<?php

declare(strict_types=1);

namespace ProxyManager\ProxyGenerator\Util;

use Zend\Code\Generator\PropertyGenerator;

/**
 * Generates code necessary to simulate a fatal error in case of unauthorized
 * access to class members in magic methods even when in child classes and dealing
 * with protected members.
 *
 * @author Marco Pivetta <ocramius@gmail.com>
 * @license MIT
 */
class PublicScopeSimulator
{
    const OPERATION_SET   = 'set';
    const OPERATION_GET   = 'get';
    const OPERATION_ISSET = 'isset';
    const OPERATION_UNSET = 'unset';

    /**
     * Generates code for simulating access to a property from the scope that is accessing a proxy.
     * This is done by introspecting `debug_backtrace()` and then binding a closure to the scope
     * of the parent caller.
     *
     * @param string            $operationType      operation to execute: one of 'get', 'set', 'isset' or 'unset'
     * @param string            $nameParameter      name of the `name` parameter of the magic method
     * @param string|null       $valueParameter     name of the `value` parameter of the magic method
     * @param PropertyGenerator $valueHolder        name of the property containing the target object from which
     *                                              to read the property. `$this` if none provided
     * @param string|null       $returnPropertyName name of the property to which we want to assign the result of
     *                                              the operation. Return directly if none provided
     *
     * @throws \InvalidArgumentException
     */
    public static function getPublicAccessSimulationCode(
        string $operationType,
        string $nameParameter,
        $valueParameter = null,
        PropertyGenerator $valueHolder = null,
        $returnPropertyName = null
    ) : string {
        $byRef  = self::getByRefReturnValue($operationType);
        $value  = static::OPERATION_SET === $operationType ? ', $value' : '';
        $target = '$this';

        if ($valueHolder) {
            $target = '$this->' . $valueHolder->getName();
        }

        return '$realInstanceReflection = new \\ReflectionClass(get_parent_class($this));' . "\n\n"
            . 'if (! $realInstanceReflection->hasProperty($' . $nameParameter . ')) {'   . "\n"
            . '    $targetObject = ' . $target . ';' . "\n\n"
            . self::getUndefinedPropertyNotice($operationType, $nameParameter)
            . '    ' . self::getOperation($operationType, $nameParameter, $valueParameter) . "\n"
            . "    return;\n"
            . '}' . "\n\n"
            . '$targetObject = ' . self::getTargetObject($valueHolder) . ";\n"
            . '$accessor = function ' . $byRef . '() use ($targetObject, $name' . $value . ') {' . "\n"
            . '    ' . self::getOperation($operationType, $nameParameter, $valueParameter) . "\n"
            . "};\n"
            . self::getScopeReBind()
            . (
                $returnPropertyName
                    ? '$' . $returnPropertyName . ' = ' . $byRef . '$accessor();'
                    : '$returnValue = ' . $byRef . '$accessor();' . "\n\n" . 'return $returnValue;'
            );
    }

    /**
     * This will generate code that triggers a notice if access is attempted on a non-existing property
     *
     * @param string $operationType
     * @param string $nameParameter
     *
     * @return string
     */
    private static function getUndefinedPropertyNotice(string $operationType, string $nameParameter) : string
    {
        if (static::OPERATION_GET !== $operationType) {
            return '';
        }

        return '    $backtrace = debug_backtrace(false);' . "\n"
            . '    trigger_error(' . "\n"
            . '        sprintf(' . "\n"
            . '            \'Undefined property: %s::$%s in %s on line %s\',' . "\n"
            . '            get_parent_class($this),' . "\n"
            . '            $' . $nameParameter . ',' . "\n"
            . '            $backtrace[0][\'file\'],' . "\n"
            . '            $backtrace[0][\'line\']' . "\n"
            . '        ),' . "\n"
            . '        \E_USER_NOTICE' . "\n"
            . '    );' . "\n";
    }

    /**
     * Defines whether the given operation produces a reference.
     *
     * Note: if the object is a wrapper, the wrapped instance is accessed directly. If the object
     * is a ghost or the proxy has no wrapper, then an instance of the parent class is created via
     * on-the-fly unserialization
     */
    private static function getByRefReturnValue(string $operationType) : string
    {
        return (static::OPERATION_GET === $operationType || static::OPERATION_SET === $operationType) ? '& ' : '';
    }

    /**
     * Retrieves the logic to fetch the object on which access should be attempted
     *
     * @param PropertyGenerator $valueHolder
     *
     * @return string
     */
    private static function getTargetObject(PropertyGenerator $valueHolder = null) : string
    {
        if ($valueHolder) {
            return '$this->' . $valueHolder->getName();
        }

        return 'unserialize(sprintf(\'O:%d:"%s":0:{}\', strlen(get_parent_class($this)), get_parent_class($this)))';
    }

    /**
     * @throws \InvalidArgumentException
     */
    private static function getOperation(string $operationType, string $nameParameter, ?string $valueParameter) : string
    {
        switch ($operationType) {
            case static::OPERATION_GET:
                return 'return $targetObject->$' . $nameParameter . ';';
            case static::OPERATION_SET:
                if (null === $valueParameter) {
                    throw new \InvalidArgumentException('Parameter $valueParameter not provided');
                }

                return 'return $targetObject->$' . $nameParameter . ' = $' . $valueParameter . ';';
            case static::OPERATION_ISSET:
                return 'return isset($targetObject->$' . $nameParameter . ');';
            case static::OPERATION_UNSET:
                return 'unset($targetObject->$' . $nameParameter . ');';
        }

        throw new \InvalidArgumentException(sprintf('Invalid operation "%s" provided', $operationType));
    }

    /**
     * Generates code to bind operations to the parent scope
     *
     * @return string
     */
    private static function getScopeReBind() : string
    {
        return '$backtrace = debug_backtrace(true);' . "\n"
            . '$scopeObject = isset($backtrace[1][\'object\'])'
            . ' ? $backtrace[1][\'object\'] : new \ProxyManager\Stub\EmptyClassStub();' . "\n"
            . '$accessor = $accessor->bindTo($scopeObject, get_class($scopeObject));' . "\n";
    }
}