<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magento\Framework\Css\PreProcessor\Instruction;

use Magento\Framework\View\Asset\LocalInterface;
use Magento\Framework\View\Asset\NotationResolver;
use Magento\Framework\View\Asset\PreProcessorInterface;
use Magento\Framework\Css\PreProcessor\FileGenerator\RelatedGenerator;
use Magento\Framework\View\Asset\PreProcessor\Chain;

/**
 * 'import' instruction preprocessor
 */
class Import implements PreProcessorInterface
{
    /**
     * Pattern of 'import' instruction
     */
    const REPLACE_PATTERN =
        '#@import[\s]*'
        .'(?P<start>[\(\),\w\s]*?[\'\"][\s]*)'
        .'(?P<path>[^\)\'\"]*?)'
        .'(?P<end>[\s]*[\'\"][\s\w]*[\)]?)[\s]*;#';

    /**
     * @var \Magento\Framework\View\Asset\NotationResolver\Module
     */
    private $notationResolver;

    /**
     * @var array
     */
    protected $relatedFiles = [];

    /**
     * @var RelatedGenerator
     */
    private $relatedFileGenerator;

    /**
     * Constructor
     *
     * @param NotationResolver\Module $notationResolver
     * @param RelatedGenerator $relatedFileGenerator
     */
    public function __construct(
        NotationResolver\Module $notationResolver,
        RelatedGenerator $relatedFileGenerator
    ) {
        $this->notationResolver = $notationResolver;
        $this->relatedFileGenerator = $relatedFileGenerator;
    }

    /**
     * {@inheritdoc}
     */
    public function process(Chain $chain)
    {
        $asset = $chain->getAsset();
        $contentType = $chain->getContentType();
        $replaceCallback = function ($matchContent) use ($asset, $contentType) {
            return $this->replace($matchContent, $asset, $contentType);
        };
        $content = $this->removeComments($chain->getContent());

        $processedContent = preg_replace_callback(self::REPLACE_PATTERN, $replaceCallback, $content);
        $this->relatedFileGenerator->generate($this);
        if ($processedContent !== $content) {
            $chain->setContent($processedContent);
        }
    }

    /**
     * Returns the content without commented lines
     *
     * @param string $content
     * @return string
     */
    private function removeComments($content)
    {
        return preg_replace("#(^\s*//.*$)|((^\s*/\*(?s).*?(\*/)(?!\*/))$)#m", '', $content);
    }

    /**
     * Retrieve information on all related files, processed so far
     *
     * BUG: this information about related files is not supposed to be in the state of this object.
     * This class is meant to be a service (shareable instance) without such a transient state.
     * The list of related files needs to be accumulated for the preprocessor,
     * because it uses a 3rd-party library, which requires the files to physically reside in the base same directory.
     *
     * @return array
     */
    public function getRelatedFiles()
    {
        return $this->relatedFiles;
    }

    /**
     * Clear the record of related files, processed so far
     *
     * @return void
     */
    public function resetRelatedFiles()
    {
        $this->relatedFiles = [];
    }

    /**
     * Add related file to the record of processed files
     *
     * @param string $matchedFileId
     * @param LocalInterface $asset
     * @return void
     */
    protected function recordRelatedFile($matchedFileId, LocalInterface $asset)
    {
        $this->relatedFiles[] = [$matchedFileId, $asset];
    }

    /**
     * Return replacement of an original @import directive
     *
     * @param array $matchedContent
     * @param LocalInterface $asset
     * @param string $contentType
     * @return string
     */
    protected function replace(array $matchedContent, LocalInterface $asset, $contentType)
    {
        $matchedFileId = $this->fixFileExtension($matchedContent['path'], $contentType);

        $start = $matchedContent['start'];
        $end = $matchedContent['end'];
        if (strpos(trim($start), 'url') !== 0) {
            $this->recordRelatedFile($matchedFileId, $asset);
        }

        $resolvedPath = $this->notationResolver->convertModuleNotationToPath($asset, $matchedFileId);

        return "@import {$start}{$resolvedPath}{$end};";
    }

    /**
     * Resolve extension of imported asset according to exact format
     *
     * @param string $fileId
     * @param string $contentType
     * @return string
     * @link http://lesscss.org/features/#import-directives-feature-file-extensions
     */
    protected function fixFileExtension($fileId, $contentType)
    {
        if (!pathinfo($fileId, PATHINFO_EXTENSION)) {
            $fileId .= '.' . $contentType;
        }
        return $fileId;
    }
}