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<?php
declare(strict_types=1);
namespace Doctrine\Common\Lexer;
use ReflectionClass;
use UnitEnum;
use function implode;
use function preg_split;
use function sprintf;
use function substr;
use const PREG_SPLIT_DELIM_CAPTURE;
use const PREG_SPLIT_NO_EMPTY;
use const PREG_SPLIT_OFFSET_CAPTURE;
/**
* Base class for writing simple lexers, i.e. for creating small DSLs.
*
* @template T of UnitEnum|string|int
* @template V of string|int
*/
abstract class AbstractLexer
{
/**
* Lexer original input string.
*/
private string $input;
/**
* Array of scanned tokens.
*
* @var list<Token<T, V>>
*/
private array $tokens = [];
/**
* Current lexer position in input string.
*/
private int $position = 0;
/**
* Current peek of current lexer position.
*/
private int $peek = 0;
/**
* The next token in the input.
*
* @var Token<T, V>|null
*/
public Token|null $lookahead;
/**
* The last matched/seen token.
*
* @var Token<T, V>|null
*/
public Token|null $token;
/**
* Composed regex for input parsing.
*
* @var non-empty-string|null
*/
private string|null $regex = null;
/**
* Sets the input data to be tokenized.
*
* The Lexer is immediately reset and the new input tokenized.
* Any unprocessed tokens from any previous input are lost.
*
* @param string $input The input to be tokenized.
*
* @return void
*/
public function setInput(string $input)
{
$this->input = $input;
$this->tokens = [];
$this->reset();
$this->scan($input);
}
/**
* Resets the lexer.
*
* @return void
*/
public function reset()
{
$this->lookahead = null;
$this->token = null;
$this->peek = 0;
$this->position = 0;
}
/**
* Resets the peek pointer to 0.
*
* @return void
*/
public function resetPeek()
{
$this->peek = 0;
}
/**
* Resets the lexer position on the input to the given position.
*
* @param int $position Position to place the lexical scanner.
*
* @return void
*/
public function resetPosition(int $position = 0)
{
$this->position = $position;
}
/**
* Retrieve the original lexer's input until a given position.
*
* @return string
*/
public function getInputUntilPosition(int $position)
{
return substr($this->input, 0, $position);
}
/**
* Checks whether a given token matches the current lookahead.
*
* @param T $type
*
* @return bool
*
* @psalm-assert-if-true !=null $this->lookahead
*/
public function isNextToken(int|string|UnitEnum $type)
{
return $this->lookahead !== null && $this->lookahead->isA($type);
}
/**
* Checks whether any of the given tokens matches the current lookahead.
*
* @param list<T> $types
*
* @return bool
*
* @psalm-assert-if-true !=null $this->lookahead
*/
public function isNextTokenAny(array $types)
{
return $this->lookahead !== null && $this->lookahead->isA(...$types);
}
/**
* Moves to the next token in the input string.
*
* @return bool
*
* @psalm-assert-if-true !null $this->lookahead
*/
public function moveNext()
{
$this->peek = 0;
$this->token = $this->lookahead;
$this->lookahead = isset($this->tokens[$this->position])
? $this->tokens[$this->position++] : null;
return $this->lookahead !== null;
}
/**
* Tells the lexer to skip input tokens until it sees a token with the given value.
*
* @param T $type The token type to skip until.
*
* @return void
*/
public function skipUntil(int|string|UnitEnum $type)
{
while ($this->lookahead !== null && ! $this->lookahead->isA($type)) {
$this->moveNext();
}
}
/**
* Checks if given value is identical to the given token.
*
* @return bool
*/
public function isA(string $value, int|string|UnitEnum $token)
{
return $this->getType($value) === $token;
}
/**
* Moves the lookahead token forward.
*
* @return Token<T, V>|null The next token or NULL if there are no more tokens ahead.
*/
public function peek()
{
if (isset($this->tokens[$this->position + $this->peek])) {
return $this->tokens[$this->position + $this->peek++];
}
return null;
}
/**
* Peeks at the next token, returns it and immediately resets the peek.
*
* @return Token<T, V>|null The next token or NULL if there are no more tokens ahead.
*/
public function glimpse()
{
$peek = $this->peek();
$this->peek = 0;
return $peek;
}
/**
* Scans the input string for tokens.
*
* @param string $input A query string.
*
* @return void
*/
protected function scan(string $input)
{
if (! isset($this->regex)) {
$this->regex = sprintf(
'/(%s)|%s/%s',
implode(')|(', $this->getCatchablePatterns()),
implode('|', $this->getNonCatchablePatterns()),
$this->getModifiers(),
);
}
$flags = PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_OFFSET_CAPTURE;
$matches = preg_split($this->regex, $input, -1, $flags);
if ($matches === false) {
// Work around https://bugs.php.net/78122
$matches = [[$input, 0]];
}
foreach ($matches as $match) {
// Must remain before 'value' assignment since it can change content
$firstMatch = $match[0];
$type = $this->getType($firstMatch);
$this->tokens[] = new Token(
$firstMatch,
$type,
$match[1],
);
}
}
/**
* Gets the literal for a given token.
*
* @param T $token
*
* @return int|string
*/
public function getLiteral(int|string|UnitEnum $token)
{
if ($token instanceof UnitEnum) {
return $token::class . '::' . $token->name;
}
$className = static::class;
$reflClass = new ReflectionClass($className);
$constants = $reflClass->getConstants();
foreach ($constants as $name => $value) {
if ($value === $token) {
return $className . '::' . $name;
}
}
return $token;
}
/**
* Regex modifiers
*
* @return string
*/
protected function getModifiers()
{
return 'iu';
}
/**
* Lexical catchable patterns.
*
* @return string[]
*/
abstract protected function getCatchablePatterns();
/**
* Lexical non-catchable patterns.
*
* @return string[]
*/
abstract protected function getNonCatchablePatterns();
/**
* Retrieve token type. Also processes the token value if necessary.
*
* @return T|null
*
* @param-out V $value
*/
abstract protected function getType(string &$value);
}
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