/*
 * Copyright 2011-2019 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "render/merge.h"

#include "util/util_array.h"
#include "util/util_map.h"
#include "util/util_system.h"
#include "util/util_time.h"
#include "util/util_unique_ptr.h"

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

OIIO_NAMESPACE_USING

CCL_NAMESPACE_BEGIN

/* Merge Image Layer */

enum MergeChannelOp {
	MERGE_CHANNEL_COPY,
	MERGE_CHANNEL_SUM,
	MERGE_CHANNEL_AVERAGE
};

struct MergeImageLayer {
	/* Layer name. */
	string name;

	/* All channels belonging to this MergeImageLayer. */
	vector<string> channel_names;
	/* Offsets of layer channels in image. */
	vector<int> channel_offsets;
	/* Type of operation to perform when merging. */
	vector<MergeChannelOp> channel_ops;

	/* Sample amount that was used for rendering this layer. */
	int samples;
};

/* Merge Image */

class MergeImage {
public:
	/* 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 {
		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 std::vector<string> &channels = in_spec.channelnames;
	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 < channels.size(); i++) {
		string layer, pass, channel;

		if(parse_channel_name(channels[i], layer, pass, channel, multiview_channels)) {
			file_layers[layer].channel_names.push_back(pass + "." + channel);
			file_layers[layer].channel_offsets.push_back(i);
			file_layers[layer].channel_ops.push_back(parse_channel_operation(pass));
		}

		/* Any unparsed channels are copied from the first image. */
	}

	/* Loop over all detected RenderLayers, check whether they contain a full set of input channels.
	 * Any channels that won't be processed internally are also passed through. */
	for(map<string, MergeImageLayer>::iterator i = file_layers.begin(); i != file_layers.end(); ++i) {
		const string& name = i->first;
		MergeImageLayer& layer = i->second;

		layer.name = name;
		layer.samples = 0;

		/* If the sample value isn't set yet, check if there is a layer-specific one in the input file. */
		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;
		}

		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.nchannels != spec.nchannels ||
			   base_spec.format != spec.format ||
			   base_spec.channelformats != spec.channelformats ||
			   base_spec.channelnames != spec.channelnames ||
			   base_spec.deep != spec.deep)
			{
				error = "Images do not have exact matching data and channel layout.";
				return false;
			}
		}

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

	return true;
}

static bool load_pixels(const MergeImage& image, array<float>& pixels, string& error)
{
	const ImageSpec& in_spec = image.in->spec();
	const size_t width = in_spec.width;
	const size_t height = in_spec.height;
	const size_t num_channels = in_spec.nchannels;

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

	/* Read all channels into buffer. Reading all channels at once is faster
	 * than individually due to interleaved EXR channel storage. */
	if(!image.in->read_image(TypeDesc::FLOAT, pixels.data())) {
		error = "Failed to read image: " + image.filepath;
		return false;
	}

	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& time_name,
                                    const bool average)
{
	for(size_t i = 0; i < images[0].layers.size(); i++) {
		string name = "cycles." + images[0].layers[i].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 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 outputput 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;
}

/* 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;
	}

	/* Merge pixels. */
	array<float> merge_pixels;
	vector<int> merge_samples;

	/* Load first image. */
	if(!load_pixels(images[0], merge_pixels, error)) {
		return false;
	}
	for(size_t layer = 0; layer < images[0].layers.size(); layer++) {
		merge_samples.push_back(images[0].layers[layer].samples);
	}

	/* Merge other images. */
	for(size_t i = 1; i < images.size(); i++) {
		const MergeImage& image = images[i];

		array<float> pixels;
		if(!load_pixels(image, pixels, error)) {
			return false;
		}

		for(size_t li = 0; li < image.layers.size(); li++) {
			const MergeImageLayer& layer = image.layers[li];

			const int *offsets = layer.channel_offsets.data();
			const MergeChannelOp *ops = layer.channel_ops.data();

			const size_t stride = image.in->spec().nchannels;
			const size_t num_channels = layer.channel_offsets.size();
			const size_t num_pixels = pixels.size();

			/* Weights based on sample metadata. */
			const int sum_samples = merge_samples[li] + layer.samples;
			const float t = (float)layer.samples / (float)sum_samples;

			for(size_t pixel = 0; pixel < num_pixels; pixel += stride) {
				for(size_t channel = 0; channel < num_channels; channel++) {
					size_t offset = pixel + offsets[channel];

					switch(ops[channel]) {
						case MERGE_CHANNEL_COPY:
							/* Already copied from first image. */
							break;
						case MERGE_CHANNEL_SUM:
							merge_pixels[offset] += pixels[offset];
							break;
						case MERGE_CHANNEL_AVERAGE:
							merge_pixels[offset] = (1.0f - t) * merge_pixels[offset] + t * pixels[offset];
							break;
					}
				}
			}

			merge_samples[li] += layer.samples;
		}
	}

	/* Save image with identical dimensions, channels and metadata. */
	ImageSpec out_spec = images[0].in->spec();

	/* Merge metadata. */
	for(size_t i = 0; i < images[0].layers.size(); i++) {
		string name = "cycles." + images[0].layers[i].name + ".samples";
		out_spec.attribute(name, TypeDesc::STRING, string_printf("%d", merge_samples[i]));
	}

	merge_render_time(out_spec, images, "RenderTime", false);
	merge_layer_render_time(out_spec, images, "total_time", false);
	merge_layer_render_time(out_spec, images, "render_time", false);
	merge_layer_render_time(out_spec, images, "synchronization_time", true);

	/* 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, merge_pixels, error);
}

CCL_NAMESPACE_END