package org.openapitools.client;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
* Utilities to support Swagger encoding formats in Feign.
*/
public final class EncodingUtils {

  /**
   * Private constructor. Do not construct this class.
   */
  private EncodingUtils() {}

  /**
   * <p>Encodes a collection of query parameters according to the Swagger
   * collection format.</p>
   *
   * <p>Of the various collection formats defined by Swagger ("csv", "tsv",
   * etc), Feign only natively supports "multi". This utility generates the
   * other format types so it will be properly processed by Feign.</p>
   *
   * <p>Note, as part of reformatting, it URL encodes the parameters as
   * well.</p>
   * @param parameters The collection object to be formatted. This object will
   *                   not be changed.
   * @param collectionFormat The Swagger collection format (eg, "csv", "tsv",
   *                         "pipes"). See the
   *                         <a href="http://swagger.io/specification/#parameter-object-44">
   *                         OpenAPI Spec</a> for more details.
   * @return An object that will be correctly formatted by Feign.
   */
  public static Object encodeCollection(Collection<?> parameters,
                                     String collectionFormat) {
    if (parameters == null) {
      return parameters;
    }
    List<String> stringValues = new ArrayList<>(parameters.size());
    for (Object parameter : parameters) {
      // ignore null values (same behavior as Feign)
      if (parameter != null) {
        stringValues.add(encode(parameter));
      }
    }
    // Feign natively handles single-element lists and the "multi" format.
    if (stringValues.size() < 2 || "multi".equals(collectionFormat)) {
      return stringValues;
    }
    // Otherwise return a formatted String
    String[] stringArray = stringValues.toArray(new String[0]);
    switch (collectionFormat) {
      case "csv":
      default:
        return StringUtil.join(stringArray, ",");
      case "ssv":
        return StringUtil.join(stringArray, " ");
      case "tsv":
        return StringUtil.join(stringArray, "\t");
      case "pipes":
        return StringUtil.join(stringArray, "|");
    }
  }

  /**
   * URL encode a single query parameter.
   * @param parameter The query parameter to encode. This object will not be
   *                  changed.
   * @return The URL encoded string representation of the parameter. If the
   *         parameter is null, returns null.
   */
  public static String encode(Object parameter) {
    if (parameter == null) {
      return null;
    }
    try {
      return URLEncoder.encode(parameter.toString(), "UTF-8");
    } catch (UnsupportedEncodingException e) {
      // Should never happen, UTF-8 is always supported
      throw new RuntimeException(e);
    }
  }
}
