// Copyright 2018 The Bazel Authors. All rights reserved.
//
// 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 com.google.devtools.build.lib.runtime;

import com.google.common.collect.ConcurrentHashMultiset;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Multiset;
import com.google.devtools.build.lib.actions.ActionResult;
import com.google.devtools.build.lib.actions.SpawnResult;
import com.google.devtools.build.lib.actions.cache.Protos.ActionCacheStatistics;
import com.google.devtools.build.lib.util.StringUtil;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import javax.annotation.concurrent.ThreadSafe;

/** Collects results from SpawnResult. */
@ThreadSafe
public class SpawnStats {
  private static final ImmutableList<String> REPORT_FIRST =
      ImmutableList.of("disk cache hit", "remote cache hit");

  private final ConcurrentHashMultiset<String> runners = ConcurrentHashMultiset.create();
  private final ConcurrentHashMap<String, String> runnerExecKinds = new ConcurrentHashMap<>();
  private final AtomicLong totalWallTimeMillis = new AtomicLong();
  // Counts all actions, where an action can run an arbitrary number of spawns (including zero).
  private final AtomicInteger allActionsCount = new AtomicInteger();
  // Counts internal actions, such as SymlinkTree actions, which are recognized by having zero
  // spawns.
  private final AtomicInteger nonInternalActionsCount = new AtomicInteger();
  private int actionCacheHitCount = 0;

  public void countActionResult(ActionResult actionResult) {
    // This method is usually not called for internal actions with {@link ActionResult#EMPTY}, but
    // just in case, we double-check here.
    if (!actionResult.spawnResults().isEmpty()) {
      nonInternalActionsCount.incrementAndGet();
    }
    for (SpawnResult r : actionResult.spawnResults()) {
      storeRunnerExecKind(r);
      runners.add(r.getRunnerName());
      totalWallTimeMillis.addAndGet(r.getMetrics().executionWallTimeInMs());
    }
  }

  private void storeRunnerExecKind(SpawnResult r) {
    String name = r.getRunnerName();
    String execKind = r.getMetrics().execKind().toString();
    runnerExecKinds.put(name, execKind);
  }

  public void incrementActionCount() {
    allActionsCount.incrementAndGet();
  }

  public long getTotalWallTimeMillis() {
    return totalWallTimeMillis.get();
  }

  public void recordActionCacheStats(ActionCacheStatistics actionCacheStatistics) {
    actionCacheHitCount = actionCacheStatistics.getHits();
  }

  /*
   * Returns a human-readable summary of spawns counted.
   */
  public ImmutableMap<String, Integer> getSummary() {
    return getSummary(REPORT_FIRST);
  }

  /*
   * Returns a human-readable summary of spawns counted.
   */
  public ImmutableMap<String, Integer> getSummary(ImmutableList<String> reportFirst) {
    ImmutableMap.Builder<String, Integer> result = ImmutableMap.builder();
    int numNonInternalActions = nonInternalActionsCount.get();
    int numAllActions = allActionsCount.get();
    result.put("total", numAllActions);

    // First report cache results.
    if (actionCacheHitCount > 0) {
      result.put("action cache hit", actionCacheHitCount);
    }
    for (String s : reportFirst) {
      int count = runners.setCount(s, 0);
      if (count > 0) {
        result.put(s, count);
      }
    }

    // Account for internal actions such as SymlinkTree.
    // This condition is always fulfilled if {@link #incrementActionCount} is called for each
    // action for which {@link #countActionResult} is called eventually.
    if (numNonInternalActions < numAllActions) {
      result.put("internal", numAllActions - numNonInternalActions);
    }

    // Sort the rest alphabetically
    ArrayList<Multiset.Entry<String>> list = new ArrayList<>(runners.entrySet());
    Collections.sort(list, Comparator.comparing(e -> e.getElement()));

    for (Multiset.Entry<String> e : list) {
      result.put(e.getElement(), e.getCount());
    }

    return result.buildOrThrow();
  }

  public String getExecKindFor(String runnerName) {
    return runnerExecKinds.getOrDefault(runnerName, null);
  }

  public static String convertSummaryToString(ImmutableMap<String, Integer> spawnSummary) {
    // This summary is misleading in a number of ways:
    // - The "processes" count is actually the number of actions, not spawns.
    // - Even if it were the number of spawns, the "* cache hit" runners do not correspond to
    //   processes executed, but rather to cache hits that avoided process execution.
    // - The total count does not include action cache hits, so the sum of the parts is greater than
    //   the total.
    // TODO: Find a better way to report this information, e.g.:
    // 15 cache hits (5 action, 5 disk, 5 remote), 10 processes (2 local, 3 remote, 5 sandboxed), 7
    // internal.
    // A large number of integration tests rely on the current format, though, so changing it is
    // non-trivial.
    Integer total = spawnSummary.get("total");
    if (total == 0) {
      return "0 processes.";
    }

    StringBuilder stringSummary = new StringBuilder();
    stringSummary.append(StringUtil.formatCount(total)).append(" process");
    if (total > 1) {
      stringSummary.append("es");
    }
    String separator = ": ";

    for (Map.Entry<String, Integer> runnerStats : spawnSummary.entrySet()) {
      if ("total".equals(runnerStats.getKey())) {
        continue;
      }
      stringSummary.append(separator);
      separator = ", ";
      stringSummary
          .append(StringUtil.formatCount(runnerStats.getValue()))
          .append(' ')
          .append(runnerStats.getKey());
    }
    stringSummary.append('.');
    return stringSummary.toString();
  }
}
