// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#include "lib/extras/exif.h"

#include <cstdint>

#include <vector>

#include "lib/jxl/base/byte_order.h"

namespace jxl {

constexpr uint16_t kExifOrientationTag = 274;

void ResetExifOrientation(std::vector<uint8_t>& exif) {

  if (exif.size() < 12) return;  // not enough bytes for a valid exif blob

  bool bigendian;

  uint8_t* t = exif.data();

  if (LoadLE32(t) == 0x2A004D4D) {

    bigendian = true;

  } else if (LoadLE32(t) == 0x002A4949) {

    bigendian = false;

  } else {

    return;  // not a valid tiff header

  }

  t += 4;

  uint64_t offset = (bigendian ? LoadBE32(t) : LoadLE32(t));

  if (exif.size() < 12 + offset + 2 || offset < 8) return;

  t += offset - 4;

  uint16_t nb_tags = (bigendian ? LoadBE16(t) : LoadLE16(t));

  t += 2;

  while (nb_tags > 0) {

    if (t + 12 >= exif.data() + exif.size()) return;

    uint16_t tag = (bigendian ? LoadBE16(t) : LoadLE16(t));

    t += 2;

    if (tag == kExifOrientationTag) {

      uint16_t type = (bigendian ? LoadBE16(t) : LoadLE16(t));

      t += 2;

      uint32_t count = (bigendian ? LoadBE32(t) : LoadLE32(t));

      t += 4;

      if (type == 3 && count == 1) {

        if (bigendian) {

          StoreBE16(1, t);

        } else {

          StoreLE16(1, t);

        }

      }

      return;

    } else {

      t += 10;

      nb_tags--;

    }

  }

}

}  // namespace jxl