SongFilter: new extensible filter syntax

Will allow more complex fitler expression, such as negation (#89).

src/SongFilter.cxx

@@ -22,10 +22,13 @@
 #include "db/LightSong.hxx"
 #include "DetachedSong.hxx"
 #include "tag/ParseName.hxx"
+#include "util/CharUtil.hxx"
 #include "util/ChronoUtil.hxx"
 #include "util/ConstBuffer.hxx"
+#include "util/RuntimeError.hxx"
 #include "util/StringAPI.hxx"
 #include "util/StringCompare.hxx"
+#include "util/StringStrip.hxx"
 #include "util/StringView.hxx"
 #include "util/ASCII.hxx"
 #include "util/TimeParser.hxx"
@@ -234,6 +237,99 @@ ParseTimeStamp(const char *s)
 	return ParseTimePoint(s, "%FT%TZ");
 }
 
+static constexpr bool
+IsTagNameChar(char ch) noexcept
+{
+	return IsAlphaASCII(ch) || ch == '_';
+}
+
+static const char *
+FirstNonTagNameChar(const char *s) noexcept
+{
+	while (IsTagNameChar(*s))
+		++s;
+	return s;
+}
+
+static auto
+ExpectFilterType(const char *&s)
+{
+	const char *end = FirstNonTagNameChar(s);
+	if (end == s)
+		throw std::runtime_error("Tag name expected");
+
+	const std::string name(s, end);
+	s = StripLeft(end);
+
+	const auto type = locate_parse_type(name.c_str());
+	if (type == TAG_NUM_OF_ITEM_TYPES)
+		throw FormatRuntimeError("Unknown filter type: %s",
+					 name.c_str());
+
+	return type;
+}
+
+static constexpr bool
+IsQuote(char ch) noexcept
+{
+	return ch == '"' || ch == '\'';
+}
+
+static std::string
+ExpectQuoted(const char *&s)
+{
+	const char quote = *s++;
+	if (!IsQuote(quote))
+		throw std::runtime_error("Quoted string expected");
+
+	const char *begin = s;
+	const char *end = strchr(s, quote);
+	if (end == nullptr)
+		throw std::runtime_error("Closing quote not found");
+
+	s = StripLeft(end + 1);
+	return {begin, end};
+}
+
+const char *
+SongFilter::ParseExpression(const char *s, bool fold_case)
+{
+	assert(*s == '(');
+
+	s = StripLeft(s + 1);
+
+	if (*s == '(')
+		throw std::runtime_error("Nested expressions not yet implemented");
+
+	const auto type = ExpectFilterType(s);
+
+	if (type == LOCATE_TAG_MODIFIED_SINCE) {
+		const auto value_s = ExpectQuoted(s);
+		if (*s != ')')
+			throw std::runtime_error("')' expected");
+		items.emplace_back(type, ParseTimeStamp(value_s.c_str()));
+		return StripLeft(s + 1);
+	} else if (type == LOCATE_TAG_BASE_TYPE) {
+		auto value = ExpectQuoted(s);
+		if (*s != ')')
+			throw std::runtime_error("')' expected");
+
+		items.emplace_back(type, std::move(value), fold_case);
+		return StripLeft(s + 1);
+	} else {
+		if (s[0] != '=' || s[1] != '=')
+			throw std::runtime_error("'==' expected");
+
+		s = StripLeft(s + 2);
+		auto value = ExpectQuoted(s);
+		if (*s != ')')
+			throw std::runtime_error("')' expected");
+
+		items.emplace_back(type, std::move(value), fold_case);
+		return StripLeft(s + 1);
+	}
+}
+
 void
 SongFilter::Parse(const char *tag_string, const char *value, bool fold_case)
 {
@@ -262,6 +358,15 @@ SongFilter::Parse(ConstBuffer<const char *> args, bool fold_case)
 		throw std::runtime_error("Incorrect number of filter arguments");
 
 	do {
+		if (*args.front() == '(') {
+			const char *s = args.shift();
+			const char *end = ParseExpression(s, fold_case);
+			if (*end != 0)
+				throw std::runtime_error("Unparsed garbage after expression");
+
+			continue;
+		}
+
 		if (args.size < 2)
 			throw std::runtime_error("Incorrect number of filter arguments");
 

src/SongFilter.hxx

@@ -142,6 +142,8 @@ public:
 	std::string ToExpression() const noexcept;
 
 private:
+	const char *ParseExpression(const char *s, bool fold_case=false);
+
 	gcc_nonnull(2,3)
 	void Parse(const char *tag, const char *value, bool fold_case=false);
 

src/command/AllCommands.cxx

@@ -94,7 +94,7 @@ static constexpr struct command commands[] = {
 	{ "config", PERMISSION_ADMIN, 0, 0, handle_config },
 	{ "consume", PERMISSION_CONTROL, 1, 1, handle_consume },
 #ifdef ENABLE_DATABASE
-	{ "count", PERMISSION_READ, 2, -1, handle_count },
+	{ "count", PERMISSION_READ, 1, -1, handle_count },
 #endif
 	{ "crossfade", PERMISSION_CONTROL, 1, 1, handle_crossfade },
 	{ "currentsong", PERMISSION_READ, 0, 0, handle_currentsong },
@@ -104,8 +104,8 @@ static constexpr struct command commands[] = {
 	{ "disableoutput", PERMISSION_ADMIN, 1, 1, handle_disableoutput },
 	{ "enableoutput", PERMISSION_ADMIN, 1, 1, handle_enableoutput },
 #ifdef ENABLE_DATABASE
-	{ "find", PERMISSION_READ, 2, -1, handle_find },
-	{ "findadd", PERMISSION_ADD, 2, -1, handle_findadd},
+	{ "find", PERMISSION_READ, 1, -1, handle_find },
+	{ "findadd", PERMISSION_ADD, 1, -1, handle_findadd},
 #endif
 	{ "idle", PERMISSION_READ, 0, -1, handle_idle },
 	{ "kill", PERMISSION_ADMIN, -1, -1, handle_kill },
@@ -149,11 +149,11 @@ static constexpr struct command commands[] = {
 	{ "playlistadd", PERMISSION_CONTROL, 2, 2, handle_playlistadd },
 	{ "playlistclear", PERMISSION_CONTROL, 1, 1, handle_playlistclear },
 	{ "playlistdelete", PERMISSION_CONTROL, 2, 2, handle_playlistdelete },
-	{ "playlistfind", PERMISSION_READ, 2, -1, handle_playlistfind },
+	{ "playlistfind", PERMISSION_READ, 1, -1, handle_playlistfind },
 	{ "playlistid", PERMISSION_READ, 0, 1, handle_playlistid },
 	{ "playlistinfo", PERMISSION_READ, 0, 1, handle_playlistinfo },
 	{ "playlistmove", PERMISSION_CONTROL, 3, 3, handle_playlistmove },
-	{ "playlistsearch", PERMISSION_READ, 2, -1, handle_playlistsearch },
+	{ "playlistsearch", PERMISSION_READ, 1, -1, handle_playlistsearch },
 	{ "plchanges", PERMISSION_READ, 1, 2, handle_plchanges },
 	{ "plchangesposid", PERMISSION_READ, 1, 2, handle_plchangesposid },
 	{ "previous", PERMISSION_CONTROL, 0, 0, handle_previous },
@@ -173,9 +173,9 @@ static constexpr struct command commands[] = {
 	{ "rm", PERMISSION_CONTROL, 1, 1, handle_rm },
 	{ "save", PERMISSION_CONTROL, 1, 1, handle_save },
 #ifdef ENABLE_DATABASE
-	{ "search", PERMISSION_READ, 2, -1, handle_search },
-	{ "searchadd", PERMISSION_ADD, 2, -1, handle_searchadd },
-	{ "searchaddpl", PERMISSION_CONTROL, 3, -1, handle_searchaddpl },
+	{ "search", PERMISSION_READ, 1, -1, handle_search },
+	{ "searchadd", PERMISSION_ADD, 1, -1, handle_searchadd },
+	{ "searchaddpl", PERMISSION_CONTROL, 2, -1, handle_searchaddpl },
 #endif
 	{ "seek", PERMISSION_CONTROL, 2, 2, handle_seek },
 	{ "seekcur", PERMISSION_CONTROL, 1, 1, handle_seekcur },