in, err = syscall.Open("/dev/tty", syscall.O_RDONLY, 0)
		if err != nil {
			return err
		}
	}

	err = setup_term()
	if err != nil {
		return fmt.Errorf("termbox: error while reading terminfo data: %v", err)
	}

	signal.Notify(sigwinch, syscall.SIGWINCH)
	signal.Notify(sigio, syscall.SIGIO)

	_, err = fcntl(in, syscall.F_SETFL, syscall.O_ASYNC|syscall.O_NONBLOCK)
	if err != nil {
		return err
	}
	_, err = fcntl(in, syscall.F_SETOWN, syscall.Getpid())
	if runtime.GOOS != "darwin" && err != nil {
		return err
	}
	err = tcgetattr(out.Fd(), &orig_tios)
	if err != nil {
		return err
	}

	tios := orig_tios
	tios.Iflag &^= syscall_IGNBRK | syscall_BRKINT | syscall_PARMRK |
		syscall_ISTRIP | syscall_INLCR | syscall_IGNCR |
		syscall_ICRNL | syscall_IXON
	tios.Lflag &^= syscall_ECHO | syscall_ECHONL | syscall_ICANON |
		syscall_ISIG | syscall_IEXTEN
	tios.Cflag &^= syscall_CSIZE | syscall_PARENB
	tios.Cflag |= syscall_CS8
	tios.Cc[syscall_VMIN] = 1
	tios.Cc[syscall_VTIME] = 0

	err = tcsetattr(out.Fd(), &tios)
	if err != nil {
		return err
	}

	out.WriteString(funcs[t_enter_ca])
	out.WriteString(funcs[t_enter_keypad])
	out.WriteString(funcs[t_hide_cursor])
	out.WriteString(funcs[t_clear_screen])

	termw, termh = get_term_size(out.Fd())
	back_buffer.init(termw, termh)
	front_buffer.init(termw, termh)
	back_buffer.clear()
	front_buffer.clear()

	go func() {
		buf := make([]byte, 128)
		for {
			select {
			case <-sigio:
				for {
					n, err := syscall.Read(in, buf)
					if err == syscall.EAGAIN || err == syscall.EWOULDBLOCK {
						break
					}
					select {
					case input_comm <- input_event{buf[:n], err}:
						ie := <-input_comm
						buf = ie.data[:128]
					case <-quit:
						return
					}
				}
			case <-quit:
				return
			}
		}
	}()

	IsInit = true
	return nil
}

// Interrupt an in-progress call to PollEvent by causing it to return
// EventInterrupt.  Note that this function will block until the PollEvent
// function has successfully been interrupted.
func Interrupt() {
	interrupt_comm <- struct{}{}
}

// Finalizes termbox library, should be called after successful initialization
// when termbox's functionality isn't required anymore.
func Close() {
	if !IsInit {
		return
	}

	quit <- 1
	out.WriteString(funcs[t_show_cursor])
	out.WriteString(funcs[t_sgr0])
	out.WriteString(funcs[t_clear_screen])
	out.WriteString(funcs[t_exit_ca])
	out.WriteString(funcs[t_exit_keypad])
	out.WriteString(funcs[t_exit_mouse])
	tcsetattr(out.Fd(), &orig_tios)

	out.Close()
	syscall.Close(in)

	// reset the state, so that on next Init() it will work again
	termw = 0
	termh = 0
	input_mode = InputEsc
	out = nil
	in = 0
	lastfg = attr_invalid
	lastbg = attr_invalid
	lastx = coord_invalid
	lasty = coord_invalid
	cursor_x = cursor_hidden
	cursor_y = cursor_hidden
	foreground = ColorDefault
	background = ColorDefault
	IsInit = false
}

// Synchronizes the internal back buffer with the terminal.
func Flush() error {
	// invalidate cursor position
	lastx = coord_invalid
	lasty = coord_invalid

	update_size_maybe()

	for y := 0; y < front_buffer.height; y++ {
		line_offset := y * front_buffer.width
		for x := 0; x < front_buffer.width; {
			cell_offset := line_offset + x
			back := &back_buffer.cells[cell_offset]
			front := &front_buffer.cells[cell_offset]
			if back.Ch < ' ' {
				back.Ch = ' '
			}
			w := runewidth.RuneWidth(back.Ch)
			if w == 0 || w == 2 && runewidth.IsAmbiguousWidth(back.Ch) {
				w = 1
			}
			if *back == *front {
				x += w
				continue
			}
			*front = *back
			send_attr(back.Fg, back.Bg)

			if w == 2 && x == front_buffer.width-1 {
				// there's not enough space for 2-cells rune,
				// let's just put a space in there
				send_char(x, y, ' ')
			} else {
				send_char(x, y, back.Ch)
				if w == 2 {
					next := cell_offset + 1
					front_buffer.cells[next] = Cell{
						Ch: 0,
						Fg: back.Fg,
						Bg: back.Bg,
					}
				}
			}
			x += w
		}
	}
	if !is_cursor_hidden(cursor_x, cursor_y) {
		write_cursor(cursor_x, cursor_y)
	}
	return flush()
}

// Sets the position of the cursor. See also HideCursor().
func SetCursor(x, y int) {
	if is_cursor_hidden(cursor_x, cursor_y) && !is_cursor_hidden(x, y) {
		outbuf.WriteString(funcs[t_show_cursor])
	}

	if !is_cursor_hidden(cursor_x, cursor_y) && is_cursor_hidden(x, y) {
		outbuf.WriteString(funcs[t_hide_cursor])
	}

	cursor_x, cursor_y = x, y
	if !is_cursor_hidden(cursor_x, cursor_y) {
		write_cursor(cursor_x, cursor_y)
	}
}

// The shortcut for SetCursor(-1, -1).
func HideCursor() {
	SetCursor(cursor_hidden, cursor_hidden)
}

// Changes cell's parameters in the internal back buffer at the specified
// position.
func SetCell(x, y int, ch rune, fg, bg Attribute) {
	if x < 0 || x >= back_buffer.width {
		return
	}
	if y < 0 || y >= back_buffer.height {
		return
	}

	back_buffer.cells[y*back_buffer.width+x] = Cell{ch, fg, bg}
}

// Returns the specified cell from the internal back buffer.
func GetCell(x, y int) Cell {
	return back_buffer.cells[y*back_buffer.width+x]
}

// Changes cell's character (rune) in the internal back buffer at the
// specified position.
func SetChar(x, y int, ch rune) {
	if x < 0 || x >= back_buffer.width {
		return
	}
	if y < 0 || y >= back_buffer.height {
		return
	}

	back_buffer.cells[y*back_buffer.width+x].Ch = ch
}

// Changes cell's foreground attributes in the internal back buffer at
// the specified position.
func SetFg(x, y int, fg Attribute) {
	if x < 0 || x >= back_buffer.width {
		return
	}
	if y < 0 || y >= back_buffer.height {
		return
	}

	back_buffer.cells[y*back_buffer.width+x].Fg = fg
}

// Changes cell's background attributes in the internal back buffer at
// the specified position.
func SetBg(x, y int, bg Attribute) {
	if x < 0 || x >= back_buffer.width {
		return
	}
	if y < 0 || y >= back_buffer.height {
		return
	}

	back_buffer.cells[y*back_buffer.width+x].Bg = bg
}

// Returns a slice into the termbox's back buffer. You can get its dimensions
// using 'Size' function. The slice remains valid as long as no 'Clear' or
// 'Flush' function calls were made after call to this function.
func CellBuffer() []Cell {
	return back_buffer.cells
}

// After getting a raw event from PollRawEvent function call, you can parse it
// again into an ordinary one using termbox logic. That is parse an event as
// termbox would do it. Returned event in addition to usual Event struct fields
// sets N field to the amount of bytes used within 'data' slice. If the length
// of 'data' slice is zero or event cannot be parsed for some other reason, the
// function will return a special event type: EventNone.
//
// IMPORTANT: EventNone may contain a non-zero N, which means you should skip
// these bytes, because termbox cannot recognize them.
//
// NOTE: This API is experimental and may change in future.
func ParseEvent(data []byte) Event {
	event := Event{Type: EventKey}
	status := extract_event(data, &event, false)
	if status != event_extracted {
		return Event{Type: EventNone, N: event.N}
	}
	return event
}

// Wait for an event and return it. This is a blocking function call. Instead
// of EventKey and EventMouse it returns EventRaw events. Raw event is written
// into `data` slice and Event's N field is set to the amount of bytes written.
// The minimum required length of the 'data' slice is 1. This requirement may
// vary on different platforms.
//
// NOTE: This API is experimental and may change in future.
func PollRawEvent(data []byte) Event {
	if len(data) == 0 {
		panic("len(data) >= 1 is a requirement")
	}

	var event Event
	if extract_raw_event(data, &event) {
		return event
	}

	for {
		select {
		case ev := <-input_comm:
			if ev.err != nil {
				return Event{Type: EventError, Err: ev.err}
			}

			inbuf = append(inbuf, ev.data...)
			input_comm <- ev
			if extract_raw_event(data, &event) {
				return event
			}
		case <-interrupt_comm:
			event.Type = EventInterrupt
			return event

		case <-sigwinch:
			event.Type = EventResize
			event.Width, event.Height = get_term_size(out.Fd())
			return event
		}
	}
}

// Wait for an event and return it. This is a blocking function call.
func PollEvent() Event {
	// Constant governing macOS specific behavior. See https://github.com/nsf/termbox-go/issues/132
	// This is an arbitrary delay which hopefully will be enough time for any lagging
	// partial escape sequences to come through.
	const esc_wait_delay = 100 * time.Millisecond

	var event Event
	var esc_wait_timer *time.Timer
	var esc_timeout <-chan time.Time

	// try to extract event from input buffer, return on success
	event.Type = EventKey
	status := extract_event(inbuf, &event, true)
	if event.N != 0 {
		copy(inbuf, inbuf[event.N:])
		inbuf = inbuf[:len(inbuf)-event.N]
	}
	if status == event_extracted {
		return event
	} else if status == esc_wait {
		esc_wait_timer = time.NewTimer(esc_wait_delay)
		esc_timeout = esc_wait_timer.C
	}

	for {
		select {
		case ev := <-input_comm:
			if esc_wait_timer != nil {
				if !esc_wait_timer.Stop() {
					<-esc_wait_timer.C
				}
				esc_wait_timer = nil
			}

			if ev.err != nil {
				return Event{Type: EventError, Err: ev.err}
			}

			inbuf = append(inbuf, ev.data...)
			input_comm <- ev
			status := extract_event(inbuf, &event, true)
			if event.N != 0 {
				copy(inbuf, inbuf[event.N:])
				inbuf = inbuf[:len(inbuf)-event.N]
			}
			if status == event_extracted {
				return event
			} else if status == esc_wait {
				esc_wait_timer = time.NewTimer(esc_wait_delay)
				esc_timeout = esc_wait_timer.C
			}
		case <-esc_timeout:
			esc_wait_timer = nil

			status := extract_event(inbuf, &event, false)
			if event.N != 0 {
				copy(inbuf, inbuf[event.N:])
				inbuf = inbuf[:len(inbuf)-event.N]
			}
			if status == event_extracted {
				return event
			}
		case <-interrupt_comm:
			event.Type = EventInterrupt
			return event

		case <-sigwinch:
			event.Type = EventResize
			event.Width, event.Height = get_term_size(out.Fd())
			return event
		}
	}
}

// Returns the size of the internal back buffer (which is mostly the same as
// terminal's window size in characters). But it doesn't always match the size
// of the terminal window, after the terminal size has changed, the internal
// back buffer will get in sync only after Clear or Flush function calls.
func Size() (width int, height int) {
	return termw, termh
}

// Clears the internal back buffer.
func Clear(fg, bg Attribute) error {
	foreground, background = fg, bg
	err := update_size_maybe()
	back_buffer.clear()
	return err
}

// Sets termbox input mode. Termbox has two input modes:
//
// 1. Esc input mode. When ESC sequence is in the buffer and it doesn't match
// any known sequence. ESC means KeyEsc. This is the default input mode.
//
// 2. Alt input mode. When ESC sequence is in the buffer and it doesn't match
// any known sequence. ESC enables ModAlt modifier for the next keyboard event.
//
// Both input modes can be OR'ed with Mouse mode. Setting Mouse mode bit up will
// enable mouse button press/release and drag events.
//
// If 'mode' is InputCurrent, returns the current input mode. See also Input*
// constants.
func SetInputMode(mode InputMode) InputMode {
	if mode == InputCurrent {
		return input_mode
	}
	if mode&(InputEsc|InputAlt) == 0 {
		mode |= InputEsc
	}
	if mode&(InputEsc|InputAlt) == InputEsc|InputAlt {
		mode &^= InputAlt
	}
	if mode&InputMouse != 0 {
		out.WriteString(funcs[t_enter_mouse])
	} else {
		out.WriteString(funcs[t_exit_mouse])
	}

	input_mode = mode
	return input_mode
}

// Sets the termbox output mode. Termbox has four output options:
//
// 1. OutputNormal => [1..8]
//    This mode provides 8 different colors:
//        black, red, green, yellow, blue, magenta, cyan, white
//    Shortcut: ColorBlack, ColorRed, ...
//    Attributes: AttrBold, AttrUnderline, AttrReverse
//
//    Example usage:
//        SetCell(x, y, '@', ColorBlack | AttrBold, ColorRed);
//
// 2. Output256 => [1..256]
//    In this mode you can leverage the 256 terminal mode:
//    0x01 - 0x08: the 8 colors as in OutputNormal
//    0x09 - 0x10: Color* | AttrBold
//    0x11 - 0xe8: 216 different colors
//    0xe9 - 0x1ff: 24 different shades of grey
//
//    Example usage:
//        SetCell(x, y, '@', 184, 240);
//        SetCell(x, y, '@', 0xb8, 0xf0);
//
// 3. Output216 => [1..216]
//    This mode supports the 3rd range of the 256 mode only.
//    But you don't need to provide an offset.
//
// 4. OutputGrayscale => [1..26]
//    This mode supports the 4th range of the 256 mode
//    and black and white colors from 3th range of the 256 mode
//    But you don't need to provide an offset.
//
// In all modes, 0x00 represents the default color.
//
// `go run _demos/output.go` to see its impact on your terminal.
//
// If 'mode' is OutputCurrent, it returns the current output mode.
//
// Note that this may return a different OutputMode than the one requested,
// as the requested mode may not be available on the target platform.
func SetOutputMode(mode OutputMode) OutputMode {
	if mode == OutputCurrent {
		return output_mode
	}

	output_mode = mode
	return output_mode
}

// Sync comes handy when something causes desync between termbox's understanding
// of a terminal buffer and the reality. Such as a third party process. Sync
// forces a complete resync between the termbox and a terminal, it may not be
// visually pretty though.
func Sync() error {
	front_buffer.clear()
	err := send_clear()
	if err != nil {
		return err
	}

	return Flush()
}
