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libphutil/src/utils/PhutilProseDiff.php
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PhutilProseDiff.php
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<?php
final class PhutilProseDiff extends Phobject {
private $parts = array();
public function addPart($type, $text) {
$this->parts[] = array(
'type' => $type,
'text' => $text,
);
return $this;
}
public function getParts() {
return $this->parts;
}
/**
* Get diff parts, but replace large blocks of unchanged text with "."
* parts representing missing context.
*/
public function getSummaryParts() {
$parts = $this->getParts();
$head_key = head_key($parts);
$last_key = last_key($parts);
$results = array();
foreach ($parts as $key => $part) {
$is_head = ($key == $head_key);
$is_last = ($key == $last_key);
switch ($part['type']) {
case '=':
$pieces = $this->splitTextForSummary($part['text']);
if ($is_head || $is_last) {
$need = 2;
} else {
$need = 3;
}
// We don't have enough pieces to omit anything, so just continue.
if (count($pieces) < $need) {
$results[] = $part;
break;
}
if (!$is_head) {
$results[] = array(
'type' => '=',
'text' => head($pieces),
);
}
$results[] = array(
'type' => '.',
'text' => null,
);
if (!$is_last) {
$results[] = array(
'type' => '=',
'text' => last($pieces),
);
}
break;
default:
$results[] = $part;
break;
}
}
return $results;
}
public function reorderParts() {
// Reorder sequences of removed and added sections to put all the "-"
// parts together first, then all the "+" parts together. This produces
// a more human-readable result than intermingling them.
$o_run = array();
$n_run = array();
$result = array();
foreach ($this->parts as $part) {
$type = $part['type'];
switch ($type) {
case '-':
$o_run[] = $part;
break;
case '+':
$n_run[] = $part;
break;
default:
if ($o_run || $n_run) {
foreach ($this->combineRuns($o_run, $n_run) as $merged_part) {
$result[] = $merged_part;
}
$o_run = array();
$n_run = array();
}
$result[] = $part;
break;
}
}
if ($o_run || $n_run) {
foreach ($this->combineRuns($o_run, $n_run) as $part) {
$result[] = $part;
}
}
// Now, combine consecuitive runs of the same type of change (like a
// series of "-" parts) into a single run.
$combined = array();
$last = null;
$last_text = null;
foreach ($result as $part) {
$type = $part['type'];
if ($last !== $type) {
if ($last !== null) {
$combined[] = array(
'type' => $last,
'text' => $last_text,
);
}
$last_text = null;
$last = $type;
}
$last_text .= $part['text'];
}
if ($last_text !== null) {
$combined[] = array(
'type' => $last,
'text' => $last_text,
);
}
$this->parts = $combined;
return $this;
}
private function combineRuns($o_run, $n_run) {
$o_merge = $this->mergeParts($o_run);
$n_merge = $this->mergeParts($n_run);
// When removed and added blocks share a prefix or suffix, we sometimes
// want to count it as unchanged (for example, if it is whitespace) but
// sometimes want to count it as changed (for example, if it is a word
// suffix like "ing"). Find common prefixes and suffixes of these layout
// characters and emit them as "=" (unchanged) blocks.
$layout_characters = array(
' ' => true,
"\n" => true,
'.' => true,
'!' => true,
',' => true,
'?' => true,
);
$o_text = $o_merge['text'];
$n_text = $n_merge['text'];
$o_len = strlen($o_text);
$n_len = strlen($n_text);
$min_len = min($o_len, $n_len);
$prefix_len = 0;
for ($pos = 0; $pos < $min_len; $pos++) {
$o = $o_text[$pos];
$n = $n_text[$pos];
if ($o !== $n) {
break;
}
if (empty($layout_characters[$o])) {
break;
}
$prefix_len++;
}
$suffix_len = 0;
for ($pos = 1; $pos <= $min_len; $pos++) {
$o = $o_text[$o_len - $pos];
$n = $n_text[$n_len - $pos];
if ($o !== $n) {
break;
}
if (empty($layout_characters[$o])) {
break;
}
$suffix_len++;
}
$results = array();
if ($prefix_len) {
$results[] = array(
'type' => '=',
'text' => substr($o_text, 0, $prefix_len),
);
}
if ($prefix_len < $o_len) {
$results[] = array(
'type' => '-',
'text' => substr($o_text, $prefix_len, $o_len - $suffix_len),
);
}
if ($prefix_len < $n_len) {
$results[] = array(
'type' => '+',
'text' => substr($n_text, $prefix_len, $n_len - $suffix_len),
);
}
if ($suffix_len) {
$results[] = array(
'type' => '=',
'text' => substr($o_text, -$suffix_len),
);
}
return $results;
}
private function mergeParts(array $parts) {
$text = '';
$type = null;
foreach ($parts as $part) {
$part_type = $part['type'];
if ($type === null) {
$type = $part_type;
}
if ($type !== $part_type) {
throw new Exception(pht('Can not merge parts of dissimilar types!'));
}
$text .= $part['text'];
}
return array(
'type' => $type,
'text' => $text,
);
}
private function splitTextForSummary($text) {
$matches = null;
$ok = preg_match('/^(\n*[^\n]+)\n/', $text, $matches);
if (!$ok) {
return array($text);
}
$head = $matches[1];
$text = substr($text, strlen($head));
$ok = preg_match('/\n([^\n]+\n*)\z/', $text, $matches);
if (!$ok) {
return array($text);
}
$last = $matches[1];
$text = substr($text, 0, -strlen($last));
if (!strlen(trim($text))) {
return array($head, $last);
} else {
return array($head, $text, $last);
}
}
}
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