<?php

namespace NoccyLabs\Shell;

use NoccyLabs\Shell\LineRead;

class Shell
{
    const EV_PROMPT = "prompt";
    const EV_COMMAND = "command";

    protected $lineReader = null;

    protected $context = null;

    protected $contextStack = [];

    protected $listeners = [];
    
    protected $timers = [];

    protected $prompt = ">";

    public function __construct()
    {
        $this->configure();
    }

    protected function configure()
    {

    }

    /**
     * Push a new primary context, saving the previous contexts on a stack.
     *
     * @param Context $context
     */
    public function pushContext(Context $context)
    {
        if ($this->context) {
            $context->setParent($this->context);
            array_unshift($this->contextStack, $this->context);
        }
        $context->setShell($this);
        $this->context = $context;
        $this->dispatchEvent("context.update", [ "context"=>$this->context ]);
    }

    /**
     * Pop the current context.
     *
     * @return Context
     */
    public function popContext()
    {
        $previous = $this->context;
        if (count($this->contextStack)>0) {
            $this->context = array_shift($this->contextStack);
        } else {
            $this->context = null;
        }
        $this->dispatchEvent("context.update", [ "context"=>$this->context ]);
        return $previous;
    }

    public function getContextPath($separator=":")
    {
        // Return null if we don't have a current context
        if (!$this->context) 
            return null;
        
        // Assemble the contexts to walk
        $stack = [ $this->context->getName() ];
        foreach ($this->contextStack as $context) {
            $stack[] = $context->getName();
        }

        // Reverse the order to make it more logical
        $stack = array_reverse($stack);
        return join($separator,$stack);
    }

    public function createContext()
    {
        $context = new Context();
        $this->pushContext($context);
        return $context;
    }

    /**
     * Add a handler to be called when an event fires.
     *
     * @param string $event
     * @param callable $handler
     */ 
    public function addListener($event, callable $handler)
    {
        if (!array_key_exists($event,$this->listeners)) {
            $this->listeners[$event] = [];
        }
        $this->listeners[$event][] = $handler;
    }

    /**
     * Invoke event handlers for event.
     *
     * @param string $event
     * @param callable $handler
     */
    protected function dispatchEvent($event, array $data=[])
    {
        if (!array_key_exists($event,$this->listeners)) {
            return;
        }
        foreach ($this->listeners[$event] as $handler) {
            call_user_func($handler, (object)$data, $this);
        }
    }

    /**
     * Add a callback to be called at a regular interval during the update phase.
     * Adding timers with a low interval (less than 200 i.e. 0.2s) may have an
     * impact on performance.
     *
     * @param int $interval Interval in ms
     * @param callable $handler The handler
     * @param array $userdata Data to be passed to the handler
     * @return Timer 
     */
    public function addTimer($interval, callable $handler, array $userdata=[])
    {
        $timer = new class($interval, $handler, $userdata) {
            private $next;
            private $interval;
            private $handler;
            private $userdata;
            public function __construct($interval, callable $handler, array $userdata) {
                $this->interval = $interval / 1000;
                $this->handler = $handler;
                $this->userdata = $userdata;
            }
            public function update() {
                $now = microtime(true);
                if ($now > $this->next) {
                    $this->next = $now + $this->interval;
                    call_user_func($this->handler, $this->userdata);
                }
            }
        };
        $this->timers[] = $timer;
        return $timer;
    }

    /**
     * Remove a created timer.
     *
     * @param Timer $timer
     */
    public function removeTimer(Timer $timer)
    {

    }

    public function setPrompt($text)
    {
        $this->prompt = $text;
    
        if ($this->lineReader) {
            $this->lineReader->setPromptText($text);
        }
    }

    /**
     * Find a command and return a closure.
     *
     * @return callable The command
     */ 
    private function findCommand($command)
    {
        // Go over current context and walk through stack until finding command
        if ($this->context->hasCommand($command)) {
            $handler = $this->context->getCommand($command);
        } else {
            foreach($this->contextStack as $context) {
                if ($context->hasCommand($command) && $context->isCommandGlobal($command)) {
                    $handler = $context->getCommand($command);
                    break;
                }
            }
        }

        // No handler...
        if (empty($handler)) {
            return false;
        }

        // Return closure
        return function (...$args) use ($handler) {
            return call_user_func($handler, ...$args);
        };
    }

    /**
     * Execute a command with arguments.
     *
     * @param string $command The command name to execute
     * @param string $args Arguments
     * @return mixed 
     * @throws Exception\BadCommandExcception
     */
    public function executeCommand($command, ...$args)
    {
        if ($this->executeBuiltin($command, ...$args)) {
            return;
        }

        // Call the handler if the command was found
        if (($target = $this->findCommand($command))) {
            $ret = $target(...$args);
            if ($ret instanceof Context) {
                $this->pushContext($ret);
            }
            return;
        }

        // Call 'execute' on the current context
        if ($this->context->execute($command, ...$args)) {
            return;
        }

        // Throw error if the command could not be found
        throw new Exception\BadCommandException("Command {$command} not found");
    }

    public function executeBuiltin($command, ...$args)
    {
        switch ($command) {
            case '.':
                $type = basename(strtr(get_class($this->context), "\\", "/"));
                printf("%s<%s>: %s\n", $type, $this->context->getName(), $this->context->getContextInfo());
                $level = 0;
                foreach ($this->contextStack as $context) {
                    $type = basename(strtr(get_class($context), "\\", "/"));
                    printf(" %s└─%s<%s>: %s\n", str_repeat("  ",$level++), $type, $context->getName(), $context->getContextInfo());
                }
                break;
            case '..':
                if (count($this->contextStack)>0)
                    $this->popContext();
                break;
            case 'help':
                $help = $this->context->getCommandHelp();
                $ghelp = [];
                foreach ($this->contextStack as $context) {
                    $commands = $context->getCommandHelp();
                    foreach ($commands as $command=>$info) {
                        if (strpos(" ",$command)!==false) {
                            list ($cmd,$arg)=explode(" ",$command,2);
                        } else {
                            $cmd = $command;
                        }
                        if ($context->isCommandGlobal($cmd)) {
                            $ghelp[$command] = $info;
                        }
                    }
                }
                ksort($ghelp);
                printf("Commands in current context:\n");
                foreach ($help as $command=>$info) {
                    printf("  %-20s  %s\n", $command, $info);
                }
                if (count($ghelp)) {
                    printf("\nImported from parent contexts:\n");
                    foreach ($ghelp as $command=>$info) {
                        printf("  %-20s  %s\n", $command, $info);
                    }
                }
                printf("\nGlobal commands:\n");
                printf("  %-20s  %s\n", "exit", "Leave the shell");
                printf("  %-20s  %s\n", "..", "Discard the current context and go to parent");
                break;
            case 'exit':
                $this->stop();
                break;
            default:
                return false;
        }        
        return true;
    }

    /**
     * Parse a string and execute the resulting command.
     *
     * @param string $command The string to parse
     * @return mixed
     */ 
    public function executeBuffer(string $command)
    {
        $args = str_getcsv($command, " ", "\"", "\\");
        $command = array_shift($args);

        try {
            $this->executeCommand($command, ...$args);
        } catch (Exception\ShellException $e) {
            echo "\e[31;91;1m{$e->getMessage()}\e[0m\n";
        }
        /*
        if (array_key_exists($commandName, $this->commands)) {
            $command = $this->commands[$commandName];
            if ($command instanceof Command) {
                $command->run($buffer);
            } else {
                call_user_func_array($command,$buffer);
            }
            return;
        }
        $this->writeln("Bad command: ".$commandName);
        */
    }

    public function run()
    {
        try {
            $this->lineReader = new LineRead();

            $this->lineReader->setPromptText($this->prompt);
            $this->lineReader->setPromptStyle(new Style(Style::BR_GREEN));
            $this->lineReader->setCommandStyle(new Style(Style::GREEN));

            $this->running = true;

            $this->dispatchEvent("prompt", [ "context"=>$this->context ]);

            while ($this->running) {
                // Update the input stuff, sleep if nothing to do.
                if (!($buffer = $this->lineReader->update())) {
                    usleep(10000);
                }
                // Escape is handy too...
                if ($buffer == "\e") {
                    $this->dispatchEvent("shell.abort");
                    continue;
                }
                // we get a ^C on ^C, so deal with the ^C.
                if ($buffer == "\x03") {
                    $this->dispatchEvent("shell.stop");
                    $this->stop();
                    continue;
                }
                // Execute the buffer
                ob_start();
                $this->dispatchEvent("update");
                foreach ($this->timers as $timer) {
                    $timer->update();
                }
                if ($buffer) {
                    $this->executeBuffer($buffer);
                }
                $output = ob_get_contents();
                ob_end_clean();

                if (trim($output)) {
                    $this->lineReader->erase();
                    echo rtrim($output)."\n";
                    $this->lineReader->redraw();
                }

                if (!$this->context) {
                    $this->stop();
                }

                if ($buffer) {
                    $this->dispatchEvent("prompt", [ "context"=>$this->context ]);
                }
            }

        } catch (\Exception $e) {
            fprintf(STDERR, "\e[31;1mFatal: Unhandled exception\e[0m\n\n%s\n", $e);
        }

        $this->lineReader = null;

    }

    public function stop()
    {
        $this->running = false;
    }
}