Footnotes implementation

MarkdownExtra.php

@@ -2,6 +2,7 @@
 
 namespace cebe\markdown;
 
+use cebe\markdown\block\FooterTrait;
 use cebe\markdown\block\TableTrait;
 
 // work around https://github.com/facebook/hhvm/issues/1120
@@ -19,6 +20,7 @@ class MarkdownExtra extends Markdown
 	// include block element parsing using traits
 	use block\TableTrait;
 	use block\FencedCodeTrait;
+	use block\FooterTrait;
 
 	// include inline element parsing using traits
 	// TODO
@@ -60,8 +62,6 @@ class MarkdownExtra extends Markdown
 
 	// TODO implement definition lists
 
-	// TODO implement footnotes
-
 	// TODO implement Abbreviations
 
 

block/FooterTrait.php

@@ -0,0 +1,154 @@
+<?php
+/**
+ * Created by Andrew Solovov.
+ * User: Andrey
+ * Date: 15.01.2021
+ * Time: 18:36
+ *
+ * Project name: markdown
+ *
+ * @author     Andrew Solovov <[email protected]>
+ * @copyright  1997-2021 Pan Russian solovov.ru
+ */
+
+namespace cebe\markdown\block;
+
+
+trait FooterTrait
+{
+
+    protected $footnotes = [];
+    protected $footnoteNum = 1;
+
+    /**
+     * @param $text
+     * @return string
+     */
+    public function parse($text)
+    {
+        $absy = $this->parseBlocks(explode("\n", $text));
+
+        foreach ($absy as $block) {
+            if ($block[0] == 'footnote') {
+                $block['num'] = $this->footnoteNum;
+                $this->footnotes[] = $block;
+                $this->footnoteNum++;
+            }
+        }
+        $markup = parent::parse($text);
+        $markup = $this->applyFooter($markup, $this->footnotes);
+
+        return $markup;
+    }
+
+    /**
+     * @param $content
+     * @param $blocks
+     * @return string
+     */
+    protected function applyFooter($content, $blocks)
+    {
+        foreach ($blocks as $block) {
+            $number = $block['num'] . ". ";
+            $link = '<a href="#fnref:' . $block['id'] . '" class="footnote-backref">↑</a>';
+            $text = $this->renderAbsy($block['content']);
+            $text = $this->renderAbsy($this->parseInline($text));
+            $text = substr_replace($text, $number, 3, 0);
+            $text = substr_replace($text, $link, -5, 0);
+
+            $content .= '<footnotes id="fn:' . $block['id'] . '">' . $text . "</footnotes>\n";
+        }
+        return $content;
+    }
+
+    /**
+     * Parses a footnote link indicated by `[^`.
+     * @marker [^
+     * @param $text
+     * @return array
+     */
+    protected function parseFootnoteLink($text)
+    {
+        if (preg_match('/^\[\^(.+?)\]/', $text, $matches)) {
+            return [
+                ['footnoteLink', $matches[1]],
+                strlen($matches[0])
+            ];
+        }
+        return [['text', $text[0]], 1];
+    }
+
+    /**
+     * @param $block
+     * @return string
+     */
+    protected function renderFootnoteLink($block)
+    {
+        $footnoteId = $block[1];
+        $num = 0;
+        $found = false;
+        foreach ($this->footnotes as $footnote) {
+            $num ++;
+            if ($footnote['id']==$footnoteId) {
+                $found = true;
+                break;
+            }
+        }
+        if (!$found)
+            $num = '?';
+
+        $text = htmlspecialchars($block[1], ENT_NOQUOTES | ENT_SUBSTITUTE, 'UTF-8');
+        return '<sup id="fnref:' . $text . '"><a href="#fn:' . $text . '" class="footnote-ref" rel="footnote">[' . $num . ']</a></sup>';
+    }
+
+    /**
+     * identify a line as the beginning of a footnote block
+     *
+     * @param $line
+     * @return false|int
+     */
+    protected function identifyFootnoteList($line)
+    {
+        return preg_match('/^\[\^(.+?)\]:/', $line);
+    }
+
+    /**
+     * Consume lines for a footnote
+     */
+    protected function consumeFootnoteList($lines, $current)
+    {
+        $id = '';
+        $content = [];
+        $count = count($lines);
+        for ($i = $current; $i < $count; $i++) {
+            $line = $lines[$i];
+
+            if ($id == '') {
+                if (preg_match('/^\[\^(.+?)\]:[ \t]+/', $line, $matches)) {
+                    $id = $matches[1];
+                    $str = substr($line, strlen($matches[0]));
+                    $content[] = $str;
+                }
+            } else if (strlen(trim($line)) == 0) {
+                break;
+            } else {
+                $content[] = ltrim($line);
+            }
+        }
+
+        $block = ['footnote', 'id' => $id, 'content' => $this->parseBlocks($content)];
+
+        return [$block, $i];
+    }
+
+    /**
+     * @param $block
+     * @return string
+     */
+    protected function renderFootnote($block)
+    {
+        return '';
+    }
+
+
+}

tests/extra-data/footernote.md

@@ -0,0 +1,3 @@
+The implementation focus is to be fast (see benchmark) and extensible [^1]
+
+[^1]: See [benchmark](https://github.com/kzykhys/Markbench#readme).

tests/extra-data/foternote.html

@@ -0,0 +1,6 @@
+The implementation focus is to be fast (see benchmark) and extensible <sup id="fnref:1"><a href="#fn:1" class="footnote-ref" rel="footnote">[1]</a></sup>
+
+<hr>
+<footnotes id="fn:1"><p>1. See <a href="https://github.com/kzykhys/Markbench#readme">benchmark</a>.
+    <a href="#fnref:1" class="footnote-backref">↑</a></p>
+</footnotes>