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package io.prometheus.client.exporter.common;

import java.io.IOException;
import java.io.Writer;
import java.util.Enumeration;

import io.prometheus.client.Collector;

public class TextFormat {
  /**
   * Content-type for text version 0.0.4.
   */
  public final static String CONTENT_TYPE_004 = "text/plain; version=0.0.4; charset=utf-8";

  /**
   * Write out the text version 0.0.4 of the given MetricFamilySamples.
   */
  public static void write004(Writer writer, Enumeration mfs) throws IOException {
    /* See http://prometheus.io/docs/instrumenting/exposition_formats/
     * for the output format specification. */
    while(mfs.hasMoreElements()) {
      Collector.MetricFamilySamples metricFamilySamples = mfs.nextElement();
      writer.write("# HELP ");
      writer.write(metricFamilySamples.name);
      writer.write(' ');
      writeEscapedHelp(writer, metricFamilySamples.help);
      writer.write('\n');

      writer.write("# TYPE ");
      writer.write(metricFamilySamples.name);
      writer.write(' ');
      writer.write(typeString(metricFamilySamples.type));
      writer.write('\n');

      for (Collector.MetricFamilySamples.Sample sample: metricFamilySamples.samples) {
        writer.write(sample.name);
        if (sample.labelNames.size() > 0) {
          writer.write('{');
          for (int i = 0; i < sample.labelNames.size(); ++i) {
            writer.write(sample.labelNames.get(i));
            writer.write("=\"");
            writeEscapedLabelValue(writer, sample.labelValues.get(i));
            writer.write("\",");
          }
          writer.write('}');
        }
        writer.write(' ');
        writer.write(Collector.doubleToGoString(sample.value));
        if (sample.timestampMs != null){
          writer.write(' ');
          writer.write(sample.timestampMs.toString());
        }
        writer.write('\n');
      }
    }
  }

  private static void writeEscapedHelp(Writer writer, String s) throws IOException {
    for (int i = 0; i < s.length(); i++) {
      char c = s.charAt(i);
      switch (c) {
        case '\\':
          writer.append("\\\\");
          break;
        case '\n':
          writer.append("\\n");
          break;
        default:
          writer.append(c);
      }
    }
  }

  private static void writeEscapedLabelValue(Writer writer, String s) throws IOException {
    for (int i = 0; i < s.length(); i++) {
      char c = s.charAt(i);
      switch (c) {
        case '\\':
          writer.append("\\\\");
          break;
        case '\"':
          writer.append("\\\"");
          break;
        case '\n':
          writer.append("\\n");
          break;
        default:
          writer.append(c);
      }
    }
  }

  private static String typeString(Collector.Type t) {
    switch (t) {
      case GAUGE:
        return "gauge";
      case COUNTER:
        return "counter";
      case SUMMARY:
        return "summary";
      case HISTOGRAM:
        return "histogram";
      default:
        return "untyped";
    }
  }
}