feat(backend/db): add function to get user's rights to a file

backend/db/files.go

@@ -12,6 +12,28 @@ import (
 	"github.com/jackc/pgx/v5"
 )
 
+// Check if user can view file
+func FileGetAccess(user_id int, file_id string) (canView, canEdit bool, err error) {
+	ctx := context.Background()
+	row := connPool.QueryRow(ctx, `
+		WITH extras AS (
+			SELECT
+				(SELECT creator_id FROM data.files WHERE id=$2)=$1 AS is_creator,
+				(SELECT is_admin FROM system.users WHERE id=$1) AS is_admin
+		)
+		SELECT
+			af.view OR (SELECT is_creator OR is_admin FROM extras),
+			af.edit OR (SELECT is_creator OR is_admin FROM extras)
+		FROM acl.files af
+		WHERE af.user_id=$1 AND af.file_id=$2
+		`, user_id, file_id)
+	err = row.Scan(&canView, &canEdit)
+	if err == pgx.ErrNoRows {
+		err = nil
+	}
+	return
+}
+
 // Get a set of files
 func FileGetSlice(user_id int, filter, sort string, limit, offset int) (files models.Slice[models.FileItem], statusCode int, err error) {
 	filterCond, statusCode, err := filterToSQL(filter)