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<?php
declare(strict_types=1);
/*
* This file is part of the league/commonmark package.
*
* (c) Colin O'Dell <colinodell@gmail.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace League\CommonMark\Parser;
use League\CommonMark\Exception\UnexpectedEncodingException;
class Cursor
{
public const INDENT_LEVEL = 4;
/** @psalm-readonly */
private string $line;
/** @psalm-readonly */
private int $length;
/**
* @var int
*
* It's possible for this to be 1 char past the end, meaning we've parsed all chars and have
* reached the end. In this state, any character-returning method MUST return null.
*/
private int $currentPosition = 0;
private int $column = 0;
private int $indent = 0;
private int $previousPosition = 0;
private ?int $nextNonSpaceCache = null;
private bool $partiallyConsumedTab = false;
/** @psalm-readonly */
private bool $lineContainsTabs;
/** @psalm-readonly */
private bool $isMultibyte;
/** @var array<int, string> */
private array $charCache = [];
/**
* @param string $line The line being parsed (ASCII or UTF-8)
*/
public function __construct(string $line)
{
if (! \mb_check_encoding($line, 'UTF-8')) {
throw new UnexpectedEncodingException('Unexpected encoding - UTF-8 or ASCII was expected');
}
$this->line = $line;
$this->length = \mb_strlen($line, 'UTF-8') ?: 0;
$this->isMultibyte = $this->length !== \strlen($line);
$this->lineContainsTabs = \strpos($line, "\t") !== false;
}
/**
* Returns the position of the next character which is not a space (or tab)
*/
public function getNextNonSpacePosition(): int
{
if ($this->nextNonSpaceCache !== null) {
return $this->nextNonSpaceCache;
}
$c = null;
$i = $this->currentPosition;
$cols = $this->column;
while (($c = $this->getCharacter($i)) !== null) {
if ($c === ' ') {
$i++;
$cols++;
} elseif ($c === "\t") {
$i++;
$cols += 4 - ($cols % 4);
} else {
break;
}
}
$nextNonSpace = $c === null ? $this->length : $i;
$this->indent = $cols - $this->column;
return $this->nextNonSpaceCache = $nextNonSpace;
}
/**
* Returns the next character which isn't a space (or tab)
*/
public function getNextNonSpaceCharacter(): ?string
{
return $this->getCharacter($this->getNextNonSpacePosition());
}
/**
* Calculates the current indent (number of spaces after current position)
*/
public function getIndent(): int
{
if ($this->nextNonSpaceCache === null) {
$this->getNextNonSpacePosition();
}
return $this->indent;
}
/**
* Whether the cursor is indented to INDENT_LEVEL
*/
public function isIndented(): bool
{
if ($this->nextNonSpaceCache === null) {
$this->getNextNonSpacePosition();
}
return $this->indent >= self::INDENT_LEVEL;
}
public function getCharacter(?int $index = null): ?string
{
if ($index === null) {
$index = $this->currentPosition;
}
// Index out-of-bounds, or we're at the end
if ($index < 0 || $index >= $this->length) {
return null;
}
if ($this->isMultibyte) {
return $this->charCache[$index] ??= \mb_substr($this->line, $index, 1, 'UTF-8');
}
return $this->line[$index];
}
/**
* Slightly-optimized version of getCurrent(null)
*/
public function getCurrentCharacter(): ?string
{
if ($this->currentPosition >= $this->length) {
return null;
}
if ($this->isMultibyte) {
return $this->charCache[$this->currentPosition] ??= \mb_substr($this->line, $this->currentPosition, 1, 'UTF-8');
}
return $this->line[$this->currentPosition];
}
/**
* Returns the next character (or null, if none) without advancing forwards
*/
public function peek(int $offset = 1): ?string
{
return $this->getCharacter($this->currentPosition + $offset);
}
/**
* Whether the remainder is blank
*/
public function isBlank(): bool
{
return $this->nextNonSpaceCache === $this->length || $this->getNextNonSpacePosition() === $this->length;
}
/**
* Move the cursor forwards
*/
public function advance(): void
{
$this->advanceBy(1);
}
/**
* Move the cursor forwards
*
* @param int $characters Number of characters to advance by
* @param bool $advanceByColumns Whether to advance by columns instead of spaces
*/
public function advanceBy(int $characters, bool $advanceByColumns = false): void
{
$this->previousPosition = $this->currentPosition;
$this->nextNonSpaceCache = null;
// Optimization to avoid tab handling logic if we have no tabs
if (! $this->lineContainsTabs) {
$this->advanceWithoutTabCharacters($characters);
return;
}
$nextFewChars = $this->isMultibyte ?
\mb_substr($this->line, $this->currentPosition, $characters, 'UTF-8') :
\substr($this->line, $this->currentPosition, $characters);
if ($nextFewChars === '') {
return;
}
// Optimization to avoid tab handling logic if we have no tabs
if (\strpos($nextFewChars, "\t") === false) {
$this->advanceWithoutTabCharacters($characters);
return;
}
if ($characters === 1) {
$asArray = [$nextFewChars];
} elseif ($this->isMultibyte) {
/** @var string[] $asArray */
$asArray = \mb_str_split($nextFewChars, 1, 'UTF-8');
} else {
$asArray = \str_split($nextFewChars);
}
foreach ($asArray as $c) {
if ($c === "\t") {
$charsToTab = 4 - ($this->column % 4);
if ($advanceByColumns) {
$this->partiallyConsumedTab = $charsToTab > $characters;
$charsToAdvance = $charsToTab > $characters ? $characters : $charsToTab;
$this->column += $charsToAdvance;
$this->currentPosition += $this->partiallyConsumedTab ? 0 : 1;
$characters -= $charsToAdvance;
} else {
$this->partiallyConsumedTab = false;
$this->column += $charsToTab;
$this->currentPosition++;
$characters--;
}
} else {
$this->partiallyConsumedTab = false;
$this->currentPosition++;
$this->column++;
$characters--;
}
if ($characters <= 0) {
break;
}
}
}
private function advanceWithoutTabCharacters(int $characters): void
{
$length = \min($characters, $this->length - $this->currentPosition);
$this->partiallyConsumedTab = false;
$this->currentPosition += $length;
$this->column += $length;
}
/**
* Advances the cursor by a single space or tab, if present
*/
public function advanceBySpaceOrTab(): bool
{
$character = $this->getCurrentCharacter();
if ($character === ' ' || $character === "\t") {
$this->advanceBy(1, true);
return true;
}
return false;
}
/**
* Parse zero or more space/tab characters
*
* @return int Number of positions moved
*/
public function advanceToNextNonSpaceOrTab(): int
{
$newPosition = $this->nextNonSpaceCache ?? $this->getNextNonSpacePosition();
if ($newPosition === $this->currentPosition) {
return 0;
}
$this->advanceBy($newPosition - $this->currentPosition);
$this->partiallyConsumedTab = false;
// We've just advanced to where that non-space is,
// so any subsequent calls to find the next one will
// always return the current position.
$this->nextNonSpaceCache = $this->currentPosition;
$this->indent = 0;
return $this->currentPosition - $this->previousPosition;
}
/**
* Parse zero or more space characters, including at most one newline.
*
* Tab characters are not parsed with this function.
*
* @return int Number of positions moved
*/
public function advanceToNextNonSpaceOrNewline(): int
{
$remainder = $this->getRemainder();
// Optimization: Avoid the regex if we know there are no spaces or newlines
if ($remainder === '' || ($remainder[0] !== ' ' && $remainder[0] !== "\n")) {
$this->previousPosition = $this->currentPosition;
return 0;
}
$matches = [];
\preg_match('/^ *(?:\n *)?/', $remainder, $matches, \PREG_OFFSET_CAPTURE);
// [0][0] contains the matched text
// [0][1] contains the index of that match
$increment = $matches[0][1] + \strlen($matches[0][0]);
$this->advanceBy($increment);
return $this->currentPosition - $this->previousPosition;
}
/**
* Move the position to the very end of the line
*
* @return int The number of characters moved
*/
public function advanceToEnd(): int
{
$this->previousPosition = $this->currentPosition;
$this->nextNonSpaceCache = null;
$this->currentPosition = $this->length;
return $this->currentPosition - $this->previousPosition;
}
public function getRemainder(): string
{
if ($this->currentPosition >= $this->length) {
return '';
}
$prefix = '';
$position = $this->currentPosition;
if ($this->partiallyConsumedTab) {
$position++;
$charsToTab = 4 - ($this->column % 4);
$prefix = \str_repeat(' ', $charsToTab);
}
$subString = $this->isMultibyte ?
\mb_substr($this->line, $position, null, 'UTF-8') :
\substr($this->line, $position);
return $prefix . $subString;
}
public function getLine(): string
{
return $this->line;
}
public function isAtEnd(): bool
{
return $this->currentPosition >= $this->length;
}
/**
* Try to match a regular expression
*
* Returns the matching text and advances to the end of that match
*/
public function match(string $regex): ?string
{
$subject = $this->getRemainder();
if (! \preg_match($regex, $subject, $matches, \PREG_OFFSET_CAPTURE)) {
return null;
}
// $matches[0][0] contains the matched text
// $matches[0][1] contains the index of that match
if ($this->isMultibyte) {
// PREG_OFFSET_CAPTURE always returns the byte offset, not the char offset, which is annoying
$offset = \mb_strlen(\substr($subject, 0, $matches[0][1]), 'UTF-8');
$matchLength = \mb_strlen($matches[0][0], 'UTF-8');
} else {
$offset = $matches[0][1];
$matchLength = \strlen($matches[0][0]);
}
// [0][0] contains the matched text
// [0][1] contains the index of that match
$this->advanceBy($offset + $matchLength);
return $matches[0][0];
}
/**
* Encapsulates the current state of this cursor in case you need to rollback later.
*
* WARNING: Do not parse or use the return value for ANYTHING except for
* passing it back into restoreState(), as the number of values and their
* contents may change in any future release without warning.
*/
public function saveState(): CursorState
{
return new CursorState([
$this->currentPosition,
$this->previousPosition,
$this->nextNonSpaceCache,
$this->indent,
$this->column,
$this->partiallyConsumedTab,
]);
}
/**
* Restore the cursor to a previous state.
*
* Pass in the value previously obtained by calling saveState().
*/
public function restoreState(CursorState $state): void
{
[
$this->currentPosition,
$this->previousPosition,
$this->nextNonSpaceCache,
$this->indent,
$this->column,
$this->partiallyConsumedTab,
] = $state->toArray();
}
public function getPosition(): int
{
return $this->currentPosition;
}
public function getPreviousText(): string
{
return \mb_substr($this->line, $this->previousPosition, $this->currentPosition - $this->previousPosition, 'UTF-8');
}
public function getSubstring(int $start, ?int $length = null): string
{
if ($this->isMultibyte) {
return \mb_substr($this->line, $start, $length, 'UTF-8');
}
if ($length !== null) {
return \substr($this->line, $start, $length);
}
return \substr($this->line, $start);
}
public function getColumn(): int
{
return $this->column;
}
}
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