package io.prometheus.metrics.model.snapshots;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/** Immutable snapshot of a Counter. */
public class CounterSnapshot extends MetricSnapshot {

  /**
   * To create a new {@link CounterSnapshot}, you can either call the constructor directly or use
   * the builder with {@link CounterSnapshot#builder()}.
   *
   * @param metadata the metric name in metadata must not include the {@code _total} suffix. See
   *     {@link MetricMetadata} for more naming conventions.
   * @param dataPoints the constructor will create a sorted copy of the collection.
   */
  public CounterSnapshot(MetricMetadata metadata, Collection<CounterDataPointSnapshot> dataPoints) {
    super(metadata, dataPoints);
  }

  @SuppressWarnings("unchecked")
  @Override
  public List<CounterDataPointSnapshot> getDataPoints() {
    return (List<CounterDataPointSnapshot>) dataPoints;
  }

  public static class CounterDataPointSnapshot extends DataPointSnapshot {

    private final double value;
    private final Exemplar exemplar; // may be null

    /**
     * To create a new {@link CounterDataPointSnapshot}, you can either call the constructor
     * directly or use the Builder with {@link CounterDataPointSnapshot#builder()}.
     *
     * @param value the counter value. Must not be negative.
     * @param labels must not be null. Use {@link Labels#EMPTY} if there are no labels.
     * @param exemplar may be null.
     * @param createdTimestampMillis timestamp (as in {@link System#currentTimeMillis()}) when the
     *     time series (this specific set of labels) was created (or reset to zero). It's optional.
     *     Use {@code 0L} if there is no created timestamp.
     */
    public CounterDataPointSnapshot(
        double value, Labels labels, Exemplar exemplar, long createdTimestampMillis) {
      this(value, labels, exemplar, createdTimestampMillis, 0);
    }

    /**
     * Constructor with an additional scrape timestamp. This is only useful in rare cases as the
     * scrape timestamp is usually set by the Prometheus server during scraping. Exceptions include
     * mirroring metrics with given timestamps from other metric sources.
     */
    @SuppressWarnings("this-escape")
    public CounterDataPointSnapshot(
        double value,
        Labels labels,
        Exemplar exemplar,
        long createdTimestampMillis,
        long scrapeTimestampMillis) {
      super(labels, createdTimestampMillis, scrapeTimestampMillis);
      this.value = value;
      this.exemplar = exemplar;
      validate();
    }

    public double getValue() {
      return value;
    }

    /** May be {@code null}. */
    public Exemplar getExemplar() {
      return exemplar;
    }

    protected void validate() {
      if (value < 0.0) {
        throw new IllegalArgumentException(value + ": counters cannot have a negative value");
      }
    }

    public static Builder builder() {
      return new Builder();
    }

    public static class Builder extends DataPointSnapshot.Builder<Builder> {

      private Exemplar exemplar = null;
      private Double value = null;
      private long createdTimestampMillis = 0L;

      private Builder() {}

      /** Counter value. This is required. The value must not be negative. */
      public Builder value(double value) {
        this.value = value;
        return this;
      }

      public Builder exemplar(Exemplar exemplar) {
        this.exemplar = exemplar;
        return this;
      }

      public Builder createdTimestampMillis(long createdTimestampMillis) {
        this.createdTimestampMillis = createdTimestampMillis;
        return this;
      }

      public CounterDataPointSnapshot build() {
        if (value == null) {
          throw new IllegalArgumentException("Missing required field: value is null.");
        }
        return new CounterDataPointSnapshot(
            value, labels, exemplar, createdTimestampMillis, scrapeTimestampMillis);
      }

      @Override
      protected Builder self() {
        return this;
      }
    }
  }

  public static Builder builder() {
    return new Builder();
  }

  public static class Builder extends MetricSnapshot.Builder<Builder> {

    private final List<CounterDataPointSnapshot> dataPoints = new ArrayList<>();

    private Builder() {}

    /** Add a data point. Can be called multiple times to add multiple data points. */
    public Builder dataPoint(CounterDataPointSnapshot dataPoint) {
      dataPoints.add(dataPoint);
      return this;
    }

    @Override
    public CounterSnapshot build() {
      return new CounterSnapshot(buildMetadata(), dataPoints);
    }

    @Override
    protected Builder self() {
      return this;
    }
  }
}