input/tidal: parse and report userMessage from error responses

src/input/plugins/TidalErrorParser.hxx

@@ -0,0 +1,74 @@
+/*
+ * 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 TIDAL_ERROR_PARSER_HXX
+#define TIDAL_ERROR_PARSER_HXX
+
+#include "check.h"
+#include "lib/yajl/Handle.hxx"
+
+#include <exception>
+#include <string>
+#include <map>
+
+template<typename T> struct ConstBuffer;
+struct StringView;
+
+/**
+ * Parse an error JSON response.
+ */
+class TidalErrorParser {
+	const unsigned status;
+
+	Yajl::Handle parser;
+
+	enum class State {
+		NONE,
+		USER_MESSAGE,
+	} state = State::NONE;
+
+	std::string message;
+
+public:
+	/**
+	 * May throw if there is a formal error in the response
+	 * headers.
+	 */
+	TidalErrorParser(unsigned status,
+			 const std::multimap<std::string, std::string> &headers);
+
+	/**
+	 * Feed response body data into the JSON parser.
+	 */
+	void OnData(ConstBuffer<void> data);
+
+	/**
+	 * Throw an exception describing the error condition.  Call
+	 * this at the end of the response body.
+	 */
+	void OnEnd();
+
+public:
+	/* yajl callbacks */
+	bool String(StringView value) noexcept;
+	bool MapKey(StringView value) noexcept;
+	bool EndMap() noexcept;
+};
+
+#endif