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PhutilProseDifferenceEngine.php
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Mon, Apr 21, 23:06

PhutilProseDifferenceEngine.php
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<?php
final class PhutilProseDifferenceEngine extends Phobject {
public function getDiff($u, $v) {
$diff = id(new PhutilProseDiff());
$this->buildDiff($diff, $u, $v, 1);
$diff->reorderParts();
return $diff;
}
private function buildDiff(PhutilProseDiff $diff, $u, $v, $level) {
if ($level == 4) {
$diff->addPart('-', $u);
$diff->addPart('+', $v);
return;
}
$u_parts = $this->splitCorpus($u, $level);
$v_parts = $this->splitCorpus($v, $level);
$matrix = id(new PhutilEditDistanceMatrix())
->setSequences($u_parts, $v_parts)
->setComputeString(true);
// For word-level and character-level changes, smooth the output string
// to reduce the choppiness of the diff.
if ($level > 1) {
$matrix->setApplySmoothing(true);
}
$u_pos = 0;
$v_pos = 0;
$edits = $matrix->getEditString();
$edits_length = strlen($edits);
for ($ii = 0; $ii < $edits_length; $ii++) {
$c = $edits[$ii];
if ($c == 's') {
$diff->addPart('=', $u_parts[$u_pos]);
$u_pos++;
$v_pos++;
} else if ($c == 'd') {
$diff->addPart('-', $u_parts[$u_pos]);
$u_pos++;
} else if ($c == 'i') {
$diff->addPart('+', $v_parts[$v_pos]);
$v_pos++;
} else if ($c == 'x') {
$this->buildDiff($diff, $u_parts[$u_pos], $v_parts[$v_pos], $level + 1);
$u_pos++;
$v_pos++;
} else {
throw new Exception(
pht(
'Unexpected character ("%s") in edit string.',
$c));
}
}
}
private function splitCorpus($corpus, $level) {
switch ($level) {
case 1:
// Level 1: Split into sentences.
$expr = '/([\n,!;?\.]+)/';
break;
case 2:
// Level 2: Split into words.
$expr = '/(\s+)/';
break;
case 3:
// Level 3: Split into characters.
return phutil_utf8v_combined($corpus);
}
$pieces = preg_split($expr, $corpus, -1, PREG_SPLIT_DELIM_CAPTURE);
return $this->stitchPieces($pieces);
}
private function stitchPieces(array $pieces) {
$results = array();
$count = count($pieces);
for ($ii = 0; $ii < $count; $ii += 2) {
$result = $pieces[$ii];
if ($ii + 1 < $count) {
$result .= $pieces[$ii + 1];
}
$results[] = $result;
}
// If the input ended with a delimiter, we can get an empty final piece.
// Just discard it.
if (last($results) == '') {
array_pop($results);
}
return $results;
}
}

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