OpenTTD/src/command_func.h

/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file command_func.h Functions related to commands. */

#ifndef COMMAND_FUNC_H
#define COMMAND_FUNC_H

#include "command_type.h"
#include "network/network_type.h"
#include "company_type.h"
#include "company_func.h"
#include "core/backup_type.hpp"
#include "misc/endian_buffer.hpp"
#include "tile_map.h"

/**
 * Define a default return value for a failed command.
 *
 * This variable contains a CommandCost object with is declared as "failed".
 * Other functions just need to return this error if there is an error,
 * which doesn't need to specific by a StringID.
 */
static const CommandCost CMD_ERROR = CommandCost(INVALID_STRING_ID);

/**
 * Returns from a function with a specific StringID as error.
 *
 * This macro is used to return from a function. The parameter contains the
 * StringID which will be returned.
 *
 * @param errcode The StringID to return
 */
#define return_cmd_error(errcode) return CommandCost(errcode);

void NetworkSendCommand(Commands cmd, StringID err_message, CommandCallback *callback, CompanyID company, TileIndex location, const CommandDataBuffer &cmd_data);

extern Money _additional_cash_required;

bool IsValidCommand(Commands cmd);
CommandFlags GetCommandFlags(Commands cmd);
const char *GetCommandName(Commands cmd);
Money GetAvailableMoneyForCommand();
bool IsCommandAllowedWhilePaused(Commands cmd);

template <Commands Tcmd>
constexpr CommandFlags GetCommandFlags()
{
	return CommandTraits<Tcmd>::flags;
}

/**
 * Extracts the DC flags needed for DoCommand from the flags returned by GetCommandFlags
 * @param cmd_flags Flags from GetCommandFlags
 * @return flags for DoCommand
 */
static constexpr inline DoCommandFlag CommandFlagsToDCFlags(CommandFlags cmd_flags)
{
	DoCommandFlag flags = DC_NONE;
	if (cmd_flags & CMD_NO_WATER) flags |= DC_NO_WATER;
	if (cmd_flags & CMD_AUTO) flags |= DC_AUTO;
	if (cmd_flags & CMD_ALL_TILES) flags |= DC_ALL_TILES;
	return flags;
}

/** Helper class to keep track of command nesting level. */
struct RecursiveCommandCounter {
	RecursiveCommandCounter() noexcept { _counter++; }
	~RecursiveCommandCounter() noexcept { _counter--; }

	/** Are we in the top-level command execution? */
	bool IsTopLevel() const { return _counter == 1; }
private:
	static int _counter;
};


template<Commands TCmd, typename T> struct CommandHelper;

class CommandHelperBase {
protected:
	static void InternalDoBefore(bool top_level, bool test);
	static void InternalDoAfter(CommandCost &res, DoCommandFlag flags, bool top_level, bool test);
	static std::tuple<bool, bool, bool> InternalPostBefore(Commands cmd, CommandFlags flags, TileIndex tile, StringID err_message, bool network_command);
	static void InternalPostResult(const CommandCost &res, TileIndex tile, bool estimate_only, bool only_sending, StringID err_message, bool my_cmd);
	static bool InternalExecutePrepTest(CommandFlags cmd_flags, TileIndex tile, Backup<CompanyID> &cur_company);
	static std::tuple<bool, bool, bool> InternalExecuteValidateTestAndPrepExec(CommandCost &res, CommandFlags cmd_flags, bool estimate_only, bool network_command, Backup<CompanyID> &cur_company);
	static CommandCost InternalExecuteProcessResult(Commands cmd, CommandFlags cmd_flags, const CommandCost &res_test, const CommandCost &res_exec, TileIndex tile, Backup<CompanyID> &cur_company);
	static void LogCommandExecution(Commands cmd, StringID err_message, TileIndex tile, const CommandDataBuffer &args, bool failed);
};

/**
 * Templated wrapper that exposes the command parameter arguments
 * for the various Command::Do/Post calls.
 * @tparam Tcmd The command-id to execute.
 * @tparam Targs The command parameter types.
 */
template <Commands Tcmd, typename... Targs>
struct CommandHelper<Tcmd, CommandCost(*)(DoCommandFlag, Targs...)> : protected CommandHelperBase {
public:
	/**
	 * This function executes a given command with the parameters from the #CommandProc parameter list.
	 * Depending on the flags parameter it executes or tests a command.
	 *
	 * @note This function is to be called from the StateGameLoop or from within the execution of a Command.
	 * This function must not be called from the context of a "player" (real person, AI, game script).
	 * Use ::Post for commands directly triggered by "players".
	 *
	 * @param flags Flags for the command and how to execute the command
	 * @param args Parameters for the command
	 * @see CommandProc
	 * @return the cost
	 */
	static CommandCost Do(DoCommandFlag flags, Targs... args)
	{
		if constexpr (std::is_same_v<TileIndex, std::tuple_element_t<0, std::tuple<Targs...>>>) {
			/* Do not even think about executing out-of-bounds tile-commands. */
			TileIndex tile = std::get<0>(std::make_tuple(args...));
			if (tile != 0 && (tile >= MapSize() || (!IsValidTile(tile) && (flags & DC_ALL_TILES) == 0))) return CMD_ERROR;
		}

		RecursiveCommandCounter counter{};

		/* Only execute the test call if it's toplevel, or we're not execing. */
		if (counter.IsTopLevel() || !(flags & DC_EXEC)) {
			InternalDoBefore(counter.IsTopLevel(), true);
			CommandCost res = CommandTraits<Tcmd>::proc(flags & ~DC_EXEC, args...);
			InternalDoAfter(res, flags, counter.IsTopLevel(), true); // Can modify res.

			if (res.Failed() || !(flags & DC_EXEC)) return res;
		}

		/* Execute the command here. All cost-relevant functions set the expenses type
		 * themselves to the cost object at some point. */
		InternalDoBefore(counter.IsTopLevel(), false);
		CommandCost res = CommandTraits<Tcmd>::proc(flags, args...);
		InternalDoAfter(res, flags, counter.IsTopLevel(), false);

		return res;
	}

	/**
	 * Shortcut for the long Post when not using a callback.
	 * @param err_message Message prefix to show on error
	 * @param args Parameters for the command
	 */
	static inline bool Post(StringID err_message, Targs... args) { return Post(err_message, nullptr, std::forward<Targs>(args)...); }
	/**
	 * Shortcut for the long Post when not using an error message.
	 * @param callback A callback function to call after the command is finished
	 * @param args Parameters for the command
	 */
	static inline bool Post(CommandCallback *callback, Targs... args) { return Post((StringID)0, callback, std::forward<Targs>(args)...); }
	/**
	 * Shortcut for the long Post when not using a callback or an error message.
	 * @param args Parameters for the command
	 */
	static inline bool Post(Targs... args) { return Post((StringID)0, nullptr, std::forward<Targs>(args)...); }

	/**
	 * Top-level network safe command execution for the current company.
	 * Must not be called recursively. The callback is called when the
	 * command succeeded or failed.
	 *
	 * @param err_message Message prefix to show on error
	 * @param callback A callback function to call after the command is finished
	 * @param args Parameters for the command
	 * @return \c true if the command succeeded, else \c false.
	 */
	static bool Post(StringID err_message, CommandCallback *callback, Targs... args)
	{
		return InternalPost(err_message, callback, true, false, std::forward_as_tuple(args...));
	}

	/**
	 * Execute a command coming from the network.
	 * @param err_message Message prefix to show on error
	 * @param callback A callback function to call after the command is finished
	 * @param my_cmd indicator if the command is from a company or server (to display error messages for a user)
	 * @param location Tile location for user feedback.
	 * @param args Parameters for the command
	 * @return \c true if the command succeeded, else \c false.
	 */
	static bool PostFromNet(StringID err_message, CommandCallback *callback, bool my_cmd, TileIndex location, std::tuple<Targs...> args)
	{
		return InternalPost(err_message, callback, my_cmd, true, location, std::move(args));
	}

	/**
	 * Prepare a command to be send over the network
	 * @param cmd The command to execute (a CMD_* value)
	 * @param err_message Message prefix to show on error
	 * @param callback A callback function to call after the command is finished
	 * @param company The company that wants to send the command
	 * @param args Parameters for the command
	 */
	static void SendNet(StringID err_message, CommandCallback *callback, CompanyID company, Targs... args)
	{
		auto args_tuple = std::forward_as_tuple(args...);

		TileIndex tile{};
		if constexpr (std::is_same_v<TileIndex, std::tuple_element_t<0, decltype(args_tuple)>>) {
			tile = std::get<0>(args_tuple);
		}

		::NetworkSendCommand(Tcmd, err_message, callback, _current_company, tile, EndianBufferWriter<CommandDataBuffer>::FromValue(args_tuple));
	}

	/**
	 * Top-level network safe command execution without safety checks.
	 * @param err_message Message prefix to show on error
	 * @param callback A callback function to call after the command is finished
	 * @param my_cmd indicator if the command is from a company or server (to display error messages for a user)
	 * @param estimate_only whether to give only the estimate or also execute the command
	 * @param location Tile location for user feedback.
	 * @param args Parameters for the command
	 * @return the command cost of this function.
	 */
	static CommandCost Unsafe(StringID err_message, CommandCallback *callback, bool my_cmd, bool estimate_only, TileIndex location, std::tuple<Targs...> args)
	{
		return Execute(err_message, callback, my_cmd, estimate_only, false, location, std::move(args));
	}

protected:
	/** Helper to process a single ClientID argument. */
	template <class T>
	static inline void SetClientIdHelper(T &data)
	{
		if constexpr (std::is_same_v<ClientID, T>) {
			if (data == INVALID_CLIENT_ID) data = CLIENT_ID_SERVER;
		}
	}

	/** Set all invalid ClientID's to the proper value. */
	template<class Ttuple, size_t... Tindices>
	static inline void SetClientIds(Ttuple &values, std::index_sequence<Tindices...>)
	{
		((SetClientIdHelper(std::get<Tindices>(values))), ...);
	}

	static bool InternalPost(StringID err_message, CommandCallback *callback, bool my_cmd, bool network_command, std::tuple<Targs...> args)
	{
		/* Where to show the message? */
		TileIndex tile{};
		if constexpr (std::is_same_v<TileIndex, std::tuple_element_t<0, decltype(args)>>) {
			tile = std::get<0>(args);
		}

		return InternalPost(err_message, callback, my_cmd, network_command, tile, std::move(args));
	}

	static bool InternalPost(StringID err_message, CommandCallback *callback, bool my_cmd, bool network_command, TileIndex tile, std::tuple<Targs...> args)
	{
		auto [err, estimate_only, only_sending] = InternalPostBefore(Tcmd, GetCommandFlags<Tcmd>(), tile, err_message, network_command);
		if (err) return false;

		/* Only set client IDs when the command does not come from the network. */
		if (!network_command && GetCommandFlags<Tcmd>() & CMD_CLIENT_ID) SetClientIds(args, std::index_sequence_for<Targs...>{});

		CommandCost res = Execute(err_message, callback, my_cmd, estimate_only, network_command, tile, args);
		InternalPostResult(res, tile, estimate_only, only_sending, err_message, my_cmd);

		if (!estimate_only && !only_sending && callback != nullptr) {
			callback(Tcmd, res, tile, EndianBufferWriter<CommandDataBuffer>::FromValue(args));
		}

		return res.Succeeded();
	}

	/** Helper to process a single ClientID argument. */
	template <class T>
	static inline bool ClientIdIsSet(T &data)
	{
		if constexpr (std::is_same_v<ClientID, T>) {
			return data != INVALID_CLIENT_ID;
		} else {
			return true;
		}
	}

	/** Check if all ClientID arguments are set to valid values. */
	template<class Ttuple, size_t... Tindices>
	static inline bool AllClientIdsSet(Ttuple &values, std::index_sequence<Tindices...>)
	{
		return (ClientIdIsSet(std::get<Tindices>(values)) && ...);
	}

	static CommandCost Execute(StringID err_message, CommandCallback *callback, bool my_cmd, bool estimate_only, bool network_command, TileIndex tile, std::tuple<Targs...> args)
	{
		/* Prevent recursion; it gives a mess over the network */
		RecursiveCommandCounter counter{};
		assert(counter.IsTopLevel());

		/* Command flags are used internally */
		constexpr CommandFlags cmd_flags = GetCommandFlags<Tcmd>();

		if constexpr ((cmd_flags & CMD_CLIENT_ID) != 0) {
			/* Make sure arguments are properly set to a ClientID also when processing external commands. */
			assert(AllClientIdsSet(args, std::index_sequence_for<Targs...>{}));
		}

		Backup<CompanyID> cur_company(_current_company, FILE_LINE);
		if (!InternalExecutePrepTest(cmd_flags, tile, cur_company)) {
			cur_company.Trash();
			return CMD_ERROR;
		}

		/* Test the command. */
		DoCommandFlag flags = CommandFlagsToDCFlags(cmd_flags);
		CommandCost res = std::apply(CommandTraits<Tcmd>::proc, std::tuple_cat(std::make_tuple(flags), args));

		auto [exit_test, desync_log, send_net] = InternalExecuteValidateTestAndPrepExec(res, cmd_flags, estimate_only, network_command, cur_company);
		if (exit_test) {
			if (desync_log) LogCommandExecution(Tcmd, err_message, tile, EndianBufferWriter<CommandDataBuffer>::FromValue(args), true);
			cur_company.Restore();
			return res;
		}

		/* If we are in network, and the command is not from the network
		 * send it to the command-queue and abort execution. */
		if (send_net) {
			::NetworkSendCommand(Tcmd, err_message, callback, _current_company, tile, EndianBufferWriter<CommandDataBuffer>::FromValue(args));
			cur_company.Restore();

			/* Don't return anything special here; no error, no costs.
			 * This way it's not handled by DoCommand and only the
			 * actual execution of the command causes messages. Also
			 * reset the storages as we've not executed the command. */
			return CommandCost();
		}

		if (desync_log) LogCommandExecution(Tcmd, err_message, tile, EndianBufferWriter<CommandDataBuffer>::FromValue(args), false);

		/* Actually try and execute the command. */
		CommandCost res2 = std::apply(CommandTraits<Tcmd>::proc, std::tuple_cat(std::make_tuple(flags | DC_EXEC), args));

		return InternalExecuteProcessResult(Tcmd, cmd_flags, res, res2, tile, cur_company);
	}
};

template <Commands Tcmd>
using Command = CommandHelper<Tcmd, typename CommandTraits<Tcmd>::ProcType>;

#endif /* COMMAND_FUNC_H */