Matching (pairing) tokens (eg, brackets or quotes) - php

Question

In short, I need a function which attempts a rudimentary code fix by adding brackets/quotes were necessary, for parsing purposes. That is, the resulting code is not expected to be runnable.
Let's see a few examples:
[1] class Aaa { $var a = "hi"; => class Aaa { $var a = "hi"; }
[2] $var a = "hi"; } => { $var a = "hi"; }
[3] class { a = "hi; function b( } => class { a = "hi; function b( }"}
[4] class { a = "hi"; function b( } => class { a = "hi"; function b() {}}
PS: The 4th example above looks quite complicated, but in fact, it's quite easy. If the engine finds an ending bracket token which doesn't match with the stack, it should the opposite token before that one. As you can see, this works pretty well.
As a function signature, it looks like: balanceTokens($code, $bracket_tokens, $quote_tokens)
The function I wrote works using a stack. Well, it doesn't exactly work, but it does use a stack.
function balanceTokens($code, $bracket_tokens, $quote_tokens){
$stack = array(); $last = null; $result = '';
foreach(str_split($code) as $c){
if($last==$c && in_array($c, $quote_tokens)){
// handle closing string
array_pop($stack);
}elseif(!in_array($last, $quote_tokens)){
// handle other tokens
if(isset($bracket_tokens[$c])){
// handle begining bracket
$stack[] = $c;
}elseif(($p = array_search($c, $bracket_tokens)) != false){
// handle ending bracket
$l = array_pop($stack);
if($l != $p)$result .= $p;
}elseif(isset($quote_tokens[$c])){
// handle begining quote
$stack[] = $c;
$last = $c;
}// else other token...
}
$result .= $c;
}
// perform fixes
foreach($stack as $token){
// fix ending brackets
if(isset($bracket_tokens[$token]))
$result .= $bracket_tokens[$token];
// fix begining brackets
if(in_array($token, $bracket_tokens))
$result = $token . $result;
}
return $result;
}
The function is called like this:
$new_code = balanceTokens(
$old_code,
array(
'<' => '>',
'{' => '}',
'(' => ')',
'[' => ']',
),
array(
'"' => '"',
"'" => "'",
)
);
Yes, it's quite generic, there aren't any hard-coded tokens.
I haven't the slightest idea why it's not working...as a matter of fact, I don't even know if it should work. I admit I didn't put much thought into writing it. Maybe there are obvious issues which I'm not seeing.

Answer 1

An alternative implementation (which does more aggressive balancing):
function balanceTokens($code) {
$tokens = [
'{' => '}',
'[' => ']',
'(' => ')',
'"' => '"',
"'" => "'",
];
$closeTokens = array_flip($tokens);
$stringTokens = ['"' => true, '"' => true];
$stack = [];
for ($i = 0, $l = strlen($code); $i < $l; ++$i) {
$c = $code[$i];
// push opening tokens to the stack (for " and ' only if there is no " or ' opened yet)
if (isset($tokens[$c]) && (!isset($stringTokens[$c]) || end($stack) != $c)) {
$stack[] = $c;
// closing tokens have to be matched up with the stack elements
} elseif (isset($closeTokens[$c])) {
$matched = false;
while ($top = array_pop($stack)) {
// stack has matching opening for current closing
if ($top == $closeTokens[$c]) {
$matched = true;
break;
}
// stack has unmatched opening, insert closing at current pos
$code = substr_replace($code, $tokens[$top], $i, 0);
$i++;
$l++;
}
// unmatched closing, insert opening at start
if (!$matched) {
$code = $closeTokens[$c] . $code;
$i++;
$l++;
}
}
}
// any elements still on the stack are unmatched opening, so insert closing
while ($top = array_pop($stack)) {
$code .= $tokens[$top];
}
return $code;
}
Some examples:
$tests = array(
'class Aaa { public $a = "hi";',
'$var = "hi"; }',
'class { a = "hi; function b( }',
'class { a = "hi"; function b( }',
'foo { bar[foo="test',
'bar { bar[foo="test] { bar: "rgba(0, 0, 0, 0.1}',
);
Passing those to the function gives:
class Aaa { public $a = "hi";}
{$var = "hi"; }
class { a = "hi; function b( )"}
class { a = "hi"; function b( )}
foo { bar[foo="test"]}
bar { bar[foo="test"] { bar: "rgba(0, 0, 0, 0.1)"}}

Answer 2

After some coffee :), I came up with a (somewhat) working prototype function.
You can see it in action here. However, it is slightly modified to add some (shiny) debug output.
/**
* Fix some possible issues with the code (eg, incompleteness).
* #param string $code The code to sanitize.
* #param array $bracket_tokens List of bracket tokens where the index is the begin bracket and the value is the end bracket.
* #param array $quote_tokens List of quote tokens where the index is the begin quote and the value is the end quote.
* #return string The sanitized code.
*/
function css_sanitize($code, $bracket_tokens, $quote_tokens){
$result = '';
$stack = array();
$last = '';
foreach(str_split($code) as $c){
if(in_array($c, $quote_tokens) && $last==$c){
array_pop($stack);
$last = '';
}elseif(!in_array($last, $quote_tokens)){
if(isset($bracket_tokens[$c])){
$stack[] = $c;
}elseif(($p = array_search($c, $bracket_tokens)) != false){
if($last != $c){
$result .= $p;
}else{
array_pop($stack);
$last = (($p = count($stack)) > 1) ? $stack[$p] : '';
}
}elseif(isset($quote_tokens[$c])){
$stack[] = $c;
$last = $c;
}
}
$result .= $c;
}
foreach(array_reverse($stack) as $token){
if(isset($bracket_tokens[$token])){
$result .= $bracket_tokens[$token];
}
if(in_array($token, $bracket_tokens)){
$result = $token . $result;
}
if(isset($quote_tokens[$token])){
$result .= $quote_tokens[$token];
}
}
return $result;
}