package terminal

import (
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"unsafe"

	"go.uber.org/zap"
)

type Terminal struct {
	lines           []Line   // lines, where 0 is earliest, n is latest
	position        Position // line and col
	lock            sync.Mutex
	pty             *os.File
	logger          *zap.SugaredLogger
	title           string
	onUpdate        []func()
	size            Winsize
	colourScheme    ColourScheme
	cellAttr        CellAttributes
	defaultCellAttr CellAttributes
}

type Line struct {
	Cells   []Cell
	wrapped bool
}

func NewLine() Line {
	return Line{
		Cells: []Cell{},
	}
}

func (line *Line) String() string {
	s := ""
	for _, c := range line.Cells {
		s += string(c.r)
	}
	return s
}

func (line *Line) CutCellsAfter(n int) []Cell {
	cut := line.Cells[n:]
	line.Cells = line.Cells[:n]
	return cut
}

func (line *Line) CutCellsFromBeginning(n int) []Cell {
	if n > len(line.Cells) {
		n = len(line.Cells)
	}
	cut := line.Cells[:n]
	line.Cells = line.Cells[n:]
	return cut
}

func (line *Line) CutCellsFromEnd(n int) []Cell {
	cut := line.Cells[len(line.Cells)-n:]
	line.Cells = line.Cells[:len(line.Cells)-n]
	return cut
}

func (line *Line) GetRenderedLength() int {
	l := 0
	for x, c := range line.Cells {
		if c.r > 0 {
			l = x
		}
	}
	return l
}

type Winsize struct {
	Height uint16
	Width  uint16
	x      uint16 //ignored, but necessary for ioctl calls
	y      uint16 //ignored, but necessary for ioctl calls
}

type Position struct {
	Line int
	Col  int
}

func New(pty *os.File, logger *zap.SugaredLogger, colourScheme ColourScheme) *Terminal {

	defaultCellAttr := CellAttributes{
		FgColour: colourScheme.DefaultFg,
		BgColour: colourScheme.DefaultBg,
	}

	return &Terminal{
		lines: []Line{
			NewLine(),
		},
		pty:             pty,
		logger:          logger,
		onUpdate:        []func(){},
		cellAttr:        defaultCellAttr,
		defaultCellAttr: defaultCellAttr,
		colourScheme:    colourScheme,
	}
}

func (terminal *Terminal) OnUpdate(handler func()) {
	terminal.onUpdate = append(terminal.onUpdate, handler)
}

func (terminal *Terminal) triggerOnUpdate() {
	for _, handler := range terminal.onUpdate {
		go handler()
	}
}

func (terminal *Terminal) getPosition() Position {
	return terminal.position
}

func (terminal *Terminal) incrementPosition() {
	position := terminal.getPosition()
	if position.Col+1 >= int(terminal.size.Width) {
		position.Line++
		position.Col = 0
	} else {
		position.Col++
	}
	terminal.SetPosition(position)
}

func (terminal *Terminal) SetPosition(position Position) {
	terminal.position = position
}

func (terminal *Terminal) GetTitle() string {
	return terminal.title
}

// Write sends data, i.e. locally typed keystrokes to the pty
func (terminal *Terminal) Write(data []byte) error {
	_, err := terminal.pty.Write(data)
	return err
}

func (terminal *Terminal) ClearToEndOfLine() {

	position := terminal.getPosition()

	if position.Line < len(terminal.lines) {
		if position.Col < len(terminal.lines[position.Line].Cells) {
			terminal.lines[position.Line].Cells = terminal.lines[position.Line].Cells[:position.Col]
		}
	}
}

// we have thousands of lines of output. if the terminal is X lines high, we just want to lookat the most recent X lines to render (unless scroll etc)
func (terminal *Terminal) getBufferedLine(line int) *Line {

	if len(terminal.lines) >= int(terminal.size.Height) {
		line = len(terminal.lines) - int(terminal.size.Height) + line
	}

	if line >= len(terminal.lines) {
		return nil
	}

	return &terminal.lines[line]
}

// Read needs to be run on a goroutine, as it continually reads output to set on the terminal
func (terminal *Terminal) Read() error {

	buffer := make(chan byte, 0xffff)

	go func() {

		// https://en.wikipedia.org/wiki/ANSI_escape_code

		for {
			b := <-buffer

			if b == 0x1b { // if the byte is an escape character, read the next byte to determine which one
				b = <-buffer
				switch b {
				case 0x5b: // CSI: Control Sequence Introducer ]
					var final byte
					params := []byte{}
					intermediate := []byte{}
				CSI:
					for {
						b = <-buffer
						switch true {
						case b >= 0x30 && b <= 0x3F:
							params = append(params, b)
						case b >= 0x20 && b <= 0x2F:
							intermediate = append(intermediate, b)
						case b >= 0x40 && b <= 0x7e:
							final = b
							break CSI
						}
					}

					switch final {
					case byte('A'):
						distance := 1
						if len(params) > 0 {
							var err error
							distance, err = strconv.Atoi(string([]byte{params[0]}))
							if err != nil {
								distance = 1
							}
						}
						if terminal.position.Line-distance >= 0 {
							terminal.position.Line -= distance
						}
					case byte('B'):
						distance := 1
						if len(params) > 0 {
							var err error
							distance, err = strconv.Atoi(string([]byte{params[0]}))
							if err != nil {
								distance = 1
							}
						}

						terminal.position.Line += distance

					case 0x4b: // K - EOL - Erase to end of line
						if len(params) == 0 || params[0] == byte('0') {
							terminal.ClearToEndOfLine()
						} else {
							terminal.logger.Errorf("Unsupported EL")
						}
					case byte('m'):
						// SGR: colour and shit
						sgr := string(params)
						sgrParams := strings.Split(sgr, ";")
						for i := range sgrParams {
							param := sgrParams[i]
							switch param {
							case "0":
								terminal.cellAttr = terminal.defaultCellAttr
							case "1":
								terminal.cellAttr.Bold = true
							case "2":
								terminal.cellAttr.Dim = true
							case "4":
								terminal.cellAttr.Underline = true
							case "5":
								terminal.cellAttr.Blink = true
							case "7":
								terminal.cellAttr.Reverse = true
							case "8":
								terminal.cellAttr.Hidden = true
							case "21":
								terminal.cellAttr.Bold = false
							case "22":
								terminal.cellAttr.Dim = false
							case "24":
								terminal.cellAttr.Underline = false
							case "25":
								terminal.cellAttr.Blink = false
							case "27":
								terminal.cellAttr.Reverse = false
							case "28":
								terminal.cellAttr.Hidden = false
							case "39":

							}
						}
						terminal.logger.Debugf("SGR params %#v intermediate %#v", params, intermediate)
					default:
						b = <-buffer
						terminal.logger.Debugf("Unknown CSI control sequence: 0x%02X (%s)", final, string([]byte{final}))
					}
				case 0x5d: // OSC: Operating System Command
					b = <-buffer
					switch b {
					case byte('0'):
						b = <-buffer
						if b == byte(';') {
							title := []byte{}
							for {
								b = <-buffer
								if b == 0x07 {
									break
								}
								title = append(title, b)
							}
							terminal.logger.Debugf("Terminal title set to: %s", string(title))
							terminal.title = string(title)
						} else {
							terminal.logger.Debugf("Invalid OSC 0 control sequence: 0x%02X", b)
						}
					default:
						terminal.logger.Debugf("Unknown OSC control sequence: 0x%02X", b)
					}
				case byte('c'):
					terminal.logger.Errorf("RIS not yet supported")
				default:
					terminal.logger.Debugf("Unknown control sequence: 0x%02X", b)
				}
			} else {

				switch b {
				case 0x0a:
					for terminal.position.Line+1 >= len(terminal.lines) {
						terminal.lines = append(terminal.lines, NewLine())
					}
					terminal.position.Line++
				case 0x0d:
					terminal.position.Col = 0
				case 0x08:
					// backspace
					terminal.position.Col--
				case 0x07:
					// @todo ring bell
				default:
					// render character at current location
					//		fmt.Printf("%s\n", string([]byte{b}))
					terminal.writeRune([]rune(string([]byte{b}))[0])
				}

			}
			terminal.triggerOnUpdate()
		}
	}()

	for {
		readBytes := make([]byte, 1024)
		n, err := terminal.pty.Read(readBytes)
		if err != nil {
			terminal.logger.Errorf("Failed to read from pty: %s", err)
			return err
		}
		if len(readBytes) > 0 {
			readBytes = readBytes[:n]
			fmt.Printf("Data in: %q\n", string(readBytes))
			for _, x := range readBytes {
				buffer <- x
			}

		}
	}
}

func (terminal *Terminal) writeRune(r rune) {
	terminal.setRuneAtPos(terminal.position, r)
	terminal.incrementPosition()

}

func (terminal *Terminal) Clear() {
	// @todo actually should just add a bunch of newlines?
	for i := 0; i < int(terminal.size.Height); i++ {
		terminal.lines = append(terminal.lines, NewLine())
	}
	terminal.SetPosition(Position{Line: 0, Col: 0})
}

func (terminal *Terminal) GetCellAtPos(pos Position) (*Cell, error) {

	if int(terminal.size.Height) <= pos.Line {
		terminal.logger.Errorf("Line %d does not exist", pos.Line)
		return nil, fmt.Errorf("Line %d does not exist", pos.Line)
	}

	if int(terminal.size.Width) <= pos.Col {
		terminal.logger.Errorf("Col %d does not exist", pos.Col)
		return nil, fmt.Errorf("Col %d does not exist", pos.Col)
	}

	line := terminal.getBufferedLine(pos.Line)
	if line == nil {
		return nil, fmt.Errorf("Line missing")
	}
	for pos.Col >= len(line.Cells) {
		line.Cells = append(line.Cells, Cell{})
	}
	return &line.Cells[pos.Col], nil
}

func (terminal *Terminal) setRuneAtPos(pos Position, r rune) error {

	if int(terminal.size.Width) <= pos.Col {
		terminal.logger.Errorf("Col %d does not exist", pos.Col)
		return fmt.Errorf("Col %d does not exist", pos.Col)
	}

	if pos.Line == 0 && pos.Col == 0 {
		fmt.Printf("\n\nSetting %d %d to %q\n\n\n", pos.Line, pos.Col, string(r))
	}

	line := terminal.getBufferedLine(pos.Line)
	if line == nil {

		return fmt.Errorf("Impossible?")

	}

	for pos.Col >= len(line.Cells) {
		line.Cells = append(line.Cells, Cell{})
	}

	line.Cells[pos.Col].attr = terminal.cellAttr
	line.Cells[pos.Col].r = r
	return nil
}

func (terminal *Terminal) GetSize() (int, int) {
	return int(terminal.size.Width), int(terminal.size.Height)
}

func (terminal *Terminal) SetSize(newCols int, newLines int) error {
	terminal.lock.Lock()
	defer terminal.lock.Unlock()

	oldCols := int(terminal.size.Width)
	oldLines := int(terminal.size.Height)

	if oldLines > 0 && oldCols > 0 { // only bother resizing content if there is some
		if newCols < oldCols { // if the width decreased, we need to do some line trimming

			for l := range terminal.lines {
				if terminal.lines[l].GetRenderedLength() > newCols {
					cells := terminal.lines[l].CutCellsAfter(newCols)
					line := Line{
						Cells:   cells,
						wrapped: true,
					}
					terminal.lines = append(terminal.lines[:l+1], append([]Line{line}, terminal.lines[l+1:]...)...)
					if terminal.getPosition().Line > l {
						terminal.position.Line++
					} else if terminal.getPosition().Line == l {
						if terminal.getPosition().Col >= newCols {
							terminal.position.Line++
						}
					}
				}
			}

		} else if newCols > oldCols { // if width increased, we need to potentially unwrap some lines
			for l := 0; l < len(terminal.lines); l++ {
				if terminal.lines[l].GetRenderedLength() < newCols { // there is space here to unwrap a line if needed
					if l+1 < len(terminal.lines) {
						if terminal.lines[l+1].wrapped {
							wrapSize := newCols - terminal.lines[l].GetRenderedLength()
							cells := terminal.lines[l+1].CutCellsFromBeginning(wrapSize)
							terminal.lines[l].Cells = append(terminal.lines[l].Cells, cells...)
							if terminal.lines[l+1].GetRenderedLength() == 0 {
								// remove line
								terminal.lines = append(terminal.lines[:l+1], terminal.lines[l+2:]...)
								if terminal.getPosition().Line >= l+1 {
									terminal.position.Line--
								}
							}
						}
					}
				}
			}

		}
	}

	terminal.size.Width = uint16(newCols)
	terminal.size.Height = uint16(newLines)

	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(terminal.pty.Fd()),
		uintptr(syscall.TIOCSWINSZ), uintptr(unsafe.Pointer(&terminal.size)))
	if err != 0 {
		return fmt.Errorf("Failed to set terminal size vai ioctl: Error no %d", err)
	}

	return nil
}

/*
------------------ ->
ssssssssssssssssss
ssssPPPPPPPPPPPPPP
xxxxxxxxx
xxxxxxxxxxxxxxxxxx
--------------------------
ssssssssssssssssss
SsssPPPPPPPPPPPPPP
xxxxxxxxx
xxxxxxxxxxxxxxxxxx




*/