Add feature: Ignore lists

doc/mpdscribble.1

@@ -126,6 +126,56 @@ Your Last.fm password, either cleartext or its MD5 sum.
 The file where mpdscribble should store its journal in case you do not
 have a connection to the scrobbler.  This option used to be called
 "cache".  It is optional.
+.TP
+.B ignore = FILE
+Include an ignore file for this scrobbler to exclude tracks from scrobbling.
+
+.SH IGNORE FILE FORMAT
+Tracks can be ignored by listing them in an \fBignore file\fP.
+Each line in the file specifies a pattern to match tracks you wish to exclude from scrobbling.
+The format is simple and flexible, allowing you to match by artist, album, title, track number or a combination of these fields.
+.SS File Format
+A tag match is specified as tagname="value", where tagname is replaced with one of the supported tags (artist, album, title, track).
+Values \fBmust\fP be quoted and spaces are not allowed surrounding the equal sign.
+
+Each line consists of one or more tag matches separated by spaces:
+.nf
+.in +4
+tag1="value1" tag2="value2" ...
+.in
+.fi
+
+Tags can appear in any order and blank lines are ignored.
+
+A backslash (\e) is interpreted as escape character and may be used to escape literal double quotes within a value.
+To write a literal backslash, use a double backslash (\e\e).
+
+Each line is limited to 4096 characters including the newline character.
+Superflous characters are silently ignored.
+
+.SS Examples
+If a tag is omitted, any value for that field is matched:
+.TP
+.B title="Bohemian Rhapsody"
+Matches any track titled \fIBohemian Rhapsody\fP.
+.TP
+.B artist="Queen"
+Matches any track by \fIQueen\fP, regardless of album or title.
+.TP
+.B artist="Queen" album="A Night at the Opera"
+Matches any track by \fIQueen\fP from \fIA Night at the Opera\fP, regardless of title.
+.TP
+.B artist="Queen" album="A Night at the Opera" title="Bohemian Rhapsody"
+Matches a specific track by \fIQueen\fP, from \fIA Night at the Opera\fP, titled \fIBohemian Rhapsody\fP.
+.TP
+.B artist="Queen" album="A Night at the Opera" track="01"
+Matches the first track on the album \fIA Night at the Opera\fP by \fIQueen\fP.
+Note that track tags are interpreted as text and not numbers, meaning "01" is not the same as "1".
+.TP
+.B artist="Clark \e"Plazmataz\e" Powell"
+Matches tracks by \fIClark "Plazmataz" Powell\fP.
+
+
 .SH FILES
 .I /etc/mpdscribble.conf
 .RS

doc/mpdscribble.conf

@@ -37,6 +37,8 @@ password =
 # The file where mpdscribble should store its Last.fm journal in case
 # you do not have a connection to the Last.fm server.
 journal = /var/cache/mpdscribble/lastfm.journal
+# Optional ignore file, see manpage for details!
+#ignore = /etc/mpdscribble_lastfm.ignore
 
 #[libre.fm]
 #url = http://turtle.libre.fm/

meson.build

@@ -208,6 +208,7 @@ executable(
   'src/MpdObserver.cxx',
   'src/Log.cxx',
   'src/XdgBaseDirectory.cxx',
+  'src/IgnoreList.cxx',
 
   include_directories: inc,
   dependencies: [

src/Config.hxx

@@ -8,6 +8,7 @@
 
 #include <forward_list>
 #include <string>
+#include <map>
 
 enum file_location { file_etc, file_home, file_unknown, };
 
@@ -17,7 +18,10 @@ NullableString(const std::string &s) noexcept
 	return s.empty() ? nullptr : s.c_str();
 }
 
+
 struct Config {
+	using IgnoreListMap = std::map<std::string, IgnoreList>;
+
 	/** don't daemonize the mpdscribble process */
 	bool no_daemon = false;
 
@@ -41,6 +45,8 @@ struct Config {
 	int verbose = -1;
 	enum file_location loc = file_unknown;
 
+	// Key=file path, value=loaded ignore list
+	IgnoreListMap ignore_lists;
 	std::forward_list<ScrobblerConfig> scrobblers;
 };
 

src/IgnoreList.cxx

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright The Music Player Daemon Project
+
+#include "IgnoreList.hxx"
+
+#include <cassert>
+#include <algorithm>
+
+[[gnu::pure]]
+static constexpr bool
+MatchIgnoreIfSpecified(std::string_view ignore, std::string_view value)
+{
+	return ignore.empty() || ignore == value;
+}
+
+bool
+IgnoreListEntry::matches_record(const Record& record) const noexcept
+{
+	/*
+	   The below logic would always return true if the entry is empty.
+	   This condition should never be true, as we don't push empty entries.
+	*/
+	assert(!artist.empty() || !album.empty() || !title.empty());
+
+	/*
+	   Note the mismatch of 'title' and 'track' field names with the Record structure.
+	   This is not a bug - the Record structure does not use the expected field names.
+	*/
+	return MatchIgnoreIfSpecified(artist, record.artist) &&
+	       MatchIgnoreIfSpecified(album, record.album) &&
+	       MatchIgnoreIfSpecified(title, record.track) &&
+	       MatchIgnoreIfSpecified(track, record.number);
+}
+
+bool
+IgnoreList::matches_record(const Record& record) const noexcept
+{
+	return std::any_of(entries.begin(),
+	                   entries.end(),
+	                   [&record](const auto& entry) { return entry.matches_record(record); });
+}

src/IgnoreList.hxx

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright The Music Player Daemon Project
+
+#ifndef IGNORE_LIST_HXX
+#define IGNORE_LIST_HXX
+
+#include <string>
+#include <vector>
+
+#include "Record.hxx"
+
+struct IgnoreListEntry {
+
+	std::string artist;
+	std::string album;
+	std::string title;
+	std::string track;
+
+	[[nodiscard]] bool matches_record(const Record& record) const noexcept;
+};
+
+struct IgnoreList {
+	std::vector<IgnoreListEntry> entries;
+
+	[[nodiscard]] bool matches_record(const Record& record) const noexcept;
+};
+
+
+#endif

src/ReadConfig.cxx

@@ -21,6 +21,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <unordered_map>
 
 #ifndef _WIN32
 #include <sys/stat.h>
@@ -231,10 +232,151 @@ load_unsigned(const IniFile &file, const char *name, unsigned *value_r)
 	return true;
 }
 
+static std::unordered_map<std::string, std::string>
+parse_ignore_list_line(std::string_view input)
+{
+	IgnoreListEntry ignore_list_entry;
+
+	/*
+	  Format: tag1="value1" tag2="value2" ...
+	  Backslash escaping is supported.
+	*/
+
+	enum class ParserState {
+		ExpectTagStart,
+		InTag,
+		ExpectQuote,
+		InValue,
+		InEscapeSequence
+	} state = ParserState::ExpectTagStart;
+
+	std::string current_tag;
+	std::string current_value;
+	std::unordered_map<std::string, std::string> result;
+
+	for (size_t i = 0; i < input.length(); ++i) {
+		char c = input[i];
+
+		switch (state) {
+			case ParserState::ExpectTagStart:
+				if (std::isspace(c)) continue;
+				if (std::isalpha(c)) {
+					current_tag = c;
+					state = ParserState::InTag;
+				} else {
+					throw FormatRuntimeError("Error at position %d: expected tag start, got: '%c'", i, c);
+				}
+				break;
+
+			case ParserState::InTag:
+				if (std::isalpha(c)) {
+					current_tag += c;
+				} else if (c == '=') {
+					state = ParserState::ExpectQuote;
+				} else {
+					throw FormatRuntimeError("Error at position %d: invalid tag character, got: '%c'", i, c);
+				}
+				break;
+
+			case ParserState::ExpectQuote:
+				if (c == '"') {
+					current_value.clear();
+					state = ParserState::InValue;
+				} else {
+					throw FormatRuntimeError("Error at position %d: expected quote, got: '%c'", i, c);
+				}
+				break;
+
+			case ParserState::InValue:
+				if (c == '\\') {
+					state = ParserState::InEscapeSequence;
+				} else if (c == '"') {
+					if (result.contains(current_tag)) {
+						throw FormatRuntimeError("Error at position %d: tag '%s' is duplicated", i, current_tag.c_str());
+					}
+					result.emplace(std::move(current_tag), std::move(current_value));
+					state = ParserState::ExpectTagStart;
+				} else {
+					current_value += c;
+				}
+				break;
+
+			case ParserState::InEscapeSequence:
+				current_value += c;
+				state = ParserState::InValue;
+				break;
+		}
+	}
+
+	if (state != ParserState::ExpectTagStart) {
+		throw FormatRuntimeError("Unexpected end of line");
+	}
+
+	return result;
+}
+
+static IgnoreList*
+load_ignore_list(const std::string& path, Config::IgnoreListMap& ignore_lists)
+{
+
+	FILE *file = fopen(path.c_str(), "r");
+	if (file == nullptr) {
+		throw FormatRuntimeError("Cannot load ignore file: cannot open '%s' for reading", path.c_str());
+	}
+
+	AtScopeExit(file) { fclose(file); };
+
+	IgnoreList ignore_list;
+
+	{
+		char line_buf[4096];
+		size_t line_num = 0;
+		while (fgets(line_buf, sizeof(line_buf), file)) {
+			std::string_view line(line_buf);
+			if (line.back() == '\n') {
+				line.remove_suffix(1);
+			}
+
+			line_num++;
+			if (line.empty()) {
+				continue;
+			}
+
+			try {
+				auto parsed_line = parse_ignore_list_line(line);
+
+				if (parsed_line.empty()) {
+					continue;
+				}
+
+				IgnoreListEntry entry{};
+
+				for (auto& [tag, value] : parsed_line) {
+#define set_tag_entry(tagname) if (tag == #tagname) { entry.tagname = std::move(value); continue; }
+					set_tag_entry(artist)
+					set_tag_entry(album)
+					set_tag_entry(title)
+					set_tag_entry(track)
+#undef set_tag_entry
+					throw FormatRuntimeError("Unsupported tag: '%s'", tag.c_str());
+				}
+
+				ignore_list.entries.emplace_back(std::move(entry));
+			} catch (const std::runtime_error& error) {
+				throw FormatRuntimeError("Error loading ignore list '%s': Error parsing line %d: %s",
+					path.c_str(), line_num, error.what());
+			}
+		}
+	}
+
+	return &(ignore_lists[path] = std::move(ignore_list));
+}
+
 static ScrobblerConfig
 load_scrobbler_config(const Config &config,
 		      const std::string &section_name,
-		      const IniSection &section)
+		      const IniSection &section,
+		      Config::IgnoreListMap& ignore_lists)
 {
 	ScrobblerConfig scrobbler;
 
@@ -270,6 +412,17 @@ load_scrobbler_config(const Config &config,
 			scrobbler.journal = get_default_cache_path(config);
 	}
 
+	std::string ignore_list = GetStdString(section, "ignore");
+	if (!ignore_list.empty()) {
+		if (auto existing_ignore_list = ignore_lists.find(ignore_list); existing_ignore_list != ignore_lists.end()) {
+			scrobbler.ignore_list = &existing_ignore_list->second;
+		} else {
+			scrobbler.ignore_list = load_ignore_list(ignore_list, ignore_lists);
+		}
+	} else {
+		scrobbler.ignore_list = nullptr;
+	}
+
 	return scrobbler;
 }
 
@@ -300,7 +453,8 @@ load_config_file(Config &config, const char *path)
 
 		config.scrobblers.emplace_front(load_scrobbler_config(config,
 								      section.first,
-								      section.second));
+								      section.second,
+								      config.ignore_lists));
 	}
 }
 

src/Scrobbler.cxx

@@ -436,6 +436,10 @@ Scrobbler::ScheduleNowPlaying(const Record &song) noexcept
 		/* there's no "now playing" support for files */
 		return;
 
+	if (config.ignore_list && config.ignore_list->matches_record(song)) {
+		return;
+	}
+
 	now_playing = song;
 
 	if (state == State::READY && !submit_timer.IsPending())
@@ -515,6 +519,10 @@ Scrobbler::Submit() noexcept
 void
 Scrobbler::Push(const Record &song) noexcept
 {
+	if (config.ignore_list && config.ignore_list->matches_record(song)) {
+		return;
+	}
+
 	if (file != nullptr) {
 		fprintf(file, "%s %s - %s\n",
 			log_date(),