<?php declare(strict_types=1);

namespace PhpParser;

use PhpParser\Node\Expr;
use PhpParser\Node\Scalar;

use function array_merge;

/**
 * Evaluates constant expressions.
 *
 * This evaluator is able to evaluate all constant expressions (as defined by PHP), which can be
 * evaluated without further context. If a subexpression is not of this type, a user-provided
 * fallback evaluator is invoked. To support all constant expressions that are also supported by
 * PHP (and not already handled by this class), the fallback evaluator must be able to handle the
 * following node types:
 *
 *  * All Scalar\MagicConst\* nodes.
 *  * Expr\ConstFetch nodes. Only null/false/true are already handled by this class.
 *  * Expr\ClassConstFetch nodes.
 *
 * The fallback evaluator should throw ConstExprEvaluationException for nodes it cannot evaluate.
 *
 * The evaluation is dependent on runtime configuration in two respects: Firstly, floating
 * point to string conversions are affected by the precision ini setting. Secondly, they are also
 * affected by the LC_NUMERIC locale.
 */
class ConstExprEvaluator {
    /** @var callable|null */
    private $fallbackEvaluator;

    /**
     * Create a constant expression evaluator.
     *
     * The provided fallback evaluator is invoked whenever a subexpression cannot be evaluated. See
     * class doc comment for more information.
     *
     * @param callable|null $fallbackEvaluator To call if subexpression cannot be evaluated
     */
    public function __construct(?callable $fallbackEvaluator = null) {
        $this->fallbackEvaluator = $fallbackEvaluator ?? function (Expr $expr) {
            throw new ConstExprEvaluationException(
                "Expression of type {$expr->getType()} cannot be evaluated"
            );
        };
    }

    /**
     * Silently evaluates a constant expression into a PHP value.
     *
     * Thrown Errors, warnings or notices will be converted into a ConstExprEvaluationException.
     * The original source of the exception is available through getPrevious().
     *
     * If some part of the expression cannot be evaluated, the fallback evaluator passed to the
     * constructor will be invoked. By default, if no fallback is provided, an exception of type
     * ConstExprEvaluationException is thrown.
     *
     * See class doc comment for caveats and limitations.
     *
     * @param Expr $expr Constant expression to evaluate
     * @return mixed Result of evaluation
     *
     * @throws ConstExprEvaluationException if the expression cannot be evaluated or an error occurred
     */
    public function evaluateSilently(Expr $expr) {
        set_error_handler(function ($num, $str, $file, $line) {
            throw new \ErrorException($str, 0, $num, $file, $line);
        });

        try {
            return $this->evaluate($expr);
        } catch (\Throwable $e) {
            if (!$e instanceof ConstExprEvaluationException) {
                $e = new ConstExprEvaluationException(
                    "An error occurred during constant expression evaluation", 0, $e);
            }
            throw $e;
        } finally {
            restore_error_handler();
        }
    }

    /**
     * Directly evaluates a constant expression into a PHP value.
     *
     * May generate Error exceptions, warnings or notices. Use evaluateSilently() to convert these
     * into a ConstExprEvaluationException.
     *
     * If some part of the expression cannot be evaluated, the fallback evaluator passed to the
     * constructor will be invoked. By default, if no fallback is provided, an exception of type
     * ConstExprEvaluationException is thrown.
     *
     * See class doc comment for caveats and limitations.
     *
     * @param Expr $expr Constant expression to evaluate
     * @return mixed Result of evaluation
     *
     * @throws ConstExprEvaluationException if the expression cannot be evaluated
     */
    public function evaluateDirectly(Expr $expr) {
        return $this->evaluate($expr);
    }

    /** @return mixed */
    private function evaluate(Expr $expr) {
        if ($expr instanceof Scalar\Int_
            || $expr instanceof Scalar\Float_
            || $expr instanceof Scalar\String_
        ) {
            return $expr->value;
        }

        if ($expr instanceof Expr\Array_) {
            return $this->evaluateArray($expr);
        }

        // Unary operators
        if ($expr instanceof Expr\UnaryPlus) {
            return +$this->evaluate($expr->expr);
        }
        if ($expr instanceof Expr\UnaryMinus) {
            return -$this->evaluate($expr->expr);
        }
        if ($expr instanceof Expr\BooleanNot) {
            return !$this->evaluate($expr->expr);
        }
        if ($expr instanceof Expr\BitwiseNot) {
            return ~$this->evaluate($expr->expr);
        }

        if ($expr instanceof Expr\BinaryOp) {
            return $this->evaluateBinaryOp($expr);
        }

        if ($expr instanceof Expr\Ternary) {
            return $this->evaluateTernary($expr);
        }

        if ($expr instanceof Expr\ArrayDimFetch && null !== $expr->dim) {
            return $this->evaluate($expr->var)[$this->evaluate($expr->dim)];
        }

        if ($expr instanceof Expr\ConstFetch) {
            return $this->evaluateConstFetch($expr);
        }

        return ($this->fallbackEvaluator)($expr);
    }

    private function evaluateArray(Expr\Array_ $expr): array {
        $array = [];
        foreach ($expr->items as $item) {
            if (null !== $item->key) {
                $array[$this->evaluate($item->key)] = $this->evaluate($item->value);
            } elseif ($item->unpack) {
                $array = array_merge($array, $this->evaluate($item->value));
            } else {
                $array[] = $this->evaluate($item->value);
            }
        }
        return $array;
    }

    /** @return mixed */
    private function evaluateTernary(Expr\Ternary $expr) {
        if (null === $expr->if) {
            return $this->evaluate($expr->cond) ?: $this->evaluate($expr->else);
        }

        return $this->evaluate($expr->cond)
            ? $this->evaluate($expr->if)
            : $this->evaluate($expr->else);
    }

    /** @return mixed */
    private function evaluateBinaryOp(Expr\BinaryOp $expr) {
        if ($expr instanceof Expr\BinaryOp\Coalesce
            && $expr->left instanceof Expr\ArrayDimFetch
        ) {
            // This needs to be special cased to respect BP_VAR_IS fetch semantics
            return $this->evaluate($expr->left->var)[$this->evaluate($expr->left->dim)]
                ?? $this->evaluate($expr->right);
        }

        // The evaluate() calls are repeated in each branch, because some of the operators are
        // short-circuiting and evaluating the RHS in advance may be illegal in that case
        $l = $expr->left;
        $r = $expr->right;
        switch ($expr->getOperatorSigil()) {
            case '&':   return $this->evaluate($l) &   $this->evaluate($r);
            case '|':   return $this->evaluate($l) |   $this->evaluate($r);
            case '^':   return $this->evaluate($l) ^   $this->evaluate($r);
            case '&&':  return $this->evaluate($l) &&  $this->evaluate($r);
            case '||':  return $this->evaluate($l) ||  $this->evaluate($r);
            case '??':  return $this->evaluate($l) ??  $this->evaluate($r);
            case '.':   return $this->evaluate($l) .   $this->evaluate($r);
            case '/':   return $this->evaluate($l) /   $this->evaluate($r);
            case '==':  return $this->evaluate($l) ==  $this->evaluate($r);
            case '>':   return $this->evaluate($l) >   $this->evaluate($r);
            case '>=':  return $this->evaluate($l) >=  $this->evaluate($r);
            case '===': return $this->evaluate($l) === $this->evaluate($r);
            case 'and': return $this->evaluate($l) and $this->evaluate($r);
            case 'or':  return $this->evaluate($l) or  $this->evaluate($r);
            case 'xor': return $this->evaluate($l) xor $this->evaluate($r);
            case '-':   return $this->evaluate($l) -   $this->evaluate($r);
            case '%':   return $this->evaluate($l) %   $this->evaluate($r);
            case '*':   return $this->evaluate($l) *   $this->evaluate($r);
            case '!=':  return $this->evaluate($l) !=  $this->evaluate($r);
            case '!==': return $this->evaluate($l) !== $this->evaluate($r);
            case '+':   return $this->evaluate($l) +   $this->evaluate($r);
            case '**':  return $this->evaluate($l) **  $this->evaluate($r);
            case '<<':  return $this->evaluate($l) <<  $this->evaluate($r);
            case '>>':  return $this->evaluate($l) >>  $this->evaluate($r);
            case '<':   return $this->evaluate($l) <   $this->evaluate($r);
            case '<=':  return $this->evaluate($l) <=  $this->evaluate($r);
            case '<=>': return $this->evaluate($l) <=> $this->evaluate($r);
        }

        throw new \Exception('Should not happen');
    }

    /** @return mixed */
    private function evaluateConstFetch(Expr\ConstFetch $expr) {
        $name = $expr->name->toLowerString();
        switch ($name) {
            case 'null': return null;
            case 'false': return false;
            case 'true': return true;
        }

        return ($this->fallbackEvaluator)($expr);
    }
}

• [D] Builder
• [D] Comment
• [D] ErrorHandler
• [D] Internal
• [D] Lexer
• [D] Node
• [D] NodeVisitor
• [D] Parser
• [D] PrettyPrinter
• [F] Builder.php
  Delete
• [F] BuilderFactory.php
  Delete
• [F] BuilderHelpers.php
  Delete
• [F] Comment.php
  Delete
• [F] compatibility_tokens.php
  Delete
• [F] ConstExprEvaluationException.php
  Delete
• [F] ConstExprEvaluator.php
  Delete
• [F] Error.php
  Delete
• [F] ErrorHandler.php
  Delete
• [F] JsonDecoder.php
  Delete
• [F] Lexer.php
  Delete
• [F] Modifiers.php
  Delete
• [F] NameContext.php
  Delete
• [F] Node.php
  Delete
• [F] NodeAbstract.php
  Delete
• [F] NodeDumper.php
  Delete
• [F] NodeFinder.php
  Delete
• [F] NodeTraverser.php
  Delete
• [F] NodeTraverserInterface.php
  Delete
• [F] NodeVisitor.php
  Delete
• [F] NodeVisitorAbstract.php
  Delete
• [F] Parser.php
  Delete
• [F] ParserAbstract.php
  Delete
• [F] ParserFactory.php
  Delete
• [F] PhpVersion.php
  Delete
• [F] PrettyPrinter.php
  Delete
• [F] PrettyPrinterAbstract.php
  Delete
• [F] Token.php
  Delete

About Section

About NFC Pay: Our Story and Mission

NFC Pay was founded with a vision to transform the way people handle transactions. Our journey is defined by a commitment to innovation, security, and convenience. We strive to deliver seamless, user-friendly payment solutions that make everyday transactions effortless and secure. Our mission is to empower you to pay with ease and confidence, anytime, anywhere.

• Simplifying Payments, One Tap at a Time.
• Reinventing Your Wallet for Modern Convenience.
• Smart Payments for a Effortless Lifestyle.
• Experience the Ease of Tap and Pay.
• Innovative Solutions for Your Daily Transactions.

FAQ Section

Frequently Asked Questions About NFC Pay

Here are answers to some common questions about NFC Pay. We aim to provide clear and concise information to help you understand how our platform works and how it can benefit you. If you have any further inquiries, please don’t hesitate to contact our support team.

How do I register for NFC Pay?

Download the app and sign up using your email or phone number, then complete the verification process.

Is my payment information secure?

Yes, we use advanced encryption and security protocols to protect your payment details.

Can I add multiple cards to my NFC Pay wallet?

Absolutely, you can link multiple debit or credit cards to your wallet.

How do I transfer money to another user?

Go to the transfer section, select the recipient, enter the amount, and authorize the transfer.

What should I do if I forget my PIN?

Use the “Forgot PIN” feature in the app to reset it following the provided instructions.

How can I activate my merchant account?

Sign up for a merchant account through the app and follow the setup instructions to start accepting payments.

Can I track my payment status?

Yes, you can view and track your payment status in the account dashboard