#pragma once

#include <memory>

#include <string>

#include <vector>

#include "envoy/common/interval_set.h"

#include "envoy/common/pure.h"

#include "envoy/stats/tag.h"

#include "absl/strings/string_view.h"

namespace Envoy {

namespace Stats {

class TagExtractionContext;

/**

 * Class to extract tags from the stat names.

 */

class TagExtractor {

public:

  /**

   * Identifier for the tag extracted by this object.

   */

  virtual absl::string_view name() const PURE;

  /**

   * Finds tags for stat_name and adds them to the tags vector. If the tag is not

   * represented in the name, the tags vector will remain unmodified. Also finds the

   * character indexes for the tags in stat_name and adds them to remove_characters (an

   * in/out arg). Returns true if a tag-match was found. The characters removed from the

   * name may be different from the values put into the tag vector for readability

   * purposes. Note: The extraction process is expected to be run iteratively, aggregating

   * the character intervals to be removed from the name after all the tag extractions are

   * complete. This approach simplifies the tag searching process because without mutations,

   * the tag extraction will be order independent, apart from the order of the tag array.

   * @param context identifies the name from which to extract tags.

   * @param tags list of tags updated with the tag name and value if found in the name.

   * @param remove_characters set of intervals of character-indices to be removed from name.

   * @return bool indicates whether a tag was found in the name.

   */

  virtual bool extractTag(TagExtractionContext& context, TagVector& tags,

                          IntervalSet<size_t>& remove_characters) const PURE;

  /**

   * Finds a prefix string associated with the matching criteria owned by the

   * extractor. This is used to reduce the number of extractors required for

   * processing each stat, by pulling the first "."-separated token on the tag.

   *

   * If a prefix cannot be extracted, an empty string_view is returned, and the

   * matcher must be applied on all inputs.

   *

   * The storage for the prefix is owned by the TagExtractor.

   *

   * @return absl::string_view the prefix, or an empty string_view if none was found.

   */

  virtual absl::string_view prefixToken() const PURE;

  virtual bool otherExtractorWithSameNameExists() const PURE;

  virtual void setOtherExtractorWithSameNameExists(bool e) PURE;

};

using TagExtractorPtr = std::unique_ptr<TagExtractor>;

} // namespace Stats

} // namespace Envoy