<?php
/**
 * Copyright 2019 Adobe
 * All Rights Reserved.
 */

declare(strict_types=1);

namespace Magento\Csp\Helper;

use Magento\Csp\Api\InlineUtilInterface;
use Magento\Csp\Model\Collector\ConfigCollector;
use Magento\Csp\Model\Collector\DynamicCollector;
use Magento\Csp\Model\Policy\FetchPolicy;
use Magento\Framework\App\ObjectManager;
use Magento\Framework\View\Helper\SecureHtmlRender\EventHandlerData;
use Magento\Framework\View\Helper\SecureHtmlRender\HtmlRenderer;
use Magento\Framework\View\Helper\SecureHtmlRender\SecurityProcessorInterface;
use Magento\Framework\View\Helper\SecureHtmlRender\TagData;

/**
 * Helper for classes responsible for rendering and templates.
 *
 * Allows to whitelist dynamic sources specific to a certain page.
 */
class InlineUtil implements InlineUtilInterface, SecurityProcessorInterface
{
    /**
     * @var DynamicCollector
     */
    private $dynamicCollector;

    /**
     * @var bool
     */
    private $useUnsafeHashes;

    /**
     * @var HtmlRenderer
     */
    private $htmlRenderer;

    /**
     * @var ConfigCollector
     */
    private $configCollector;

    /**
     * @var CspNonceProvider
     */
    private CspNonceProvider $nonceProvider;

    /**
     * @var array[]
     */
    private static $tagMeta = [
        'script' => ['id' => 'script-src', 'remote' => ['src'], 'hash' => true],
        'style' => ['id' => 'style-src', 'remote' => [], 'hash' => true],
        'img' => ['id' => 'img-src', 'remote' => ['src']],
        'audio' => ['id' => 'media-src', 'remote' => ['src']],
        'video' => ['id' => 'media-src', 'remote' => ['src']],
        'track' => ['id' => 'media-src', 'remote' => ['src']],
        'source' => ['id' => 'media-src', 'remote' => ['src']],
        'object' => ['id' => 'object-src', 'remote' => ['data', 'archive']],
        'embed' => ['id' => 'object-src', 'remote' => ['src']],
        'applet' => ['id' => 'object-src', 'remote' => ['code', 'archive']],
        'link' => ['id' => 'style-src', 'remote' => ['href']],
        'form' => ['id' => 'form-action', 'remote' => ['action']],
        'iframe' => ['id' => 'frame-src', 'remote' => ['src']],
        'frame' => ['id' => 'frame-src', 'remote' => ['src']]
    ];

    /**
     * @param DynamicCollector $dynamicCollector
     * @param bool $useUnsafeHashes Use 'unsafe-hashes' policy (not supported by CSP v2).
     * @param HtmlRenderer|null $htmlRenderer
     * @param ConfigCollector|null $configCollector
     * @param CspNonceProvider|null $nonceProvider
     */
    public function __construct(
        DynamicCollector $dynamicCollector,
        bool $useUnsafeHashes = false,
        ?HtmlRenderer $htmlRenderer = null,
        ?ConfigCollector $configCollector = null,
        ?CspNonceProvider $nonceProvider = null
    ) {
        $this->dynamicCollector = $dynamicCollector;
        $this->useUnsafeHashes = $useUnsafeHashes;
        $this->htmlRenderer = $htmlRenderer ?? ObjectManager::getInstance()->get(HtmlRenderer::class);
        $this->configCollector = $configCollector ?? ObjectManager::getInstance()->get(ConfigCollector::class);
        $this->nonceProvider = $nonceProvider ?? ObjectManager::getInstance()->get(CspNonceProvider::class);
    }

    /**
     * Generate fetch policy hash for some content.
     *
     * @param string $content
     * @return array Hash data to insert into a FetchPolicy.
     */
    private function generateHashValue(string $content): array
    {
        return [base64_encode(hash('sha256', $content, true)) => 'sha256'];
    }

    /**
     * Extract host for a fetch policy from a URL.
     *
     * @param string $url
     * @return string|null Null is returned when URL does not point to a remote host.
     */
    private function extractHost(string $url): ?string
    {
        // phpcs:ignore Magento2.Functions.DiscouragedFunction
        $urlData = parse_url($url);
        if (!$urlData
            || empty($urlData['scheme'])
            || ($urlData['scheme'] !== 'http' && $urlData['scheme'] !== 'https')
        ) {
            return null;
        }

        return $urlData['scheme'] .'://' .$urlData['host'];
    }

    /**
     * Extract remote hosts used to get fonts.
     *
     * @param string $styleContent
     * @return string[]
     */
    private function extractRemoteFonts(string $styleContent): array
    {
        $urlsFound = [];
        preg_match_all('/\@font\-face\s*?\{([^\}]*)[^\}]*?\}/im', $styleContent, $fontFaces);
        foreach ($fontFaces[1] as $fontFaceContent) {
            preg_match_all('/url\([\'\"]?(http(s)?\:[^\)]+)[\'\"]?\)/i', $fontFaceContent, $urls);
            $urlsFound[] = $urls[1];
        }

        return array_map([$this, 'extractHost'], array_merge([], ...$urlsFound));
    }

    /**
     * Extract remote hosts utilized.
     *
     * @param string $tag
     * @param string[] $attributes
     * @param string|null $content
     * @return string[]
     */
    private function extractRemoteHosts(string $tag, array $attributes, ?string $content): array
    {
        /** @var string[] $remotes */
        $remotes = [];
        foreach (self::$tagMeta[$tag]['remote'] as $remoteAttr) {
            if (!empty($attributes[$remoteAttr]) && $host = $this->extractHost($attributes[$remoteAttr])) {
                $remotes[] = $host;
                break;
            }
        }
        if ($tag === 'style' && $content) {
            $remotes += $this->extractRemoteFonts($content);
        }

        return $remotes;
    }

    /**
     * @inheritDoc
     */
    public function renderTag(string $tagName, array $attributes, ?string $content = null): string
    {
        if (!array_key_exists($tagName, self::$tagMeta)) {
            throw new \InvalidArgumentException('Unknown source type - ' .$tagName);
        }

        return $this->htmlRenderer->renderTag($this->processTag(new TagData($tagName, $attributes, $content, false)));
    }

    /**
     * @inheritDoc
     */
    public function renderEventListener(string $eventName, string $javascript): string
    {
        return $this->htmlRenderer->renderEventHandler(
            $this->processEventHandler(new EventHandlerData($eventName, $javascript))
        );
    }

    /**
     * @inheritDoc
     */
    public function processTag(TagData $tagData): TagData
    {
        //Processing tag data
        if (array_key_exists($tagData->getTag(), self::$tagMeta)) {
            /** @var string $policyId */
            $policyId = self::$tagMeta[$tagData->getTag()]['id'];
            $remotes = $this->extractRemoteHosts($tagData->getTag(), $tagData->getAttributes(), $tagData->getContent());
            if (empty($remotes) && !$tagData->getContent()) {
                throw new \InvalidArgumentException('Either remote URL or hashable content is required to whitelist');
            }

            //Adding required policies.
            if ($remotes) {
                $this->dynamicCollector->add(
                    new FetchPolicy($policyId, false, $remotes)
                );
            }
            if ($tagData->getContent()
                && !empty(self::$tagMeta[$tagData->getTag()]['hash'])
                && $this->isInlineDisabled(self::$tagMeta[$tagData->getTag()]['id'])
            ) {
                /** create new tagData with a nonce */
                if ($tagData->getTag() === 'script') {
                    $nonce = $this->nonceProvider->generateNonce();
                    $tagAttributes = $tagData->getAttributes();
                    $tagAttributes['nonce'] = $nonce;
                    $newTagData = new TagData(
                        $tagData->getTag(),
                        $tagAttributes,
                        $tagData->getContent(),
                        $tagData->isTextContent()
                    );

                    $tagData = $newTagData;
                } else {
                    $this->dynamicCollector->add(
                        new FetchPolicy(
                            $policyId,
                            false,
                            [],
                            [],
                            false,
                            false,
                            false,
                            [],
                            $this->generateHashValue($tagData->getContent())
                        )
                    );
                }
            }
        }

        return $tagData;
    }

    /**
     * @inheritDoc
     */
    public function processEventHandler(EventHandlerData $eventHandlerData): EventHandlerData
    {
        if ($this->useUnsafeHashes) {
            $policy = new FetchPolicy(
                'script-src',
                false,
                [],
                [],
                false,
                false,
                false,
                [],
                $this->generateHashValue($eventHandlerData->getCode()),
                false,
                true
            );
        } else {
            $policy = new FetchPolicy('script-src', false, [], [], false, true);
        }
        $this->dynamicCollector->add($policy);

        return $eventHandlerData;
    }

    /**
     * Check if inline sources are prohibited.
     *
     * @param string $policyId
     * @return bool
     */
    private function isInlineDisabled(string $policyId): bool
    {
        foreach ($this->configCollector->collect() as $policy) {
            if ($policy->getId() === $policyId && $policy instanceof FetchPolicy) {
                return !$policy->isInlineAllowed();
            }
        }

        return false;
    }
}
