Add Store.open() method

It automatically determines whether to use a DiskStore or FlatFileStore.

Signed-off-by: Graham <gpe@openrs2.dev>

cache/src/main/java/dev/openrs2/cache/DiskStore.kt

@@ -462,7 +462,7 @@ public class DiskStore private constructor(
         private const val INDEX_BUFFER_SIZE = INDEX_ENTRY_SIZE * 1000
         private const val DATA_BUFFER_SIZE = BLOCK_SIZE * 10
 
-        private fun dataPath(root: Path): Path {
+        internal fun dataPath(root: Path): Path {
             return root.resolve("main_file_cache.dat2")
         }
 

cache/src/main/java/dev/openrs2/cache/Store.kt

@@ -5,6 +5,8 @@ import java.io.Closeable
 import java.io.FileNotFoundException
 import java.io.Flushable
 import java.io.IOException
+import java.nio.file.Files
+import java.nio.file.Path
 
 /**
  * A low-level interface for reading and writing raw groups directly to and
@@ -118,5 +120,19 @@ public interface Store : Flushable, Closeable {
          * The maximum length of a group's contents in bytes.
          */
         public const val MAX_GROUP_SIZE: Int = (1 shl 24) - 1
+
+        /**
+         * Opens a [Store], automatically detecting the type based on the
+         * presence or absence of the `main_file_cache.dat2` file.
+         * @param root the store's root directory.
+         * @throws IOException if an underlying I/O error occurs.
+         */
+        public fun open(root: Path): Store {
+            return if (Files.isRegularFile(DiskStore.dataPath(root))) {
+                DiskStore.open(root)
+            } else {
+                FlatFileStore.open(root)
+            }
+        }
     }
 }

cache/src/test/java/dev/openrs2/cache/StoreTest.kt

@@ -0,0 +1,21 @@
+package dev.openrs2.cache
+
+import java.nio.file.Paths
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+object StoreTest {
+    private val DISK_ROOT = Paths.get(StoreTest::class.java.getResource("disk-store/empty").toURI())
+    private val FLAT_FILE_ROOT = Paths.get(StoreTest::class.java.getResource("flat-file-store/empty").toURI())
+
+    @Test
+    fun testOpen() {
+        Store.open(DISK_ROOT).use { store ->
+            assertTrue(store is DiskStore)
+        }
+
+        Store.open(FLAT_FILE_ROOT).use { store ->
+            assertTrue(store is FlatFileStore)
+        }
+    }
+}