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<?php declare(strict_types=1); |
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/** |
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* ownCloud - Music app |
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* |
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* This file is licensed under the Affero General Public License version 3 or |
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* later. See the COPYING file. |
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* |
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* @author Pauli Järvinen <[email protected]> |
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* @copyright Pauli Järvinen 2020 - 2025 |
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*/ |
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namespace OCA\Music\Service; |
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class LyricsParser { |
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/** |
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* Take the timestamped lyrics as returned by `LyricsParser::parseSyncedLyrics` and |
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* return the corresponding plain text representation with no LRC tags. |
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* Input value null will give null result. |
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* |
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* @param array|null $parsedSyncedLyrics |
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* @return string|null |
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*/ |
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public static function syncedToUnsynced(?array $parsedSyncedLyrics) { |
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return ($parsedSyncedLyrics === null) ? null : \implode("\n", $parsedSyncedLyrics); |
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} |
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/** |
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* Parse timestamped lyrics from the given string, and return the parsed data. |
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* Return null if the string does not appear to be timestamped lyric in the LRC format. |
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* |
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* @return array|null The keys of the array are timestamps in milliseconds and values are |
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* corresponding lines of lyrics. |
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*/ |
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public static function parseSyncedLyrics(?string $data) : ?array { |
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$parsedLyrics = []; |
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if (!empty($data)) { |
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$offset = 0; |
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$fp = \fopen("php://temp", 'r+'); |
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\assert($fp !== false, 'Unexpected error: opening temporary stream failed'); |
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\fputs($fp, $data); |
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\rewind($fp); |
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while ($line = \fgets($fp)) { |
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$lineParseResult = self::parseTimestampedLrcLine($line, $offset); |
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$parsedLyrics += $lineParseResult; |
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} |
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\fclose($fp); |
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// sort the parsed lyric lines according the timestamps (which are keys of the array) |
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\ksort($parsedLyrics); |
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} |
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return \count($parsedLyrics) > 0 ? $parsedLyrics : null; |
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} |
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/** |
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* Parse a single line of LRC formatted data. The result is array where keys are |
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* timestamps and values are corresponding lyrics. A single line of LRC may span out to |
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* a) 0 actual timestamp lines, if the line is empty, or contains just metadata, or contains no tags |
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* b) 1 actual timestamp line (the "normal" case) |
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* c) several actual timestamp lines, in case the line contains several timestamps, |
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* meaning that the same line of text is repeated multiple times during the song |
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* |
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* If the line defines a time offset, this is returned in the reference parameter. If the offset |
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* parameter holds a non-zero value on call, the offset is applied on any extracted timestamps. |
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* |
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* @param string $line One line from the LRC data |
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* @param int $offset Input/output value for time offset in milliseconds |
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* @return array |
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*/ |
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private static function parseTimestampedLrcLine(string $line, int &$offset) : array { |
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$result = []; |
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$line = \trim($line); |
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$matches = []; |
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if (\preg_match('/(\[.+\])(.*)/', $line, $matches)) { |
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// 1st group captures tag(s), 2nd group anything after the tag(s). |
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$tags = $matches[1]; |
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$text = $matches[2]; |
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// Extract timestamp tags and the offset tag and discard any other metadata tags. |
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$timestampMatches = []; |
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$offsetMatch = []; |
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if (\preg_match('/\[offset:(\d+)\]/', $tags, $offsetMatch)) { |
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$offset = \intval($offsetMatch[1]); |
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} elseif (\preg_match_all('/\[(\d\d:\d\d(\.\d\d)?)\]/', $tags, $timestampMatches)) { |
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// some timestamp(s) were found |
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$timestamps = $timestampMatches[1]; |
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// add the line text to the result set on each found timestamp |
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foreach ($timestamps as $timestamp) { |
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$result[self::timestampToMs($timestamp) - $offset] = $text; |
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} |
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} |
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} |
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return $result; |
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} |
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/** |
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* Convert timestamp in "mm:ss.ff" format to milliseconds |
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*/ |
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private static function timestampToMs(string $timestamp) : int { |
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list($minutes, $seconds) = \sscanf($timestamp, "%d:%f"); |
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return \intval($seconds * 1000 + $minutes * 60 * 1000); |
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} |
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} |
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