/*
 * 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>.
 */

/** @file script_scanner.cpp Allows scanning for scripts. */

#include "../stdafx.h"
#include "../debug.h"
#include "../string_func.h"
#include "../settings_type.h"

#include "../script/squirrel.hpp"
#include "script_scanner.hpp"
#include "script_info.hpp"
#include "script_fatalerror.hpp"

#include "../network/network_content.h"
#include "../3rdparty/md5/md5.h"
#include "../tar_type.h"

#include "../safeguards.h"

bool ScriptScanner::AddFile(const std::string &filename, size_t, const std::string &tar_filename)
{
	this->main_script = filename;
	this->tar_file = tar_filename;

	auto p = this->main_script.find_last_of(PATHSEPCHAR);
	this->main_script.erase(p != std::string::npos ? p + 1 : 0);
	this->main_script += "main.nut";

	if (!FioCheckFileExists(filename, this->subdir) || !FioCheckFileExists(this->main_script, this->subdir)) return false;

	this->ResetEngine();
	try {
		this->engine->LoadScript(filename);
	} catch (Script_FatalError &e) {
		Debug(script, 0, "Fatal error '{}' when trying to load the script '{}'.", e.GetErrorMessage(), filename);
		return false;
	}
	return true;
}

ScriptScanner::ScriptScanner() = default;

void ScriptScanner::ResetEngine()
{
	this->engine->Reset();
	this->engine->SetGlobalPointer(this);
	this->RegisterAPI(*this->engine);
}

void ScriptScanner::Initialize(std::string_view name)
{
	this->engine = std::make_unique<Squirrel>(name);

	this->RescanDir();

	this->ResetEngine();
}

ScriptScanner::~ScriptScanner()
{
	this->Reset();
}

void ScriptScanner::RescanDir()
{
	/* Forget about older scans */
	this->Reset();

	/* Scan for scripts */
	this->Scan(this->GetFileName(), this->GetDirectory());
}

void ScriptScanner::Reset()
{
	this->info_list.clear();
	this->info_single_list.clear();
	this->info_vector.clear();
}

void ScriptScanner::RegisterScript(std::unique_ptr<ScriptInfo> &&info)
{
	std::string script_original_name = this->GetScriptName(*info);
	std::string script_name = fmt::format("{}.{}", script_original_name, info->GetVersion());

	/* Check if GetShortName follows the rules */
	if (info->GetShortName().size() != 4) {
		Debug(script, 0, "The script '{}' returned a string from GetShortName() which is not four characters. Unable to load the script.", info->GetName());
		return;
	}

	if (auto it = this->info_list.find(script_name); it != this->info_list.end()) {
		/* This script was already registered */
#ifdef _WIN32
		/* Windows doesn't care about the case */
		if (StrEqualsIgnoreCase(it->second->GetMainScript(), info->GetMainScript())) {
#else
		if (it->second->GetMainScript() == info->GetMainScript()) {
#endif
			return;
		}

		Debug(script, 1, "Registering two scripts with the same name and version");
		Debug(script, 1, "  1: {}", it->second->GetMainScript());
		Debug(script, 1, "  2: {}", info->GetMainScript());
		Debug(script, 1, "The first is taking precedence.");

		return;
	}

	ScriptInfo *script_info = this->info_vector.emplace_back(std::move(info)).get();
	this->info_list[script_name] = script_info;

	if (!script_info->IsDeveloperOnly() || _settings_client.gui.ai_developer_tools) {
		/* Add the script to the 'unique' script list, where only the highest version
		 *  of the script is registered. */
		auto it = this->info_single_list.find(script_original_name);
		if (it == this->info_single_list.end()) {
			this->info_single_list[script_original_name] = script_info;
		} else if (it->second->GetVersion() < script_info->GetVersion()) {
			it->second = script_info;
		}
	}
}

void ScriptScanner::GetConsoleList(std::back_insert_iterator<std::string> &output_iterator, bool newest_only) const
{
	fmt::format_to(output_iterator, "List of {}:\n", this->GetScannerName());
	const ScriptInfoList &list = newest_only ? this->info_single_list : this->info_list;
	for (const auto &item : list) {
		ScriptInfo *i = item.second;
		fmt::format_to(output_iterator, "{:>10} (v{:d}): {}\n", i->GetName(), i->GetVersion(), i->GetDescription());
	}
	fmt::format_to(output_iterator, "\n");
}

/** Helper for creating a MD5sum of all files within of a script. */
struct ScriptFileChecksumCreator : FileScanner {
	MD5Hash md5sum; ///< The final md5sum.
	Subdirectory dir; ///< The directory to look in.

	/**
	 * Initialise the md5sum to be all zeroes,
	 * so we can easily xor the data.
	 * @param dir The directory to look in.
	 */
	ScriptFileChecksumCreator(Subdirectory dir) : dir(dir) {}

	/* Add the file and calculate the md5 sum. */
	bool AddFile(const std::string &filename, size_t, const std::string &) override
	{
		Md5 checksum;
		uint8_t buffer[1024];
		size_t len, size;

		/* Open the file ... */
		auto f = FioFOpenFile(filename, "rb", this->dir, &size);
		if (!f.has_value()) return false;

		/* ... calculate md5sum... */
		while ((len = fread(buffer, 1, (size > sizeof(buffer)) ? sizeof(buffer) : size, *f)) != 0 && size != 0) {
			size -= len;
			checksum.Append(buffer, len);
		}

		MD5Hash tmp_md5sum;
		checksum.Finish(tmp_md5sum);

		/* ... and xor it to the overall md5sum. */
		this->md5sum ^= tmp_md5sum;

		return true;
	}
};

/**
 * Check whether the script given in info is the same as in ci based
 * on the shortname and md5 sum.
 * @param ci The information to compare to.
 * @param md5sum Whether to check the MD5 checksum.
 * @param info The script to get the shortname and md5 sum from.
 * @param dir The directory to look in for scripts.
 * @return True iff they're the same.
 */
static bool IsSameScript(const ContentInfo &ci, bool md5sum, const ScriptInfo &info, Subdirectory dir)
{
	uint32_t id = 0;
	auto str = std::string_view{info.GetShortName()}.substr(0, 4);
	for (size_t j = 0; j < str.size(); j++) id |= static_cast<uint8_t>(str[j]) << (8 * j);

	if (id != ci.unique_id) return false;
	if (!md5sum) return true;

	ScriptFileChecksumCreator checksum(dir);
	const auto &tar_filename = info.GetTarFile();
	TarList::iterator iter;
	if (!tar_filename.empty() && (iter = _tar_list[dir].find(tar_filename)) != _tar_list[dir].end()) {
		/* The main script is in a tar file, so find all files that
		 * are in the same tar and add them to the MD5 checksumming. */
		for (const auto &tar : _tar_filelist[dir]) {
			/* Not in the same tar. */
			if (tar.second.tar_filename != iter->first) continue;

			/* Check the extension. */
			auto ext = tar.first.rfind('.');
			if (ext == std::string_view::npos || !StrEqualsIgnoreCase(tar.first.substr(ext), ".nut")) continue;

			checksum.AddFile(tar.first, 0, tar_filename);
		}
	} else {
		/* There'll always be at least 1 path separator character in a script
		 * main script name as the search algorithm requires the main script to
		 * be in a subdirectory of the script directory; so <dir>/<path>/main.nut. */
		const std::string &main_script = info.GetMainScript();
		std::string path = main_script.substr(0, main_script.find_last_of(PATHSEPCHAR));
		checksum.Scan(".nut", path);
	}

	return ci.md5sum == checksum.md5sum;
}

bool ScriptScanner::HasScript(const ContentInfo &ci, bool md5sum)
{
	for (const auto &item : this->info_list) {
		if (IsSameScript(ci, md5sum, *item.second, this->GetDirectory())) return true;
	}
	return false;
}

std::optional<std::string_view> ScriptScanner::FindMainScript(const ContentInfo &ci, bool md5sum)
{
	for (const auto &item : this->info_list) {
		if (IsSameScript(ci, md5sum, *item.second, this->GetDirectory())) return item.second->GetMainScript();
	}
	return std::nullopt;
}
