[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

internal/db/sqlite/errors.go

@@ -0,0 +1,62 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !wasmsqlite3
+
+package sqlite
+
+import (
+	"database/sql/driver"
+	"fmt"
+
+	"modernc.org/sqlite"
+	sqlite3 "modernc.org/sqlite/lib"
+
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+)
+
+// processSQLiteError processes an sqlite3.Error to
+// handle conversion to any of our common db types.
+func processSQLiteError(err error) error {
+	// Attempt to cast as sqlite error.
+	sqliteErr, ok := err.(*sqlite.Error)
+	if !ok {
+		return err
+	}
+
+	// Handle supplied error code:
+	switch sqliteErr.Code() {
+	case sqlite3.SQLITE_CONSTRAINT_UNIQUE,
+		sqlite3.SQLITE_CONSTRAINT_PRIMARYKEY:
+		return db.ErrAlreadyExists
+
+	// Busy should be very rare, but
+	// on busy tell the database to close
+	// the connection, re-open and re-attempt
+	// which should give a necessary timeout.
+	case sqlite3.SQLITE_BUSY,
+		sqlite3.SQLITE_BUSY_RECOVERY,
+		sqlite3.SQLITE_BUSY_SNAPSHOT:
+		return driver.ErrBadConn
+	}
+
+	// Wrap the returned error with the code and
+	// extended code for easier debugging later.
+	return fmt.Errorf("%w (code=%d)", err,
+		sqliteErr.Code(),
+	)
+}