<?php
/*
* Copyright 2018 Google LLC
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
namespace Google\ApiCore\ResourceTemplate;
use Google\ApiCore\ValidationException;
/**
* Collection of methods for parsing Segments.
*/
class Parser
{
/**
* Parses a path into an array of segments.
*
* @param string $path
* @return array
* @throws ValidationException
*/
public static function parseSegments($path)
{
if (empty($path)) {
throw new ValidationException("Cannot parse empty path");
}
$segments = [];
$index = 0;
$nextLiteral = '';
$segments[] = self::parseSegmentFromPath($path, $nextLiteral, $index);
while ($index < strlen($path)) {
self::parseLiteralFromPath($nextLiteral, $path, $index);
$segments[] = self::parseSegmentFromPath($path, $nextLiteral, $index);
}
return $segments;
}
/**
* Given a path and an index, reads a Segment from the path and updates
* the index.
*
* @param string $path
* @param string $nextLiteral
* @param int $index
* @return Segment
* @throws ValidationException
*/
private static function parseSegmentFromPath($path, &$nextLiteral, &$index)
{
if ($index >= strlen($path)) {
// A trailing '/' has caused the index to exceed the bounds
// of the string - provide a helpful error message.
throw self::parseError($path, strlen($path) - 1, "invalid trailing '/'");
}
if ($path[$index] === '{') {
// Validate that the { has a matching }
$closingBraceIndex = strpos($path, '}', $index);
if ($closingBraceIndex === false) {
throw self::parseError(
$path,
strlen($path),
"Expected '}' to match '{' at index $index, got end of string"
);
}
$segmentStringLengthWithoutBraces = $closingBraceIndex - $index - 1;
$segmentStringWithoutBraces = substr($path, $index + 1, $segmentStringLengthWithoutBraces);
$index = $closingBraceIndex + 1;
$nextLiteral = '/';
$remainingPath = substr($path, $index);
if (!empty($remainingPath)) {
// Find the firstnon-slash separator seen, if any.
$nextSlashIndex = strpos($remainingPath, '/', 0);
$nonSlashSeparators = ['-', '_', '~', '.'];
foreach ($nonSlashSeparators as $nonSlashSeparator) {
$nonSlashSeparatorIndex = strpos($remainingPath, $nonSlashSeparator, 0);
$nextOpenBraceIndex = strpos($remainingPath, '{', 0);
if ($nonSlashSeparatorIndex !== false && $nonSlashSeparatorIndex === $nextOpenBraceIndex - 1) {
$index += $nonSlashSeparatorIndex;
$nextLiteral = $nonSlashSeparator;
break;
}
}
}
return self::parseVariableSegment($segmentStringWithoutBraces, $nextLiteral);
} else {
$nextSlash = strpos($path, '/', $index);
if ($nextSlash === false) {
$nextSlash = strlen($path);
}
$segmentString = substr($path, $index, $nextSlash - $index);
$nextLiteral = '/';
$index = $nextSlash;
return self::parse($segmentString, $path, $index);
}
}
/**
* @param string $segmentString
* @param string $path
* @param int $index
* @return Segment
* @throws ValidationException
*/
private static function parse($segmentString, $path, $index)
{
if ($segmentString === '*') {
return new Segment(Segment::WILDCARD_SEGMENT);
} elseif ($segmentString === '**') {
return new Segment(Segment::DOUBLE_WILDCARD_SEGMENT);
} else {
if (!self::isValidLiteral($segmentString)) {
if (empty($segmentString)) {
// Create user friendly message in case of empty segment
throw self::parseError($path, $index, "Unexpected empty segment (consecutive '/'s are invalid)");
} else {
throw self::parseError($path, $index, "Unexpected characters in literal segment $segmentString");
}
}
return new Segment(Segment::LITERAL_SEGMENT, $segmentString);
}
}
/**
* @param string $segmentStringWithoutBraces
* @param string $separatorLiteral
* @return Segment
* @throws ValidationException
*/
private static function parseVariableSegment($segmentStringWithoutBraces, $separatorLiteral)
{
// Validate there are no nested braces
$nestedOpenBracket = strpos($segmentStringWithoutBraces, '{');
if ($nestedOpenBracket !== false) {
throw new ValidationException(
"Unexpected '{' parsing segment $segmentStringWithoutBraces at index $nestedOpenBracket"
);
}
$equalsIndex = strpos($segmentStringWithoutBraces, '=');
if ($equalsIndex === false) {
// If the variable does not contain '=', we assume the pattern is '*' as per google.rpc.Http
$variableKey = $segmentStringWithoutBraces;
$nestedResource = new RelativeResourceTemplate("*");
} else {
$variableKey = substr($segmentStringWithoutBraces, 0, $equalsIndex);
$nestedResourceString = substr($segmentStringWithoutBraces, $equalsIndex + 1);
$nestedResource = new RelativeResourceTemplate($nestedResourceString);
}
if (!self::isValidLiteral($variableKey)) {
throw new ValidationException(
"Unexpected characters in variable name $variableKey"
);
}
return new Segment(Segment::VARIABLE_SEGMENT, null, $variableKey, $nestedResource, $separatorLiteral);
}
/**
* @param string $literal
* @param string $path
* @param int $index
* @return string
* @throws ValidationException
*/
private static function parseLiteralFromPath($literal, $path, &$index)
{
$literalLength = strlen($literal);
if (strlen($path) < ($index + $literalLength)) {
throw self::parseError($path, $index, "expected '$literal'");
}
$consumedLiteral = substr($path, $index, $literalLength);
if ($consumedLiteral !== $literal) {
throw self::parseError($path, $index, "expected '$literal'");
}
$index += $literalLength;
return $consumedLiteral;
}
private static function parseError($path, $index, $reason)
{
return new ValidationException("Error parsing '$path' at index $index: $reason");
}
/**
* Check if $literal is a valid segment literal. Segment literals may only contain numbers,
* letters, and any of the following: .-~_
*
* @param string $literal
* @return bool
*/
private static function isValidLiteral($literal)
{
return preg_match("/^[0-9a-zA-Z\\.\\-~_]+$/", $literal) === 1;
}
}