<?php

namespace NoccyLabs\React\Shell;

use Evenement\EventEmitterInterface;
use Evenement\EventEmitterTrait;
use React\EventLoop\Loop;
use React\Stream\ReadableResourceStream;
use React\Stream\ReadableStreamInterface;
use React\Stream\WritableResourceStream;
use React\Stream\WritableStreamInterface;

class Shell implements WritableStreamInterface, EventEmitterInterface
{
    use EventEmitterTrait;

    private ReadableStreamInterface $istream;

    private WritableStreamInterface $ostream;

    private string $oldStty;

    private bool $isPrompting = false;

    private string $buffer = '';

    private int $cursorPos = 0;

    private int $termWidth = 0;

    private int $scrollOffset = 0;

    private string $prompt = '';

    private int $promptWidth = 0;

    public function __construct(?ReadableStreamInterface $input=null, ?WritableStreamInterface $output=null)
    {
        $this->istream = $input ?? new ReadableResourceStream(STDIN);
        $this->ostream = $output ?? new WritableResourceStream(STDOUT);

        $this->istream->on('data', $this->handleInput(...));
        
        Loop::futureTick($this->redrawPrompt(...));

        // Save terminal settings and disable inupt buffering
        $this->oldStty = exec("stty -g");
        exec("stty -icanon min 1 time 0 -echo");
    }

    public function  __destruct()
    {
        // Restore the terminal to regular buffered mode
        exec("stty {$this->oldStty}");
    }

    public function setPrompt(string $prompt): void
    {
        $this->prompt = $prompt;
        $this->promptWidth = mb_strlen($this->prompt);        
    }

    private function handleInput($v) {

        switch ($v) {

            case "\x03": 
                exit(0);

            case "\n":
                $buffer = str_getcsv($this->buffer, " ");
                $this->buffer = '';
                $this->cursorPos = 0;
                $this->scrollOffset = 0;
                $this->emit('input', [ $buffer ]);
                break;

            case "\x7F": // backspace
                if ($this->cursorPos < 1) return;
                $this->buffer = mb_substr($this->buffer, 0, $this->cursorPos - 1) .
                                mb_substr($this->buffer, $this->cursorPos);
                $this->cursorPos--;
                break;

            case "\e[3~": // delete
                $this->buffer = mb_substr($this->buffer, 0, $this->cursorPos) .
                                mb_substr($this->buffer, $this->cursorPos + 1);
                break;
    
            case "\e[A": // up
            case "\e[B": // down
                break;

            case "\e[H": // home
            case "\e[F": // end
                    break;
        
            case "\e[D": // left
                if ($this->cursorPos < 1) return;
                $this->cursorPos--;                
                break;

            case "\e[C": // right
                if ($this->cursorPos >= mb_strlen($this->buffer)) return;
                $this->cursorPos++;
                break;

            default:
                if (mb_strlen($v) == 1 && ord($v) >= 32) {
                    $this->buffer = mb_substr($this->buffer, 0, $this->cursorPos) .
                                    $v . 
                                    mb_substr($this->buffer, $this->cursorPos);
                    $this->cursorPos++;
                } else {
                    $this->ostream->write("\e[7m".substr($v,2)."\e[27m");
                    return;
                }
        }
        $this->updatePrompt();
    }


    public function write($data)
    {
        $this->hidePrompt();
        $this->ostream->write($data);
        $this->redrawPrompt();
        return true;
    }

    public function isWritable()
    {
        return true;
    }

    public function end($data = null)
    {
        // NOP
    }

    public function close()
    {
        // NOP
    }


    public function hidePrompt(): void
    {
        if (!$this->isPrompting) return;

        $this->isPrompting = false;

        $this->ostream->write("\r\e[K");
    }

    public function redrawPrompt(): void
    {
        $prompt = $this->emit("prompt");

        $this->termWidth = intval(exec("tput cols"));
        $this->isPrompting = true;

        $this->updatePrompt();
    }

    private function updatePrompt(): void
    {
        if (!$this->isPrompting) return;

        $pos = $this->promptWidth + $this->cursorPos - $this->scrollOffset + 1;

        $obuf = "\r" . "\e[1m" . $this->prompt . "\e[22m";
        $ostr = mb_substr($this->buffer, $this->scrollOffset) . " ";
        $ostr = mb_substr($ostr, 0, $this->termWidth - $this->promptWidth);
        $obuf .= $ostr . "\e[K\e[" . $pos . "G";

        $this->ostream->write($obuf);
    }
}