xobject-template/src/Html/SubsetHtmlParser.php at 06a5628ab0079d312d0f1ebc3defab059410e69a · LibreSign/xobject-template · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
<?php

// SPDX-FileCopyrightText: 2026 LibreSign
// SPDX-License-Identifier: AGPL-3.0-or-later

declare(strict_types=1);

namespace LibreSign\XObjectTemplate\Html;

use DOMDocument;
use DOMElement;
use DOMNode;
use LibreSign\XObjectTemplate\Exception\UnsupportedSubsetException;

final class SubsetHtmlParser
{
    private const HTML_WRAPPER = '<?xml encoding="utf-8" ?><body>%s</body>';
    private const LIBXML_HTML_PARSE_FLAGS = 96; // LIBXML_NOERROR | LIBXML_NOWARNING
    private const INHERITABLE_STYLE_PROPERTIES = [
        'color' => true,
        'font-family' => true,
        'font-size' => true,
        'font-weight' => true,
        'line-height' => true,
        'text-align' => true,
    ];

    /** @var array<string, true> */
    private array $allowedTags = [
        'div' => true,
        'span' => true,
        'p' => true,
        'br' => true,
        'img' => true,
    ];

    /**
     * @return list<Node>
     *
     * @throws UnsupportedSubsetException If the HTML fragment contains an element outside the supported subset.
     */
    public function parse(string $html): array
    {
        $dom = new DOMDocument('1.0', 'UTF-8');
        $prevLibxmlErrors = libxml_use_internal_errors(true);
        $dom->loadHTML(
            sprintf(self::HTML_WRAPPER, $html),
            self::LIBXML_HTML_PARSE_FLAGS,
        );
        libxml_clear_errors();
        libxml_use_internal_errors($prevLibxmlErrors);

        $body = $dom->getElementsByTagName('body')->item(0);
        if ($body === null) {
            return [];
        }

        $nodes = [];
        foreach ($body->childNodes as $child) {
            $parsed = $this->parseDomNode($child, '');
            if ($parsed !== null) {
                $nodes[] = $parsed;
            }
        }

        return $nodes;
    }

    private function parseDomNode(DOMNode $node, string $inheritedStyle): ?Node
    {
        if ($node instanceof DOMElement) {
            return $this->parseElementNode($node, $inheritedStyle);
        }

        return $this->parseTextNode($node, $inheritedStyle);
    }

    private function parseElementNode(DOMElement $node, string $inheritedStyle): Node
    {
        $tag = $node->tagName;
        if (!isset($this->allowedTags[$tag])) {
            throw new UnsupportedSubsetException(sprintf('Tag <%s> is not supported.', $tag));
        }

        $attributes = $this->collectAttributes($node);
        $effectiveStyle = $this->mergeStyle($inheritedStyle, $attributes['style'] ?? '');
        unset($attributes['style']);
        if ($effectiveStyle !== '') {
            $attributes['style'] = $effectiveStyle;
        }

        $children = [];
        foreach ($node->childNodes as $childNode) {
            $child = $this->parseDomNode($childNode, $effectiveStyle);
            if ($child !== null) {
                $children[] = $child;
            }
        }

        return new Node(
            tag: $tag,
            text: '',
            attributes: $attributes,
            children: $children,
        );
    }

    private function parseTextNode(DOMNode $node, string $inheritedStyle): ?Node
    {
        $text = trim($node->textContent);
        if ($text === '') {
            return null;
        }

        $attributes = [];
        if ($inheritedStyle !== '') {
            $attributes['style'] = $inheritedStyle;
        }

        return new Node(tag: 'span', text: $text, attributes: $attributes);
    }

    /**
     * @return array<string, string>
     */
    private function collectAttributes(DOMElement $node): array
    {
        $attributes = [];
        $nodeAttrs = $node->attributes;
        if ($nodeAttrs !== null) {
            foreach ($nodeAttrs as $attribute) {
                $attributes[$attribute->name] = trim($attribute->value);
            }
        }

        return $attributes;
    }

    private function mergeStyle(string $inheritedStyle, string $ownStyle): string
    {
        $inheritedStyle = $this->filterInheritableStyle($inheritedStyle);

        if ($inheritedStyle === '') {
            return $ownStyle;
        }

        if ($ownStyle === '') {
            return $inheritedStyle;
        }

        return $inheritedStyle . ';' . $ownStyle;
    }

    private function filterInheritableStyle(string $style): string
    {
        if ($style === '') {
            return '';
        }

        $resolvedDeclarations = [];

        foreach (explode(';', $style) as $declaration) {
            $trimmedDeclaration = trim($declaration);
            if ($trimmedDeclaration === '') {
                continue;
            }

            $segments = explode(':', $trimmedDeclaration, 2);
            if (count($segments) !== 2) {
                continue;
            }

            $property = strtolower(trim($segments[0]));
            $value = trim($segments[1]);
            if ($value === '' || !isset(self::INHERITABLE_STYLE_PROPERTIES[$property])) {
                continue;
            }

            $resolvedDeclarations[$property] = $property . ':' . $value;
        }

        return implode(';', array_values($resolvedDeclarations));
    }
}