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// Copyright 2015-2024 Nstream, inc.
//
// Licensed under the Redis Source Available License 2.0 (RSALv2) Agreement;
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://redis.com/legal/rsalv2-agreement/
//
// 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 nstream.adapter.common.patches;

import java.util.Map;
import nstream.adapter.common.NstreamAgent;
import swim.api.SwimLane;
import swim.api.lane.CommandLane;
import swim.api.lane.MapLane;
import swim.structure.Selector;
import swim.structure.Value;

public class HistoryPatch extends NstreamAgent {

  public HistoryPatch() {
  }

  protected long extractEpochMillisFromEvent(Value event) {
    final Value extractDef = getProp("extractEpochMillisFromEvent");
    if (extractDef.isDistinct() && extractDef instanceof Selector) {
      return extractDef.evaluate(event).longValue();
    } else {
      return defaultExtractEpochMillisFromEvent(event);
    }
  }

  protected long defaultExtractEpochMillisFromEvent(Value event) {
    return System.currentTimeMillis();
  }

  protected Value extractValueFromEvent(Value event) {
    final Value extractDef = getProp("extractValueFromEvent");
    if (extractDef.isDistinct() && extractDef instanceof Selector) {
      return extractDef.evaluate(event).toValue();
    } else {
      return defaultExtractValueFromEvent(event);
    }
  }

  protected Value defaultExtractValueFromEvent(Value event) {
    return event;
  }

  protected boolean shouldDropOldEntry(Map.Entry entry) {
    return false;
  }

  protected int maxHistorySize() {
    return getProp("maxHistorySize").intValue(Integer.MAX_VALUE);
  }

  protected void clearUnwantedHistory() {
    int dropCount = 0;
    for (Map.Entry entry : this.history.entrySet()) {
      while (shouldDropOldEntry(entry)) {
        dropCount++;
      }
    }
    dropCount = Math.max(this.history.size() - maxHistorySize(), dropCount);
    this.history.drop(dropCount);
  }

  @SwimLane("history")
  protected MapLane history = this.mapLane()
      .didUpdate((k, n, o) -> {
        trace("(HistoryPatch) " + nodeUri() + ".history#didUpdate(): "
            + "key=" + k + ", newValue=" + n + ", oldValue=" + o);
        clearUnwantedHistory();
      })
      .didDrop(lower -> {
        info("(HistoryPatch) " + nodeUri() + ".history#didDrop(): "
            + "lower=" + lower);
      });

  @SwimLane("addEvent")
  protected CommandLane addEvent = this.commandLane()
      .onCommand(v -> {
        trace("(HistoryPatch) " + nodeUri()
            + ".addEvent#onCommand(): value=" + v);
        this.history.put(extractEpochMillisFromEvent(v), extractValueFromEvent(v));
      });

  @Override
  public void didStart() {
    info("(HistoryPatch) " + nodeUri() + ": didStart");
  }
}