command_func.h

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/*
 * 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 <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#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"

static const CommandCost CMD_ERROR = CommandCost(INVALID_STRING_ID);
 
void NetworkSendCommand(Commands cmd, StringID err_message, CommandCallback *callback, CompanyID company, const CommandDataBuffer &cmd_data);
bool IsNetworkRegisteredCallback(CommandCallback *callback);
 
bool IsValidCommand(Commands cmd);
CommandFlags GetCommandFlags(Commands cmd);
std::string_view GetCommandName(Commands cmd);
bool IsCommandAllowedWhilePaused(Commands cmd);
 
template <Commands Tcmd>
constexpr CommandFlags GetCommandFlags()
{
  return CommandTraits<Tcmd>::flags;
}

static constexpr inline DoCommandFlags CommandFlagsToDCFlags(CommandFlags cmd_flags)
{
  DoCommandFlags flags = {};
  if (cmd_flags.Test(CommandFlag::NoWater)) flags.Set(DoCommandFlag::NoWater);
  if (cmd_flags.Test(CommandFlag::Auto)) flags.Set(DoCommandFlag::Auto);
  if (cmd_flags.Test(CommandFlag::AllTiles)) flags.Set(DoCommandFlag::AllTiles);
  return flags;
}

struct RecursiveCommandCounter {
  RecursiveCommandCounter() noexcept { _counter++; }
  ~RecursiveCommandCounter() noexcept { _counter--; }

  bool IsTopLevel() const { return _counter == 1; }
private:
  static int _counter; 
};
 
#if defined(__GNUC__) && !defined(__clang__)
/*
 * We cast specialized function pointers to a generic one, but don't use the
 * converted value to call the function, which is safe, except that GCC
 * helpfully thinks it is not.
 *
 * "Any pointer to function can be converted to a pointer to a different function type.
 * Calling the function through a pointer to a different function type is undefined,
 * but converting such pointer back to pointer to the original function type yields
 * the pointer to the original function." */
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wcast-function-type"
# define SILENCE_GCC_FUNCTION_POINTER_CAST
#endif
 
template <Commands TCmd, typename T, bool THasTile> struct CommandHelper;
 
class CommandHelperBase {
protected:
  static void InternalDoBefore(bool top_level, bool test);
  static void InternalDoAfter(CommandCost &res, DoCommandFlags 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(CommandCost &res, TileIndex tile, bool estimate_only, bool only_sending, StringID err_message, bool my_cmd);
  static bool InternalExecutePrepTest(CommandFlags cmd_flags, 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, Money extra_cash, TileIndex tile, Backup<CompanyID> &cur_company);
  static void LogCommandExecution(Commands cmd, StringID err_message, const CommandDataBuffer &args, bool failed);
};

template <typename Tret>
inline CommandCost &ExtractCommandCost(Tret &ret)
{
  if constexpr (std::is_same_v<Tret, CommandCost>) {
    return ret;
  } else {
    static_assert(std::is_same_v<std::tuple_element_t<0, Tret>, CommandCost>);
    return std::get<0>(ret);
  }
}

template <typename Tret>
inline CommandCost ExtractCommandCost(Tret &&ret)
{
  if constexpr (std::is_same_v<Tret, CommandCost>) {
    return ret;
  } else {
    static_assert(std::is_same_v<std::tuple_element_t<0, Tret>, CommandCost>);
    return std::get<0>(ret);
  }
}

template <Commands Tcmd, typename Tret, typename... Targs>
struct CommandHelper<Tcmd, Tret(*)(DoCommandFlags, Targs...), true> : protected CommandHelperBase {
private:
  static inline Tret MakeResult(const CommandCost &cost)
  {
    Tret ret{};
    ExtractCommandCost(ret) = cost;
    return ret;
  }
 
public:
  static Tret Do(DoCommandFlags 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 >= Map::Size() || (!IsValidTile(tile) && !flags.Test(DoCommandFlag::AllTiles)))) return MakeResult(CMD_ERROR);
    }
 
    RecursiveCommandCounter counter{};
 
    /* Only execute the test call if it's toplevel, or we're not execing. */
    if (counter.IsTopLevel() || !flags.Test(DoCommandFlag::Execute)) {
      InternalDoBefore(counter.IsTopLevel(), true);
      Tret res = CommandTraits<Tcmd>::proc(DoCommandFlags{flags}.Reset(DoCommandFlag::Execute), args...);
      InternalDoAfter(ExtractCommandCost(res), flags, counter.IsTopLevel(), true); // Can modify res.
 
      if (ExtractCommandCost(res).Failed() || !flags.Test(DoCommandFlag::Execute)) 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);
    Tret res = CommandTraits<Tcmd>::proc(flags, args...);
    InternalDoAfter(ExtractCommandCost(res), flags, counter.IsTopLevel(), false);
 
    return res;
  }

  static inline bool Post(StringID err_message, Targs... args) { return Post<CommandCallback>(err_message, nullptr, std::forward<Targs>(args)...); }

  template <typename Tcallback>
  static inline bool Post(Tcallback *callback, Targs... args) { return Post((StringID)0, callback, std::forward<Targs>(args)...); }

  static inline bool Post(Targs... args) { return Post<CommandCallback>((StringID)0, nullptr, std::forward<Targs>(args)...); }

  template <typename Tcallback>
  static bool Post(StringID err_message, Tcallback *callback, Targs... args)
  {
    assert(::IsNetworkRegisteredCallback(reinterpret_cast<CommandCallback *>(reinterpret_cast<void(*)()>(callback))));
    return InternalPost(err_message, callback, true, false, std::forward_as_tuple(args...));
  }

  template <typename Tcallback>
  static bool PostFromNet(StringID err_message, Tcallback *callback, bool my_cmd, std::tuple<Targs...> args)
  {
    return InternalPost(err_message, callback, my_cmd, true, std::move(args));
  }

  static void SendNet(StringID err_message, CompanyID company, Targs... args)
  {
    auto args_tuple = std::forward_as_tuple(args...);
 
    ::NetworkSendCommand(Tcmd, err_message, nullptr, company, EndianBufferWriter<CommandDataBuffer>::FromValue(args_tuple));
  }

  template <typename Tcallback>
  static Tret Unsafe(StringID err_message, Tcallback *callback, bool my_cmd, bool estimate_only, TileIndex location, std::tuple<Targs...> args)
  {
    return Execute(err_message, reinterpret_cast<CommandCallback *>(reinterpret_cast<void(*)()>(callback)), my_cmd, estimate_only, false, location, std::move(args));
  }
 
protected:
  template <class T>
  static inline void SetClientIdHelper([[maybe_unused]] T &data)
  {
    if constexpr (std::is_same_v<ClientID, T>) {
      if (data == INVALID_CLIENT_ID) data = CLIENT_ID_SERVER;
    }
  }

  template <class Ttuple, size_t... Tindices>
  static inline void SetClientIds(Ttuple &values, std::index_sequence<Tindices...>)
  {
    ((SetClientIdHelper(std::get<Tindices>(values))), ...);
  }

  template <template <typename...> typename Tt, typename T1, typename... Ts>
  static inline Tt<Ts...> RemoveFirstTupleElement(const Tt<T1, Ts...> &tuple)
  {
    return std::apply([](auto &&, const auto&... args) { return std::tie(args...); }, tuple);
  }
 
  template <typename Tcallback>
  static bool InternalPost(StringID err_message, Tcallback *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));
  }
 
  template <typename Tcallback>
  static bool InternalPost(StringID err_message, Tcallback *callback, bool my_cmd, bool network_command, TileIndex tile, std::tuple<Targs...> args)
  {
    /* Do not even think about executing out-of-bounds tile-commands. */
    if (tile != 0 && (tile >= Map::Size() || (!IsValidTile(tile) && !GetCommandFlags<Tcmd>().Test(CommandFlag::AllTiles)))) return false;
 
    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>().Test(CommandFlag::ClientID)) SetClientIds(args, std::index_sequence_for<Targs...>{});
 
    Tret res = Execute(err_message, reinterpret_cast<CommandCallback *>(reinterpret_cast<void(*)()>(callback)), my_cmd, estimate_only, network_command, tile, args);
    InternalPostResult(ExtractCommandCost(res), tile, estimate_only, only_sending, err_message, my_cmd);
 
    if (!estimate_only && !only_sending && callback != nullptr) {
      if constexpr (std::is_same_v<Tcallback, CommandCallback>) {
        /* Callback that doesn't need any command arguments. */
        callback(Tcmd, ExtractCommandCost(res), tile);
      } else if constexpr (std::is_same_v<Tcallback, CommandCallbackData>) {
        /* Generic callback that takes packed arguments as a buffer. */
        if constexpr (std::is_same_v<Tret, CommandCost>) {
          callback(Tcmd, ExtractCommandCost(res), EndianBufferWriter<CommandDataBuffer>::FromValue(args), {});
        } else {
          callback(Tcmd, ExtractCommandCost(res), EndianBufferWriter<CommandDataBuffer>::FromValue(args), EndianBufferWriter<CommandDataBuffer>::FromValue(RemoveFirstTupleElement(res)));
        }
      } else if constexpr (!std::is_same_v<Tret, CommandCost> && std::is_same_v<Tcallback *, typename CommandTraits<Tcmd>::RetCallbackProc>) {
        std::apply(callback, std::tuple_cat(std::make_tuple(Tcmd), res));
      } else {
        /* Callback with arguments. We assume that the tile is only interesting if it actually is in the command arguments. */
        if constexpr (std::is_same_v<Tret, CommandCost>) {
          std::apply(callback, std::tuple_cat(std::make_tuple(Tcmd, res), args));
        } else {
          std::apply(callback, std::tuple_cat(std::make_tuple(Tcmd), res, args));
        }
      }
    }
 
    return ExtractCommandCost(res).Succeeded();
  }

  template <class T>
  static inline bool ClientIdIsSet([[maybe_unused]] T &data)
  {
    if constexpr (std::is_same_v<ClientID, T>) {
      return data != INVALID_CLIENT_ID;
    } else {
      return true;
    }
  }

  template <class Ttuple, size_t... Tindices>
  static inline bool AllClientIdsSet(Ttuple &values, std::index_sequence<Tindices...>)
  {
    return (ClientIdIsSet(std::get<Tindices>(values)) && ...);
  }
 
  template <class Ttuple>
  static inline Money ExtractAdditionalMoney([[maybe_unused]] Ttuple &values)
  {
    if constexpr (std::is_same_v<std::tuple_element_t<1, Tret>, Money>) {
      return std::get<1>(values);
    } else {
      return {};
    }
  }
 
  static Tret Execute(StringID err_message, CommandCallback *callback, bool, 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.Test(CommandFlag::ClientID)) {
      /* 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);
    if (!InternalExecutePrepTest(cmd_flags, cur_company)) {
      cur_company.Trash();
      return MakeResult(CMD_ERROR);
    }
 
    /* Test the command. */
    DoCommandFlags flags = CommandFlagsToDCFlags(cmd_flags);
    Tret res = std::apply(CommandTraits<Tcmd>::proc, std::tuple_cat(std::make_tuple(flags), args));
 
    auto [exit_test, desync_log, send_net] = InternalExecuteValidateTestAndPrepExec(ExtractCommandCost(res), cmd_flags, estimate_only, network_command, cur_company);
    if (exit_test) {
      if (desync_log) LogCommandExecution(Tcmd, err_message, 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, 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 {};
    }
 
    if (desync_log) LogCommandExecution(Tcmd, err_message, EndianBufferWriter<CommandDataBuffer>::FromValue(args), false);
 
    /* Actually try and execute the command. */
    Tret res2 = std::apply(CommandTraits<Tcmd>::proc, std::tuple_cat(std::make_tuple(flags | DoCommandFlag::Execute), args));
 
    /* Convention: If the second result element is of type Money,
     * this is the additional cash required for the command. */
    Money additional_money{};
    if constexpr (!std::is_same_v<Tret, CommandCost>) { // No short-circuiting for 'if constexpr'.
      additional_money = ExtractAdditionalMoney(res2);
    }
 
    if constexpr (std::is_same_v<Tret, CommandCost>) {
      return InternalExecuteProcessResult(Tcmd, cmd_flags, res, res2, additional_money, tile, cur_company);
    } else {
      ExtractCommandCost(res2) = InternalExecuteProcessResult(Tcmd, cmd_flags, ExtractCommandCost(res), ExtractCommandCost(res2), additional_money, tile, cur_company);
      return res2;
    }
  }
};

template <Commands Tcmd, typename Tret, typename... Targs>
struct CommandHelper<Tcmd, Tret(*)(DoCommandFlags, Targs...), false> : CommandHelper<Tcmd, Tret(*)(DoCommandFlags, Targs...), true>
{
  /* Do not allow Post without explicit location. */
  static inline bool Post(StringID err_message, Targs... args) = delete;
  template <typename Tcallback>
  static inline bool Post(Tcallback *callback, Targs... args) = delete;
  static inline bool Post(Targs... args) = delete;
  template <typename Tcallback>
  static bool Post(StringID err_message, Tcallback *callback, Targs... args) = delete;

  static inline bool Post(StringID err_message, TileIndex location, Targs... args) { return Post<CommandCallback>(err_message, nullptr, location, std::forward<Targs>(args)...); }

  template <typename Tcallback>
  static inline bool Post(Tcallback *callback, TileIndex location, Targs... args) { return Post((StringID)0, callback, location, std::forward<Targs>(args)...); }

  static inline bool Post(TileIndex location, Targs... args) { return Post<CommandCallback>((StringID)0, nullptr, location, std::forward<Targs>(args)...); }

  template <typename Tcallback>
  static inline bool Post(StringID err_message, Tcallback *callback, TileIndex location, Targs... args)
  {
    return CommandHelper<Tcmd, Tret(*)(DoCommandFlags, Targs...), true>::InternalPost(err_message, callback, true, false, location, std::forward_as_tuple(args...));
  }
};
 
#ifdef SILENCE_GCC_FUNCTION_POINTER_CAST
# pragma GCC diagnostic pop
#endif
 
template <Commands Tcmd>
using Command = CommandHelper<Tcmd, typename CommandTraits<Tcmd>::ProcType, !GetCommandFlags<Tcmd>().Test(CommandFlag::Location)>;
 
#endif /* COMMAND_FUNC_H */