<?php

/*
 * Copyright (C) 2014, NoccyLabs
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 */

namespace NoccyLabs\Gpio;

use NoccyLabs\Gpio\Exception\HardwareException;

class Gpio implements \ArrayAccess
{
    // Direction
    const DIR_IN       = "in";
    const DIR_OUT      = "out";
    // Values
    const VAL_HIGH     = 1;
    const VAL_LOW      = 0;
    // Edges
    const EDGE_NONE    = "none";
    const EDGE_RISING  = "rising";
    const EDGE_FALLING = "faling";
    const EDGE_BOTH    = "both";

    protected $gpio = array();
    
    /** @var NoccyLabs\Gpio\GpioMapperInterface */
    protected $mapper;
    
    protected $dummy;
    
    public function __construct($dummy=false)
    {
        if (!$dummy) {
            if (!file_exists("/sys/class/gpio")) {
                throw new HardwareException("gpio sysfs is not available");
            }
            if (!is_writable("/sys/class/gpio/export")) {
                throw new HardwareException("gpio sysfs is not writable");
            }
        }
        $this->dummy = $dummy;
    }
    
    public function setMapper(GpioMapperInterface $mapper=null)
    {
        $this->mapper = $mapper;
        return $this;
    }
    
    /**
     * Get a pin, optionally via previously specified mapper.
     *
     * @interface ArrayAccess
     * @param int
     */    
    public function offsetGet($index)
    {
        if ($this->mapper) {
            $index = $this->mapper->mapLogicalToGpioPin($index);
        }
        if (empty($this->gpio[$index])) {
            if ($this->dummy) {
                $gpio = new DummyGpioPin($index, $this);
            } else {
                $gpio = new GpioPin($index, $this);
            }
            $this->gpio[$index] = $gpio;
        }
        return $this->gpio[$index];
    }

    /**
     * Check if a GPIO is exported
     *
     * @interface ArrayAccess
     * @param int
     */    
    public function offsetExists($index)
    {
        return array_key_exists($index, $this->gpio);
    }

    /**
     * Not callable, get the requested pin via offsetGet() instead.
     *
     * @interface ArrayAccess
     * @throws Exception
     * @param int
     * @param mixed
     */    
    public function offsetSet($index,$value)
    {   throw new \Exception(); }
    
    /**
     * Unlink and unexport an exported GPIO
     *
     * @interface ArrayAccess
     * @param int
     */    
    public function offsetUnset($index)
    {   
        $this->gpio[$index]->unexport();
        unset($this->gpio[$index]);
    }
    
}