CORE: REST Catalog - Response class for server provided configuration

core/src/main/java/org/apache/iceberg/rest/responses/RESTCatalogConfigResponse.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.rest.responses;
+
+import java.util.Map;
+import java.util.Objects;
+import org.apache.iceberg.relocated.com.google.common.base.MoreObjects;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableMap;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+
+/**
+ * Represents a response to requesting server-side provided configuration for the REST catalog.
+ * This allows client provided values to be overridden by the server or defaulted if not provided by the client.
+ * <p>
+ * The catalog properties, with overrides and defaults applied, should be used to configure the catalog and for all
+ * subsequent requests after this initial config request.
+ * <p>
+ * Configuration from the server consists of two sets of key/value pairs.
+ * <ul>
+ *   <li> defaults - properties that should be used as default configuration </li>
+ *   <li> overrides - properties that should be used to override client configuration </li>
+ * </ul>
+ */
+public class RESTCatalogConfigResponse {
+
+  private Map<String, String> defaults;
+  private Map<String, String> overrides;
+
+  public RESTCatalogConfigResponse() {
+    // Required for Jackson deserialization
+  }
+
+  private RESTCatalogConfigResponse(Map<String, String> defaults, Map<String, String> overrides) {
+    this.defaults = defaults;
+    this.overrides = overrides;
+    validate();
+  }
+
+  RESTCatalogConfigResponse validate() {
+    return this;
+  }
+
+  /**
+   * Properties that should be used as default configuration. {@code defaults} have the lowest priority
+   * and should be applied before the client provided configuration.
+   *
+   * @return properties that should be used as default configuration
+   */
+  public Map<String, String> defaults() {
+    return defaults != null ? defaults : ImmutableMap.of();
+  }
+
+  /**
+   * Properties that should be used to override client configuration. {@code overrides} have the highest priority
+   * and should be applied after defaults and any client-provided configuration properties.
+   *
+   * @return properties that should be given higher precedence than any client provided input
+   */
+  public Map<String, String> overrides() {
+    return overrides != null ? overrides : ImmutableMap.of();
+  }
+
+  /**
+   * Merge client-provided config with server side provided configuration to return a single
+   * properties map which will be used for instantiating and configuring the REST catalog.
+   *
+   * @param clientProperties - Client provided configuration
+   * @return Merged configuration, with precedence in the order overrides, then client properties, and then defaults.
+   */
+  public Map<String, String> merge(Map<String, String> clientProperties) {
+    Preconditions.checkNotNull(clientProperties,
+        "Cannot merge client properties with server-provided properties. Invalid client configuration: null");
+    Map<String, String> merged = Maps.newHashMap(defaults);
+    merged.putAll(clientProperties);
+    merged.putAll(overrides);
+    return ImmutableMap.copyOf(Maps.filterValues(merged, Objects::nonNull));
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("defaults", defaults)
+        .add("overrides", overrides)
+        .toString();
+  }
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public static class Builder {
+    private final Map<String, String> defaults;
+    private final Map<String, String> overrides;
+
+    private Builder() {
+      this.defaults = Maps.newHashMap();
+      this.overrides = Maps.newHashMap();
+    }
+
+    public Builder withDefault(String key, String value) {
+      Preconditions.checkNotNull(key, "Invalid default property: null");
+      defaults.put(key, value);
+      return this;
+    }
+
+    public Builder withOverride(String key, String value) {
+      Preconditions.checkNotNull(key, "Invalid override property: null");
+      overrides.put(key, value);
+      return this;
+    }
+
+    /**
+     * Adds the passed in map entries to the existing `defaults` of this Builder.
+     */
+    public Builder withDefaults(Map<String, String> defaultsToAdd) {
+      Preconditions.checkNotNull(defaultsToAdd, "Invalid default properties map: null");
+      Preconditions.checkArgument(!defaultsToAdd.containsKey(null), "Invalid default property: null");
+      defaults.putAll(defaultsToAdd);
+      return this;
+    }
+
+    /**
+     * Adds the passed in map entries to the existing `overrides` of this Builder.
+     */
+    public Builder withOverrides(Map<String, String> overridesToAdd) {
+      Preconditions.checkNotNull(overridesToAdd, "Invalid override properties map: null");
+      Preconditions.checkArgument(!overridesToAdd.containsKey(null), "Invalid override property: null");
+      overrides.putAll(overridesToAdd);
+      return this;
+    }
+
+    public RESTCatalogConfigResponse build() {
+      return new RESTCatalogConfigResponse(defaults, overrides);
+    }
+  }
+}