<?php
namespace Rs\Json;
use Rs\Json\Pointer\InvalidJsonException;
use Rs\Json\Pointer\InvalidPointerException;
use Rs\Json\Pointer\NonexistentValueReferencedException;
use Rs\Json\Pointer\NonWalkableJsonException;
class Pointer
{
const POINTER_CHAR = '/';
const LAST_ARRAY_ELEMENT_CHAR = '-';
/**
* @var array
*/
private $json;
/**
* @var string
*/
private $pointer;
/**
* @param string $json The Json structure to point through.
* @throws \Rs\Json\Pointer\InvalidJsonException
* @throws \Rs\Json\Pointer\NonWalkableJsonException
*/
public function __construct($json)
{
$this->json = json_decode($json);
if (json_last_error() !== JSON_ERROR_NONE) {
throw new InvalidJsonException('Cannot operate on invalid Json.');
}
if (!$this->isWalkableJson()) {
throw new NonWalkableJsonException('Non walkable Json to point through');
}
}
/**
* @param string $pointer The Json Pointer.
* @throws \Rs\Json\Pointer\InvalidPointerException
* @throws \Rs\Json\Pointer\NonexistentValueReferencedException
*
* @return mixed
*/
public function get($pointer)
{
if ($pointer === '') {
$output = json_encode($this->json, JSON_UNESCAPED_UNICODE);
// workaround for https://bugs.php.net/bug.php?id=46600
return str_replace('"_empty_"', '""', $output);
}
$this->validatePointer($pointer);
$this->pointer = $pointer;
$plainPointerParts = array_slice(
array_map('urldecode', explode('/', $pointer)),
1
);
return $this->traverse($this->json, $this->evaluatePointerParts($plainPointerParts));
}
/**
* @return string
*/
public function getPointer()
{
return $this->pointer;
}
/**
* @param array|\stdClass $json The json_decoded Json structure.
* @param array $pointerParts The parts of the fed pointer.
*
* @throws \Rs\Json\Pointer\NonexistentValueReferencedException
*
* @return mixed
*/
private function traverse(&$json, array $pointerParts)
{
$pointerPart = array_shift($pointerParts);
if (is_array($json) && isset($json[$pointerPart])) {
if (count($pointerParts) === 0) {
return $json[$pointerPart];
}
if ((is_array($json[$pointerPart]) || is_object($json[$pointerPart])) && is_array($pointerParts)) {
return $this->traverse($json[$pointerPart], $pointerParts);
}
} elseif (is_object($json) && in_array($pointerPart, array_keys(get_object_vars($json)))) {
if (count($pointerParts) === 0) {
return $json->{$pointerPart};
}
if ((is_object($json->{$pointerPart}) || is_array($json->{$pointerPart})) && is_array($pointerParts)) {
return $this->traverse($json->{$pointerPart}, $pointerParts);
}
} elseif (is_object($json) && empty($pointerPart) && array_key_exists('_empty_', get_object_vars($json))) {
$pointerPart = '_empty_';
if (count($pointerParts) === 0) {
return $json->{$pointerPart};
}
if ((is_object($json->{$pointerPart}) || is_array($json->{$pointerPart})) && is_array($pointerParts)) {
return $this->traverse($json->{$pointerPart}, $pointerParts);
}
} elseif ($pointerPart === self::LAST_ARRAY_ELEMENT_CHAR && is_array($json)) {
return end($json);
} elseif (is_array($json) && count($json) < $pointerPart) {
// Do nothing, let Exception bubble up
} elseif (is_array($json) && array_key_exists($pointerPart, $json) && $json[$pointerPart] === null) {
return $json[$pointerPart];
}
$exceptionMessage = sprintf(
"Json Pointer '%s' references a nonexistent value",
$this->getPointer()
);
throw new NonexistentValueReferencedException($exceptionMessage);
}
/**
* @return boolean
*/
private function isWalkableJson()
{
if ($this->json !== null && (is_array($this->json) || $this->json instanceof \stdClass)) {
return true;
}
return false;
}
/**
* @param string $pointer The Json Pointer to validate.
* @throws \Rs\Json\Pointer\InvalidPointerException
*/
private function validatePointer($pointer)
{
if ($pointer !== '' && !is_string($pointer)) {
throw new InvalidPointerException('Pointer is not a string');
}
$firstPointerCharacter = substr($pointer, 0, 1);
if ($firstPointerCharacter !== self::POINTER_CHAR) {
throw new InvalidPointerException('Pointer starts with invalid character');
}
}
/**
* @param array $pointerParts The Json Pointer parts to evaluate.
*
* @return array
*/
private function evaluatePointerParts(array $pointerParts)
{
$searchables = array('~1', '~0');
$evaluations = array('/', '~');
$parts = array();
array_filter($pointerParts, function ($v) use (&$parts, &$searchables, &$evaluations) {
return $parts[] = str_replace($searchables, $evaluations, $v);
});
return $parts;
}
}