<?hh // strict

/**

* Copyright (c) 2015-present, Facebook, Inc.

* All rights reserved.

*

* This source code is licensed under the BSD-style license found in the

* LICENSE file in the root directory of this source tree. An additional grant

* of patent rights can be found in the PATENTS file in the same directory.

*/

/**

* Manage partially generated code. The main operation is to merge existing

* code (that probably has some handwritten code) with generated code.

*/

final class PartiallyGeneratedCode {

private string $code;

private static string $manualBegin = '/* BEGIN MANUAL SECTION %s */';

private static string $manualEnd = '/* END MANUAL SECTION */';

public function __construct(string $code) {

$this->code = $code;

}

public static function getBeginManualSection(string $id): string {

return sprintf('/* BEGIN MANUAL SECTION %s */', $id);

}

private static function getBeginManualSectionRegex(string $regex): string {

// this needs to be kept in sync with getBeginManualSection.

return sprintf('|/\* BEGIN MANUAL SECTION %s \*/|', $regex);

}

public static function getEndManualSection(): string {

return '/* END MANUAL SECTION */';

}

public static function containsManualSection(string $code): bool {

return strpos($code, self::getEndManualSection()) !== false;

}

/**

* Merge the code with the existing code. The manual sections of

* the existing code will be merged into the corresponding sections

* of the new code.

*

* If rekeys is specified, we will attempt to pull code from sections

* with different names, as specified by the mapping.

*/

public function merge(

string $existing_code,

?Map<string, Vector<string>> $rekeys = null): string {

$merged = array();

$existing = $this->extractManualCode($existing_code);

$generated = $this->iterateCodeSections($this->code);

foreach ($generated as $section) {

list($id, $chunk) = $section;

if ($id === null) {

// Autogenerated section, add it as it is

$merged[] = $chunk;

} else {

if ($existing->containsKey($id)) {

// This manual section was present in the existing code, so insert it

$merged[] = $existing[$id];

} else {

$content = array();

if ($rekeys !== null) {

if ($rekeys->containsKey($id)) {

foreach ($rekeys[$id] as $old_id) {

if ($existing->containsKey($old_id)) {

$content[] = $existing[$old_id];

}

}

}

}

if ($content) {

$merged[] = implode("\n\n", $content);

} else {

// This manual section is new, so insert inside it the chunk from

// the generated code (e.g. the generated code can have a comment

// saying what that manual section should be used for)

$merged[] = $chunk;

}

}

}

}

return implode("\n", array_filter($merged));

}

/**

* Extract manually generated code and returns a map of ids to chunks of code

*/

private function extractManualCode(string $code): Map<string, string> {

$manual = Map {};

foreach ($this->iterateCodeSections($code) as $section) {

list($id, $chunk) = $section;

if ($id !== null) {

$manual[$id] = $chunk;

}

}

return $manual;

}

/**

* Extract the generated code and returns it as a string.

*/

public function extractGeneratedCode(): string {

$generated = array();

foreach ($this->iterateCodeSections($this->code) as $section) {

list($id, $chunk) = $section;

if ($id === null) {

$generated[] = $chunk;

}

}

return implode("\n", $generated);

}

/**

* Validate the manual sections and throws PartiallyGeneratedCodeException

* if there are any errors (e.g. unfinished manual section, nested

* manual sections, duplicated ids, etc)

*/

public function assertValidManualSections(): void {

foreach ($this->iterateCodeSections($this->code) as $section) {}

}

/**

* Iterates through the code yielding tuples of ($id, $chunk), where

* $id is the id of the manual section or null if it's an auto-generated

* section, and chunk is the code belonging to that section.

* The lines containing begin/end of manual section belong to the

* autogenerated sections.

*/

private function iterateCodeSections(

string $code

): Generator<int, (?string, string), void> {

// Regular expression to match the beginning of a manual section

$quoted = preg_quote(self::$manualBegin, '/');

$begin = self::getBeginManualSectionRegex('(.*)');

$valid_begin = self::getBeginManualSectionRegex('([A-Za-z0-9:_]+)');

$seen_ids = Set {};

$current_id = null;

$chunk = array();

$manual = array();

$lines = explode("\n", $code);

foreach ($lines as $line) {

if (strpos($line, self::$manualEnd) !== false) {

yield tuple($current_id, implode("\n", $chunk));

$chunk = array($line);

$current_id = null;

} else if (preg_match($begin, $line) === 1) {

if ($current_id !== null) {

throw new PartiallyGeneratedCodeException(

"The manual section $current_id was open before ".

"the previous one was closed"

);

}

if (!preg_match($valid_begin, $line)) {

throw new PartiallyGeneratedCodeException(

"Invalid id specified: " . $line

);

}

$chunk[] = $line;

yield tuple(null, implode("\n", $chunk));

$chunk = array();

$current_id = trim(preg_replace($begin, '\\1', $line));

if ($seen_ids->contains($current_id)) {

throw new PartiallyGeneratedCodeException(

"Duplicate manual section id: $current_id"

);

}

$seen_ids->add($current_id);

} else {

$chunk[] = $line;

}

}

if ($current_id !== null) {

throw new PartiallyGeneratedCodeException(

"The manual section $current_id was not closed at the end of code"

);

}

if ($code) {

yield tuple(null, implode("\n", $chunk));

}

}

}

final class PartiallyGeneratedCodeException extends Exception {};