1 files changed, 151 insertions, 0 deletions
diff --git a/primedev/mods/autodownload/moddownloader.h b/primedev/mods/autodownload/moddownloader.h
new file mode 100644
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--- /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();
+};