package com.datadoghq.trace.propagation;

import com.datadoghq.trace.DDSpanContext;
import io.opentracing.propagation.TextMap;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import lombok.extern.slf4j.Slf4j;

/** A codec designed for HTTP transport via headers */
@Slf4j
public class HTTPCodec implements Codec<TextMap> {

  private static final String OT_PREFIX = "ot-tracer-";
  private static final String OT_BAGGAGE_PREFIX = "ot-baggage-";
  private static final String TRACE_ID_KEY = OT_PREFIX + "traceid";
  private static final String SPAN_ID_KEY = OT_PREFIX + "spanid";

  @Override
  public void inject(final DDSpanContext context, final TextMap carrier) {

    carrier.put(TRACE_ID_KEY, String.valueOf(context.getTraceId()));
    carrier.put(SPAN_ID_KEY, String.valueOf(context.getSpanId()));

    for (final Map.Entry<String, String> entry : context.baggageItems()) {
      carrier.put(OT_BAGGAGE_PREFIX + entry.getKey(), encode(entry.getValue()));
    }
  }

  @Override
  public DDSpanContext extract(final TextMap carrier) {

    Map<String, String> baggage = Collections.emptyMap();
    Long traceId = 0L;
    Long spanId = 0L;

    for (final Map.Entry<String, String> entry : carrier) {

      if (entry.getKey().equals(TRACE_ID_KEY)) {
        traceId = Long.parseLong(entry.getValue());
      } else if (entry.getKey().equals(SPAN_ID_KEY)) {
        spanId = Long.parseLong(entry.getValue());
      } else if (entry.getKey().startsWith(OT_BAGGAGE_PREFIX)) {
        if (baggage.isEmpty()) {
          baggage = new HashMap<>();
        }
        baggage.put(entry.getKey().replace(OT_BAGGAGE_PREFIX, ""), decode(entry.getValue()));
      }
    }
    DDSpanContext context = null;
    if (traceId != 0L) {

      context =
          new DDSpanContext(
              traceId, spanId, 0L, null, null, null, baggage, false, null, null, null, null);

      log.debug("{} - Parent context extracted", context);
    }

    return context;
  }

  private String encode(final String value) {
    String encoded = value;
    try {
      encoded = URLEncoder.encode(value, "UTF-8");
    } catch (final UnsupportedEncodingException e) {
      log.info("Failed to encode value - {}", value);
    }
    return encoded;
  }

  private String decode(final String value) {
    String decoded = value;
    try {
      decoded = URLDecoder.decode(value, "UTF-8");
    } catch (final UnsupportedEncodingException e) {
      log.info("Failed to decode value - {}", value);
    }
    return decoded;
  }
}