song/PrioritySongFilter: new filter

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1412

NEWS

@@ -1,6 +1,7 @@
 ver 0.24 (not yet released)
 * protocol
   - "playlistfind"/"playlistsearch" have "sort" and "window" parameters
+  - filter "prio" (for "playlistfind"/"playlistsearch")
 * player
   - add option "mixramp_analyzer" to scan MixRamp tags on-the-fly
 * tags

doc/protocol.rst

@@ -220,6 +220,9 @@ of:
   matches the audio format with the given mask (i.e. one
   or more attributes may be ``*``).
 
+- ``(priority >= 42)``:
+  compares the priority of queued songs.
+
 - ``(!EXPRESSION)``: negate an expression.  Note that each expression
   must be enclosed in parentheses, e.g. :code:`(!(artist == 'VALUE'))`
   (which is equivalent to :code:`(artist != 'VALUE')`)

src/queue/Queue.cxx

@@ -45,6 +45,7 @@ Queue::GetLight(unsigned position) const noexcept
 	assert(position < length);
 
 	LightSong song{Get(position)};
+	song.priority = GetPriorityAtPosition(position);
 	return song;
 }
 

src/song/Filter.cxx

@@ -25,6 +25,7 @@
 #include "TagSongFilter.hxx"
 #include "ModifiedSinceSongFilter.hxx"
 #include "AudioFormatSongFilter.hxx"
+#include "PrioritySongFilter.hxx"
 #include "pcm/AudioParser.hxx"
 #include "tag/ParseName.hxx"
 #include "time/ISO8601.hxx"
@@ -53,6 +54,7 @@ enum {
 
 	LOCATE_TAG_MODIFIED_SINCE,
 	LOCATE_TAG_AUDIO_FORMAT,
+	LOCATE_TAG_PRIORITY,
 	LOCATE_TAG_FILE_TYPE,
 	LOCATE_TAG_ANY_TYPE,
 };
@@ -80,6 +82,9 @@ locate_parse_type(const char *str) noexcept
 	if (StringEqualsCaseASCII(str, "AudioFormat"))
 		return LOCATE_TAG_AUDIO_FORMAT;
 
+	if (StringEqualsCaseASCII(str, "prio"))
+		return LOCATE_TAG_PRIORITY;
+
 	return tag_name_parse_i(str);
 }
 
@@ -322,6 +327,27 @@ SongFilter::ParseExpression(const char *&s, bool fold_case)
 		s = StripLeft(s + 1);
 
 		return std::make_unique<AudioFormatSongFilter>(value);
+	} else if (type == LOCATE_TAG_PRIORITY) {
+		if (s[0] == '>' && s[1] == '=') {
+			// TODO support more operators
+		} else
+			throw std::runtime_error("'>=' expected");
+
+		s = StripLeft(s + 2);
+
+		char *endptr;
+		const auto value = strtoul(s, &endptr, 10);
+		if (endptr == s)
+			throw std::runtime_error("Number expected");
+
+		if (value > 0xff)
+			throw std::runtime_error("Invalid priority value");
+
+		if (*endptr != ')')
+			throw std::runtime_error("')' expected");
+		s = StripLeft(endptr + 1);
+
+		return std::make_unique<PrioritySongFilter>(value);
 	} else {
 		auto string_filter = ParseStringFilter(s, fold_case);
 		if (*s != ')')

src/song/LightSong.hxx

@@ -84,6 +84,11 @@ struct LightSong {
 	 */
 	AudioFormat audio_format = AudioFormat::Undefined();
 
+	/**
+	 * Copy of Queue::Item::priority.
+	 */
+	uint8_t priority = 0;
+
 	LightSong(const char *_uri, const Tag &_tag) noexcept
 		:uri(_uri), tag(_tag) {}
 

src/song/PrioritySongFilter.cxx

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "PrioritySongFilter.hxx"
+#include "LightSong.hxx"
+#include "time/ISO8601.hxx"
+#include "util/StringBuffer.hxx"
+
+#include <fmt/format.h>
+
+std::string
+PrioritySongFilter::ToExpression() const noexcept
+{
+	return fmt::format(FMT_STRING("(prio >= {})"), value);
+}
+
+bool
+PrioritySongFilter::Match(const LightSong &song) const noexcept
+{
+	return song.priority >= value;
+}

src/song/PrioritySongFilter.hxx

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#pragma once
+
+#include "ISongFilter.hxx"
+
+#include <chrono>
+
+class PrioritySongFilter final : public ISongFilter {
+	const uint8_t value;
+
+public:
+	explicit PrioritySongFilter(uint8_t _value) noexcept
+		:value(_value) {}
+
+	ISongFilterPtr Clone() const noexcept override {
+		return std::make_unique<PrioritySongFilter>(*this);
+	}
+
+	std::string ToExpression() const noexcept override;
+	bool Match(const LightSong &song) const noexcept override;
+};

src/song/meson.build

@@ -7,6 +7,7 @@ song = static_library(
   'BaseSongFilter.cxx',
   'TagSongFilter.cxx',
   'ModifiedSinceSongFilter.cxx',
+  'PrioritySongFilter.cxx',
   'AudioFormatSongFilter.cxx',
   'AndSongFilter.cxx',
   'OptimizeFilter.cxx',
@@ -15,6 +16,7 @@ song = static_library(
   include_directories: inc,
   dependencies: [
     pcre_dep,
+    fmt_dep,
   ],
 )