<?php
namespace JmesPath;
/**
* Tree visitor used to evaluates JMESPath AST expressions.
*/
class TreeInterpreter
{
/** @var callable */
private $fnDispatcher;
/**
* @param callable $fnDispatcher Function dispatching function that accepts
* a function name argument and an array of
* function arguments and returns the result.
*/
public function __construct(callable $fnDispatcher = null)
{
$this->fnDispatcher = $fnDispatcher ?: FnDispatcher::getInstance();
}
/**
* Visits each node in a JMESPath AST and returns the evaluated result.
*
* @param array $node JMESPath AST node
* @param mixed $data Data to evaluate
*
* @return mixed
*/
public function visit(array $node, $data)
{
return $this->dispatch($node, $data);
}
/**
* Recursively traverses an AST using depth-first, pre-order traversal.
* The evaluation logic for each node type is embedded into a large switch
* statement to avoid the cost of "double dispatch".
* @return mixed
*/
private function dispatch(array $node, $value)
{
$dispatcher = $this->fnDispatcher;
switch ($node['type']) {
case 'field':
if (is_array($value) || $value instanceof \ArrayAccess) {
return isset($value[$node['value']]) ? $value[$node['value']] : null;
} elseif ($value instanceof \stdClass) {
return isset($value->{$node['value']}) ? $value->{$node['value']} : null;
}
return null;
case 'subexpression':
return $this->dispatch(
$node['children'][1],
$this->dispatch($node['children'][0], $value)
);
case 'index':
if (!Utils::isArray($value)) {
return null;
}
$idx = $node['value'] >= 0
? $node['value']
: $node['value'] + count($value);
return isset($value[$idx]) ? $value[$idx] : null;
case 'projection':
$left = $this->dispatch($node['children'][0], $value);
switch ($node['from']) {
case 'object':
if (!Utils::isObject($left)) {
return null;
}
break;
case 'array':
if (!Utils::isArray($left)) {
return null;
}
break;
default:
if (!is_array($left) || !($left instanceof \stdClass)) {
return null;
}
}
$collected = [];
foreach ((array) $left as $val) {
$result = $this->dispatch($node['children'][1], $val);
if ($result !== null) {
$collected[] = $result;
}
}
return $collected;
case 'flatten':
static $skipElement = [];
$value = $this->dispatch($node['children'][0], $value);
if (!Utils::isArray($value)) {
return null;
}
$merged = [];
foreach ($value as $values) {
// Only merge up arrays lists and not hashes
if (is_array($values) && isset($values[0])) {
$merged = array_merge($merged, $values);
} elseif ($values !== $skipElement) {
$merged[] = $values;
}
}
return $merged;
case 'literal':
return $node['value'];
case 'current':
return $value;
case 'or':
$result = $this->dispatch($node['children'][0], $value);
return Utils::isTruthy($result)
? $result
: $this->dispatch($node['children'][1], $value);
case 'and':
$result = $this->dispatch($node['children'][0], $value);
return Utils::isTruthy($result)
? $this->dispatch($node['children'][1], $value)
: $result;
case 'not':
return !Utils::isTruthy(
$this->dispatch($node['children'][0], $value)
);
case 'pipe':
return $this->dispatch(
$node['children'][1],
$this->dispatch($node['children'][0], $value)
);
case 'multi_select_list':
if ($value === null) {
return null;
}
$collected = [];
foreach ($node['children'] as $node) {
$collected[] = $this->dispatch($node, $value);
}
return $collected;
case 'multi_select_hash':
if ($value === null) {
return null;
}
$collected = [];
foreach ($node['children'] as $node) {
$collected[$node['value']] = $this->dispatch(
$node['children'][0],
$value
);
}
return $collected;
case 'comparator':
$left = $this->dispatch($node['children'][0], $value);
$right = $this->dispatch($node['children'][1], $value);
if ($node['value'] == '==') {
return Utils::isEqual($left, $right);
} elseif ($node['value'] == '!=') {
return !Utils::isEqual($left, $right);
} else {
return self::relativeCmp($left, $right, $node['value']);
}
case 'condition':
return Utils::isTruthy($this->dispatch($node['children'][0], $value))
? $this->dispatch($node['children'][1], $value)
: null;
case 'function':
$args = [];
foreach ($node['children'] as $arg) {
$args[] = $this->dispatch($arg, $value);
}
return $dispatcher($node['value'], $args);
case 'slice':
return is_string($value) || Utils::isArray($value)
? Utils::slice(
$value,
$node['value'][0],
$node['value'][1],
$node['value'][2]
) : null;
case 'expref':
$apply = $node['children'][0];
return function ($value) use ($apply) {
return $this->visit($apply, $value);
};
default:
throw new \RuntimeException("Unknown node type: {$node['type']}");
}
}
/**
* @return bool
*/
private static function relativeCmp($left, $right, $cmp)
{
if (!is_int($left) || !is_int($right)) {
return false;
}
switch ($cmp) {
case '>': return $left > $right;
case '>=': return $left >= $right;
case '<': return $left < $right;
case '<=': return $left <= $right;
default: throw new \RuntimeException("Invalid comparison: $cmp");
}
}
}
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