From e5e623ffaa957f97c3e1d56435ed01da39a8aead Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Wed, 25 Jul 2018 10:19:49 +0200
Subject: [PATCH] SongFilter: add class NotSongFilter

---
 doc/protocol.xml           |  6 +++++
 src/song/Filter.cxx        | 15 ++++++++++++
 src/song/NotSongFilter.hxx | 50 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)
 create mode 100644 src/song/NotSongFilter.hxx

diff --git a/doc/protocol.xml b/doc/protocol.xml
index 7b384e4da..f68375c6b 100644
--- a/doc/protocol.xml
+++ b/doc/protocol.xml
@@ -276,6 +276,12 @@
           </para>
         </listitem>
 
+        <listitem>
+          <para>
+            "<code>(!EXPRESSION)</code>": negate an expression.
+          </para>
+        </listitem>
+
         <listitem>
           <para>
             "<code>(EXPRESSION1 AND EXPRESSION2 ...)</code>": combine two or
diff --git a/src/song/Filter.cxx b/src/song/Filter.cxx
index e9d978dd5..c96ecb8dc 100644
--- a/src/song/Filter.cxx
+++ b/src/song/Filter.cxx
@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "Filter.hxx"
+#include "NotSongFilter.hxx"
 #include "UriSongFilter.hxx"
 #include "BaseSongFilter.hxx"
 #include "TagSongFilter.hxx"
@@ -214,6 +215,20 @@ SongFilter::ParseExpression(const char *&s, bool fold_case)
 		}
 	}
 
+	if (*s == '!') {
+		s = StripLeft(s + 1);
+
+		if (*s != '(')
+			throw std::runtime_error("'(' expected");
+
+		auto inner = ParseExpression(s, fold_case);
+		if (*s != ')')
+			throw std::runtime_error("')' expected");
+		s = StripLeft(s + 1);
+
+		return std::make_unique<NotSongFilter>(std::move(inner));
+	}
+
 	auto type = ExpectFilterType(s);
 
 	if (type == LOCATE_TAG_MODIFIED_SINCE) {
diff --git a/src/song/NotSongFilter.hxx b/src/song/NotSongFilter.hxx
new file mode 100644
index 000000000..000ac1f69
--- /dev/null
+++ b/src/song/NotSongFilter.hxx
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2003-2018 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.
+ */
+
+#ifndef MPD_NOT_SONG_FILTER_HXX
+#define MPD_NOT_SONG_FILTER_HXX
+
+#include "ISongFilter.hxx"
+
+/**
+ * Negate an #ISongFilter.
+ */
+class NotSongFilter final : public ISongFilter {
+	ISongFilterPtr child;
+
+public:
+	template<typename C>
+	explicit NotSongFilter(C &&_child) noexcept
+		:child(std::forward<C>(_child)) {}
+
+	/* virtual methods from ISongFilter */
+	ISongFilterPtr Clone() const noexcept override {
+		return std::make_unique<NotSongFilter>(child->Clone());
+	}
+
+	std::string ToExpression() const noexcept override {
+		return "(!" + child->ToExpression() + ")";
+	}
+
+	bool Match(const LightSong &song) const noexcept override {
+		return !child->Match(song);
+	}
+};
+
+#endif