/*
 * 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 script_instance.cpp Implementation of ScriptInstance. */

#include "../stdafx.h"
#include "../debug.h"
#include "../saveload/saveload.h"

#include "../script/squirrel_class.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_base.h"
#include "../company_func.h"
#include "../fileio_func.h"
#include "../league_type.h"
#include "../misc/endian_buffer.hpp"

#include "../safeguards.h"

ScriptStorage::~ScriptStorage()
{
	/* Free our pointers */
	if (event_data != nullptr) ScriptEventController::FreeEventPointer();
	if (log_data != nullptr) ScriptLog::FreeLogPointer();
}

/**
 * Callback called by squirrel when a script uses "print" and for error messages.
 * @param error_msg Is this an error message?
 * @param message The actual message text.
 */
static void PrintFunc(bool error_msg, const SQChar *message)
{
	/* Convert to OpenTTD internal capable string */
	ScriptController::Print(error_msg, message);
}

ScriptInstance::ScriptInstance(const char *APIName) :
	engine(nullptr),
	versionAPI(nullptr),
	controller(nullptr),
	storage(nullptr),
	instance(nullptr),
	is_started(false),
	is_dead(false),
	is_save_data_on_stack(false),
	suspend(0),
	is_paused(false),
	in_shutdown(false),
	callback(nullptr)
{
	this->storage = new ScriptStorage();
	this->engine  = new Squirrel(APIName);
	this->engine->SetPrintFunction(&PrintFunc);
}

void ScriptInstance::Initialize(const char *main_script, const char *instance_name, CompanyID company)
{
	ScriptObject::ActiveInstance active(this);

	this->controller = new ScriptController(company);

	/* Register the API functions and classes */
	this->engine->SetGlobalPointer(this->engine);
	this->RegisterAPI();

	try {
		ScriptObject::SetAllowDoCommand(false);
		/* Load and execute the script for this script */
		if (strcmp(main_script, "%_dummy") == 0) {
			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 = new SQObject();
		if (!this->engine->CreateClassInstance(instance_name, this->controller, this->instance)) {
			/* If CreateClassInstance has returned false instance has not been
			 * registered with squirrel, so avoid trying to Release it by clearing it now */
			delete this->instance;
			this->instance = nullptr;
			this->Died();
			return;
		}
		ScriptObject::SetAllowDoCommand(true);
	} catch (Script_FatalError &e) {
		this->is_dead = true;
		this->engine->ThrowError(e.GetErrorMessage().c_str());
		this->engine->ResumeError();
		this->Died();
	}
}

void ScriptInstance::RegisterAPI()
{
	extern void squirrel_register_std(Squirrel *engine);
	squirrel_register_std(this->engine);
}

bool ScriptInstance::LoadCompatibilityScripts(const char *api_version, Subdirectory dir)
{
	char script_name[32];
	seprintf(script_name, lastof(script_name), "compat_%s.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.c_str())) return true;

		ScriptLog::Error("Failed to load API compatibility script");
		Debug(script, 0, "Error compiling / running API compatibility script: {}", buf);
		return false;
	}

	ScriptLog::Warning("API compatibility script not found");
	return true;
}

ScriptInstance::~ScriptInstance()
{
	ScriptObject::ActiveInstance active(this);
	this->in_shutdown = true;

	if (instance != nullptr) this->engine->ReleaseObject(this->instance);
	if (engine != nullptr) delete this->engine;
	delete this->storage;
	delete this->controller;
	delete this->instance;
}

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);
	delete this->instance;
	delete this->engine;
	this->instance = nullptr;
	this->engine = nullptr;
}

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::SetAllowDoCommand(false);
			/* 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;
			}
			ScriptObject::SetAllowDoCommand(true);
			/* 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().c_str());
			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().c_str());
		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()
{
	return this->storage;
}

void *ScriptInstance::GetLogPointer()
{
	ScriptObject::ActiveInstance active(this);

	return ScriptObject::GetLogPointer();
}

/*
 * 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).
 *  - 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.
 */

/** The type of the data that follows in the savegame. */
enum SQSaveLoadType {
	SQSL_INT             = 0x00, ///< The following data is an integer.
	SQSL_STRING          = 0x01, ///< The following data is an string.
	SQSL_ARRAY           = 0x02, ///< The following data is an array.
	SQSL_TABLE           = 0x03, ///< The following data is an table.
	SQSL_BOOL            = 0x04, ///< The following data is a boolean.
	SQSL_NULL            = 0x05, ///< A null variable.
	SQSL_ARRAY_TABLE_END = 0xFF, ///< Marks the end of an array or table, no data follows.
};

static byte _script_sl_byte; ///< Used as source/target by the script saveload code to store/load a single byte.

/** SaveLoad array that saves/loads exactly one 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 value = (int64)res;
				SlCopy(&value, 1, SLE_INT64);
			}
			return true;
		}

		case OT_STRING: {
			if (!test) {
				_script_sl_byte = SQSL_STRING;
				SlObject(nullptr, _script_byte);
			}
			const SQChar *buf;
			sq_getstring(vm, index, &buf);
			size_t len = strlen(buf) + 1;
			if (len >= 255) {
				ScriptLog::Error("Maximum string length is 254 chars. No data saved.");
				return false;
			}
			if (!test) {
				_script_sl_byte = (byte)len;
				SlObject(nullptr, _script_byte);
				SlCopy(const_cast<char *>(buf), 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;
		}

		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;
		/* We don't want to be interrupted during the save function. */
		bool backup_allow = ScriptObject::GetAllowDoCommand();
		ScriptObject::SetAllowDoCommand(false);
		try {
			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().c_str());
			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;
		}
		ScriptObject::SetAllowDoCommand(backup_allow);

		if (!sq_istable(savedata)) {
			ScriptLog::Error(this->engine->IsSuspended() ? "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(HSQUIRRELVM vm)
{
	SlObject(nullptr, _script_byte);
	switch (_script_sl_byte) {
		case SQSL_INT: {
			int64 value;
			SlCopy(&value, 1, IsSavegameVersionBefore(SLV_SCRIPT_INT64) ? SLE_FILE_I32 | SLE_VAR_I64 : SLE_INT64);
			if (vm != nullptr) sq_pushinteger(vm, (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);
			StrMakeValidInPlace(buf, buf + _script_sl_byte);
			if (vm != nullptr) sq_pushstring(vm, buf, -1);
			return true;
		}

		case SQSL_ARRAY: {
			if (vm != nullptr) sq_newarray(vm, 0);
			while (LoadObjects(vm)) {
				if (vm != nullptr) sq_arrayappend(vm, -2);
				/* The value is popped from the stack by squirrel. */
			}
			return true;
		}

		case SQSL_TABLE: {
			if (vm != nullptr) sq_newtable(vm);
			while (LoadObjects(vm)) {
				LoadObjects(vm);
				if (vm != nullptr) sq_rawset(vm, -3);
				/* The key (-2) and value (-1) are popped from the stack by squirrel. */
			}
			return true;
		}

		case SQSL_BOOL: {
			SlObject(nullptr, _script_byte);
			if (vm != nullptr) sq_pushbool(vm, (SQBool)(_script_sl_byte != 0));
			return true;
		}

		case SQSL_NULL: {
			if (vm != nullptr) sq_pushnull(vm);
			return true;
		}

		case SQSL_ARRAY_TABLE_END: {
			return false;
		}

		default: NOT_REACHED();
	}
}

/* static */ void ScriptInstance::LoadEmpty()
{
	SlObject(nullptr, _script_byte);
	/* Check if there was anything saved at all. */
	if (_script_sl_byte == 0) return;

	LoadObjects(nullptr);
}

void ScriptInstance::Load(int version)
{
	ScriptObject::ActiveInstance active(this);

	if (this->engine == nullptr || version == -1) {
		LoadEmpty();
		return;
	}
	HSQUIRRELVM vm = this->engine->GetVM();

	SlObject(nullptr, _script_byte);
	/* Check if there was anything saved at all. */
	if (_script_sl_byte == 0) return;

	sq_pushinteger(vm, version);
	LoadObjects(vm);
	this->is_save_data_on_stack = true;
}

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", -1);
	/* 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, SQFalse, 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, TileIndex tile, const CommandDataBuffer &data, CommandDataBuffer result_data, Commands cmd)
{
	ScriptObject::ActiveInstance active(this);

	if (!ScriptObject::CheckLastCommand(tile, 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(INVALID_TILE, {}, CMD_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);
}