More robust s3 path resolve

src/main/java/org/carlspring/cloud/storage/s3fs/S3Path.java

@@ -32,6 +32,7 @@ public class S3Path
 
     public static final String PATH_SEPARATOR = "/";
     public static final String PATH_OTHER_INSTANCE_MESSAGE = "other must be an instance of %s";
+    public static final String PATH_OTHER_INSTANCE_OR_RELATIVE_MESSAGE = "other must be an instance of %s or a relative Path";
 
     /**
      * S3FileStore which represents the Bucket this path resides in.
@@ -444,16 +445,34 @@ public Path normalize()
     @Override
     public Path resolve(Path other)
     {
+        String otherUri = "";
         if (other.isAbsolute())
         {
             Preconditions.checkArgument(other instanceof S3Path,
-                                        PATH_OTHER_INSTANCE_MESSAGE,
+                                        PATH_OTHER_INSTANCE_OR_RELATIVE_MESSAGE,
                                         S3Path.class.getName());
 
             return other;
         }
+        else if (other instanceof S3Path)
+        {
+            S3Path otherS3Path = (S3Path) other;
+            otherUri = otherS3Path.uri;
+        }
+        else
+        {
+            int nameCount = other.getNameCount();
+            for (int i = 0; i < nameCount; i++)
+            {
+                if (i > 0)
+                {
+                    otherUri += PATH_SEPARATOR;
+                }
+
+                otherUri += other.getName(i);
+            }
+        }
 
-        S3Path otherS3Path = (S3Path) other;
         StringBuilder pathBuilder = new StringBuilder();
 
         if (this.isAbsolute())
@@ -463,9 +482,9 @@ public Path resolve(Path other)
 
         pathBuilder.append(this.uri);
 
-        if (!otherS3Path.uri.isEmpty())
+        if (!otherUri.isEmpty())
         {
-            pathBuilder.append(PATH_SEPARATOR + otherS3Path.uri);
+            pathBuilder.append(PATH_SEPARATOR + otherUri);
         }
 
         return new S3Path(this.fileSystem, pathBuilder.toString());

src/test/java/org/carlspring/cloud/storage/s3fs/path/ResolveTest.java

@@ -6,12 +6,14 @@
 import org.carlspring.cloud.storage.s3fs.util.S3EndpointConstant;
 
 import java.io.IOException;
+import java.nio.file.Paths;
 
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import static org.carlspring.cloud.storage.s3fs.util.S3EndpointConstant.S3_GLOBAL_URI_TEST;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 class ResolveTest
         extends S3UnitTestBase
@@ -64,4 +66,34 @@ void resolve()
         assertEquals(getPath("/bucket2/other/child"), getPath("/bucket/path/to/file").resolve("/bucket2/other/child"));
     }
 
+
+    @Test
+    void nonS3Paths()
+    {
+        S3Path parent = getPath("/bucket");
+        S3Path child = getPath("/bucket/rabbit");
+        S3Path deepChild = getPath("/bucket/rabbit/in/space");
+        S3Path resolved = (S3Path) parent.resolve(child);
+
+        assertEquals(child, resolved);
+
+        resolved = (S3Path) parent.resolve("rabbit");
+        assertEquals(child, resolved);
+
+        resolved = (S3Path) parent.resolve(Paths.get("rabbit")); //unixPath
+        assertEquals(child, resolved);
+
+        resolved = (S3Path) parent.resolve(Paths.get("rabbit").resolve("in").resolve("space"));
+        assertEquals(deepChild, resolved);
+
+        resolved = (S3Path) parent.resolve(Paths.get("./rabbit")); //unixPath
+        assertEquals("s3://s3.test.amazonaws.com/bucket/./rabbit", resolved.toString());
+
+        resolved = (S3Path) parent.resolve(Paths.get("./rabbit in space")); //unixPath
+        assertEquals("s3://s3.test.amazonaws.com/bucket/./rabbit%20in%20space", resolved.toString());
+
+        IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () ->
+                parent.resolve(Paths.get("tempDirectory").toAbsolutePath()));
+        assertEquals("other must be an instance of org.carlspring.cloud.storage.s3fs.S3Path or a relative Path", e.getMessage());
+    }
 }