// 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/common.h"

#include <jxl/codestream_header.h>

#include <jxl/types.h>

#include <cstddef>

#include <vector>

#include "lib/extras/packed_image.h"

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

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

namespace jxl {

namespace extras {

Status SelectFormat(const std::vector<JxlPixelFormat>& accepted_formats,

                    const JxlBasicInfo& basic_info, JxlPixelFormat* format) {

  const size_t original_bit_depth = basic_info.bits_per_sample;

  size_t current_bit_depth = 0;

  size_t num_alpha_channels = (basic_info.alpha_bits != 0 ? 1 : 0);

  size_t num_channels = basic_info.num_color_channels + num_alpha_channels;

  for (;;) {

    for (const JxlPixelFormat& candidate : accepted_formats) {

      if (candidate.num_channels != num_channels) continue;

      const size_t candidate_bit_depth =

          PackedImage::BitsPerChannel(candidate.data_type);

      if (

          // Candidate bit depth is less than what we have and still enough

          (original_bit_depth <= candidate_bit_depth &&

           candidate_bit_depth < current_bit_depth) ||

          // Or larger than the too-small bit depth we currently have

          (current_bit_depth < candidate_bit_depth &&

           current_bit_depth < original_bit_depth)) {

        *format = candidate;

        current_bit_depth = candidate_bit_depth;

      }

    }

    if (current_bit_depth == 0) {

      if (num_channels > basic_info.num_color_channels) {

        // Try dropping the alpha channel.

        --num_channels;

        continue;

      }

      return JXL_FAILURE("no appropriate format found");

    }

    break;

  }

  if (current_bit_depth < original_bit_depth) {

    JXL_WARNING("encoding %" PRIuS "-bit original to %" PRIuS " bits",

                original_bit_depth, current_bit_depth);

  }

  return true;

}

}  // namespace extras

}  // namespace jxl