script_instance.cpp

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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>.
 */

 
#include "../stdafx.h"
#include "../debug.h"
#include "../saveload/saveload.h"
 
#include "../script/squirrel_class.hpp"
#include "../script/squirrel_std.hpp"
 
#include "script_fatalerror.hpp"
#include "script_storage.hpp"
#include "script_info.hpp"
#include "script_instance.hpp"
 
#include "api/script_controller.hpp"
#include "api/script_error.hpp"
#include "api/script_event.hpp"
#include "api/script_log.hpp"
 
#include "../company_type.h"
#include "../fileio_func.h"
#include "../goal_type.h"
#include "../league_type.h"
#include "../signs_type.h"
#include "../story_type.h"
#include "../misc/endian_buffer.hpp"
 
#include "../safeguards.h"
 
ScriptStorage::ScriptStorage() = default;
ScriptStorage::~ScriptStorage() = default;

static void PrintFunc(bool error_msg, std::string_view message)
{
  /* Convert to OpenTTD internal capable string */
  ScriptController::Print(error_msg, std::string{message});
}
 
ScriptInstance::ScriptInstance(std::string_view api_name)
{
  this->storage = std::make_unique<ScriptStorage>();
  this->engine = std::make_unique<Squirrel>(api_name);
  this->engine->SetPrintFunction(&PrintFunc);
}
 
void ScriptInstance::Initialize(const std::string &main_script, const std::string &instance_name, CompanyID company)
{
  ScriptObject::ActiveInstance active(*this);
 
  this->controller = std::make_unique<ScriptController>(company);
 
  /* Register the API functions and classes */
  this->engine->SetGlobalPointer(this->engine.get());
  this->RegisterAPI();
  if (this->IsDead()) {
    /* Failed to register API; a message has already been logged. */
    return;
  }
 
  try {
    ScriptObject::DisableDoCommandScope disabler{};
    /* Load and execute the script for this script */
    if (main_script == "%_dummy") {
      this->LoadDummyScript();
    } else if (!this->engine->LoadScript(main_script) || this->engine->IsSuspended()) {
      if (this->engine->IsSuspended()) ScriptLog::Error("This script took too long to load script. AI is not started.");
      this->Died();
      return;
    }
 
    /* Create the main-class */
    this->instance = std::make_unique<SQObject>();
    if (!this->engine->CreateClassInstance(instance_name, this->controller.get(), this->instance.get())) {
      /* If CreateClassInstance has returned false instance has not been
       * registered with squirrel, so avoid trying to Release it by clearing it now */
      this->instance.reset();
      this->Died();
      return;
    }
  } catch (Script_FatalError &e) {
    this->is_dead = true;
    this->engine->ThrowError(e.GetErrorMessage());
    this->engine->ResumeError();
    this->Died();
  }
}
 
void ScriptInstance::RegisterAPI()
{
  squirrel_register_std(*this->engine);
}
 
bool ScriptInstance::LoadCompatibilityScript(std::string_view api_version, Subdirectory dir)
{
  std::string script_name = fmt::format("compat_{}.nut", api_version);
 
  for (Searchpath sp : _valid_searchpaths) {
    std::string buf = FioGetDirectory(sp, dir);
    buf += script_name;
    if (!FileExists(buf)) continue;
 
    if (this->engine->LoadScript(buf)) return true;
 
    ScriptLog::Error(fmt::format("Failed to load API compatibility script for {}", api_version));
    Debug(script, 0, "Error compiling / running API compatibility script: {}", buf);
    return false;
  }
 
  ScriptLog::Warning(fmt::format("API compatibility script for {} not found", api_version));
  return true;
}
 
bool ScriptInstance::LoadCompatibilityScripts(Subdirectory dir, std::span<const std::string_view> api_versions)
{
  /* Don't try to load compatibility scripts for the current version. */
  if (this->api_version == api_versions.back()) return true;
 
  ScriptLog::Info(fmt::format("Downgrading API to be compatible with version {}", this->api_version));
 
  HSQUIRRELVM vm = this->engine->GetVM();
  sq_pushroottable(vm);
  sq_pushstring(vm, "CompatScriptRootTable");
  sq_pushroottable(vm);
  sq_newslot(vm, -3, SQFalse);
  sq_pop(vm, 1);
 
  /* Downgrade the API till we are the same version as the script. The last
   * entry in the list is always the current version, so skip that one. */
  for (auto it = std::rbegin(api_versions) + 1; it != std::rend(api_versions); ++it) {
    if (!this->LoadCompatibilityScript(*it, dir)) return false;
 
    if (*it == this->api_version) break;
  }
 
  sq_pushroottable(vm);
  sq_pushstring(vm, "CompatScriptRootTable");
  sq_deleteslot(vm, -2, SQFalse);
  sq_pop(vm, 1);
 
  return true;
}

ScriptInstance::~ScriptInstance()
{
  ScriptObject::ActiveInstance active(*this);
  this->in_shutdown = true;
 
  if (instance != nullptr) this->engine->ReleaseObject(this->instance.get());
 
  /* Engine must be reset explicitly in scope of the active instance. */
  this->engine.reset();
}
 
void ScriptInstance::Continue()
{
  assert(this->suspend < 0);
  this->suspend = -this->suspend - 1;
}
 
void ScriptInstance::Died()
{
  Debug(script, 0, "The script died unexpectedly.");
  this->is_dead = true;
  this->in_shutdown = true;
 
  this->last_allocated_memory = this->GetAllocatedMemory(); // Update cache
 
  if (this->instance != nullptr) this->engine->ReleaseObject(this->instance.get());
  this->engine.reset();
  this->instance.reset();
}
 
void ScriptInstance::GameLoop()
{
  ScriptObject::ActiveInstance active(*this);
 
  if (this->IsDead()) return;
  if (this->engine->HasScriptCrashed()) {
    /* The script crashed during saving, kill it here. */
    this->Died();
    return;
  }
  if (this->is_paused) return;
  this->controller->ticks++;
 
  if (this->suspend   < -1) this->suspend++; // Multiplayer suspend, increase up to -1.
  if (this->suspend   < 0)  return;          // Multiplayer suspend, wait for Continue().
  if (--this->suspend > 0)  return;          // Singleplayer suspend, decrease to 0.
 
  _current_company = ScriptObject::GetCompany();
 
  /* If there is a callback to call, call that first */
  if (this->callback != nullptr) {
    if (this->is_save_data_on_stack) {
      sq_poptop(this->engine->GetVM());
      this->is_save_data_on_stack = false;
    }
    try {
      this->callback(*this);
    } catch (Script_Suspend &e) {
      this->suspend  = e.GetSuspendTime();
      this->callback = e.GetSuspendCallback();
 
      return;
    }
  }
 
  this->suspend  = 0;
  this->callback = nullptr;
 
  if (!this->is_started) {
    try {
      {
        ScriptObject::DisableDoCommandScope disabler{};
        /* Run the constructor if it exists. Don't allow any DoCommands in it. */
        if (this->engine->MethodExists(*this->instance, "constructor")) {
          if (!this->engine->CallMethod(*this->instance, "constructor", MAX_CONSTRUCTOR_OPS) || this->engine->IsSuspended()) {
            if (this->engine->IsSuspended()) ScriptLog::Error("This script took too long to initialize. Script is not started.");
            this->Died();
            return;
          }
        }
        if (!this->CallLoad() || this->engine->IsSuspended()) {
          if (this->engine->IsSuspended()) ScriptLog::Error("This script took too long in the Load function. Script is not started.");
          this->Died();
          return;
        }
      }
      /* Start the script by calling Start() */
      if (!this->engine->CallMethod(*this->instance, "Start",  _settings_game.script.script_max_opcode_till_suspend) || !this->engine->IsSuspended()) this->Died();
    } catch (Script_Suspend &e) {
      this->suspend  = e.GetSuspendTime();
      this->callback = e.GetSuspendCallback();
    } catch (Script_FatalError &e) {
      this->is_dead = true;
      this->engine->ThrowError(e.GetErrorMessage());
      this->engine->ResumeError();
      this->Died();
    }
 
    this->is_started = true;
    return;
  }
  if (this->is_save_data_on_stack) {
    sq_poptop(this->engine->GetVM());
    this->is_save_data_on_stack = false;
  }
 
  /* Continue the VM */
  try {
    if (!this->engine->Resume(_settings_game.script.script_max_opcode_till_suspend)) this->Died();
  } catch (Script_Suspend &e) {
    this->suspend  = e.GetSuspendTime();
    this->callback = e.GetSuspendCallback();
  } catch (Script_FatalError &e) {
    this->is_dead = true;
    this->engine->ThrowError(e.GetErrorMessage());
    this->engine->ResumeError();
    this->Died();
  }
}
 
void ScriptInstance::CollectGarbage()
{
  if (this->is_started && !this->IsDead()) {
    ScriptObject::ActiveInstance active(*this);
    this->engine->CollectGarbage();
  }
}
 
/* static */ void ScriptInstance::DoCommandReturn(ScriptInstance &instance)
{
  instance.engine->InsertResult(ScriptObject::GetLastCommandRes());
}
 
/* static */ void ScriptInstance::DoCommandReturnVehicleID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<VehicleID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnSignID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<SignID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnGroupID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<GroupID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnGoalID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<GoalID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnStoryPageID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<StoryPageID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnStoryPageElementID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<StoryPageElementID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnLeagueTableElementID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<LeagueTableElementID>(ScriptObject::GetLastCommandResData()));
}
 
/* static */ void ScriptInstance::DoCommandReturnLeagueTableID(ScriptInstance &instance)
{
  instance.engine->InsertResult(EndianBufferReader::ToValue<LeagueTableID>(ScriptObject::GetLastCommandResData()));
}
 
 
ScriptStorage &ScriptInstance::GetStorage()
{
  assert(this->storage != nullptr);
  return *this->storage;
}
 
ScriptLogTypes::LogData &ScriptInstance::GetLogData()
{
  ScriptObject::ActiveInstance active(*this);
 
  return ScriptObject::GetLogData();
}
 
/*
 * All data is stored in the following format:
 * First 1 byte indicating if there is a data blob at all.
 * 1 byte indicating the type of data.
 * The data itself, this differs per type:
 *  - integer: a binary representation of the integer (int32_t).
 *  - string:  First one byte with the string length, then a 0-terminated char
 *             array. The string can't be longer than 255 bytes (including
 *             terminating '\0').
 *  - array:   All data-elements of the array are saved recursive in this
 *             format, and ended with an element of the type
 *             SQSL_ARRAY_TABLE_END.
 *  - table:   All key/value pairs are saved in this format (first key 1, then
 *             value 1, then key 2, etc.). All keys and values can have an
 *             arbitrary type (as long as it is supported by the save function
 *             of course). The table is ended with an element of the type
 *             SQSL_ARRAY_TABLE_END.
 *  - bool:    A single byte with value 1 representing true and 0 false.
 *  - null:    No data.
 */
 
static uint8_t _script_sl_byte; 

static const SaveLoad _script_byte[] = {
  SLEG_VAR("type", _script_sl_byte, SLE_UINT8),
};
 
/* static */ bool ScriptInstance::SaveObject(HSQUIRRELVM vm, SQInteger index, int max_depth, bool test)
{
  if (max_depth == 0) {
    ScriptLog::Error("Savedata can only be nested to 25 deep. No data saved."); // SQUIRREL_MAX_DEPTH = 25
    return false;
  }
 
  switch (sq_gettype(vm, index)) {
    case OT_INTEGER: {
      if (!test) {
        _script_sl_byte = SQSL_INT;
        SlObject(nullptr, _script_byte);
      }
      SQInteger res;
      sq_getinteger(vm, index, &res);
      if (!test) {
        int64_t value = (int64_t)res;
        SlCopy(&value, 1, SLE_INT64);
      }
      return true;
    }
 
    case OT_STRING: {
      if (!test) {
        _script_sl_byte = SQSL_STRING;
        SlObject(nullptr, _script_byte);
      }
      std::string_view view;
      sq_getstring(vm, index, view);
      size_t len = view.size() + 1;
      if (len >= 255) {
        ScriptLog::Error("Maximum string length is 254 chars. No data saved.");
        return false;
      }
      if (!test) {
        _script_sl_byte = (uint8_t)len;
        SlObject(nullptr, _script_byte);
        SlCopy(const_cast<char *>(view.data()), len, SLE_CHAR);
      }
      return true;
    }
 
    case OT_ARRAY: {
      if (!test) {
        _script_sl_byte = SQSL_ARRAY;
        SlObject(nullptr, _script_byte);
      }
      sq_pushnull(vm);
      while (SQ_SUCCEEDED(sq_next(vm, index - 1))) {
        /* Store the value */
        bool res = SaveObject(vm, -1, max_depth - 1, test);
        sq_pop(vm, 2);
        if (!res) {
          sq_pop(vm, 1);
          return false;
        }
      }
      sq_pop(vm, 1);
      if (!test) {
        _script_sl_byte = SQSL_ARRAY_TABLE_END;
        SlObject(nullptr, _script_byte);
      }
      return true;
    }
 
    case OT_TABLE: {
      if (!test) {
        _script_sl_byte = SQSL_TABLE;
        SlObject(nullptr, _script_byte);
      }
      sq_pushnull(vm);
      while (SQ_SUCCEEDED(sq_next(vm, index - 1))) {
        /* Store the key + value */
        bool res = SaveObject(vm, -2, max_depth - 1, test) && SaveObject(vm, -1, max_depth - 1, test);
        sq_pop(vm, 2);
        if (!res) {
          sq_pop(vm, 1);
          return false;
        }
      }
      sq_pop(vm, 1);
      if (!test) {
        _script_sl_byte = SQSL_ARRAY_TABLE_END;
        SlObject(nullptr, _script_byte);
      }
      return true;
    }
 
    case OT_BOOL: {
      if (!test) {
        _script_sl_byte = SQSL_BOOL;
        SlObject(nullptr, _script_byte);
      }
      SQBool res;
      sq_getbool(vm, index, &res);
      if (!test) {
        _script_sl_byte = res ? 1 : 0;
        SlObject(nullptr, _script_byte);
      }
      return true;
    }
 
    case OT_NULL: {
      if (!test) {
        _script_sl_byte = SQSL_NULL;
        SlObject(nullptr, _script_byte);
      }
      return true;
    }
 
    case OT_INSTANCE:{
      if (!test) {
        _script_sl_byte = SQSL_INSTANCE;
        SlObject(nullptr, _script_byte);
      }
      SQInteger top = sq_gettop(vm);
      try {
        ScriptObject *obj = static_cast<ScriptObject *>(Squirrel::GetRealInstance(vm, -1, "Object"));
        if (!obj->SaveObject(vm)) throw std::exception();
        if (sq_gettop(vm) != top + 2) throw std::exception();
        if (sq_gettype(vm, -2) != OT_STRING || !SaveObject(vm, -2, max_depth - 1, test)) throw std::exception();
        if (!SaveObject(vm, -1, max_depth - 1, test)) throw std::exception();
        sq_settop(vm, top);
        return true;
      } catch (...) {
        ScriptLog::Error("You tried to save an unsupported type. No data saved.");
        sq_settop(vm, top);
        return false;
      }
    }
 
    default:
      ScriptLog::Error("You tried to save an unsupported type. No data saved.");
      return false;
  }
}
 
/* static */ void ScriptInstance::SaveEmpty()
{
  _script_sl_byte = 0;
  SlObject(nullptr, _script_byte);
}
 
void ScriptInstance::Save()
{
  ScriptObject::ActiveInstance active(*this);
 
  /* Don't save data if the script didn't start yet or if it crashed. */
  if (this->engine == nullptr || this->engine->HasScriptCrashed()) {
    SaveEmpty();
    return;
  }
 
  HSQUIRRELVM vm = this->engine->GetVM();
  if (this->is_save_data_on_stack) {
    _script_sl_byte = 1;
    SlObject(nullptr, _script_byte);
    /* Save the data that was just loaded. */
    SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, false);
  } else if (!this->is_started) {
    SaveEmpty();
    return;
  } else if (this->engine->MethodExists(*this->instance, "Save")) {
    HSQOBJECT savedata;
    try {
      /* We don't want to be interrupted during the save function. */
      ScriptObject::DisableDoCommandScope disabler{};
      if (!this->engine->CallMethod(*this->instance, "Save", &savedata, MAX_SL_OPS)) {
        /* The script crashed in the Save function. We can't kill
         * it here, but do so in the next script tick. */
        SaveEmpty();
        this->engine->CrashOccurred();
        return;
      }
    } catch (Script_FatalError &e) {
      /* If we don't mark the script as dead here cleaning up the squirrel
       * stack could throw Script_FatalError again. */
      this->is_dead = true;
      this->engine->ThrowError(e.GetErrorMessage());
      this->engine->ResumeError();
      SaveEmpty();
      /* We can't kill the script here, so mark it as crashed (not dead) and
       * kill it in the next script tick. */
      this->is_dead = false;
      this->engine->CrashOccurred();
      return;
    }
 
    if (!sq_istable(savedata)) {
      ScriptLog::Error(this->GetOpsTillSuspend() <= 0 ? "This script took too long to Save." : "Save function should return a table.");
      SaveEmpty();
      this->engine->CrashOccurred();
      return;
    }
    sq_pushobject(vm, savedata);
    if (SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, true)) {
      _script_sl_byte = 1;
      SlObject(nullptr, _script_byte);
      SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, false);
      this->is_save_data_on_stack = true;
    } else {
      SaveEmpty();
      this->engine->CrashOccurred();
    }
  } else {
    ScriptLog::Warning("Save function is not implemented");
    _script_sl_byte = 0;
    SlObject(nullptr, _script_byte);
  }
}
 
void ScriptInstance::Pause()
{
  /* Suspend script. */
  HSQUIRRELVM vm = this->engine->GetVM();
  Squirrel::DecreaseOps(vm, _settings_game.script.script_max_opcode_till_suspend);
 
  this->is_paused = true;
}
 
void ScriptInstance::Unpause()
{
  this->is_paused = false;
}
 
bool ScriptInstance::IsPaused()
{
  return this->is_paused;
}
 
/* static */ bool ScriptInstance::LoadObjects(ScriptData *data)
{
  SlObject(nullptr, _script_byte);
  switch (_script_sl_byte) {
    case SQSL_INT: {
      int64_t value;
      SlCopy(&value, 1, IsSavegameVersionBefore(SLV_SCRIPT_INT64) ? SLE_FILE_I32 | SLE_VAR_I64 : SLE_INT64);
      if (data != nullptr) data->push_back(static_cast<SQInteger>(value));
      return true;
    }
 
    case SQSL_STRING: {
      SlObject(nullptr, _script_byte);
      static char buf[std::numeric_limits<decltype(_script_sl_byte)>::max()];
      SlCopy(buf, _script_sl_byte, SLE_CHAR);
      if (data != nullptr) data->push_back(StrMakeValid(std::string_view(buf, _script_sl_byte)));
      return true;
    }
 
    case SQSL_ARRAY:
    case SQSL_TABLE: {
      if (data != nullptr) data->push_back(static_cast<SQSaveLoadType>(_script_sl_byte));
      while (LoadObjects(data));
      return true;
    }
 
    case SQSL_BOOL: {
      SlObject(nullptr, _script_byte);
      if (data != nullptr) data->push_back(static_cast<SQBool>(_script_sl_byte != 0));
      return true;
    }
 
    case SQSL_NULL: {
      if (data != nullptr) data->push_back(static_cast<SQSaveLoadType>(_script_sl_byte));
      return true;
    }
 
    case SQSL_INSTANCE: {
      if (data != nullptr) data->push_back(static_cast<SQSaveLoadType>(_script_sl_byte));
      return true;
    }
 
    case SQSL_ARRAY_TABLE_END: {
      if (data != nullptr) data->push_back(static_cast<SQSaveLoadType>(_script_sl_byte));
      return false;
    }
 
    default: SlErrorCorrupt("Invalid script data type");
  }
}
 
/* static */ bool ScriptInstance::LoadObjects(HSQUIRRELVM vm, ScriptData *data)
{
  ScriptDataVariant value = data->front();
  data->pop_front();
 
  struct visitor {
    HSQUIRRELVM vm;
    ScriptData *data;
 
    bool operator()(const SQInteger &value) { sq_pushinteger(this->vm, value); return true; }
    bool operator()(const std::string &value) { sq_pushstring(this->vm, value); return true; }
    bool operator()(const SQBool &value) { sq_pushbool(this->vm, value); return true; }
    bool operator()(const SQSaveLoadType &type)
    {
      switch (type) {
        case SQSL_ARRAY:
          sq_newarray(this->vm, 0);
          while (LoadObjects(this->vm, this->data)) {
            sq_arrayappend(this->vm, -2);
            /* The value is popped from the stack by squirrel. */
          }
          return true;
 
        case SQSL_TABLE:
          sq_newtable(this->vm);
          while (LoadObjects(this->vm, this->data)) {
            LoadObjects(this->vm, this->data);
            sq_rawset(this->vm, -3);
            /* The key (-2) and value (-1) are popped from the stack by squirrel. */
          }
          return true;
 
        case SQSL_NULL:
          sq_pushnull(this->vm);
          return true;
 
        case SQSL_INSTANCE: {
          SQInteger top = sq_gettop(this->vm);
          LoadObjects(this->vm, this->data);
          std::string_view view;
          sq_getstring(this->vm, -1, view);
          Squirrel *engine = static_cast<Squirrel *>(sq_getforeignptr(this->vm));
          std::string class_name = fmt::format("{}{}", engine->GetAPIName(), view);
          sq_pushroottable(this->vm);
          sq_pushstring(this->vm, class_name);
          if (SQ_FAILED(sq_get(this->vm, -2))) throw Script_FatalError(fmt::format("'{}' doesn't exist", class_name));
          sq_pushroottable(vm);
          if (SQ_FAILED(sq_call(this->vm, 1, SQTrue, SQFalse))) throw Script_FatalError(fmt::format("Failed to instantiate '{}'", class_name));
          HSQOBJECT res;
          sq_getstackobj(vm, -1, &res);
          sq_addref(vm, &res);
          sq_settop(this->vm, top);
          sq_pushobject(vm, res);
          sq_release(vm, &res);
          ScriptObject *obj = static_cast<ScriptObject *>(Squirrel::GetRealInstance(vm, -1, "Object"));
          LoadObjects(this->vm, this->data);
          if (!obj->LoadObject(vm)) throw Script_FatalError(fmt::format("Failed to load '{}'", class_name));
          sq_pop(this->vm, 1);
          return true;
        }
 
        case SQSL_ARRAY_TABLE_END:
          return false;
 
        default: NOT_REACHED();
      }
    }
  };
 
  return std::visit(visitor{vm, data}, value);
}
 
/* static */ void ScriptInstance::LoadEmpty()
{
  SlObject(nullptr, _script_byte);
  /* Check if there was anything saved at all. */
  if (_script_sl_byte == 0) return;
 
  LoadObjects(nullptr);
}
 
/* static */ ScriptInstance::ScriptData *ScriptInstance::Load(int version)
{
  if (version == -1) {
    LoadEmpty();
    return nullptr;
  }
 
  SlObject(nullptr, _script_byte);
  /* Check if there was anything saved at all. */
  if (_script_sl_byte == 0) return nullptr;
 
  ScriptData *data = new ScriptData();
  data->push_back((SQInteger)version);
  LoadObjects(data);
  return data;
}
 
void ScriptInstance::LoadOnStack(ScriptData *data)
{
  ScriptObject::ActiveInstance active(*this);
 
  if (this->IsDead() || data == nullptr) return;
 
  HSQUIRRELVM vm = this->engine->GetVM();
 
  ScriptDataVariant version = data->front();
  data->pop_front();
  SQInteger top = sq_gettop(vm);
  try {
    sq_pushinteger(vm, std::get<SQInteger>(version));
    LoadObjects(vm, data);
    this->is_save_data_on_stack = true;
  } catch (Script_FatalError &e) {
    ScriptLog::Warning(fmt::format("Loading failed: {}", e.GetErrorMessage()));
    /* Discard partially loaded savegame data and version. */
    sq_settop(vm, top);
  }
}
 
bool ScriptInstance::CallLoad()
{
  HSQUIRRELVM vm = this->engine->GetVM();
  /* Is there save data that we should load? */
  if (!this->is_save_data_on_stack) return true;
  /* Whatever happens, after CallLoad the savegame data is removed from the stack. */
  this->is_save_data_on_stack = false;
 
  if (!this->engine->MethodExists(*this->instance, "Load")) {
    ScriptLog::Warning("Loading failed: there was data for the script to load, but the script does not have a Load() function.");
 
    /* Pop the savegame data and version. */
    sq_pop(vm, 2);
    return true;
  }
 
  /* Go to the instance-root */
  sq_pushobject(vm, *this->instance);
  /* Find the function-name inside the script */
  sq_pushstring(vm, "Load");
  /* Change the "Load" string in a function pointer */
  sq_get(vm, -2);
  /* Push the main instance as "this" object */
  sq_pushobject(vm, *this->instance);
  /* Push the version data and savegame data as arguments */
  sq_push(vm, -5);
  sq_push(vm, -5);
 
  /* Call the script load function. sq_call removes the arguments (but not the
   * function pointer) from the stack. */
  if (SQ_FAILED(sq_call(vm, 3, SQFalse, SQTrue, MAX_SL_OPS))) return false;
 
  /* Pop 1) The version, 2) the savegame data, 3) the object instance, 4) the function pointer. */
  sq_pop(vm, 4);
  return true;
}
 
SQInteger ScriptInstance::GetOpsTillSuspend()
{
  return this->engine->GetOpsTillSuspend();
}
 
bool ScriptInstance::DoCommandCallback(const CommandCost &result, const CommandDataBuffer &data, CommandDataBuffer result_data, Commands cmd)
{
  ScriptObject::ActiveInstance active(*this);
 
  if (!ScriptObject::CheckLastCommand(data, cmd)) {
    Debug(script, 1, "DoCommandCallback terminating a script, last command does not match expected command");
    return false;
  }
 
  ScriptObject::SetLastCommandRes(result.Succeeded());
  ScriptObject::SetLastCommandResData(std::move(result_data));
 
  if (result.Failed()) {
    ScriptObject::SetLastError(ScriptError::StringToError(result.GetErrorMessage()));
  } else {
    ScriptObject::IncreaseDoCommandCosts(result.GetCost());
    ScriptObject::SetLastCost(result.GetCost());
  }
 
  ScriptObject::SetLastCommand({}, Commands::End);
 
  return true;
}
 
void ScriptInstance::InsertEvent(class ScriptEvent *event)
{
  ScriptObject::ActiveInstance active(*this);
 
  ScriptEventController::InsertEvent(event);
}
 
size_t ScriptInstance::GetAllocatedMemory() const
{
  if (this->engine == nullptr) return this->last_allocated_memory;
  return this->engine->GetAllocatedMemory();
}
 
void ScriptInstance::ReleaseSQObject(HSQOBJECT *obj)
{
  if (!this->in_shutdown) this->engine->ReleaseObject(obj);
}