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/*
 * Copyright The OpenZipkin Authors
 * SPDX-License-Identifier: Apache-2.0
 */
package zipkin2.reporter;

import java.util.List;

/**
 * This includes the formats Zipkin server accepts.
 *
 * @since 3.0
 */
public enum Encoding {
  JSON {
    /** Encoding overhead of a single element is brackets */
    @Override public int listSizeInBytes(int encodedSizeInBytes) {
      return 2 + encodedSizeInBytes;
    }

    /** Encoding overhead is brackets and a comma for each span over 1 */
    @Override public int listSizeInBytes(List values) {
      int sizeInBytes = 2; // brackets
      for (int i = 0, length = values.size(); i < length; ) {
        sizeInBytes += values.get(i++).length;
        if (i < length) sizeInBytes++;
      }
      return sizeInBytes;
    }

    @SuppressWarnings("deprecation")
    @Override public byte[] encode(List encodedSpans) {
      return BytesMessageEncoder.JSON.encode(encodedSpans);
    }

    @Override public String mediaType() {
      return "application/json";
    }
  },
  /**
   * The first format of Zipkin was TBinaryProtocol, big-endian thrift. It is no longer used, but
   * defined here to allow collectors to support reading old data.
   *
   * The message's binary data includes a list header followed by N spans serialized in
   * TBinaryProtocol
   *
   * @deprecated this format is deprecated in favor of json or proto3
   */
  @Deprecated
  THRIFT {
    /** Encoding overhead is thrift type plus 32-bit length prefix */
    @Override public int listSizeInBytes(int encodedSizeInBytes) {
      return 5 + encodedSizeInBytes;
    }

    /** Encoding overhead is thrift type plus 32-bit length prefix */
    @Override public int listSizeInBytes(List values) {
      int sizeInBytes = 5;
      for (int i = 0, length = values.size(); i < length; i++) {
        sizeInBytes += values.get(i).length;
      }
      return sizeInBytes;
    }

    @SuppressWarnings("deprecation")
    @Override public byte[] encode(List encodedSpans) {
      return BytesMessageEncoder.THRIFT.encode(encodedSpans);
    }

    @Override public String mediaType() {
      return "application/x-thrift";
    }
  },
  /**
   * Repeated (type 2) fields are length-prefixed. A list is a concatenation of fields with no
   * additional overhead.
   *
   * 
See https://developers.google.com/protocol-buffers/docs/encoding#optional
   */
  PROTO3 {
    /** Returns the input as it is assumed to be length-prefixed field from a protobuf message */
    @Override public int listSizeInBytes(int encodedSizeInBytes) {
      return encodedSizeInBytes;
    }

    /** Returns a concatenation of sizes */
    @Override public int listSizeInBytes(List values) {
      int sizeInBytes = 0;
      for (int i = 0, length = values.size(); i < length; ) {
        sizeInBytes += values.get(i++).length;
      }
      return sizeInBytes;
    }

    @SuppressWarnings("deprecation")
    @Override public byte[] encode(List encodedSpans) {
      return BytesMessageEncoder.PROTO3.encode(encodedSpans);
    }

    @Override public String mediaType() {
      return "application/x-protobuf";
    }
  };

  /**
   * Combines a list of encoded spans into an encoded list. For example, in {@linkplain #THRIFT},
   * this would be length-prefixed, whereas in {@linkplain #JSON}, this would be comma-separated and
   * enclosed by brackets.
   *
   * The primary use of this is batch reporting spans. For example, spans are {@link
   * BytesEncoder#encode(Object) encoded} one-by-one into a queue. This queue is drained up to a byte
   * threshold. Then, the list is encoded with this function and reported out-of-process.
   *
   * @since 3.3
   */
  public abstract byte[] encode(List encodedSpans);

  /** Like {@link #listSizeInBytes(List)}, except for a single element. */
  public abstract int listSizeInBytes(int encodedSizeInBytes);

  public abstract int listSizeInBytes(List values);

  /**
   * Returns this message's "Content-Type" for use in an HTTP {@link BytesMessageSender sender}
   * targeting the Zipkin POST endpoint.
   *
   * @since 3.3
   */
  public abstract String mediaType();
}