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phabricator/src/infrastructure/diff/PhabricatorDiffScopeEngine.php
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PhabricatorDiffScopeEngine.php
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<?php
final class PhabricatorDiffScopeEngine
extends Phobject {
private $lineTextMap;
private $lineDepthMap;
public function setLineTextMap(array $map) {
if (array_key_exists(0, $map)) {
throw new Exception(
pht('ScopeEngine text map must be a 1-based map of lines.'));
}
$expect = 1;
foreach ($map as $key => $value) {
if ($key === $expect) {
$expect++;
continue;
}
throw new Exception(
pht(
'ScopeEngine text map must be a contiguous map of '.
'lines, but is not: found key "%s" where key "%s" was expected.',
$key,
$expect));
}
$this->lineTextMap = $map;
return $this;
}
public function getLineTextMap() {
if ($this->lineTextMap === null) {
throw new PhutilInvalidStateException('setLineTextMap');
}
return $this->lineTextMap;
}
public function getScopeStart($line) {
$text_map = $this->getLineTextMap();
$depth_map = $this->getLineDepthMap();
$length = count($text_map);
// Figure out the effective depth of the line we're getting scope for.
// If the line is just whitespace, it may have no depth on its own. In
// this case, we look for the next line.
$line_depth = null;
for ($ii = $line; $ii <= $length; $ii++) {
if ($depth_map[$ii] !== null) {
$line_depth = $depth_map[$ii];
break;
}
}
// If we can't find a line depth for the target line, just bail.
if ($line_depth === null) {
return null;
}
// Limit the maximum number of lines we'll examine. If a user has a
// million-line diff of nonsense, scanning the whole thing is a waste
// of time.
$search_range = 1000;
$search_until = max(0, $ii - $search_range);
for ($ii = $line - 1; $ii > $search_until; $ii--) {
$line_text = $text_map[$ii];
// This line is in missing context: the diff was diffed with partial
// context, and we ran out of context before finding a good scope line.
// Bail out, we don't want to jump across missing context blocks.
if ($line_text === null) {
return null;
}
$depth = $depth_map[$ii];
// This line is all whitespace. This isn't a possible match.
if ($depth === null) {
continue;
}
// Don't match context lines which are too deeply indented, since they
// are very unlikely to be symbol definitions.
if ($depth > 2) {
continue;
}
// The depth is the same as (or greater than) the depth we started with,
// so this isn't a possible match.
if ($depth >= $line_depth) {
continue;
}
// Reject lines which begin with "}" or "{". These lines are probably
// never good matches.
if (preg_match('/^\s*[{}]/i', $line_text)) {
continue;
}
return $ii;
}
return null;
}
private function getLineDepthMap() {
if (!$this->lineDepthMap) {
$this->lineDepthMap = $this->newLineDepthMap();
}
return $this->lineDepthMap;
}
private function getTabWidth() {
// TODO: This should be configurable once we handle tab widths better.
return 2;
}
private function newLineDepthMap() {
$text_map = $this->getLineTextMap();
$tab_width = $this->getTabWidth();
$depth_map = array();
foreach ($text_map as $line_number => $line_text) {
if ($line_text === null) {
$depth_map[$line_number] = null;
continue;
}
$len = strlen($line_text);
// If the line has no actual text, don't assign it a depth.
if (!$len || !strlen(trim($line_text))) {
$depth_map[$line_number] = null;
continue;
}
$count = 0;
for ($ii = 0; $ii < $len; $ii++) {
$c = $line_text[$ii];
if ($c == ' ') {
$count++;
} else if ($c == "\t") {
$count += $tab_width;
} else {
break;
}
}
// Round down to cheat our way through the " *" parts of docblock
// comments.
$depth = (int)floor($count / $tab_width);
$depth_map[$line_number] = $depth;
}
return $depth_map;
}
}

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