<?php

/*
 * This file is part of the league/commonmark package.
 *
 * (c) Colin O'Dell <colinodell@gmail.com>
 *
 * Original code based on the CommonMark JS reference parser (https://bitly.com/commonmark-js)
 *  - (c) John MacFarlane
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace League\CommonMark\Inline\Parser;

use League\CommonMark\Delimiter\Delimiter;
use League\CommonMark\Environment;
use League\CommonMark\EnvironmentAwareInterface;
use League\CommonMark\Inline\Element\Text;
use League\CommonMark\InlineParserContext;
use League\CommonMark\Util\Configuration;
use League\CommonMark\Util\RegexHelper;

class EmphasisParser extends AbstractInlineParser implements EnvironmentAwareInterface
{
    protected $config;

    public function __construct(array $newConfig = [])
    {
        $this->config = new Configuration([
            'use_asterisk'   => true,
            'use_underscore' => true,
            'enable_em'      => true,
            'enable_strong'  => true,
        ]);
        $this->config->mergeConfig($newConfig);
    }

    public function setEnvironment(Environment $environment)
    {
        $this->config->mergeConfig($environment->getConfig());
    }

    /**
     * @return string[]
     */
    public function getCharacters()
    {
        if (!$this->config->getConfig('enable_em') && !$this->config->getConfig('enable_strong')) {
            return [];
        }

        $chars = [];
        if ($this->config->getConfig('use_asterisk')) {
            $chars[] = '*';
        }
        if ($this->config->getConfig('use_underscore')) {
            $chars[] = '_';
        }

        return $chars;
    }

    /**
     * @param InlineParserContext $inlineContext
     *
     * @return bool
     */
    public function parse(InlineParserContext $inlineContext)
    {
        $character = $inlineContext->getCursor()->getCharacter();
        if (!in_array($character, $this->getCharacters())) {
            return false;
        }

        $numDelims = 0;

        $cursor = $inlineContext->getCursor();
        $charBefore = $cursor->peek(-1);
        if ($charBefore === null) {
            $charBefore = "\n";
        }

        while ($cursor->peek($numDelims) === $character) {
            ++$numDelims;
        }

        if ($numDelims === 0) {
            return false;
        }

        // Skip single delims if emphasis is disabled
        if ($numDelims === 1 && !$this->config->getConfig('enable_em')) {
            return false;
        }

        $cursor->advanceBy($numDelims);

        $charAfter = $cursor->getCharacter();
        if ($charAfter === null) {
            $charAfter = "\n";
        }

        list($canOpen, $canClose) = $this->determineCanOpenOrClose($charBefore, $charAfter, $character);

        $node = new Text($cursor->getPreviousText(), [
            'delim'           => true,
            'emphasis_config' => $this->config,
        ]);
        $inlineContext->getContainer()->appendChild($node);

        // Add entry to stack to this opener
        $delimiter = new Delimiter($character, $numDelims, $node, $canOpen, $canClose);
        $inlineContext->getDelimiterStack()->push($delimiter);

        return true;
    }

    /**
     * @param string $charBefore
     * @param string $charAfter
     * @param string $character
     *
     * @return bool[]
     */
    private function determineCanOpenOrClose($charBefore, $charAfter, $character)
    {
        $afterIsWhitespace = preg_match(RegexHelper::REGEX_UNICODE_WHITESPACE_CHAR, $charAfter);
        $afterIsPunctuation = preg_match(RegexHelper::REGEX_PUNCTUATION, $charAfter);
        $beforeIsWhitespace = preg_match(RegexHelper::REGEX_UNICODE_WHITESPACE_CHAR, $charBefore);
        $beforeIsPunctuation = preg_match(RegexHelper::REGEX_PUNCTUATION, $charBefore);

        $leftFlanking = !$afterIsWhitespace && (!$afterIsPunctuation || $beforeIsWhitespace || $beforeIsPunctuation);
        $rightFlanking = !$beforeIsWhitespace && (!$beforeIsPunctuation || $afterIsWhitespace || $afterIsPunctuation);

        if ($character === '_') {
            $canOpen = $leftFlanking && (!$rightFlanking || $beforeIsPunctuation);
            $canClose = $rightFlanking && (!$leftFlanking || $afterIsPunctuation);
        } else {
            $canOpen = $leftFlanking;
            $canClose = $rightFlanking;
        }

        return [$canOpen, $canClose];
    }
}