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// A class handling the converter on the session layer.

#ifndef MOZC_ENGINE_SESSION_CONVERTER_INTERFACE_H_
#define MOZC_ENGINE_SESSION_CONVERTER_INTERFACE_H_

#include <cstddef>
#include <memory>
#include <optional>
#include <string>

#include "absl/strings/string_view.h"
#include "composer/composer.h"
#include "protocol/commands.pb.h"
#include "protocol/config.pb.h"
#include "transliteration/transliteration.h"

namespace mozc {
namespace engine {

struct ConversionPreferences {
  bool use_history;

  // This is a flag to check if the converter should return the suggestion
  // or not. Indeed, the design is actually twisted, because clients should
  // be able to avoid the invocation of EngineConverter::Suggest, if they'd
  // like. However, The current EngineConverter's architecture is too
  // complicated and has too many limitations to ensure the full state
  // transition. In order to support "skipping suggestion" for the performance
  // without current client's breakage in short period, this flag is
  // introduced.
  // TODO(hidehiko,komatsu): Remove this flag, when the full EngineConverter
  //   refactoring is done and gets safer for future development/extensions.
  bool request_suggestion;
};

// Class handling ConverterInterface with a session state.  This class
// support stateful operations related with the converter.
class EngineConverterInterface {
 public:
  virtual ~EngineConverterInterface() = default;

  typedef int States;
  enum State {
    NO_STATE = 0,
    COMPOSITION = 1,
    SUGGESTION = 2,
    PREDICTION = 4,
    CONVERSION = 8,
  };

  // Check if the current state is in the state bitmap.
  virtual bool CheckState(States) const = 0;

  // Indicate if the conversion session is active or not.  In general,
  // Convert functions make it active and Cancel, Reset and Commit
  // functions make it deactive.
  virtual bool IsActive() const = 0;

  // Return the default conversion preferences to be used for custom
  // conversion.
  virtual const ConversionPreferences& conversion_preferences() const = 0;

  // Send a conversion request to the converter.
  virtual bool Convert(const composer::Composer& composer) = 0;
  virtual bool ConvertWithPreferences(
      const composer::Composer& composer,
      const ConversionPreferences& preferences) = 0;

  // Get reading text (e.g. from "猫" to "ねこ").
  virtual bool GetReadingText(absl::string_view str, std::string* reading) = 0;

  // Send a transliteration request to the converter.
  virtual bool ConvertToTransliteration(
      const composer::Composer& composer,
      transliteration::TransliterationType type) = 0;

  // Convert the current composition to half-width characters.
  // NOTE(komatsu): This function might be merged to ConvertToTransliteration.
  virtual bool ConvertToHalfWidth(const composer::Composer& composer) = 0;

  // Switch the composition to Hiragana, full-width Katakana or
  // half-width Katakana by rotation.
  virtual bool SwitchKanaType(const composer::Composer& composer) = 0;

  // Send a suggestion request to the converter.
  virtual bool Suggest(const composer::Composer& composer,
                       const commands::Context& context) = 0;
  virtual bool SuggestWithPreferences(
      const composer::Composer& composer, const commands::Context& context,
      const ConversionPreferences& preferences) = 0;

  // Send a prediction request to the converter.
  virtual bool Predict(const composer::Composer& composer) = 0;
  virtual bool PredictWithPreferences(
      const composer::Composer& composer,
      const ConversionPreferences& preferences) = 0;

  // Clear conversion segments, but keep the context.
  virtual void Cancel() = 0;

  // Clear conversion segments and the context.
  virtual void Reset() = 0;

  // Fix the conversion with the current status.
  virtual void Commit(const composer::Composer& composer,
                      const commands::Context& context) = 0;

  // Commit the current context and update the converter's state.
  // Used for synchronizing context updates with the converter whenever the user
  // performs an edit (e.g., via Backspace).
  virtual void CommitContext(const composer::Composer& composer,
                             const commands::Context& context) = 0;

  // Fix the suggestion candidate.  True is returned if the selected
  // candidate is successfully committed.
  virtual bool CommitSuggestionByIndex(size_t index,
                                       const composer::Composer& composer,
                                       const commands::Context& context,
                                       size_t* committed_key_size) = 0;

  // Select a candidate and commit the selected candidate.  True is
  // returned if the selected candidate is successfully committed.
  virtual bool CommitSuggestionById(int id, const composer::Composer& composer,
                                    const commands::Context& context,
                                    size_t* committed_key_size) = 0;

  // Fix only the conversion of the first segment, and keep the rest.
  // The caller should delete characters from composer based on returned
  // |committed_key_size|.
  virtual void CommitFirstSegment(const composer::Composer& composer,
                                  const commands::Context& context,
                                  size_t* committed_key_size) = 0;

  // Fix only the [0, focused] conversion segments, and keep the rest.
  // The caller should delete characters from composer based on returned
  // |committed_key_size|.
  virtual void CommitHeadToFocusedSegments(const composer::Composer& composer,
                                           const commands::Context& context,
                                           size_t* committed_key_size) = 0;

  // Commit the preedit string represented by Composer.
  virtual void CommitPreedit(const composer::Composer& composer,
                             const commands::Context& context) = 0;

  // Commit prefix of the preedit string represented by Composer.
  // The caller should delete characters from composer based on returned
  // |committed_size|.
  virtual void CommitHead(size_t count, const composer::Composer& composer,
                          size_t* committed_size) = 0;

  // Revert the last "Commit" operation
  virtual void Revert() = 0;

  // Delete candidate from user input history.
  // Try to delete the current selected candidate if |id| is not specified.
  // Returns false if the candidate was not found or deletion failed.
  virtual bool DeleteCandidateFromHistory(std::optional<int> id) = 0;

  // Move the focus of segments.
  virtual void SegmentFocusRight() = 0;
  virtual void SegmentFocusLast() = 0;
  virtual void SegmentFocusLeft() = 0;
  virtual void SegmentFocusLeftEdge() = 0;

  // Resize the focused segment.
  virtual void SegmentWidthExpand(const composer::Composer& composer) = 0;
  virtual void SegmentWidthShrink(const composer::Composer& composer) = 0;

  // Move the focus of candidates.
  virtual void CandidateNext(const composer::Composer& composer) = 0;
  virtual void CandidateNextPage() = 0;
  virtual void CandidatePrev() = 0;
  virtual void CandidatePrevPage() = 0;
  // Move the focus to the candidate represented by the id.
  virtual void CandidateMoveToId(int id,
                                 const composer::Composer& composer) = 0;
  // Move the focus to the index from the beginning of the current page.
  virtual void CandidateMoveToPageIndex(size_t index) = 0;
  // Move the focus to the candidate represented by the shortcut.  If
  // the shortcut is not bound with any candidate, false is returned.
  virtual bool CandidateMoveToShortcut(char shortcut) = 0;

  // Operation for the candidate list.
  virtual void SetCandidateListVisible(bool visible) = 0;

  // Fill protocol buffers and update internal status.
  virtual void PopOutput(const composer::Composer& composer,
                         commands::Output* output) = 0;

  // Fill preedit
  virtual void FillPreedit(const composer::Composer& composer,
                           commands::Preedit* preedit) const = 0;

  // Fill protocol buffers
  virtual void FillOutput(const composer::Composer& composer,
                          commands::Output* output) const = 0;

  // Set setting by the request.
  // Currently this is especially for EngineConverter.
  virtual void SetRequest(std::shared_ptr<const commands::Request> request) = 0;

  // Set setting by the config.
  // Currently this is especially for EngineConverter.
  virtual void SetConfig(std::shared_ptr<const config::Config> config) = 0;

  // Update the internal state by the context.
  virtual void OnStartComposition(const commands::Context& context) = 0;

  // Clone instance.
  // Callee object doesn't have the ownership of the cloned instance.
  virtual EngineConverterInterface* Clone() const = 0;

  virtual void set_selection_shortcut(
      config::Config::SelectionShortcut selection_shortcut) = 0;

  virtual void set_use_cascading_window(bool use_cascading_window) = 0;
};

}  // namespace engine
}  // namespace mozc

#endif  // MOZC_ENGINE_SESSION_CONVERTER_INTERFACE_H_
