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PhutilArgumentSpellingCorrector.php
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Sun, Nov 24, 14:15

PhutilArgumentSpellingCorrector.php
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<?php
final class PhutilArgumentSpellingCorrector extends Phobject {
private $editDistanceMatrix;
private $maximumDistance;
private $mode;
const MODE_COMMANDS = 'commands';
const MODE_FLAGS = 'flags';
/**
* Build a new corrector with parameters for correcting commands, like
* fixing "dfif" into "diff" in "arc diff".
*
* @return PhutilArgumentSpellingCorrector Configured corrector.
*/
public static function newCommandCorrector() {
// When correcting argument spelling, we're relatively liberal about
// selecting alternatives and allow multiple mistakes.
$max_distance = 2;
// Adjust to the scaled edit costs we use below, so "2" roughly means
// "2 edits".
$max_distance = $max_distance * 3;
// These costs are somewhat made up, but the theory is that it is far more
// likely you will mis-strike a key ("lans" for "land") or press two keys
// out of order ("alnd" for "land") than omit keys or press extra keys.
$matrix = id(new PhutilEditDistanceMatrix())
->setInsertCost(4)
->setDeleteCost(4)
->setReplaceCost(3)
->setTransposeCost(2);
return id(new self())
->setEditDistanceMatrix($matrix)
->setMode(self::MODE_COMMANDS)
->setMaximumDistance($max_distance);
}
/**
* Build a new corrector with parameters for correcting flags, like
* fixing "--nolint" into "--no-lint".
*
* @return PhutilArgumentSpellingCorrector Configured corrector.
*/
public static function newFlagCorrector() {
// When correcting flag spelling, we're stricter than we are when
// correcting command spelling: we allow only one inserted or deleted
// character. It is mainly to handle cases like "--no-lint" versus
// "--nolint" or "--reviewer" versus "--reviewers".
$max_distance = 1;
$matrix = id(new PhutilEditDistanceMatrix())
->setInsertCost(1)
->setDeleteCost(1)
->setReplaceCost(10);
return id(new self())
->setEditDistanceMatrix($matrix)
->setMode(self::MODE_FLAGS)
->setMaximumDistance($max_distance);
}
public function setMode($mode) {
$this->mode = $mode;
return $this;
}
public function getMode() {
return $this->mode;
}
public function setEditDistanceMatrix(PhutilEditDistanceMatrix $matrix) {
$this->editDistanceMatrix = $matrix;
return $this;
}
public function getEditDistanceMatrix() {
return $this->editDistanceMatrix;
}
public function setMaximumDistance($maximum_distance) {
$this->maximumDistance = $maximum_distance;
return $this;
}
public function getMaximumDistance() {
return $this->maximumDistance;
}
public function correctSpelling($input, array $options) {
$matrix = $this->getEditDistanceMatrix();
if (!$matrix) {
throw new PhutilInvalidStateException('setEditDistanceMatrix');
}
$max_distance = $this->getMaximumDistance();
if (!$max_distance) {
throw new PhutilInvalidStateException('setMaximumDistance');
}
// If we're correcting commands, never correct an input which begins
// with "-", since this is almost certainly intended to be a flag.
if ($this->getMode() === self::MODE_COMMANDS) {
if (preg_match('/^-/', $input)) {
return array();
}
}
$input = $this->normalizeString($input);
foreach ($options as $key => $option) {
$options[$key] = $this->normalizeString($option);
}
$distances = array();
$inputv = phutil_utf8v($input);
foreach ($options as $option) {
$optionv = phutil_utf8v($option);
$matrix->setSequences($optionv, $inputv);
$distances[$option] = $matrix->getEditDistance();
}
asort($distances);
$best = min($max_distance, head($distances));
foreach ($distances as $option => $distance) {
if ($distance > $best) {
unset($distances[$option]);
}
}
// Before filtering, check if we have multiple equidistant matches and
// return them if we do. This prevents us from, e.g., matching "alnd" with
// both "land" and "amend", then dropping "land" for being too short, and
// incorrectly completing to "amend".
if (count($distances) > 1) {
return array_keys($distances);
}
foreach ($distances as $option => $distance) {
if (phutil_utf8_strlen($option) < $distance) {
unset($distances[$option]);
}
}
return array_keys($distances);
}
private function normalizeString($string) {
return phutil_utf8_strtolower($string);
}
}

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