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PhutilRemarkupEngineRemarkupListBlockRule.php
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Sat, Nov 23, 14:35

PhutilRemarkupEngineRemarkupListBlockRule.php
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<?php
/**
* @group markup
*/
final class PhutilRemarkupEngineRemarkupListBlockRule
extends PhutilRemarkupEngineBlockRule {
/**
* The maximum sub-list depth you can nest to. Avoids silliness and blowing
* the stack.
*/
const MAXIMUM_LIST_NESTING_DEPTH = 12;
public function getBlockPattern() {
// Support either "-" or "*" or "#" lists.
return '/^\s*[-*#]+\s+/';
}
public function shouldMergeBlocks() {
return true;
}
public function markupText($text) {
$items = array();
$lines = explode("\n", $text);
// We allow users to delimit lists using either differing indentation
// levels:
//
// - a
// - b
//
// ...or differing numbers of item-delimiter characters:
//
// - a
// -- b
//
// If they use the second style but block-indent the whole list, we'll
// get the depth counts wrong for the first item. To prevent this,
// un-indent every item by the minimum indentation level for the whole
// block before we begin parsing.
$min_space = PHP_INT_MAX;
foreach ($lines as $line) {
$matches = null;
if (preg_match($this->getBlockPattern(), $line)) {
if (preg_match('/^(\s+)/', $line, $matches)) {
$space = strlen($matches[1]);
} else {
$space = 0;
}
$min_space = min($min_space, $space);
}
}
if ($min_space) {
foreach ($lines as $key => $line) {
if (preg_match($this->getBlockPattern(), $line)) {
$lines[$key] = substr($line, $min_space);
}
}
}
// The input text may have linewraps in it, like this:
//
// - derp derp derp derp
// derp derp derp derp
// - blarp blarp blarp blarp
//
// Group text lines together into list items, stored in $items. So the
// result in the above case will be:
//
// array(
// array(
// "- derp derp derp derp",
// " derp derp derp derp",
// ),
// array(
// "- blarp blarp blarp blarp",
// ),
// );
$item = array();
foreach ($lines as $line) {
if (preg_match($this->getBlockPattern(), $line)) {
if ($item) {
$items[] = $item;
$item = array();
}
}
$item[] = $line;
}
if ($item) {
$items[] = $item;
}
// Process each item to normalize the text, remove line wrapping, and
// determine its depth (indentation level) and style (ordered vs unordered).
//
// Given the above example, the processed array will look like:
//
// array(
// array(
// 'text' => 'derp derp derp derp derp derp derp derp',
// 'depth' => 0,
// 'style' => '-',
// ),
// array(
// 'text' => 'blarp blarp blarp blarp',
// 'depth' => 0,
// 'style' => '-',
// ),
// );
foreach ($items as $key => $item) {
$item = preg_replace('/\s*\n\s*/', ' ', implode("\n", $item));
$item = rtrim($item);
if (!strlen($item)) {
unset($items[$key]);
continue;
}
$matches = null;
if (preg_match('/^\s*([-*#]{2,})/', $item, $matches)) {
// Alternate-style indents; use number of list item symbols.
$depth = strlen($matches[1]) - 1;
} else if (preg_match('/^(\s+)/', $item, $matches)) {
// Markdown-style indents; use indent depth.
$depth = strlen($matches[1]);
} else {
$depth = 0;
}
if (preg_match('/^\s*#/', $item)) {
$style = '#';
} else {
$style = '-';
}
$items[$key] = array(
'text' => preg_replace($this->getBlockPattern(), '', $item),
'depth' => $depth,
'style' => $style,
);
}
$items = array_values($items);
// Users can create a sub-list by indenting any deeper amount than the
// previous list, so these are both valid:
//
// - a
// - b
//
// - a
// - b
//
// In the former case, we'll have depths (0, 2). In the latter case, depths
// (0, 4). We don't actually care about how many spaces there are, only
// how many list indentation levels (that is, we want to map both of
// those cases to (0, 1), indicating "outermost list" and "first sublist").
//
// This is made more complicated because lists at two different indentation
// levels might be at the same list level:
//
// - a
// - b
// - c
// - d
//
// Here, 'b' and 'd' are at the same list level (2) but different indent
// levels (2, 4).
//
// Users can also create "staircases" like this:
//
// - a
// - b
// # c
//
// While this is silly, we'd like to render it as faithfully as possible.
//
// In order to do this, we convert the list of nodes into a tree,
// normalizing indentation levels and inserting dummy nodes as necessary to
// make the tree well-formed. See additional notes at buildTree().
//
// In the case above, the result is a tree like this:
//
// - <null>
// - <null>
// - a
// - b
// # c
$l = 0;
$r = count($items);
$tree = $this->buildTree($items, $l, $r, $cur_level = 0);
// We may need to open a list on a <null> node, but they do not have
// list style information yet. We need to propagate list style inforamtion
// backward through the tree. In the above example, the tree now looks
// like this:
//
// - <null (style=#)>
// - <null (style=-)>
// - a
// - b
// # c
$this->adjustTreeStyleInformation($tree);
// Finally, we have enough information to render the tree.
$out = $this->renderTree($tree);
return implode('', $out);
}
/**
* See additional notes in markupText().
*/
private function buildTree(array $items, $l, $r, $cur_level) {
if ($l == $r) {
return array();
}
if ($cur_level > self::MAXIMUM_LIST_NESTING_DEPTH) {
// This algorithm is recursive and we don't need you blowing the stack
// with your oh-so-clever 50,000-item-deep list. Cap indentation levels
// at a reasonable number and just shove everything deeper up to this
// level.
$nodes = array();
for ($ii = $l; $ii < $r; $ii++) {
$nodes[] = array(
'level' => $cur_level,
'items' => array(),
) + $items[$ii];
}
return $nodes;
}
$min = $l;
for ($ii = $r - 1; $ii >= $l; $ii--) {
if ($items[$ii]['depth'] < $items[$min]['depth']) {
$min = $ii;
}
}
$min_depth = $items[$min]['depth'];
$nodes = array();
if ($min != $l) {
$nodes[] = array(
'text' => null,
'level' => $cur_level,
'style' => null,
'items' => $this->buildTree($items, $l, $min, $cur_level + 1),
);
}
$last = $min;
for ($ii = $last + 1; $ii < $r; $ii++) {
if ($items[$ii]['depth'] == $min_depth) {
$nodes[] = array(
'level' => $cur_level,
'items' => $this->buildTree($items, $last + 1, $ii, $cur_level + 1),
) + $items[$last];
$last = $ii;
}
}
$nodes[] = array(
'level' => $cur_level,
'items' => $this->buildTree($items, $last + 1, $r, $cur_level + 1),
) + $items[$last];
return $nodes;
}
/**
* See additional notes in markupText().
*/
private function adjustTreeStyleInformation(array &$tree) {
// The effect here is just to walk backward through the nodes at this level
// and apply the first style in the list to any empty nodes we inserted
// before it. As we go, also recurse down the tree.
$style = '-';
for ($ii = count($tree) - 1; $ii >= 0; $ii--) {
if ($tree[$ii]['style'] !== null) {
// This is the earliest node we've seen with style, so set the
// style to its style.
$style = $tree[$ii]['style'];
} else {
// This node has no style, so apply the current style.
$tree[$ii]['style'] = $style;
}
if ($tree[$ii]['items']) {
$this->adjustTreeStyleInformation($tree[$ii]['items']);
}
}
}
/**
* See additional notes in markupText().
*/
private function renderTree(array $tree) {
$style = idx(head($tree), 'style');
$out = array();
switch ($style) {
case '#':
$out[] = "<ol>\n";
break;
case '-':
$out[] = "<ul>\n";
break;
}
foreach ($tree as $item) {
if ($item['text'] === null) {
$out[] = '<li class="phantom-item">';
} else {
$out[] = '<li>';
$out[] = $this->applyRules($item['text']);
}
if ($item['items']) {
foreach ($this->renderTree($item['items']) as $i) {
$out[] = $i;
}
}
$out[] = "</li>\n";
}
switch ($style) {
case '#':
$out[] = '</ol>';
break;
case '-':
$out[] = '</ul>';
break;
}
return $out;
}
}

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