Added embedded/external lyrics support: parsing + indexing, ref #379
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emeric
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/*
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* Copyright (C) 2024 Emeric Poupon
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*
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* This file is part of LMS.
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*
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* LMS is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* LMS is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with LMS. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "metadata/Lyrics.hpp"
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#include <cassert>
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#include <regex>
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#include "core/String.hpp"
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namespace lms::metadata
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{
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std::span<const std::filesystem::path> getSupportedLyricsFileExtensions()
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{
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static const std::array<std::filesystem::path, 1> fileExtensions{ ".lrc" }; // TODO handle ".txt" and ".elrc"
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return fileExtensions;
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}
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namespace
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{
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std::string_view getSubmatchString(const std::csub_match& submatch)
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{
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assert(submatch.matched);
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return std::string_view{ submatch.first, static_cast<std::string_view::size_type>(submatch.length()) };
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}
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// Parse a single line with ID tags like [ar: Artist] and set the appropriate fields in the Lyrics object
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bool parseIDTag(std::string_view line, Lyrics& lyrics)
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{
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static const std::regex idTagRegex{ R"(^\[([a-zA-Z_]+):(.+?)\])" };
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std::cmatch match;
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if (std::regex_search(line.data(), line.data() + line.size(), match, idTagRegex))
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{
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std::string_view tagType{ getSubmatchString(match[1]) };
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std::string_view tagValue{ core::stringUtils::stringTrim(getSubmatchString(match[2])) };
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if (tagType == "ar")
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{
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lyrics.displayArtist = tagValue;
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}
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else if (tagType == "al")
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{
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lyrics.displayAlbum = tagValue;
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}
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else if (tagType == "ti")
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{
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lyrics.displayTitle = tagValue;
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}
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else if (tagType == "la")
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{
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lyrics.language = tagValue;
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}
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else if (tagType == "offset")
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{
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if (const auto value{ core::stringUtils::readAs<int>(tagValue) })
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lyrics.offset = std::chrono::milliseconds{ *value };
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}
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// not interrested by other tags like 'duration', 'id', etc.
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return true;
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}
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return false;
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}
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// Parse timestamps from a line and return the associated times in milliseconds
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void extractTimestamps(std::string_view line, std::vector<std::chrono::milliseconds>& timestamps)
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{
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timestamps.clear();
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static const std::regex timeTagRegex{ R"(\[(?:(\d{1,2}):)?(\d{1,2}):(\d{1,2})(?:\.(\d{1,3}))?\])" };
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std::cregex_iterator regexIt(line.begin(), line.end(), timeTagRegex);
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std::cregex_iterator regexEnd;
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while (regexIt != regexEnd)
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{
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std::cmatch match{ *regexIt };
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int hour{ match[1].matched ? std::stoi(match[1].str()) : 0 };
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int minute{ std::stoi(match[2].str()) };
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int second{ std::stoi(match[3].str()) };
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int fractional{ match[4].matched ? std::stoi(match[4].str()) : 0 };
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std::chrono::milliseconds currentTimestamp{ std::chrono::hours{ hour } + std::chrono::minutes{ minute } + std::chrono::seconds{ second } };
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if (match[4].length() == 2) // Centiseconds
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{
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currentTimestamp += std::chrono::milliseconds{ fractional * 10 };
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}
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else // Milliseconds
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{
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currentTimestamp += std::chrono::milliseconds{ fractional };
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}
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timestamps.push_back(currentTimestamp);
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++regexIt;
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}
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}
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// Extract the lyric text from a line, removing any timestamps
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std::string_view extractLyricText(std::string_view line)
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{
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return line.substr(line.find_last_of(']') + 1);
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}
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} // namespace
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// Main function to parse lyrics from an input stream
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Lyrics parseLyrics(std::istream& is)
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{
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Lyrics lyrics;
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enum class State
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{
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None,
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SynchronizedLyrics,
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UnsynchronizedLyrics,
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};
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State currentState{ State::None };
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std::vector<std::chrono::milliseconds> lastTimestamps;
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std::vector<std::chrono::milliseconds> timestamps;
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std::string accumulatedLyrics;
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auto applyAccumulatedLyrics = [&](bool skipTrailingEmptyLines = false)
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{
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if (lastTimestamps.empty())
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return;
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if (skipTrailingEmptyLines)
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accumulatedLyrics.resize(core::stringUtils::stringTrimEnd(accumulatedLyrics, " \t\r\n").size());
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if (accumulatedLyrics.empty())
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return;
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for (std::chrono::milliseconds timestamp : lastTimestamps)
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{
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std::string& synchronizedLine{ lyrics.synchronizedLines.find(timestamp)->second };
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synchronizedLine += accumulatedLyrics;
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}
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accumulatedLyrics.clear();
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};
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std::string line;
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while (std::getline(is, line))
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{
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std::string_view trimmedLine{ core::stringUtils::stringTrimEnd(line) };
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// Skip comments
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if (!trimmedLine.empty() && trimmedLine.front() == '#')
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continue;
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// Skip empty lines before actual lyrics
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if (currentState == State::None && trimmedLine.empty())
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continue;
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if (parseIDTag(trimmedLine, lyrics))
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continue;
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extractTimestamps(trimmedLine, timestamps);
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// If there are timestamps, add as synchronized lyrics
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if (!timestamps.empty())
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{
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if (currentState == State::UnsynchronizedLyrics)
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lyrics.unsynchronizedLines.clear(); // choice: discard all lyrics parsed so far
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currentState = State::SynchronizedLyrics;
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applyAccumulatedLyrics();
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std::string_view lyricText{ extractLyricText(trimmedLine) };
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for (std::chrono::milliseconds timestamp : timestamps)
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lyrics.synchronizedLines.emplace(timestamp, lyricText);
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lastTimestamps = timestamps;
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}
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else
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{
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if (!lastTimestamps.empty())
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{
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accumulatedLyrics += '\n';
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accumulatedLyrics += trimmedLine;
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}
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else
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{
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assert(currentState != State::SynchronizedLyrics); // should be handled
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currentState = State::UnsynchronizedLyrics;
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lyrics.unsynchronizedLines.push_back(std::string{ trimmedLine });
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}
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}
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}
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if (currentState == State::SynchronizedLyrics)
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applyAccumulatedLyrics(true);
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return lyrics;
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}
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} // namespace lms::metadata
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