adding resolver for NBIO cache

nb-api/src/main/java/io/nosqlbench/nb/api/nbio/ResolverForNBIOCache.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package io.nosqlbench.nb.api.nbio;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.net.URI;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+public class ResolverForNBIOCache implements ContentResolver {
+    public static final ResolverForNBIOCache INSTANCE = new ResolverForNBIOCache();
+    private final static Logger logger = LogManager.getLogger(ResolverForNBIOCache.class);
+    //TODO: This needs to be set somehow - envvar, yaml setting, etc.
+    private static final String cache = "/tmp/nbio-cache";
+    @Override
+    public List<Content<?>> resolve(URI uri) {
+        List<Content<?>> contents = new ArrayList<>();
+        Path path = resolvePath(uri);
+
+        if (path != null) {
+            contents.add(new PathContent(path));
+        }
+        return contents;
+    }
+
+    private Path resolvePath(URI uri) {
+        /*
+         * 1st time through this will just be the name of the file. On the second path it will include the full
+         * URI, including the scheme (eg file:/// or https://, etc.). Since we need to at least verify the
+         * existence of the remote file, and more typically compare checksums, we don't do anything until
+         * we get the full URI
+         */
+        if (uri.getScheme() != null && !uri.getScheme().isEmpty() &&
+            (uri.getScheme().equalsIgnoreCase("http") ||
+                uri.getScheme().equalsIgnoreCase("https"))) {
+
+            Path cachePath = Path.of(cache + uri.getPath());
+            if (Files.isReadable(cachePath)) {
+                return pathFromLocalCache(cachePath, uri);
+            }
+            else {
+                return pathFromRemoteUrl(uri);
+            }
+        }
+        return null;
+    }
+
+    private Path pathFromRemoteUrl(URI uri) {
+        URLContent urlContent = resolveURI(uri);
+        /*
+         * File is not in cache - next steps:
+         * 1. Download the file and put it in the cache
+         *   1a. If the remote file does not exist throw an exception
+         *   1b. If the download fails jump to step 6
+         * 2. Download the checksum and put it in the cache
+         * 3. Generate a new checksum for the file
+         * 4. compare the checksums
+         * 5. If they match, return the path to the file in the cache
+         * 6. If they don't match/exception downloading repeat steps 1-5 up to a configurable number of times
+         *   6a. If the max attempts have been exceeded throw an exception and clean up the cache
+         */
+        return null;
+    }
+
+    private Path pathFromLocalCache(Path cachePath, URI uri) {
+        /*
+         * File is in cache - next steps:
+         * 1. Check "force update" option
+         *   1a. If true remove file from cache and go to "File is not in cache" operations
+         *   1b. If not specified default to false
+         * 2. Check for existence of remote file
+         *   2a. If the remote file does not exist generate warning message and return local file
+         * 3. Check "checksum verification" option (default = true)
+         *   3a. If false generate warning message and return local file
+         * 4. If a local checksum exists compare it against the remote checksum
+         *   4a. If none exists generate a new one and compare it against the remote checksum
+         * 5. If checksums match return the local file
+         * 6. If checksums do not match remove the local file and go to "File is not in cache" operations
+         */
+        return null;
+    }
+
+    private URLContent resolveURI(URI uri) {
+        return null;
+    }
+
+    @Override
+    public List<Path> resolveDirectory(URI uri) {
+        List<Path> dirs = new ArrayList<>();
+
+        Path path = resolvePath(uri);
+        if (path!=null && Files.isDirectory(path)) {
+            dirs.add(path);
+        }
+        return dirs;
+    }
+}