<?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\Bus;

class SoftwareSpiBus extends Bus
{
    protected $buffer = null;

    protected function configure()
    {
        $this->addPin("sclk");
        $this->addPin("mosi");
        $this->addPin("miso");
    }

    protected function spiExchangeByte($byte)
    {
        $in = 0;
        if (is_string($byte)) { $byte = ord($byte); }
        for($bit=0; $bit<8; $bit++) {
            $this->setValue("sclk", 0);
            $this->setValue("mosi", (($byte & 1<<$bit)>0));
            usleep(5000);
            $this->setValue("sclk", 1);
            usleep(5000);
            if ($this->getValue("miso")) {
                $in |= 1<<$bit;
            }
        }
        return chr($in);
    }
    
    protected function setValue($pin,$value)
    {
        echo "{$pin}→{$value}\n";
    }
    protected function getValue($pin)
    {
        echo "{$pin}←0\n";
        return 0;
    }
    
    public function write($data)
    {
        for($n = 0; $n < strlen($data); $n++) {
            $this->buffer .= $this->spiExchangeByte($data[$n]);
        }
    }
    
    public function read($bytes)
    {
        $ret = null;
        if (strlen($this->buffer)>0) {
            if (strlen($this->buffer)<$bytes) {
                $ret = $this->buffer; 
                $bytes -= strlen($this->buffer);
                $this->buffer = null; 
            } else {
                $ret = substr($this->buffer,0,$bytes);
                $this->buffer = substr($this->buffer,$bytes);
                return $ret;
            }
        }
        for($n = 0; $n < $bytes; $n++) {
            $ret.= $this->spiExchangeByte(0x00);
        }
        return $ret;
    }
    
    public function getBufferFill()
    {
        return strlen($this->buffer);
    }

}