class Database : public node::ObjectWrap {
public:

	INIT(Init) {
		v8::Local<v8::FunctionTemplate> t = NewConstructorTemplate(isolate, data, JS_new, "Database");
		SetPrototypeMethod(isolate, data, t, "prepare", JS_prepare);
		SetPrototypeMethod(isolate, data, t, "exec", JS_exec);
		SetPrototypeMethod(isolate, data, t, "pragma", JS_pragma);
		SetPrototypeMethod(isolate, data, t, "backup", JS_backup);
		SetPrototypeMethod(isolate, data, t, "function", JS_function);
		SetPrototypeMethod(isolate, data, t, "aggregate", JS_aggregate);
		SetPrototypeMethod(isolate, data, t, "loadExtension", JS_loadExtension);
		SetPrototypeMethod(isolate, data, t, "close", JS_close);
		SetPrototypeMethod(isolate, data, t, "defaultSafeIntegers", JS_defaultSafeIntegers);
		SetPrototypeMethod(isolate, data, t, "unsafeMode", JS_unsafeMode);
		SetPrototypeGetter(isolate, data, t, "open", JS_open);
		SetPrototypeGetter(isolate, data, t, "inTransaction", JS_inTransaction);
		return t->GetFunction(OnlyContext).ToLocalChecked();
	}

	// Used to support ordered containers.
	class CompareDatabase { public:
		bool operator() (Database const * const a, Database const * const b) const {
			return a < b;
		}
	};
	class CompareStatement { public:
		bool operator() (Statement const * const a, Statement const * const b) const {
			return Statement::Compare(a, b);
		}
	};
	class CompareBackup { public:
		bool operator() (Backup const * const a, Backup const * const b) const {
			return Backup::Compare(a, b);
		}
	};

	// Proper error handling logic for when an sqlite3 operation fails.
	void ThrowDatabaseError() {
		if (was_js_error) was_js_error = false;
		else ThrowSqliteError(addon, db_handle);
	}
	static void ThrowSqliteError(Addon* addon, sqlite3* db_handle) {
		assert(db_handle != NULL);
		ThrowSqliteError(addon, sqlite3_errmsg(db_handle), sqlite3_extended_errcode(db_handle));
	}
	static void ThrowSqliteError(Addon* addon, const char* message, int code) {
		assert(message != NULL);
		assert((code & 0xff) != SQLITE_OK);
		assert((code & 0xff) != SQLITE_ROW);
		assert((code & 0xff) != SQLITE_DONE);
		EasyIsolate;
		v8::Local<v8::Value> args[2] = {
			StringFromUtf8(isolate, message, -1),
			addon->cs.Code(isolate, code)
		};
		isolate->ThrowException(v8::Local<v8::Function>::New(isolate, addon->SqliteError)
			->NewInstance(OnlyContext, 2, args)
			.ToLocalChecked());
	}

	// Allows Statements to log their executed SQL.
	bool Log(v8::Isolate* isolate, sqlite3_stmt* handle) {
		assert(was_js_error == false);
		if (!has_logger) return false;
		char* expanded = sqlite3_expanded_sql(handle);
		v8::Local<v8::Value> arg = StringFromUtf8(isolate, expanded ? expanded : sqlite3_sql(handle), -1);
		was_js_error = v8::Local<v8::Function>::Cast(v8::Local<v8::Value>::New(isolate, logger))
			->Call(OnlyContext, v8::Undefined(isolate), 1, &arg)
			.IsEmpty();
		if (expanded) sqlite3_free(expanded);
		return was_js_error;
	}

	// Allow Statements to manage themselves when created and garbage collected.
	inline void AddStatement(Statement* stmt) { stmts.insert(stmts.end(), stmt); }
	inline void RemoveStatement(Statement* stmt) { stmts.erase(stmt); }

	// Allow Backups to manage themselves when created and garbage collected.
	inline void AddBackup(Backup* backup) { backups.insert(backups.end(), backup); }
	inline void RemoveBackup(Backup* backup) { backups.erase(backup); }

	// A view for Statements to see and modify Database state.
	// The order of these fields must exactly match their actual order.
	struct State {
		const bool open;
		bool busy;
		const bool safe_ints;
		const bool unsafe_mode;
		bool was_js_error;
		const bool has_logger;
		unsigned short iterators;
		Addon* const addon;
	};
	inline State* GetState() {
		return reinterpret_cast<State*>(&open);
	}
	inline sqlite3* GetHandle() {
		return db_handle;
	}
	inline Addon* GetAddon() {
		return addon;
	}

	// Whenever this is used, addon->dbs.erase() must be invoked beforehand.
	void CloseHandles() {
		if (open) {
			open = false;
			for (Statement* stmt : stmts) stmt->CloseHandles();
			for (Backup* backup : backups) backup->CloseHandles();
			stmts.clear();
			backups.clear();
			int status = sqlite3_close(db_handle);
			assert(status == SQLITE_OK); ((void)status);
		}
	}

	~Database() {
		if (open) addon->dbs.erase(this);
		CloseHandles();
	}

private:

	explicit Database(sqlite3* _db_handle, v8::Isolate* isolate, Addon* _addon, v8::Local<v8::Value> _logger) : node::ObjectWrap(),
		db_handle(_db_handle),
		open(true),
		busy(false),
		safe_ints(false),
		unsafe_mode(false),
		was_js_error(false),
		has_logger(_logger->IsFunction()),
		iterators(0),
		addon(_addon),
		logger(isolate, _logger),
		stmts(),
		backups() {
		assert(_db_handle != NULL);
		addon->dbs.insert(this);
	}

	NODE_METHOD(JS_new) {
		assert(info.IsConstructCall());
		REQUIRE_ARGUMENT_STRING(first, v8::Local<v8::String> filename);
		REQUIRE_ARGUMENT_STRING(second, v8::Local<v8::String> filenameGiven);
		REQUIRE_ARGUMENT_BOOLEAN(third, bool in_memory);
		REQUIRE_ARGUMENT_BOOLEAN(fourth, bool readonly);
		REQUIRE_ARGUMENT_BOOLEAN(fifth, bool must_exist);
		REQUIRE_ARGUMENT_INT32(sixth, int timeout);
		REQUIRE_ARGUMENT_ANY(seventh, v8::Local<v8::Value> logger);

		UseAddon;
		UseIsolate;
		sqlite3* db_handle;
		v8::String::Utf8Value utf8(isolate, filename);
		int mask = readonly ? SQLITE_OPEN_READONLY
			: must_exist ? SQLITE_OPEN_READWRITE
			: (SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE);

		if (sqlite3_open_v2(*utf8, &db_handle, mask, NULL) != SQLITE_OK) {
			ThrowSqliteError(addon, db_handle);
			int status = sqlite3_close(db_handle);
			assert(status == SQLITE_OK); ((void)status);
			return;
		}

		assert(sqlite3_db_mutex(db_handle) == NULL);
		sqlite3_extended_result_codes(db_handle, 1);
		sqlite3_busy_timeout(db_handle, timeout);
		sqlite3_limit(db_handle, SQLITE_LIMIT_LENGTH, MAX_BUFFER_SIZE < MAX_STRING_SIZE ? MAX_BUFFER_SIZE : MAX_STRING_SIZE);
		sqlite3_limit(db_handle, SQLITE_LIMIT_SQL_LENGTH, MAX_STRING_SIZE);
		int status = sqlite3_db_config(db_handle, SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION, 1, NULL);
		assert(status == SQLITE_OK);
		status = sqlite3_db_config(db_handle, SQLITE_DBCONFIG_DEFENSIVE, 1, NULL);
		assert(status == SQLITE_OK);

		UseContext;
		Database* db = new Database(db_handle, isolate, addon, logger);
		db->Wrap(info.This());
		SetFrozen(isolate, ctx, info.This(), addon->cs.memory, v8::Boolean::New(isolate, in_memory));
		SetFrozen(isolate, ctx, info.This(), addon->cs.readonly, v8::Boolean::New(isolate, readonly));
		SetFrozen(isolate, ctx, info.This(), addon->cs.name, filenameGiven);

		info.GetReturnValue().Set(info.This());
	}

	NODE_METHOD(JS_prepare) {
		REQUIRE_ARGUMENT_STRING(first, v8::Local<v8::String> source);
		(void)source;
		UseAddon;
		UseIsolate;
		v8::Local<v8::Function> c = v8::Local<v8::Function>::New(isolate, addon->Statement);
		addon->privileged_info = &info;
		v8::MaybeLocal<v8::Object> maybe_statement = c->NewInstance(OnlyContext, 0, NULL);
		addon->privileged_info = NULL;
		if (!maybe_statement.IsEmpty()) info.GetReturnValue().Set(maybe_statement.ToLocalChecked());
	}

	NODE_METHOD(JS_exec) {
		Database* db = Unwrap<Database>(info.This());
		REQUIRE_ARGUMENT_STRING(first, v8::Local<v8::String> source);
		REQUIRE_DATABASE_OPEN(db);
		REQUIRE_DATABASE_NOT_BUSY(db);
		REQUIRE_DATABASE_NO_ITERATORS_UNLESS_UNSAFE(db);
		db->busy = true;

		UseIsolate;
		v8::String::Utf8Value utf8(isolate, source);
		const char* sql = *utf8;
		const char* tail;

		int status;
		const bool has_logger = db->has_logger;
		sqlite3* const db_handle = db->db_handle;
		sqlite3_stmt* handle;

		for (;;) {
			while (IS_SKIPPED(*sql)) ++sql;
			status = sqlite3_prepare_v2(db_handle, sql, -1, &handle, &tail);
			sql = tail;
			if (!handle) break;
			if (has_logger && db->Log(isolate, handle)) {
				sqlite3_finalize(handle);
				status = -1;
				break;
			}
			do status = sqlite3_step(handle);
			while (status == SQLITE_ROW);
			status = sqlite3_finalize(handle);
			if (status != SQLITE_OK) break;
		}

		db->busy = false;
		if (status == SQLITE_OK) info.GetReturnValue().Set(info.This());
		else db->ThrowDatabaseError();
	}

	NODE_METHOD(JS_pragma) {
		REQUIRE_ARGUMENT_BOOLEAN(first, bool active);
		OnlyAddon->SetPragmaMode(active);
	}

	NODE_METHOD(JS_backup) {
		REQUIRE_ARGUMENT_STRING(first, v8::Local<v8::String> attachedName);
		REQUIRE_ARGUMENT_STRING(second, v8::Local<v8::String> destFile);
		REQUIRE_ARGUMENT_BOOLEAN(third, bool unlink);
		(void)attachedName;
		(void)destFile;
		(void)unlink;
		UseAddon;
		UseIsolate;
		v8::Local<v8::Function> c = v8::Local<v8::Function>::New(isolate, addon->Backup);
		addon->privileged_info = &info;
		v8::MaybeLocal<v8::Object> maybe_backup = c->NewInstance(OnlyContext, 0, NULL);
		addon->privileged_info = NULL;
		if (!maybe_backup.IsEmpty()) info.GetReturnValue().Set(maybe_backup.ToLocalChecked());
	}

	NODE_METHOD(JS_function) {
		Database* db = Unwrap<Database>(info.This());
		REQUIRE_ARGUMENT_FUNCTION(first, v8::Local<v8::Function> fn);
		REQUIRE_ARGUMENT_STRING(second, v8::Local<v8::String> nameString);
		REQUIRE_ARGUMENT_INT32(third, int argc);
		REQUIRE_ARGUMENT_INT32(fourth, int safe_ints);
		REQUIRE_ARGUMENT_BOOLEAN(fifth, bool deterministic);
		REQUIRE_DATABASE_OPEN(db);
		REQUIRE_DATABASE_NOT_BUSY(db);
		REQUIRE_DATABASE_NO_ITERATORS(db);

		UseIsolate;
		v8::String::Utf8Value name(isolate, nameString);
		int mask = deterministic ? SQLITE_UTF8 | SQLITE_DETERMINISTIC : SQLITE_UTF8;
		safe_ints = safe_ints < 2 ? safe_ints : static_cast<int>(db->safe_ints);

		if (sqlite3_create_function_v2(db->db_handle, *name, argc, mask, new CustomFunction(isolate, db, fn, *name, safe_ints), CustomFunction::xFunc, NULL, NULL, CustomFunction::xDestroy) != SQLITE_OK) {
			return db->ThrowDatabaseError();
		}
		info.GetReturnValue().Set(info.This());
	}

	NODE_METHOD(JS_aggregate) {
		Database* db = Unwrap<Database>(info.This());
		REQUIRE_ARGUMENT_ANY(first, v8::Local<v8::Value> start);
		REQUIRE_ARGUMENT_FUNCTION(second, v8::Local<v8::Function> step);
		REQUIRE_ARGUMENT_ANY(third, v8::Local<v8::Value> inverse);
		REQUIRE_ARGUMENT_ANY(fourth, v8::Local<v8::Value> result);
		REQUIRE_ARGUMENT_STRING(fifth, v8::Local<v8::String> nameString);
		REQUIRE_ARGUMENT_INT32(sixth, int argc);
		REQUIRE_ARGUMENT_INT32(seventh, int safe_ints);
		REQUIRE_ARGUMENT_BOOLEAN(eighth, bool deterministic);
		REQUIRE_DATABASE_OPEN(db);
		REQUIRE_DATABASE_NOT_BUSY(db);
		REQUIRE_DATABASE_NO_ITERATORS(db);

		UseIsolate;
		v8::String::Utf8Value name(isolate, nameString);
		auto xInverse = inverse->IsFunction() ? CustomAggregate::xInverse : NULL;
		auto xValue = xInverse ? CustomAggregate::xValue : NULL;
		int mask = deterministic ? SQLITE_UTF8 | SQLITE_DETERMINISTIC : SQLITE_UTF8;
		safe_ints = safe_ints < 2 ? safe_ints : static_cast<int>(db->safe_ints);

		if (sqlite3_create_window_function(db->db_handle, *name, argc, mask, new CustomAggregate(isolate, db, start, step, inverse, result, *name, safe_ints), CustomAggregate::xStep, CustomAggregate::xFinal, xValue, xInverse, CustomAggregate::xDestroy) != SQLITE_OK) {
			return db->ThrowDatabaseError();
		}
		info.GetReturnValue().Set(info.This());
	}

	NODE_METHOD(JS_loadExtension) {
		Database* db = Unwrap<Database>(info.This());
		v8::Local<v8::String> entryPoint;
		REQUIRE_ARGUMENT_STRING(first, v8::Local<v8::String> filename);
		if (info.Length() > 1) { REQUIRE_ARGUMENT_STRING(second, entryPoint); }
		REQUIRE_DATABASE_OPEN(db);
		REQUIRE_DATABASE_NOT_BUSY(db);
		REQUIRE_DATABASE_NO_ITERATORS(db);
		UseIsolate;
		char* error;
		int status = sqlite3_load_extension(
			db->db_handle,
			*v8::String::Utf8Value(isolate, filename),
			entryPoint.IsEmpty() ? NULL : *v8::String::Utf8Value(isolate, entryPoint),
			&error
		);
		if (status == SQLITE_OK) info.GetReturnValue().Set(info.This());
		else ThrowSqliteError(db->addon, error, status);
		sqlite3_free(error);
	}

	NODE_METHOD(JS_close) {
		Database* db = Unwrap<Database>(info.This());
		if (db->open) {
			REQUIRE_DATABASE_NOT_BUSY(db);
			REQUIRE_DATABASE_NO_ITERATORS(db);
			db->addon->dbs.erase(db);
			db->CloseHandles();
		}
		info.GetReturnValue().Set(info.This());
	}

	NODE_METHOD(JS_defaultSafeIntegers) {
		Database* db = Unwrap<Database>(info.This());
		if (info.Length() == 0) db->safe_ints = true;
		else { REQUIRE_ARGUMENT_BOOLEAN(first, db->safe_ints); }
		info.GetReturnValue().Set(info.This());
	}

	NODE_METHOD(JS_unsafeMode) {
		Database* db = Unwrap<Database>(info.This());
		if (info.Length() == 0) db->unsafe_mode = true;
		else { REQUIRE_ARGUMENT_BOOLEAN(first, db->unsafe_mode); }
		sqlite3_db_config(db->db_handle, SQLITE_DBCONFIG_DEFENSIVE, static_cast<int>(!db->unsafe_mode), NULL);
		info.GetReturnValue().Set(info.This());
	}

	NODE_GETTER(JS_open) {
		info.GetReturnValue().Set(Unwrap<Database>(info.This())->open);
	}

	NODE_GETTER(JS_inTransaction) {
		Database* db = Unwrap<Database>(info.This());
		info.GetReturnValue().Set(db->open && !static_cast<bool>(sqlite3_get_autocommit(db->db_handle)));
	}

	static const int MAX_BUFFER_SIZE = node::Buffer::kMaxLength > INT_MAX ? INT_MAX : static_cast<int>(node::Buffer::kMaxLength);
	static const int MAX_STRING_SIZE = v8::String::kMaxLength > INT_MAX ? INT_MAX : static_cast<int>(v8::String::kMaxLength);

	sqlite3* const db_handle;
	bool open;
	bool busy;
	bool safe_ints;
	bool unsafe_mode;
	bool was_js_error;
	const bool has_logger;
	unsigned short iterators;
	Addon* const addon;
	const CopyablePersistent<v8::Value> logger;
	std::set<Statement*, CompareStatement> stmts;
	std::set<Backup*, CompareBackup> backups;
};