// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_FONT_FEATURES_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_FONT_FEATURES_H_

#include <optional>

#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

struct hb_feature_t;

namespace blink {

class FontDescription;

//
// Represents an OpenType font feature tag.
//
// This struct is compatible with `hb_tag_t`.
//
struct PLATFORM_EXPORT FontFeatureTag {
  constexpr FontFeatureTag() = default;
  constexpr FontFeatureTag(uint32_t tag) : tag(tag) {}
  constexpr FontFeatureTag(uint8_t c1, uint8_t c2, uint8_t c3, uint8_t c4)
      : tag((((((static_cast<uint32_t>(c1) << 8) | c2) << 8) | c3) << 8) | c4) {
  }

  operator uint32_t() const { return tag; }

  uint32_t tag = 0;
};

//
// Represents an OpenType font feature with its value.
//
struct PLATFORM_EXPORT FontFeatureValue : public FontFeatureTag {
  uint32_t value = 0;
};

//
// Represents an OpenType font feature with its value and text range.
//
struct PLATFORM_EXPORT FontFeatureRange : public FontFeatureValue {
  // The size produced by `FromFontDescription()` for the initial style.
  static constexpr wtf_size_t kInitialSize = 1;

  // Initialize the list from |FontDescription|.
  template <wtf_size_t InlineCapacity>
  static void FromFontDescription(const FontDescription&,
                                  Vector<FontFeatureRange, InlineCapacity>&);

  // This struct has the same size and layout as `hb_feature_t`.
  static const hb_feature_t* ToHarfBuzzData(const FontFeatureRange* features) {
    return reinterpret_cast<const hb_feature_t*>(features);
  }

  uint32_t start = 0;
  uint32_t end = static_cast<uint32_t>(-1);
};

//
// Represents a list of `FontFeatureRange`.
//
using FontFeatureRanges = Vector<FontFeatureRange, 6>;

//
// Saves `FontFeatureRanges` and restores it in the destructor.
//
// It works only for additions.
//
class PLATFORM_EXPORT FontFeatureRangesSaver {
  STACK_ALLOCATED();

 public:
  explicit FontFeatureRangesSaver(FontFeatureRanges* features)
      : features_(features), num_features_before_(features->size()) {
#if EXPENSIVE_DCHECKS_ARE_ON()
    saved_features_.append_range(*features);
#endif  // EXPENSIVE_DCHECKS_ARE_ON()
  }

  ~FontFeatureRangesSaver() {
#if EXPENSIVE_DCHECKS_ARE_ON()
    CheckIsAdditionsOnly();
#endif  // EXPENSIVE_DCHECKS_ARE_ON()
    if (features_->size() > num_features_before_) {
      features_->Shrink(num_features_before_);
    }
  }

 private:
#if EXPENSIVE_DCHECKS_ARE_ON()
  void CheckIsAdditionsOnly() const;
#endif  // EXPENSIVE_DCHECKS_ARE_ON()

  FontFeatureRanges* features_;
  wtf_size_t num_features_before_;
#if EXPENSIVE_DCHECKS_ARE_ON()
  FontFeatureRanges saved_features_;
#endif  // EXPENSIVE_DCHECKS_ARE_ON()
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_FONT_FEATURES_H_