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engines/mutationofjb/commands/command.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef MUTATIONOFJB_COMMAND_H
+#define MUTATIONOFJB_COMMAND_H
+
+namespace Common {
+class String;
+}
+
+namespace MutationOfJB {
+
+class Command;
+class ScriptExecutionContext;
+class ScriptParseContext;
+
+/**
+ * Base class for command parsers.
+ *
+ * The parser's main job is to create a Command instance from input line.
+ */
+class CommandParser {
+public:
+	virtual ~CommandParser();
+
+	/**
+	 * Parses the specified line and possibly returns a Command instance.
+	 *
+	 * @param line Line to parse.
+	 * @param parseCtx Parse context.
+	 * @param command Output parameter for newly created command.
+	 * @return True if the line has been successfully parsed by this parser, false otherwise.
+	 * @note You may return true and set command to nullptr.
+	 * That means the line has been successfully parsed, but no command is needed.
+	 */
+	virtual bool parse(const Common::String &line, ScriptParseContext &parseCtx, Command *&command) = 0;
+
+	/**
+	 * Called when transitioning parsing between two commands.
+	 *
+	 * For example, cmdParserA->transition(parseCtx, cmdA, cmdB, cmdParserB) is called after command B is done parsing
+	 * to notify command A parser about the transition from command A to command B.
+	 * This is useful for sequential commands, because at the time command A is being parsed,
+	 * we don't have any information about command B, so we cannot set the next pointer.
+	 * Transition method can be used to set the next pointer after command B is available.
+	 *
+	 * @param parseCtx Parse context.
+	 * @param oldCommand Old command (created by this parser).
+	 * @param newCommand New command (created by newCommandParser).
+	 * @param newCommandParser Command parser which created the new command.
+	 */
+	virtual void transition(ScriptParseContext &parseCtx, Command *oldCommand, Command *newCommand, CommandParser *newCommandParser);
+
+	/**
+	 * Called after the whole script is parsed.
+	 *
+	 * Can be used for cleanup.
+	 *
+	 * @param parseCtx Parse context.
+	 */
+	virtual void finish(ScriptParseContext &parseCtx);
+};
+
+/**
+ * Base class for script commands.
+ */
+class Command {
+public:
+	enum ExecuteResult {
+		None,
+		Finished,
+		InProgress
+	};
+
+	virtual ~Command();
+
+	virtual ExecuteResult execute(ScriptExecutionContext &scriptExecCtx) = 0;
+	virtual Command *next() const = 0;
+
+	virtual Common::String debugString() const = 0;
+};
+
+}
+
+#endif