/*
 * 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.hadoop.hbase.client;

import static org.apache.hadoop.hbase.HConstants.EMPTY_END_ROW;
import static org.apache.hadoop.hbase.HConstants.EMPTY_START_ROW;
import static org.apache.hadoop.hbase.client.ConnectionUtils.createScanResultCache;
import static org.apache.hadoop.hbase.client.ConnectionUtils.getLocateType;
import static org.apache.hadoop.hbase.client.ConnectionUtils.incMillisBetweenNextsMetrics;
import static org.apache.hadoop.hbase.client.ConnectionUtils.incRPCCallsMetrics;
import static org.apache.hadoop.hbase.client.ConnectionUtils.incRPCRetriesMetrics;
import static org.apache.hadoop.hbase.client.ConnectionUtils.incRegionCountMetrics;
import static org.apache.hadoop.hbase.client.ConnectionUtils.isRemote;
import static org.apache.hadoop.hbase.client.ConnectionUtils.timelineConsistentRead;
import static org.apache.hadoop.hbase.util.FutureUtils.addListener;

import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.StatusCode;
import io.opentelemetry.context.Scope;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
import org.apache.hadoop.hbase.client.trace.TableOperationSpanBuilder;
import org.apache.hadoop.hbase.ipc.HBaseRpcController;
import org.apache.hadoop.hbase.trace.TraceUtil;
import org.apache.yetus.audience.InterfaceAudience;

import org.apache.hbase.thirdparty.io.netty.util.Timer;

import org.apache.hadoop.hbase.shaded.protobuf.RequestConverter;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ClientService;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ClientService.Interface;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ScanRequest;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ScanResponse;

/**
 * The asynchronous client scanner implementation.
 * <p>
 * Here we will call OpenScanner first and use the returned scannerId to create a
 * {@link AsyncScanSingleRegionRpcRetryingCaller} to do the real scan operation. The return value of
 * {@link AsyncScanSingleRegionRpcRetryingCaller} will tell us whether open a new scanner or finish
 * scan.
 */
@InterfaceAudience.Private
class AsyncClientScanner {

  // We will use this scan object during the whole scan operation. The
  // AsyncScanSingleRegionRpcRetryingCaller will modify this scan object directly.
  private final Scan scan;

  private final ScanMetrics scanMetrics;

  private final AdvancedScanResultConsumer consumer;

  private final TableName tableName;

  private final AsyncConnectionImpl conn;

  private final Timer retryTimer;

  private final long pauseNs;

  private final long pauseNsForServerOverloaded;

  private final int maxAttempts;

  private final long scanTimeoutNs;

  private final long rpcTimeoutNs;

  private final int startLogErrorsCnt;

  private final ScanResultCache resultCache;

  private final Span span;

  private final Map<String, byte[]> requestAttributes;

  private final boolean isScanMetricsByRegionEnabled;

  public AsyncClientScanner(Scan scan, AdvancedScanResultConsumer consumer, TableName tableName,
    AsyncConnectionImpl conn, Timer retryTimer, long pauseNs, long pauseNsForServerOverloaded,
    int maxAttempts, long scanTimeoutNs, long rpcTimeoutNs, int startLogErrorsCnt,
    Map<String, byte[]> requestAttributes) {
    if (scan.getStartRow() == null) {
      scan.withStartRow(EMPTY_START_ROW, scan.includeStartRow());
    }
    if (scan.getStopRow() == null) {
      scan.withStopRow(EMPTY_END_ROW, scan.includeStopRow());
    }
    this.scan = scan;
    this.consumer = consumer;
    this.tableName = tableName;
    this.conn = conn;
    this.retryTimer = retryTimer;
    this.pauseNs = pauseNs;
    this.pauseNsForServerOverloaded = pauseNsForServerOverloaded;
    this.maxAttempts = maxAttempts;
    this.scanTimeoutNs = scanTimeoutNs;
    this.rpcTimeoutNs = rpcTimeoutNs;
    this.startLogErrorsCnt = startLogErrorsCnt;
    this.resultCache = createScanResultCache(scan);
    this.requestAttributes = requestAttributes;
    boolean isScanMetricsByRegionEnabled = false;
    if (scan.isScanMetricsEnabled()) {
      this.scanMetrics = new ScanMetrics();
      consumer.onScanMetricsCreated(scanMetrics);
      if (this.scan.isScanMetricsByRegionEnabled()) {
        isScanMetricsByRegionEnabled = true;
      }
    } else {
      this.scanMetrics = null;
    }
    this.isScanMetricsByRegionEnabled = isScanMetricsByRegionEnabled;

    /*
     * Assumes that the `start()` method is called immediately after construction. If this is no
     * longer the case, for tracing correctness, we should move the start of the span into the
     * `start()` method. The cost of doing so would be making access to the `span` safe for
     * concurrent threads.
     */
    span = new TableOperationSpanBuilder(conn).setTableName(tableName).setOperation(scan).build();
    if (consumer instanceof AsyncTableResultScanner) {
      AsyncTableResultScanner scanner = (AsyncTableResultScanner) consumer;
      scanner.setSpan(span);
    }
  }

  private static final class OpenScannerResponse {

    public final HRegionLocation loc;

    public final boolean isRegionServerRemote;

    public final ClientService.Interface stub;

    public final HBaseRpcController controller;

    public final ScanResponse resp;

    public OpenScannerResponse(HRegionLocation loc, boolean isRegionServerRemote, Interface stub,
      HBaseRpcController controller, ScanResponse resp) {
      this.loc = loc;
      this.isRegionServerRemote = isRegionServerRemote;
      this.stub = stub;
      this.controller = controller;
      this.resp = resp;
    }
  }

  private final AtomicInteger openScannerTries = new AtomicInteger();

  private CompletableFuture<OpenScannerResponse> callOpenScanner(HBaseRpcController controller,
    HRegionLocation loc, ClientService.Interface stub) {
    try (Scope ignored = span.makeCurrent()) {
      boolean isRegionServerRemote = isRemote(loc.getHostname());
      incRPCCallsMetrics(scanMetrics, isRegionServerRemote);
      if (openScannerTries.getAndIncrement() > 1) {
        incRPCRetriesMetrics(scanMetrics, isRegionServerRemote);
      }
      CompletableFuture<OpenScannerResponse> future = new CompletableFuture<>();
      try {
        ScanRequest request = RequestConverter.buildScanRequest(loc.getRegion().getRegionName(),
          scan, scan.getCaching(), false);
        stub.scan(controller, request, resp -> {
          try (Scope ignored1 = span.makeCurrent()) {
            if (controller.failed()) {
              final IOException e = controller.getFailed();
              future.completeExceptionally(e);
              TraceUtil.setError(span, e);
              span.end();
              return;
            }
            future
              .complete(new OpenScannerResponse(loc, isRegionServerRemote, stub, controller, resp));
          }
        });
      } catch (IOException e) {
        // span is closed by listener attached to the Future in `openScanner()`
        future.completeExceptionally(e);
      }
      return future;
    }
  }

  // lastNextCallNanos is used to calculate the MILLIS_BETWEEN_NEXTS scan metrics
  private void startScan(OpenScannerResponse resp, long lastNextCallNanos) {
    AsyncScanSingleRegionRpcRetryingCaller scanSingleRegionCaller =
      conn.callerFactory.scanSingleRegion().id(resp.resp.getScannerId()).location(resp.loc)
        .remote(resp.isRegionServerRemote)
        .scannerLeaseTimeoutPeriod(resp.resp.getTtl(), TimeUnit.MILLISECONDS).stub(resp.stub)
        .setScan(scan).metrics(scanMetrics).consumer(consumer).resultCache(resultCache)
        .rpcTimeout(rpcTimeoutNs, TimeUnit.NANOSECONDS)
        .scanTimeout(scanTimeoutNs, TimeUnit.NANOSECONDS).pause(pauseNs, TimeUnit.NANOSECONDS)
        .lastNextCallNanos(lastNextCallNanos)
        .pauseForServerOverloaded(pauseNsForServerOverloaded, TimeUnit.NANOSECONDS)
        .maxAttempts(maxAttempts).startLogErrorsCnt(startLogErrorsCnt)
        .setRequestAttributes(requestAttributes).build();
    addListener(scanSingleRegionCaller.start(resp.controller, resp.resp), (hasMore, error) -> {
      try (Scope ignored = span.makeCurrent()) {
        if (error != null) {
          try {
            consumer.onError(error);
            return;
          } finally {
            TraceUtil.setError(span, error);
            span.end();
          }
        }
        if (hasMore) {
          openScanner(scanSingleRegionCaller);
        } else {
          try {
            consumer.onComplete();
          } finally {
            span.setStatus(StatusCode.OK);
            span.end();
          }
        }
      }
    });
  }

  private CompletableFuture<OpenScannerResponse> openScanner(int replicaId) {
    try (Scope ignored = span.makeCurrent()) {
      return conn.callerFactory.<OpenScannerResponse> single().table(tableName)
        .row(scan.getStartRow()).replicaId(replicaId).locateType(getLocateType(scan))
        .priority(scan.getPriority()).rpcTimeout(rpcTimeoutNs, TimeUnit.NANOSECONDS)
        .operationTimeout(scanTimeoutNs, TimeUnit.NANOSECONDS).pause(pauseNs, TimeUnit.NANOSECONDS)
        .pauseForServerOverloaded(pauseNsForServerOverloaded, TimeUnit.NANOSECONDS)
        .maxAttempts(maxAttempts).startLogErrorsCnt(startLogErrorsCnt)
        .setRequestAttributes(requestAttributes).action(this::callOpenScanner).call();
    }
  }

  private long getPrimaryTimeoutNs() {
    return TableName.isMetaTableName(tableName)
      ? conn.connConf.getPrimaryMetaScanTimeoutNs()
      : conn.connConf.getPrimaryScanTimeoutNs();
  }

  private void openScanner(AsyncScanSingleRegionRpcRetryingCaller previousScanSingleRegionCaller) {
    if (this.isScanMetricsByRegionEnabled) {
      scanMetrics.moveToNextRegion();
    }
    incRegionCountMetrics(scanMetrics);
    long openScannerStartNanos = System.nanoTime();
    if (previousScanSingleRegionCaller != null) {
      // open scanner is also a next call
      incMillisBetweenNextsMetrics(scanMetrics, TimeUnit.NANOSECONDS
        .toMillis(openScannerStartNanos - previousScanSingleRegionCaller.getLastNextCallNanos()));
    }
    openScannerTries.set(1);
    addListener(timelineConsistentRead(conn.getLocator(), tableName, scan, scan.getStartRow(),
      getLocateType(scan), this::openScanner, rpcTimeoutNs, getPrimaryTimeoutNs(), retryTimer,
      conn.getConnectionMetrics()), (resp, error) -> {
        try (Scope ignored = span.makeCurrent()) {
          if (error != null) {
            try {
              consumer.onError(error);
              return;
            } finally {
              TraceUtil.setError(span, error);
              span.end();
            }
          }
          if (this.isScanMetricsByRegionEnabled) {
            HRegionLocation loc = resp.loc;
            this.scanMetrics.initScanMetricsRegionInfo(loc.getRegion().getEncodedName(),
              loc.getServerName());
          }
          startScan(resp, openScannerStartNanos);
        }
      });
  }

  public void start() {
    try (Scope ignored = span.makeCurrent()) {
      openScanner(null);
    }
  }
}