<?php
/*
* This file is part of the JShrink package.
*
* (c) Robert Hafner <tedivm@tedivm.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

/**
* JShrink
*
*
* @package JShrink
* @author Robert Hafner <tedivm@tedivm.com>
*/

namespace JShrink;

/**
* Minifier
*
* Usage - Minifier::minify($js);
* Usage - Minifier::minify($js, $options);
* Usage - Minifier::minify($js, array('flaggedComments' => false));
*
* @package JShrink
* @author Robert Hafner <tedivm@tedivm.com>
* @license http://www.opensource.org/licenses/bsd-license.php BSD License
*/
class Minifier
{
/**
* The input javascript to be minified.
*
* @var string
*/
protected $input;

/**
* The location of the character (in the input string) that is next to be
* processed.
*
* @var int
*/
protected $index = 0;

/**
* The first of the characters currently being looked at.
*
* @var string
*/
protected $a = '';

/**
* The next character being looked at (after a);
*
* @var string
*/
protected $b = '';

/**
* This character is only active when certain look ahead actions take place.
*
* @var string
*/
protected $c;

/**
* Contains the options for the current minification process.
*
* @var array
*/
protected $options;

/**
* These characters are used to define strings.
*/
protected $stringDelimiters = ['\'', '"', '`'];

/**
* Contains the default options for minification. This array is merged with
* the one passed in by the user to create the request specific set of
* options (stored in the $options attribute).
*
* @var array
*/
protected static $defaultOptions = array('flaggedComments' => true);

/**
* Contains lock ids which are used to replace certain code patterns and
* prevent them from being minified
*
* @var array
*/
protected $locks = array();

/**
* Takes a string containing javascript and removes unneeded characters in
* order to shrink the code without altering it's functionality.
*
* @param string $js The raw javascript to be minified
* @param array $options Various runtime options in an associative array
* @throws \Exception
* @return bool|string
*/
public static function minify($js, $options = array())
{
try {
ob_start();

$jshrink = new Minifier();
$js = $jshrink->lock($js);
$jshrink->minifyDirectToOutput($js, $options);

// Sometimes there's a leading new line, so we trim that out here.
$js = ltrim(ob_get_clean());
$js = $jshrink->unlock($js);
unset($jshrink);

return $js;
} catch (\Exception $e) {
if (isset($jshrink)) {
// Since the breakdownScript function probably wasn't finished
// we clean it out before discarding it.
$jshrink->clean();
unset($jshrink);
}

// without this call things get weird, with partially outputted js.
ob_end_clean();
throw $e;
}
}

/**
* Processes a javascript string and outputs only the required characters,
* stripping out all unneeded characters.
*
* @param string $js The raw javascript to be minified
* @param array $options Various runtime options in an associative array
*/
protected function minifyDirectToOutput($js, $options)
{
$this->initialize($js, $options);
$this->loop();
$this->clean();
}

/**
* Initializes internal variables, normalizes new lines,
*
* @param string $js The raw javascript to be minified
* @param array $options Various runtime options in an associative array
*/
protected function initialize($js, $options)
{
$this->options = array_merge(static::$defaultOptions, $options);
$js = str_replace("\r\n", "\n", $js);
$js = str_replace('/**/', '', $js);
$this->input = str_replace("\r", "\n", $js);

// We add a newline to the end of the script to make it easier to deal
// with comments at the bottom of the script- this prevents the unclosed
// comment error that can otherwise occur.
$this->input .= PHP_EOL;

// Populate "a" with a new line, "b" with the first character, before
// entering the loop
$this->a = "\n";
$this->b = $this->getReal();
}

/**
* The primary action occurs here. This function loops through the input string,
* outputting anything that's relevant and discarding anything that is not.
*/
protected function loop()
{
while ($this->a !== false && !is_null($this->a) && $this->a !== '') {
switch ($this->a) {
// new lines
case "\n":
// if the next line is something that can't stand alone preserve the newline
if ($this->b !== false && strpos('(-+[@', $this->b) !== false) {
echo $this->a;
$this->saveString();
break;
}

// if B is a space we skip the rest of the switch block and go down to the
// string/regex check below, resetting $this->b with getReal
if ($this->b === ' ') {
break;
}

// otherwise we treat the newline like a space

// no break
case ' ':
if (static::isAlphaNumeric($this->b)) {
echo $this->a;
}

$this->saveString();
break;

default:
switch ($this->b) {
case "\n":
if (strpos('}])+-"\'', $this->a) !== false) {
echo $this->a;
$this->saveString();
break;
} else {
if (static::isAlphaNumeric($this->a)) {
echo $this->a;
$this->saveString();
}
}
break;

case ' ':
if (!static::isAlphaNumeric($this->a)) {
break;
}

// no break
default:
// check for some regex that breaks stuff
if ($this->a === '/' && ($this->b === '\'' || $this->b === '"')) {
$this->saveRegex();
continue 3;
}

echo $this->a;
$this->saveString();
break;
}
}

// do reg check of doom
$this->b = $this->getReal();

if (($this->b == '/' && strpos('(,=:[!&|?', $this->a) !== false)) {
$this->saveRegex();
}
}
}

/**
* Resets attributes that do not need to be stored between requests so that
* the next request is ready to go. Another reason for this is to make sure
* the variables are cleared and are not taking up memory.
*/
protected function clean()
{
unset($this->input);
$this->index = 0;
$this->a = $this->b = '';
unset($this->c);
unset($this->options);
}

/**
* Returns the next string for processing based off of the current index.
*
* @return string
*/
protected function getChar()
{
// Check to see if we had anything in the look ahead buffer and use that.
if (isset($this->c)) {
$char = $this->c;
unset($this->c);
} else {
// Otherwise we start pulling from the input.
$char = substr($this->input, $this->index, 1);

// If the next character doesn't exist return false.
if (isset($char) && $char === false) {
return false;
}

// Otherwise increment the pointer and use this char.
$this->index++;
}

// Normalize all whitespace except for the newline character into a
// standard space.
if ($char !== "\n" && ord($char) < 32) {
return ' ';
}

return $char;
}

/**
* This function gets the next "real" character. It is essentially a wrapper
* around the getChar function that skips comments. This has significant
* performance benefits as the skipping is done using native functions (ie,
* c code) rather than in script php.
*
*
* @return string Next 'real' character to be processed.
* @throws \RuntimeException
*/
protected function getReal()
{
$startIndex = $this->index;
$char = $this->getChar();

// Check to see if we're potentially in a comment
if ($char !== '/') {
return $char;
}

$this->c = $this->getChar();

if ($this->c === '/') {
$this->processOneLineComments($startIndex);

return $this->getReal();
} elseif ($this->c === '*') {
$this->processMultiLineComments($startIndex);

return $this->getReal();
}

return $char;
}

/**
* Removed one line comments, with the exception of some very specific types of
* conditional comments.
*
* @param int $startIndex The index point where "getReal" function started
* @return void
*/
protected function processOneLineComments($startIndex)
{
$thirdCommentString = substr($this->input, $this->index, 1);

// kill rest of line
$this->getNext("\n");

unset($this->c);

if ($thirdCommentString == '@') {
$endPoint = $this->index - $startIndex;
$this->c = "\n" . substr($this->input, $startIndex, $endPoint);
}
}

/**
* Skips multiline comments where appropriate, and includes them where needed.
* Conditional comments and "license" style blocks are preserved.
*
* @param int $startIndex The index point where "getReal" function started
* @return void
* @throws \RuntimeException Unclosed comments will throw an error
*/
protected function processMultiLineComments($startIndex)
{
$this->getChar(); // current C
$thirdCommentString = $this->getChar();

// kill everything up to the next */ if it's there
if ($this->getNext('*/')) {
$this->getChar(); // get *
$this->getChar(); // get /
$char = $this->getChar(); // get next real character

// Now we reinsert conditional comments and YUI-style licensing comments
if (($this->options['flaggedComments'] && $thirdCommentString === '!')
|| ($thirdCommentString === '@')) {

// If conditional comments or flagged comments are not the first thing in the script
// we need to echo a and fill it with a space before moving on.
if ($startIndex > 0) {
echo $this->a;
$this->a = " ";

// If the comment started on a new line we let it stay on the new line
if ($this->input[($startIndex - 1)] === "\n") {
echo "\n";
}
}

$endPoint = ($this->index - 1) - $startIndex;
echo substr($this->input, $startIndex, $endPoint);

$this->c = $char;

return;
}
} else {
$char = false;
}

if ($char === false) {
throw new \RuntimeException('Unclosed multiline comment at position: ' . ($this->index - 2));
}

// if we're here c is part of the comment and therefore tossed
$this->c = $char;
}

/**
* Pushes the index ahead to the next instance of the supplied string. If it
* is found the first character of the string is returned and the index is set
* to it's position.
*
* @param string $string
* @return string|false Returns the first character of the string or false.
*/
protected function getNext($string)
{
// Find the next occurrence of "string" after the current position.
$pos = strpos($this->input, $string, $this->index);

// If it's not there return false.
if ($pos === false) {
return false;
}

// Adjust position of index to jump ahead to the asked for string
$this->index = $pos;

// Return the first character of that string.
return substr($this->input, $this->index, 1);
}

/**
* When a javascript string is detected this function crawls for the end of
* it and saves the whole string.
*
* @throws \RuntimeException Unclosed strings will throw an error
*/
protected function saveString()
{
$startpos = $this->index;

// saveString is always called after a gets cleared, so we push b into
// that spot.
$this->a = $this->b;

// If this isn't a string we don't need to do anything.
if (!in_array($this->a, $this->stringDelimiters)) {
return;
}

// String type is the quote used, " or '
$stringType = $this->a;

// Echo out that starting quote
echo $this->a;

// Loop until the string is done
// Grab the very next character and load it into a
while (($this->a = $this->getChar()) !== false) {
switch ($this->a) {

// If the string opener (single or double quote) is used
// output it and break out of the while loop-
// The string is finished!
case $stringType:
break 2;

// New lines in strings without line delimiters are bad- actual
// new lines will be represented by the string \n and not the actual
// character, so those will be treated just fine using the switch
// block below.
case "\n":
if ($stringType === '`') {
echo $this->a;
} else {
throw new \RuntimeException('Unclosed string at position: ' . $startpos);
}
break;

// Escaped characters get picked up here. If it's an escaped new line it's not really needed
case '\\':

// a is a slash. We want to keep it, and the next character,
// unless it's a new line. New lines as actual strings will be
// preserved, but escaped new lines should be reduced.
$this->b = $this->getChar();

// If b is a new line we discard a and b and restart the loop.
if ($this->b === "\n") {
break;
}

// echo out the escaped character and restart the loop.
echo $this->a . $this->b;
break;


// Since we're not dealing with any special cases we simply
// output the character and continue our loop.
default:
echo $this->a;
}
}
}

/**
* When a regular expression is detected this function crawls for the end of
* it and saves the whole regex.
*
* @throws \RuntimeException Unclosed regex will throw an error
*/
protected function saveRegex()
{
echo $this->a . $this->b;

while (($this->a = $this->getChar()) !== false) {
if ($this->a === '/') {
break;
}

if ($this->a === '\\') {
echo $this->a;
$this->a = $this->getChar();
}

if ($this->a === "\n") {
throw new \RuntimeException('Unclosed regex pattern at position: ' . $this->index);
}

echo $this->a;
}
$this->b = $this->getReal();
}

/**
* Checks to see if a character is alphanumeric.
*
* @param string $char Just one character
* @return bool
*/
protected static function isAlphaNumeric($char)
{
return preg_match('/^[\w\$\pL]$/', $char) === 1 || $char == '/';
}

/**
* Replace patterns in the given string and store the replacement
*
* @param string $js The string to lock
* @return bool
*/
protected function lock($js)
{
/* lock things like <code>"asd" + ++x;</code> */
$lock = '"LOCK---' . crc32(time()) . '"';

$matches = array();
preg_match('/([+-])(\s+)([+-])/S', $js, $matches);
if (empty($matches)) {
return $js;
}

$this->locks[$lock] = $matches[2];

$js = preg_replace('/([+-])\s+([+-])/S', "$1{$lock}$2", $js);
/* -- */

return $js;
}

/**
* Replace "locks" with the original characters
*
* @param string $js The string to unlock
* @return bool
*/
protected function unlock($js)
{
if (empty($this->locks)) {
return $js;
}

foreach ($this->locks as $lock => $replacement) {
$js = str_replace($lock, $replacement, $js);
}

return $js;
}
}