#include "utils/cel_to_cl2.hpp"

#include <cstring>

#include <vector>

#ifdef DEBUG_CEL_TO_CL2_SIZE
#include <iomanip>
#include <iostream>
#endif

#include "appfat.h"
#include "utils/endian.hpp"

namespace devilution {

namespace {

constexpr bool IsCelTransparent(uint8_t control)
{
	constexpr uint8_t CelTransparentMin = 0x80;
	return control >= CelTransparentMin;
}

constexpr uint8_t GetCelTransparentWidth(uint8_t control)
{
	return -static_cast<int8_t>(control);
}

void AppendCl2TransparentRun(unsigned width, std::vector<uint8_t> &out)
{
	while (width >= 0x7F) {
		out.push_back(0x7F);
		width -= 0x7F;
	}
	if (width == 0)
		return;
	out.push_back(width);
}

void AppendCl2FillRun(uint8_t color, unsigned width, std::vector<uint8_t> &out)
{
	while (width >= 0x3F) {
		out.push_back(0x80);
		out.push_back(color);
		width -= 0x3F;
	}
	if (width == 0)
		return;
	out.push_back(0xBF - width);
	out.push_back(color);
}

void AppendCl2PixelsRun(const uint8_t *src, unsigned width, std::vector<uint8_t> &out)
{
	while (width >= 0x41) {
		out.push_back(0xBF);
		for (size_t i = 0; i < 0x41; ++i)
			out.push_back(src[i]);
		width -= 0x41;
		src += 0x41;
	}
	if (width == 0)
		return;
	out.push_back(256 - width);
	for (size_t i = 0; i < width; ++i)
		out.push_back(src[i]);
}

void AppendCl2PixelsOrFillRun(const uint8_t *src, unsigned length, std::vector<uint8_t> &out)
{
	const uint8_t *begin = src;
	const uint8_t *prevColorBegin = src;
	unsigned prevColorRunLength = 1;
	uint8_t prevColor = *src++;
	while (--length > 0) {
		const uint8_t color = *src;
		if (prevColor == color) {
			++prevColorRunLength;
		} else {
			// A tunable parameter that decides at which minimum length we encode a fill run.
			// 3 appears to be optimal for most of our data (much better than 2, rarely very slightly worse than 4).
			constexpr unsigned MinFillRunLength = 3;
			if (prevColorRunLength >= MinFillRunLength) {
				AppendCl2PixelsRun(begin, prevColorBegin - begin, out);
				AppendCl2FillRun(prevColor, prevColorRunLength, out);
				begin = src;
			}
			prevColorBegin = src;
			prevColorRunLength = 1;
			prevColor = color;
		}
		++src;
	}
	AppendCl2PixelsRun(begin, prevColorBegin - begin, out);
	AppendCl2FillRun(prevColor, prevColorRunLength, out);
}

} // namespace

OwnedCelSprite CelToCl2(const uint8_t *data, size_t size, PointerOrValue<uint16_t> widthOrWidths)
{
	// A CEL file either begins with:
	// 1. A CEL header.
	// 2. A list of offsets to frame groups (each group is a CEL file).
	size_t groupsHeaderSize = 0;
	uint32_t numGroups = 1;
	const uint32_t maybeNumFrames = LoadLE32(data);

	std::vector<uint8_t> cl2Data;

	// Most files become smaller with CL2. Allocate exactly enough bytes to avoid reallocation.
	// The only file that becomes larger is Data\hf_logo3.CEL, by exactly 4445 bytes.
	cl2Data.reserve(size + 4445);

	// If it is a number of frames, then the last frame offset will be equal to the size of the file.
	if (LoadLE32(&data[maybeNumFrames * 4 + 4]) != size) {
		// maybeNumFrames is the address of the first group, right after
		// the list of group offsets.
		numGroups = maybeNumFrames / 4;
		groupsHeaderSize = maybeNumFrames;
		data += groupsHeaderSize;
		cl2Data.resize(groupsHeaderSize);
	}

	for (size_t group = 0; group < numGroups; ++group) {
		uint32_t numFrames;
		if (numGroups == 1) {
			numFrames = maybeNumFrames;
		} else {
			numFrames = LoadLE32(data);
			WriteLE32(&cl2Data[4 * group], cl2Data.size());
		}

		// CL2 header: frame count, frame offset for each frame, file size
		const size_t cl2DataOffset = cl2Data.size();
		cl2Data.resize(cl2Data.size() + 4 * (2 + static_cast<size_t>(numFrames)));
		WriteLE32(cl2Data.data(), numFrames);

		const uint8_t *srcEnd = &data[LoadLE32(&data[4])];
		for (size_t frame = 1; frame <= numFrames; ++frame) {
			const uint8_t *src = srcEnd;
			srcEnd = &data[LoadLE32(&data[4 * (frame + 1)])];
			WriteLE32(&cl2Data[cl2DataOffset + 4 * frame], static_cast<uint32_t>(cl2Data.size() - cl2DataOffset));

			// Skip CEL frame header if there is one.
			constexpr size_t CelFrameHeaderSize = 10;
			const bool celFrameHasHeader = LoadLE16(src) == CelFrameHeaderSize;
			if (celFrameHasHeader)
				src += CelFrameHeaderSize;

			const unsigned frameWidth = widthOrWidths.HoldsPointer() ? widthOrWidths.AsPointer()[frame - 1] : widthOrWidths.AsValue();

			// Frame header: 5 16-bit offsets to 32-pixel height blocks.
			const size_t frameHeaderPos = cl2Data.size();
			constexpr size_t FrameHeaderSize = 10;
			cl2Data.resize(cl2Data.size() + FrameHeaderSize);

			// Frame header offset (first of five):
			WriteLE16(&cl2Data[frameHeaderPos], FrameHeaderSize);

			unsigned transparentRunWidth = 0;
			size_t line = 0;
			while (src != srcEnd) {
				// Process line:
				for (unsigned remainingCelWidth = frameWidth; remainingCelWidth != 0;) {
					uint8_t val = *src++;
					if (IsCelTransparent(val)) {
						val = GetCelTransparentWidth(val);
						transparentRunWidth += val;
					} else {
						AppendCl2TransparentRun(transparentRunWidth, cl2Data);
						transparentRunWidth = 0;
						AppendCl2PixelsOrFillRun(src, val, cl2Data);
						src += val;
					}
					remainingCelWidth -= val;
				}

				// Frame header offset:
				switch (++line) {
				case 32:
				case 64:
				case 96:
				case 128:
					// Finish any active transparent run to not allow it to go over an offset line boundary.
					AppendCl2TransparentRun(transparentRunWidth, cl2Data);
					transparentRunWidth = 0;
					WriteLE16(&cl2Data[frameHeaderPos + line / 16], static_cast<uint16_t>(cl2Data.size() - frameHeaderPos));
					break;
				}
			}
			AppendCl2TransparentRun(transparentRunWidth, cl2Data);
		}

		WriteLE32(&cl2Data[cl2DataOffset + 4 * (1 + static_cast<size_t>(numFrames))], static_cast<uint32_t>(cl2Data.size() - cl2DataOffset));
		data = srcEnd;
	}

	auto out = std::unique_ptr<byte[]>(new byte[cl2Data.size()]);
	memcpy(&out[0], cl2Data.data(), cl2Data.size());
#ifdef DEBUG_CEL_TO_CL2_SIZE
	std::cout << "\t" << size << "\t" << cl2Data.size() << "\t" << std::setprecision(1) << std::fixed << (static_cast<int>(cl2Data.size()) - static_cast<int>(size)) / ((float)size) * 100 << "%" << std::endl;
#endif
	return OwnedCelSprite { std::move(out), widthOrWidths };
}

} // namespace devilution