<?php

namespace YaySMTP\Aws3\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 ?: \YaySMTP\Aws3\JmesPath\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], $value));
      case 'index':
        if (!\YaySMTP\Aws3\JmesPath\Utils::isArray($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 (!\YaySMTP\Aws3\JmesPath\Utils::isObject($left)) {
              return null;
            }
            break;
          case 'array':
            if (!\YaySMTP\Aws3\JmesPath\Utils::isArray($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], $value);
        if (!\YaySMTP\Aws3\JmesPath\Utils::isArray($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], $value);
        return \YaySMTP\Aws3\JmesPath\Utils::isTruthy($result) ? $result : $this->dispatch($node['children'][1], $value);
      case 'and':
        $result = $this->dispatch($node['children'][0], $value);
        return \YaySMTP\Aws3\JmesPath\Utils::isTruthy($result) ? $this->dispatch($node['children'][1], $value) : $result;
      case 'not':
        return !\YaySMTP\Aws3\JmesPath\Utils::isTruthy($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 \YaySMTP\Aws3\JmesPath\Utils::isEqual($left, $right);
        } elseif ($node['value'] == '!=') {
          return !\YaySMTP\Aws3\JmesPath\Utils::isEqual($left, $right);
        } else {
          return self::relativeCmp($left, $right, $node['value']);
        }
      case 'condition':
        return \YaySMTP\Aws3\JmesPath\Utils::isTruthy($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) || \YaySMTP\Aws3\JmesPath\Utils::isArray($value) ? \YaySMTP\Aws3\JmesPath\Utils::slice($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_float($left)) || !(is_int($right) || is_float($right))) {
      return false;
    }
    switch ($cmp) {
      case '>':
        return $left > $right;
      case '>=':
        return $left >= $right;
      case '<':
        return $left < $right;
      case '<=':
        return $left <= $right;
      default:
        throw new \RuntimeException("Invalid comparison: {$cmp}");
    }
  }
}