Folder restructuring from primedev (#624)v1.21.2-rc3v1.21.2

Copies of over the primedev folder structure for easier cherry-picking of further changes

Co-authored-by: F1F7Y <filip.bartos07@proton.me>

2 files changed, 789 insertions, 0 deletions

diff --git a/primedev/mods/autodownload/moddownloader.cpp b/primedev/mods/autodownload/moddownloader.cpp
new file mode 100644
index 00000000..165399e3
--- /dev/null
+++ b/primedev/mods/autodownload/moddownloader.cpp
@@ -0,0 +1,638 @@
+#include "moddownloader.h"
+#include <rapidjson/fwd.h>
+#include <mz_strm_mem.h>
+#include <mz.h>
+#include <mz_strm.h>
+#include <mz_zip.h>
+#include <mz_compat.h>
+#include <thread>
+#include <future>
+#include <bcrypt.h>
+#include <winternl.h>
+#include <fstream>
+
+ModDownloader* g_pModDownloader;
+
+ModDownloader::ModDownloader()
+{
+	spdlog::info("Mod downloader initialized");
+
+	// Initialise mods list URI
+	char* clachar = strstr(GetCommandLineA(), CUSTOM_MODS_URL_FLAG);
+	if (clachar)
+	{
+		std::string url;
+		int iFlagStringLength = strlen(CUSTOM_MODS_URL_FLAG);
+		std::string cla = std::string(clachar);
+		if (strncmp(cla.substr(iFlagStringLength, 1).c_str(), "\"", 1))
+		{
+			int space = cla.find(" ");
+			url = cla.substr(iFlagStringLength, space - iFlagStringLength);
+		}
+		else
+		{
+			std::string quote = "\"";
+			int quote1 = cla.find(quote);
+			int quote2 = (cla.substr(quote1 + 1)).find(quote);
+			url = cla.substr(quote1 + 1, quote2);
+		}
+		spdlog::info("Found custom verified mods URL in command line argument: {}", url);
+		modsListUrl = strdup(url.c_str());
+	}
+	else
+	{
+		spdlog::info("Custom verified mods URL not found in command line arguments, using default URL.");
+		modsListUrl = strdup(DEFAULT_MODS_LIST_URL);
+	}
+}
+
+size_t WriteToString(void* ptr, size_t size, size_t count, void* stream)
+{
+	((std::string*)stream)->append((char*)ptr, 0, size * count);
+	return size * count;
+}
+
+void ModDownloader::FetchModsListFromAPI()
+{
+	std::thread requestThread(
+		[this]()
+		{
+			CURLcode result;
+			CURL* easyhandle;
+			rapidjson::Document verifiedModsJson;
+			std::string url = modsListUrl;
+
+			curl_global_init(CURL_GLOBAL_ALL);
+			easyhandle = curl_easy_init();
+			std::string readBuffer;
+
+			// Fetching mods list from GitHub repository
+			curl_easy_setopt(easyhandle, CURLOPT_CUSTOMREQUEST, "GET");
+			curl_easy_setopt(easyhandle, CURLOPT_TIMEOUT, 30L);
+			curl_easy_setopt(easyhandle, CURLOPT_URL, url.c_str());
+			curl_easy_setopt(easyhandle, CURLOPT_FAILONERROR, 1L);
+			curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, &readBuffer);
+			curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, WriteToString);
+			result = curl_easy_perform(easyhandle);
+
+			if (result == CURLcode::CURLE_OK)
+			{
+				spdlog::info("Mods list successfully fetched.");
+			}
+			else
+			{
+				spdlog::error("Fetching mods list failed: {}", curl_easy_strerror(result));
+				goto REQUEST_END_CLEANUP;
+			}
+
+			// Load mods list into local state
+			spdlog::info("Loading mods configuration...");
+			verifiedModsJson.Parse(readBuffer);
+			for (auto i = verifiedModsJson.MemberBegin(); i != verifiedModsJson.MemberEnd(); ++i)
+			{
+				std::string name = i->name.GetString();
+				std::string dependency = i->value["DependencyPrefix"].GetString();
+
+				std::unordered_map<std::string, VerifiedModVersion> modVersions;
+				rapidjson::Value& versions = i->value["Versions"];
+				assert(versions.IsArray());
+				for (auto& attribute : versions.GetArray())
+				{
+					assert(attribute.IsObject());
+					std::string version = attribute["Version"].GetString();
+					std::string checksum = attribute["Checksum"].GetString();
+					modVersions.insert({version, {.checksum = checksum}});
+				}
+
+				VerifiedModDetails modConfig = {.dependencyPrefix = dependency, .versions = modVersions};
+				verifiedMods.insert({name, modConfig});
+				spdlog::info("==> Loaded configuration for mod \"" + name + "\"");
+			}
+
+			spdlog::info("Done loading verified mods list.");
+
+		REQUEST_END_CLEANUP:
+			curl_easy_cleanup(easyhandle);
+		});
+	requestThread.detach();
+}
+
+size_t WriteData(void* ptr, size_t size, size_t nmemb, FILE* stream)
+{
+	size_t written;
+	written = fwrite(ptr, size, nmemb, stream);
+	return written;
+}
+
+int ModDownloader::ModFetchingProgressCallback(
+	void* ptr, curl_off_t totalDownloadSize, curl_off_t finishedDownloadSize, curl_off_t totalToUpload, curl_off_t nowUploaded)
+{
+	if (totalDownloadSize != 0 && finishedDownloadSize != 0)
+	{
+		ModDownloader* instance = static_cast<ModDownloader*>(ptr);
+		auto currentDownloadProgress = roundf(static_cast<float>(finishedDownloadSize) / totalDownloadSize * 100);
+		instance->modState.progress = finishedDownloadSize;
+		instance->modState.total = totalDownloadSize;
+		instance->modState.ratio = currentDownloadProgress;
+	}
+
+	return 0;
+}
+
+std::optional<fs::path> ModDownloader::FetchModFromDistantStore(std::string_view modName, std::string_view modVersion)
+{
+	// Retrieve mod prefix from local mods list, or use mod name as mod prefix if bypass flag is set
+	std::string modPrefix = strstr(GetCommandLineA(), VERIFICATION_FLAG) ? modName.data() : verifiedMods[modName.data()].dependencyPrefix;
+	// Build archive distant URI
+	std::string archiveName = std::format("{}-{}.zip", modPrefix, modVersion.data());
+	std::string url = STORE_URL + archiveName;
+	spdlog::info(std::format("Fetching mod archive from {}", url));
+
+	// Download destination
+	std::filesystem::path downloadPath = std::filesystem::temp_directory_path() / archiveName;
+	spdlog::info(std::format("Downloading archive to {}", downloadPath.generic_string()));
+
+	// Update state
+	modState.state = DOWNLOADING;
+
+	// Download the actual archive
+	bool failed = false;
+	FILE* fp = fopen(downloadPath.generic_string().c_str(), "wb");
+	CURLcode result;
+	CURL* easyhandle;
+	easyhandle = curl_easy_init();
+
+	curl_easy_setopt(easyhandle, CURLOPT_URL, url.data());
+	curl_easy_setopt(easyhandle, CURLOPT_FAILONERROR, 1L);
+	curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, fp);
+	curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, WriteData);
+	curl_easy_setopt(easyhandle, CURLOPT_NOPROGRESS, 0L);
+	curl_easy_setopt(easyhandle, CURLOPT_XFERINFOFUNCTION, ModDownloader::ModFetchingProgressCallback);
+	curl_easy_setopt(easyhandle, CURLOPT_XFERINFODATA, this);
+	result = curl_easy_perform(easyhandle);
+
+	if (result == CURLcode::CURLE_OK)
+	{
+		spdlog::info("Mod archive successfully fetched.");
+		goto REQUEST_END_CLEANUP;
+	}
+	else
+	{
+		spdlog::error("Fetching mod archive failed: {}", curl_easy_strerror(result));
+		failed = true;
+		goto REQUEST_END_CLEANUP;
+	}
+
+REQUEST_END_CLEANUP:
+	curl_easy_cleanup(easyhandle);
+	fclose(fp);
+	return failed ? std::optional<fs::path>() : std::optional<fs::path>(downloadPath);
+}
+
+bool ModDownloader::IsModLegit(fs::path modPath, std::string_view expectedChecksum)
+{
+	if (strstr(GetCommandLineA(), VERIFICATION_FLAG))
+	{
+		spdlog::info("Bypassing mod verification due to flag set up.");
+		return true;
+	}
+
+	// Update state
+	modState.state = CHECKSUMING;
+
+	NTSTATUS status;
+	BCRYPT_ALG_HANDLE algorithmHandle = NULL;
+	BCRYPT_HASH_HANDLE hashHandle = NULL;
+	std::vector<uint8_t> hash;
+	DWORD hashLength = 0;
+	DWORD resultLength = 0;
+	std::stringstream ss;
+
+	constexpr size_t bufferSize {1 << 12};
+	std::vector<char> buffer(bufferSize, '\0');
+	std::ifstream fp(modPath.generic_string(), std::ios::binary);
+
+	// Open an algorithm handle
+	// This sample passes BCRYPT_HASH_REUSABLE_FLAG with BCryptAlgorithmProvider(...) to load a provider which supports reusable hash
+	status = BCryptOpenAlgorithmProvider(
+		&algorithmHandle, // Alg Handle pointer
+		BCRYPT_SHA256_ALGORITHM, // Cryptographic Algorithm name (null terminated unicode string)
+		NULL, // Provider name; if null, the default provider is loaded
+		BCRYPT_HASH_REUSABLE_FLAG); // Flags; Loads a provider which supports reusable hash
+	if (!NT_SUCCESS(status))
+	{
+		modState.state = MOD_CORRUPTED;
+		goto cleanup;
+	}
+
+	// Obtain the length of the hash
+	status = BCryptGetProperty(
+		algorithmHandle, // Handle to a CNG object
+		BCRYPT_HASH_LENGTH, // Property name (null terminated unicode string)
+		(PBYTE)&hashLength, // Address of the output buffer which recieves the property value
+		sizeof(hashLength), // Size of the buffer in bytes
+		&resultLength, // Number of bytes that were copied into the buffer
+		0); // Flags
+	if (!NT_SUCCESS(status))
+	{
+		// goto cleanup;
+		modState.state = MOD_CORRUPTED;
+		return false;
+	}
+
+	// Create a hash handle
+	status = BCryptCreateHash(
+		algorithmHandle, // Handle to an algorithm provider
+		&hashHandle, // A pointer to a hash handle - can be a hash or hmac object
+		NULL, // Pointer to the buffer that recieves the hash/hmac object
+		0, // Size of the buffer in bytes
+		NULL, // A pointer to a key to use for the hash or MAC
+		0, // Size of the key in bytes
+		0); // Flags
+	if (!NT_SUCCESS(status))
+	{
+		modState.state = MOD_CORRUPTED;
+		goto cleanup;
+	}
+
+	// Hash archive content
+	if (!fp.is_open())
+	{
+		spdlog::error("Unable to open archive.");
+		modState.state = FAILED_READING_ARCHIVE;
+		return false;
+	}
+	fp.seekg(0, fp.beg);
+	while (fp.good())
+	{
+		fp.read(buffer.data(), bufferSize);
+		std::streamsize bytesRead = fp.gcount();
+		if (bytesRead > 0)
+		{
+			status = BCryptHashData(hashHandle, (PBYTE)buffer.data(), bytesRead, 0);
+			if (!NT_SUCCESS(status))
+			{
+				modState.state = MOD_CORRUPTED;
+				goto cleanup;
+			}
+		}
+	}
+
+	hash = std::vector<uint8_t>(hashLength);
+
+	// Obtain the hash of the message(s) into the hash buffer
+	status = BCryptFinishHash(
+		hashHandle, // Handle to the hash or MAC object
+		hash.data(), // A pointer to a buffer that receives the hash or MAC value
+		hashLength, // Size of the buffer in bytes
+		0); // Flags
+	if (!NT_SUCCESS(status))
+	{
+		modState.state = MOD_CORRUPTED;
+		goto cleanup;
+	}
+
+	// Convert hash to string using bytes raw values
+	ss << std::hex << std::setfill('0');
+	for (int i = 0; i < hashLength; i++)
+	{
+		ss << std::hex << std::setw(2) << static_cast<int>(hash.data()[i]);
+	}
+
+	spdlog::info("Expected checksum: {}", expectedChecksum.data());
+	spdlog::info("Computed checksum: {}", ss.str());
+	return expectedChecksum.compare(ss.str()) == 0;
+
+cleanup:
+	if (NULL != hashHandle)
+	{
+		BCryptDestroyHash(hashHandle); // Handle to hash/MAC object which needs to be destroyed
+	}
+
+	if (NULL != algorithmHandle)
+	{
+		BCryptCloseAlgorithmProvider(
+			algorithmHandle, // Handle to the algorithm provider which needs to be closed
+			0); // Flags
+	}
+
+	return false;
+}
+
+bool ModDownloader::IsModAuthorized(std::string_view modName, std::string_view modVersion)
+{
+	if (strstr(GetCommandLineA(), VERIFICATION_FLAG))
+	{
+		spdlog::info("Bypassing mod verification due to flag set up.");
+		return true;
+	}
+
+	if (!verifiedMods.contains(modName.data()))
+	{
+		return false;
+	}
+
+	std::unordered_map<std::string, VerifiedModVersion> versions = verifiedMods[modName.data()].versions;
+	return versions.count(modVersion.data()) != 0;
+}
+
+int GetModArchiveSize(unzFile file, unz_global_info64 info)
+{
+	int totalSize = 0;
+
+	for (int i = 0; i < info.number_entry; i++)
+	{
+		char zipFilename[256];
+		unz_file_info64 fileInfo;
+		unzGetCurrentFileInfo64(file, &fileInfo, zipFilename, sizeof(zipFilename), NULL, 0, NULL, 0);
+
+		totalSize += fileInfo.uncompressed_size;
+
+		if ((i + 1) < info.number_entry)
+		{
+			unzGoToNextFile(file);
+		}
+	}
+
+	// Reset file pointer for archive extraction
+	unzGoToFirstFile(file);
+
+	return totalSize;
+}
+
+void ModDownloader::ExtractMod(fs::path modPath)
+{
+	unzFile file;
+	std::string name;
+	fs::path modDirectory;
+
+	file = unzOpen(modPath.generic_string().c_str());
+	if (file == NULL)
+	{
+		spdlog::error("Cannot open archive located at {}.", modPath.generic_string());
+		modState.state = FAILED_READING_ARCHIVE;
+		goto EXTRACTION_CLEANUP;
+	}
+
+	unz_global_info64 gi;
+	int status;
+	status = unzGetGlobalInfo64(file, &gi);
+	if (status != UNZ_OK)
+	{
+		spdlog::error("Failed getting information from archive (error code: {})", status);
+		modState.state = FAILED_READING_ARCHIVE;
+		goto EXTRACTION_CLEANUP;
+	}
+
+	// Update state
+	modState.state = EXTRACTING;
+	modState.total = GetModArchiveSize(file, gi);
+	modState.progress = 0;
+
+	// Mod directory name (removing the ".zip" fom the archive name)
+	name = modPath.filename().string();
+	name = name.substr(0, name.length() - 4);
+	modDirectory = GetRemoteModFolderPath() / name;
+
+	for (int i = 0; i < gi.number_entry; i++)
+	{
+		char zipFilename[256];
+		unz_file_info64 fileInfo;
+		status = unzGetCurrentFileInfo64(file, &fileInfo, zipFilename, sizeof(zipFilename), NULL, 0, NULL, 0);
+
+		// Extract file
+		{
+			std::error_code ec;
+			fs::path fileDestination = modDirectory / zipFilename;
+			spdlog::info("=> {}", fileDestination.generic_string());
+
+			// Create parent directory if needed
+			if (!std::filesystem::exists(fileDestination.parent_path()))
+			{
+				spdlog::info("Parent directory does not exist, creating it.", fileDestination.generic_string());
+				if (!std::filesystem::create_directories(fileDestination.parent_path(), ec) && ec.value() != 0)
+				{
+					spdlog::error("Parent directory ({}) creation failed.", fileDestination.parent_path().generic_string());
+					modState.state = FAILED_WRITING_TO_DISK;
+					goto EXTRACTION_CLEANUP;
+				}
+			}
+
+			// If current file is a directory, create directory...
+			if (fileDestination.generic_string().back() == '/')
+			{
+				// Create directory
+				if (!std::filesystem::create_directory(fileDestination, ec) && ec.value() != 0)
+				{
+					spdlog::error("Directory creation failed: {}", ec.message());
+					modState.state = FAILED_WRITING_TO_DISK;
+					goto EXTRACTION_CLEANUP;
+				}
+			}
+			// ...else create file
+			else
+			{
+				// Ensure file is in zip archive
+				if (unzLocateFile(file, zipFilename, 0) != UNZ_OK)
+				{
+					spdlog::error("File \"{}\" was not found in archive.", zipFilename);
+					modState.state = FAILED_READING_ARCHIVE;
+					goto EXTRACTION_CLEANUP;
+				}
+
+				// Create file
+				const int bufferSize = 8192;
+				void* buffer;
+				int err = UNZ_OK;
+				FILE* fout = NULL;
+
+				// Open zip file to prepare its extraction
+				status = unzOpenCurrentFile(file);
+				if (status != UNZ_OK)
+				{
+					spdlog::error("Could not open file {} from archive.", zipFilename);
+					modState.state = FAILED_READING_ARCHIVE;
+					goto EXTRACTION_CLEANUP;
+				}
+
+				// Create destination file
+				fout = fopen(fileDestination.generic_string().c_str(), "wb");
+				if (fout == NULL)
+				{
+					spdlog::error("Failed creating destination file.");
+					modState.state = FAILED_WRITING_TO_DISK;
+					goto EXTRACTION_CLEANUP;
+				}
+
+				// Allocate memory for buffer
+				buffer = (void*)malloc(bufferSize);
+				if (buffer == NULL)
+				{
+					spdlog::error("Error while allocating memory.");
+					modState.state = FAILED_WRITING_TO_DISK;
+					goto EXTRACTION_CLEANUP;
+				}
+
+				// Extract file to destination
+				do
+				{
+					err = unzReadCurrentFile(file, buffer, bufferSize);
+					if (err < 0)
+					{
+						spdlog::error("error {} with zipfile in unzReadCurrentFile", err);
+						break;
+					}
+					if (err > 0)
+					{
+						if (fwrite(buffer, (unsigned)err, 1, fout) != 1)
+						{
+							spdlog::error("error in writing extracted file\n");
+							err = UNZ_ERRNO;
+							break;
+						}
+					}
+
+					// Update extraction stats
+					modState.progress += bufferSize;
+					modState.ratio = roundf(static_cast<float>(modState.progress) / modState.total * 100);
+				} while (err > 0);
+
+				if (err != UNZ_OK)
+				{
+					spdlog::error("An error occurred during file extraction (code: {})", err);
+					modState.state = FAILED_WRITING_TO_DISK;
+					goto EXTRACTION_CLEANUP;
+				}
+				err = unzCloseCurrentFile(file);
+				if (err != UNZ_OK)
+				{
+					spdlog::error("error {} with zipfile in unzCloseCurrentFile", err);
+				}
+
+				// Cleanup
+				if (fout)
+					fclose(fout);
+			}
+		}
+
+		// Go to next file
+		if ((i + 1) < gi.number_entry)
+		{
+			status = unzGoToNextFile(file);
+			if (status != UNZ_OK)
+			{
+				spdlog::error("Error while browsing archive files (error code: {}).", status);
+				goto EXTRACTION_CLEANUP;
+			}
+		}
+	}
+
+EXTRACTION_CLEANUP:
+	if (unzClose(file) != MZ_OK)
+	{
+		spdlog::error("Failed closing mod archive after extraction.");
+	}
+}
+
+void ModDownloader::DownloadMod(std::string modName, std::string modVersion)
+{
+	// Check if mod can be auto-downloaded
+	if (!IsModAuthorized(std::string_view(modName), std::string_view(modVersion)))
+	{
+		spdlog::warn("Tried to download a mod that is not verified, aborting.");
+		return;
+	}
+
+	std::thread requestThread(
+		[this, modName, modVersion]()
+		{
+			fs::path archiveLocation;
+
+			// Download mod archive
+			std::string expectedHash = verifiedMods[modName].versions[modVersion].checksum;
+			std::optional<fs::path> fetchingResult = FetchModFromDistantStore(std::string_view(modName), std::string_view(modVersion));
+			if (!fetchingResult.has_value())
+			{
+				spdlog::error("Something went wrong while fetching archive, aborting.");
+				modState.state = MOD_FETCHING_FAILED;
+				goto REQUEST_END_CLEANUP;
+			}
+			archiveLocation = fetchingResult.value();
+			if (!IsModLegit(archiveLocation, std::string_view(expectedHash)))
+			{
+				spdlog::warn("Archive hash does not match expected checksum, aborting.");
+				modState.state = MOD_CORRUPTED;
+				goto REQUEST_END_CLEANUP;
+			}
+
+			// Extract downloaded mod archive
+			ExtractMod(archiveLocation);
+
+		REQUEST_END_CLEANUP:
+			try
+			{
+				remove(archiveLocation);
+			}
+			catch (const std::exception& a)
+			{
+				spdlog::error("Error while removing downloaded archive: {}", a.what());
+			}
+
+			modState.state = DONE;
+			spdlog::info("Done downloading {}.", modName);
+		});
+
+	requestThread.detach();
+}
+
+ON_DLL_LOAD_RELIESON("engine.dll", ModDownloader, (ConCommand), (CModule module))
+{
+	g_pModDownloader = new ModDownloader();
+	g_pModDownloader->FetchModsListFromAPI();
+}
+
+ADD_SQFUNC(
+	"bool", NSIsModDownloadable, "string name, string version", "", ScriptContext::SERVER | ScriptContext::CLIENT | ScriptContext::UI)
+{
+	g_pSquirrel<context>->newarray(sqvm, 0);
+
+	const SQChar* modName = g_pSquirrel<context>->getstring(sqvm, 1);
+	const SQChar* modVersion = g_pSquirrel<context>->getstring(sqvm, 2);
+
+	bool result = g_pModDownloader->IsModAuthorized(modName, modVersion);
+	g_pSquirrel<context>->pushbool(sqvm, result);
+
+	return SQRESULT_NOTNULL;
+}
+
+ADD_SQFUNC("void", NSDownloadMod, "string name, string version", "", ScriptContext::SERVER | ScriptContext::CLIENT | ScriptContext::UI)
+{
+	const SQChar* modName = g_pSquirrel<context>->getstring(sqvm, 1);
+	const SQChar* modVersion = g_pSquirrel<context>->getstring(sqvm, 2);
+	g_pModDownloader->DownloadMod(modName, modVersion);
+
+	return SQRESULT_NOTNULL;
+}
+
+ADD_SQFUNC("ModInstallState", NSGetModInstallState, "", "", ScriptContext::SERVER | ScriptContext::CLIENT | ScriptContext::UI)
+{
+	g_pSquirrel<context>->pushnewstructinstance(sqvm, 4);
+
+	// state
+	g_pSquirrel<context>->pushinteger(sqvm, g_pModDownloader->modState.state);
+	g_pSquirrel<context>->sealstructslot(sqvm, 0);
+
+	// progress
+	g_pSquirrel<context>->pushinteger(sqvm, g_pModDownloader->modState.progress);
+	g_pSquirrel<context>->sealstructslot(sqvm, 1);
+
+	// total
+	g_pSquirrel<context>->pushinteger(sqvm, g_pModDownloader->modState.total);
+	g_pSquirrel<context>->sealstructslot(sqvm, 2);
+
+	// ratio
+	g_pSquirrel<context>->pushfloat(sqvm, g_pModDownloader->modState.ratio);
+	g_pSquirrel<context>->sealstructslot(sqvm, 3);
+
+	return SQRESULT_NOTNULL;
+}
diff --git a/primedev/mods/autodownload/moddownloader.h b/primedev/mods/autodownload/moddownloader.h
new file mode 100644
index 00000000..5302c21e
--- /dev/null
+++ b/primedev/mods/autodownload/moddownloader.h
@@ -0,0 +1,151 @@
+class ModDownloader
+{
+private:
+	const char* VERIFICATION_FLAG = "-disablemodverification";
+	const char* CUSTOM_MODS_URL_FLAG = "-customverifiedurl=";
+	const char* STORE_URL = "https://gcdn.thunderstore.io/live/repository/packages/";
+	const char* DEFAULT_MODS_LIST_URL = "https://raw.githubusercontent.com/R2Northstar/VerifiedMods/master/verified-mods.json";
+	char* modsListUrl;
+
+	struct VerifiedModVersion
+	{
+		std::string checksum;
+	};
+	struct VerifiedModDetails
+	{
+		std::string dependencyPrefix;
+		std::unordered_map<std::string, VerifiedModVersion> versions = {};
+	};
+	std::unordered_map<std::string, VerifiedModDetails> verifiedMods = {};
+
+	/**
+	 * Mod archive download callback.
+	 *
+	 * This function is called by curl as it's downloading the mod archive; this
+	 * will retrieve the current `ModDownloader` instance and update its `modState`
+	 * member accordingly.
+	 */
+	static int ModFetchingProgressCallback(
+		void* ptr, curl_off_t totalDownloadSize, curl_off_t finishedDownloadSize, curl_off_t totalToUpload, curl_off_t nowUploaded);
+
+	/**
+	 * Downloads a mod archive from distant store.
+	 *
+	 * This rebuilds the URI of the mod archive using both a predefined store URI
+	 * and the mod dependency string from the `verifiedMods` variable, or using
+	 * input mod name as mod dependency string if bypass flag is set up; fetched
+	 * archive is then stored in a temporary location.
+	 *
+	 * If something went wrong during archive download, this will return an empty
+	 * optional object.
+	 *
+	 * @param modName name of the mod to be downloaded
+	 * @param modVersion version of the mod to be downloaded
+	 * @returns location of the downloaded archive
+	 */
+	std::optional<fs::path> FetchModFromDistantStore(std::string_view modName, std::string_view modVersion);
+
+	/**
+	 * Tells if a mod archive has not been corrupted.
+	 *
+	 * The mod validation procedure includes computing the SHA256 hash of the final
+	 * archive, which is stored in the verified mods list. This hash is used by this
+	 * very method to ensure the archive downloaded from the Internet is the exact
+	 * same that has been manually verified.
+	 *
+	 * @param modPath path of the archive to check
+	 * @param expectedChecksum checksum the archive should have
+	 * @returns whether archive is legit
+	 */
+	bool IsModLegit(fs::path modPath, std::string_view expectedChecksum);
+
+	/**
+	 * Extracts a mod archive to the game folder.
+	 *
+	 * This extracts a downloaded mod archive from its original location to the
+	 * current game profile, in the remote mods folder.
+	 *
+	 * @param modPath location of the downloaded archive
+	 * @returns nothing
+	 */
+	void ExtractMod(fs::path modPath);
+
+public:
+	ModDownloader();
+
+	/**
+	 * Retrieves the verified mods list from the central authority.
+	 *
+	 * The Northstar auto-downloading feature does NOT allow automatically installing
+	 * all mods for various (notably security) reasons; mods that are candidate to
+	 * auto-downloading are rather listed on a GitHub repository
+	 * (https://raw.githubusercontent.com/R2Northstar/VerifiedMods/master/verified-mods.json),
+	 * which this method gets via a HTTP call to load into local state.
+	 *
+	 * If list fetching fails, local mods list will be initialized as empty, thus
+	 * preventing any mod from being auto-downloaded.
+	 *
+	 * @returns nothing
+	 */
+	void FetchModsListFromAPI();
+
+	/**
+	 * Checks whether a mod is verified.
+	 *
+	 * A mod is deemed verified/authorized through a manual validation process that is
+	 * described here: https://github.com/R2Northstar/VerifiedMods; in practice, a mod
+	 * is considered authorized if their name AND exact version appear in the
+	 * `verifiedMods` variable.
+	 *
+	 * @param modName name of the mod to be checked
+	 * @param modVersion version of the mod to be checked, must follow semantic versioning
+	 * @returns whether the mod is authorized and can be auto-downloaded
+	 */
+	bool IsModAuthorized(std::string_view modName, std::string_view modVersion);
+
+	/**
+	 * Downloads a given mod from Thunderstore API to local game profile.
+	 *
+	 * @param modName name of the mod to be downloaded
+	 * @param modVersion version of the mod to be downloaded
+	 * @returns nothing
+	 **/
+	void DownloadMod(std::string modName, std::string modVersion);
+
+	enum ModInstallState
+	{
+		// Normal installation process
+		DOWNLOADING,
+		CHECKSUMING,
+		EXTRACTING,
+		DONE, // Everything went great, mod can be used in-game
+
+		// Errors
+		FAILED, // Generic error message, should be avoided as much as possible
+		FAILED_READING_ARCHIVE,
+		FAILED_WRITING_TO_DISK,
+		MOD_FETCHING_FAILED,
+		MOD_CORRUPTED, // Downloaded archive checksum does not match verified hash
+		NO_DISK_SPACE_AVAILABLE,
+		NOT_FOUND // Mod is not currently being auto-downloaded
+	};
+
+	struct MOD_STATE
+	{
+		ModInstallState state;
+		int progress;
+		int total;
+		float ratio;
+	} modState = {};
+
+	/**
+	 * Cancels installation of the mod.
+	 *
+	 * Prevents installation of the mod currently being installed, no matter the install
+	 * progress (downloading, checksuming, extracting), and frees all resources currently
+	 * being used in this purpose.
+	 *
+	 * @returns nothing
+	 */
+	void CancelDownload();
+};