/* SPDX-License-Identifier: Apache-2.0
 * Copyright 2011-2022 Blender Foundation */

#include "session/merge.h"

#include "util/array.h"
#include "util/map.h"
#include "util/system.h"
#include "util/time.h"
#include "util/unique_ptr.h"

#include <OpenImageIO/filesystem.h>
#include <OpenImageIO/imageio.h>

OIIO_NAMESPACE_USING

CCL_NAMESPACE_BEGIN

/* Merge Image Layer */

enum MergeChannelOp {
  MERGE_CHANNEL_NOP,
  MERGE_CHANNEL_COPY,
  MERGE_CHANNEL_SUM,
  MERGE_CHANNEL_AVERAGE,
  MERGE_CHANNEL_SAMPLES,
};

struct MergeImagePass {
  /* Full channel name. */
  string channel_name;
  /* Pass name. */
  string name;
  /* Channel format in the file. */
  TypeDesc format;
  /* Type of operation to perform when merging. */
  MergeChannelOp op;
  /* Offset of layer channels in input image. */
  int offset;
  /* Offset of layer channels in merged image. */
  int merge_offset;
};

struct SampleCount {
  /* Total number of samples. */
  int total;
  /* Buffer for actual number of samples rendered per pixel. */
  array<float> per_pixel;
};

struct MergeImageLayer {
  /* Layer name. */
  string name;
  /* Passes. */
  vector<MergeImagePass> passes;
  /* Sample amount that was used for rendering this layer. */
  int samples;
  /* Indicates if this layer has "Debug Sample Count" pass. */
  bool has_sample_pass;
  /* Offset of the "Debug Sample Count" pass if it exists. */
  int sample_pass_offset;
};

/* Merge Image */

struct MergeImage {
  /* OIIO file handle. */
  unique_ptr<ImageInput> in;
  /* Image file path. */
  string filepath;
  /* Render layers. */
  vector<MergeImageLayer> layers;
};

/* Channel Parsing */

static MergeChannelOp parse_channel_operation(const string &pass_name)
{
  if (pass_name == "Depth" || pass_name == "IndexMA" || pass_name == "IndexOB" ||
      string_startswith(pass_name, "Crypto")) {
    return MERGE_CHANNEL_COPY;
  }
  else if (string_startswith(pass_name, "Debug BVH") ||
           string_startswith(pass_name, "Debug Ray") ||
           string_startswith(pass_name, "Debug Render Time")) {
    return MERGE_CHANNEL_SUM;
  }
  else if (string_startswith(pass_name, "Debug Sample Count")) {
    return MERGE_CHANNEL_SAMPLES;
  }
  else {
    return MERGE_CHANNEL_AVERAGE;
  }
}

/* Splits in at its last dot, setting suffix to the part after the dot and
 * into the part before it. Returns whether a dot was found. */
static bool split_last_dot(string &in, string &suffix)
{
  size_t pos = in.rfind(".");
  if (pos == string::npos) {
    return false;
  }
  suffix = in.substr(pos + 1);
  in = in.substr(0, pos);
  return true;
}

/* Separate channel names as generated by Blender.
 * Multiview format: RenderLayer.Pass.View.Channel
 * Otherwise: RenderLayer.Pass.Channel */
static bool parse_channel_name(
    string name, string &renderlayer, string &pass, string &channel, bool multiview_channels)
{
  if (!split_last_dot(name, channel)) {
    return false;
  }
  string view;
  if (multiview_channels && !split_last_dot(name, view)) {
    return false;
  }
  if (!split_last_dot(name, pass)) {
    return false;
  }
  renderlayer = name;

  if (multiview_channels) {
    renderlayer += "." + view;
  }

  return true;
}

static bool parse_channels(const ImageSpec &in_spec,
                           vector<MergeImageLayer> &layers,
                           string &error)
{
  const ParamValue *multiview = in_spec.find_attribute("multiView");
  const bool multiview_channels = (multiview && multiview->type().basetype == TypeDesc::STRING &&
                                   multiview->type().arraylen >= 2);

  layers.clear();

  /* Loop over all the channels in the file, parse their name and sort them
   * by RenderLayer.
   * Channels that can't be parsed are directly passed through to the output. */
  map<string, MergeImageLayer> file_layers;
  for (int i = 0; i < in_spec.nchannels; i++) {
    MergeImagePass pass;
    pass.channel_name = in_spec.channelnames[i];
    pass.format = (in_spec.channelformats.size() > 0) ? in_spec.channelformats[i] : in_spec.format;
    pass.offset = i;
    pass.merge_offset = i;

    string layername, channelname;
    if (parse_channel_name(
            pass.channel_name, layername, pass.name, channelname, multiview_channels)) {
      /* Channel part of a render layer. */
      pass.op = parse_channel_operation(pass.name);
    }
    else {
      /* Other channels are added in unnamed layer. */
      layername = "";
      pass.op = parse_channel_operation(pass.channel_name);
    }

    file_layers[layername].passes.push_back(pass);
  }

  /* If file contains a single unnamed layer, name it after the first layer metadata we find. */
  if (file_layers.size() == 1 && file_layers.find("") != file_layers.end()) {
    for (const ParamValue &attrib : in_spec.extra_attribs) {
      const string attrib_name = attrib.name().string();
      if (string_startswith(attrib_name, "cycles.") && string_endswith(attrib_name, ".samples")) {
        /* Extract layer name. */
        const size_t start = strlen("cycles.");
        const size_t end = attrib_name.size() - strlen(".samples");
        const string layername = attrib_name.substr(start, end - start);

        /* Reinsert as named instead of unnamed layer. */
        const MergeImageLayer layer = file_layers[""];
        file_layers.clear();
        file_layers[layername] = layer;
      }
    }
  }

  /* Loop over all detected render-layers, check whether they contain a full set of input
   * channels. Any channels that won't be processed internally are also passed through. */
  for (auto &[name, layer] : file_layers) {
    layer.name = name;
    layer.samples = 0;

    /* Determine number of samples from metadata. */
    if (layer.name == "") {
      layer.samples = 1;
    }
    else if (layer.samples < 1) {
      string sample_string = in_spec.get_string_attribute("cycles." + name + ".samples", "");
      if (sample_string != "") {
        if (!sscanf(sample_string.c_str(), "%d", &layer.samples)) {
          error = "Failed to parse samples metadata: " + sample_string;
          return false;
        }
      }
    }

    if (layer.samples < 1) {
      error = string_printf(
          "No sample number specified in the file for layer %s or on the command line",
          name.c_str());
      return false;
    }

    /* Check if the layer has "Debug Sample Count" pass. */
    auto sample_pass_it = find_if(
        layer.passes.begin(), layer.passes.end(), [](const MergeImagePass &pass) {
          return pass.name == "Debug Sample Count";
        });
    if (sample_pass_it != layer.passes.end()) {
      layer.has_sample_pass = true;
      layer.sample_pass_offset = distance(layer.passes.begin(), sample_pass_it);
    }
    else {
      layer.has_sample_pass = false;
    }

    layers.push_back(layer);
  }

  return true;
}

static bool open_images(const vector<string> &filepaths, vector<MergeImage> &images, string &error)
{
  for (const string &filepath : filepaths) {
    unique_ptr<ImageInput> in(ImageInput::open(filepath));
    if (!in) {
      error = "Couldn't open file: " + filepath;
      return false;
    }

    MergeImage image;
    image.in = std::move(in);
    image.filepath = filepath;
    if (!parse_channels(image.in->spec(), image.layers, error)) {
      return false;
    }

    if (image.layers.size() == 0) {
      error = "Could not find a render layer for merging";
      return false;
    }

    if (image.in->spec().deep) {
      error = "Merging deep images not supported.";
      return false;
    }

    if (images.size() > 0) {
      const ImageSpec &base_spec = images[0].in->spec();
      const ImageSpec &spec = image.in->spec();

      if (base_spec.width != spec.width || base_spec.height != spec.height ||
          base_spec.depth != spec.depth || base_spec.format != spec.format ||
          base_spec.deep != spec.deep) {
        error = "Images do not have matching size and data layout.";
        return false;
      }
    }

    images.push_back(std::move(image));
  }

  return true;
}

static void merge_render_time(ImageSpec &spec,
                              const vector<MergeImage> &images,
                              const string &name,
                              const bool average)
{
  double time = 0.0;

  for (const MergeImage &image : images) {
    string time_str = image.in->spec().get_string_attribute(name, "");
    time += time_human_readable_to_seconds(time_str);
  }

  if (average) {
    time /= images.size();
  }

  spec.attribute(name, TypeDesc::STRING, time_human_readable_from_seconds(time));
}

static void merge_layer_render_time(ImageSpec &spec,
                                    const vector<MergeImage> &images,
                                    const string &layer_name,
                                    const string &time_name,
                                    const bool average)
{
  string name = "cycles." + layer_name + "." + time_name;
  double time = 0.0;

  for (const MergeImage &image : images) {
    string time_str = image.in->spec().get_string_attribute(name, "");
    time += time_human_readable_to_seconds(time_str);
  }

  if (average) {
    time /= images.size();
  }

  spec.attribute(name, TypeDesc::STRING, time_human_readable_from_seconds(time));
}

static void merge_channels_metadata(vector<MergeImage> &images, ImageSpec &out_spec)
{
  /* Based on first image. */
  out_spec = images[0].in->spec();

  /* Merge channels and compute offsets. */
  out_spec.nchannels = 0;
  out_spec.channelformats.clear();
  out_spec.channelnames.clear();

  for (MergeImage &image : images) {
    for (MergeImageLayer &layer : image.layers) {
      for (MergeImagePass &pass : layer.passes) {
        /* Test if matching channel already exists in merged image. */
        auto channel = find_if(
            out_spec.channelnames.begin(),
            out_spec.channelnames.end(),
            [&pass](const auto &channel_name) { return pass.channel_name == channel_name; });

        if (channel != out_spec.channelnames.end()) {
          int index = distance(out_spec.channelnames.begin(), channel);
          pass.merge_offset = index;

          /* First image wins for channels that can't be averaged or summed. */
          if (pass.op == MERGE_CHANNEL_COPY) {
            pass.op = MERGE_CHANNEL_NOP;
          }
        }
        else {
          /* Add new channel. */
          pass.merge_offset = out_spec.nchannels;

          out_spec.channelnames.push_back(pass.channel_name);
          out_spec.channelformats.push_back(pass.format);
          out_spec.nchannels++;
        }
      }
    }
  }

  /* Merge metadata. */
  merge_render_time(out_spec, images, "RenderTime", false);

  map<string, int> layer_num_samples;
  for (MergeImage &image : images) {
    for (MergeImageLayer &layer : image.layers) {
      if (layer.name != "") {
        layer_num_samples[layer.name] += layer.samples;
      }
    }
  }

  for (const auto &[layer_name, layer_samples] : layer_num_samples) {
    string name = "cycles." + layer_name + ".samples";
    out_spec.attribute(name, TypeDesc::STRING, to_string(layer_samples));

    merge_layer_render_time(out_spec, images, layer_name, "total_time", false);
    merge_layer_render_time(out_spec, images, layer_name, "render_time", false);
    merge_layer_render_time(out_spec, images, layer_name, "synchronization_time", true);
  }
}

static void alloc_pixels(const ImageSpec &spec, array<float> &pixels)
{
  const size_t width = spec.width;
  const size_t height = spec.height;
  const size_t num_channels = spec.nchannels;

  const size_t num_pixels = width * height;
  pixels.resize(num_pixels * num_channels);
}

static bool merge_pixels(const vector<MergeImage> &images,
                         const ImageSpec &out_spec,
                         const unordered_map<string, SampleCount> &layer_samples,
                         array<float> &out_pixels,
                         string &error)
{
  alloc_pixels(out_spec, out_pixels);
  memset(out_pixels.data(), 0, out_pixels.size() * sizeof(float));

  for (const MergeImage &image : images) {
    /* Read all channels into buffer. Reading all channels at once is
     * faster than individually due to interleaved EXR channel storage. */
    array<float> pixels;
    alloc_pixels(image.in->spec(), pixels);

    if (!image.in->read_image(TypeDesc::FLOAT, pixels.data())) {
      error = "Failed to read image: " + image.filepath;
      return false;
    }

    for (const MergeImageLayer &layer : image.layers) {
      const size_t stride = image.in->spec().nchannels;
      const size_t out_stride = out_spec.nchannels;
      const size_t num_pixels = pixels.size();

      for (const MergeImagePass &pass : layer.passes) {
        size_t offset = pass.offset;
        size_t out_offset = pass.merge_offset;

        switch (pass.op) {
          case MERGE_CHANNEL_NOP:
            break;
          case MERGE_CHANNEL_COPY:
            for (; offset < num_pixels; offset += stride, out_offset += out_stride) {
              out_pixels[out_offset] = pixels[offset];
            }
            break;
          case MERGE_CHANNEL_SUM:
            for (; offset < num_pixels; offset += stride, out_offset += out_stride) {
              out_pixels[out_offset] += pixels[offset];
            }
            break;
          case MERGE_CHANNEL_AVERAGE: {
            /* Weights based on sample count passes and sample metadata. Per channel since not
             * all files are guaranteed to have the same channels. */
            size_t sample_pass_offset = layer.sample_pass_offset;
            const auto &samples = layer_samples.at(layer.name);

            for (size_t i = 0; offset < num_pixels;
                 offset += stride, sample_pass_offset += stride, out_offset += out_stride, i++) {
              const float total_samples = samples.per_pixel[i];

              float layer_samples;
              if (layer.has_sample_pass) {
                layer_samples = pixels[sample_pass_offset] * layer.samples;
              }
              else {
                layer_samples = layer.samples;
              }

              out_pixels[out_offset] += pixels[offset] * (1.0f * layer_samples / total_samples);
            }
            break;
          }
          case MERGE_CHANNEL_SAMPLES: {
            const auto &samples = layer_samples.at(layer.name);
            for (size_t i = 0; offset < num_pixels;
                 offset += stride, out_offset += out_stride, i++) {
              out_pixels[out_offset] = 1.0f * samples.per_pixel[i] / samples.total;
            }
            break;
          }
        }
      }
    }
  }

  return true;
}

static bool save_output(const string &filepath,
                        const ImageSpec &spec,
                        const array<float> &pixels,
                        string &error)
{
  /* Write to temporary file path, so we merge images in place and don't
   * risk destroying files when something goes wrong in file saving. */
  string extension = OIIO::Filesystem::extension(filepath);
  string unique_name = ".merge-tmp-" + OIIO::Filesystem::unique_path();
  string tmp_filepath = filepath + unique_name + extension;
  unique_ptr<ImageOutput> out(ImageOutput::create(tmp_filepath));

  if (!out) {
    error = "Failed to open temporary file " + tmp_filepath + " for writing";
    return false;
  }

  /* Open temporary file and write image buffers. */
  if (!out->open(tmp_filepath, spec)) {
    error = "Failed to open file " + tmp_filepath + " for writing: " + out->geterror();
    return false;
  }

  bool ok = true;
  if (!out->write_image(TypeDesc::FLOAT, pixels.data())) {
    error = "Failed to write to file " + tmp_filepath + ": " + out->geterror();
    ok = false;
  }

  if (!out->close()) {
    error = "Failed to save to file " + tmp_filepath + ": " + out->geterror();
    ok = false;
  }

  out.reset();

  /* Copy temporary file to output filepath. */
  string rename_error;
  if (ok && !OIIO::Filesystem::rename(tmp_filepath, filepath, rename_error)) {
    error = "Failed to move merged image to " + filepath + ": " + rename_error;
    ok = false;
  }

  if (!ok) {
    OIIO::Filesystem::remove(tmp_filepath);
  }

  return ok;
}

static void read_layer_samples(vector<MergeImage> &images,
                               unordered_map<string, SampleCount> &layer_samples)
{
  for (auto &image : images) {
    const ImageSpec &in_spec = image.in->spec();

    for (auto &layer : image.layers) {
      bool initialize = (layer_samples.count(layer.name) == 0);
      auto &current_layer_samples = layer_samples[layer.name];

      if (initialize) {
        current_layer_samples.total = 0;
        current_layer_samples.per_pixel.resize(in_spec.width * in_spec.height);
        std::fill(
            current_layer_samples.per_pixel.begin(), current_layer_samples.per_pixel.end(), 0.0f);
      }

      if (layer.has_sample_pass) {
        /* Load the "Debug Sample Count" pass and add the samples to the layer's sample count. */
        array<float> sample_count_buffer;
        sample_count_buffer.resize(in_spec.width * in_spec.height);
        image.in->read_image(0,
                             0,
                             layer.sample_pass_offset,
                             layer.sample_pass_offset,
                             TypeDesc::FLOAT,
                             (void *)sample_count_buffer.data());

        for (size_t i = 0; i < current_layer_samples.per_pixel.size(); i++) {
          current_layer_samples.per_pixel[i] += sample_count_buffer[i] * layer.samples;
        }
      }
      else {
        /* Use sample count from metadata if there's no "Debug Sample Count" pass. */
        for (size_t i = 0; i < current_layer_samples.per_pixel.size(); i++) {
          current_layer_samples.per_pixel[i] += layer.samples;
        }
      }

      current_layer_samples.total += layer.samples;
    }
  }
}
/* Image Merger */

ImageMerger::ImageMerger()
{
}

bool ImageMerger::run()
{
  if (input.empty()) {
    error = "No input file paths specified.";
    return false;
  }
  if (output.empty()) {
    error = "No output file path specified.";
    return false;
  }

  /* Open images and verify they have matching layout. */
  vector<MergeImage> images;
  if (!open_images(input, images, error)) {
    return false;
  }

  /* Load and sum sample count for each render layer. */
  unordered_map<string, SampleCount> layer_samples;
  read_layer_samples(images, layer_samples);

  /* Merge metadata and setup channels and offsets. */
  ImageSpec out_spec;
  merge_channels_metadata(images, out_spec);

  /* Merge pixels. */
  array<float> out_pixels;
  if (!merge_pixels(images, out_spec, layer_samples, out_pixels, error)) {
    return false;
  }

  /* We don't need input anymore at this point, and will possibly
   * overwrite the same file. */
  images.clear();

  /* Save output file. */
  return save_output(output, out_spec, out_pixels, error);
}

CCL_NAMESPACE_END