/*
* Copyright 2016 Nu-book Inc.
* Copyright 2016 ZXing authors
*/
// SPDX-License-Identifier: Apache-2.0

#include "QRBitMatrixParser.h"

#include "BitArray.h"
#include "BitMatrix.h"
#include "ByteArray.h"
#include "QRDataMask.h"
#include "QRFormatInformation.h"
#include "QRVersion.h"

#include <utility>

namespace ZXing::QRCode {

static bool getBit(const BitMatrix& bitMatrix, int x, int y, bool mirrored = false)
{
	return mirrored ? bitMatrix.get(y, x) : bitMatrix.get(x, y);
}

static bool hasValidDimension(const BitMatrix& bitMatrix, bool isMicro)
{
	int dimension = bitMatrix.height();
	if (isMicro)
		return dimension >= 11 && dimension <= 17 && (dimension % 2) == 1;
	else
		return dimension >= 21 && dimension <= 177 && (dimension % 4) == 1;
}

const Version* ReadVersion(const BitMatrix& bitMatrix)
{
	int dimension = bitMatrix.height();
	bool isMicro = dimension < 21;

	if (!hasValidDimension(bitMatrix, isMicro))
		return nullptr;

	int provisionalVersion = (dimension - Version::DimensionOffset(isMicro)) / Version::DimensionStep(isMicro);

	if (provisionalVersion <= 6)
		return Version::VersionForNumber(provisionalVersion, isMicro);

	for (bool mirror : {false, true}) {
		// Read top-right/bottom-left version info: 3 wide by 6 tall (depending on mirrored)
		int versionBits = 0;
		for (int y = 5; y >= 0; --y)
			for (int x = dimension - 9; x >= dimension - 11; --x)
				AppendBit(versionBits, getBit(bitMatrix, x, y, mirror));

		auto theParsedVersion = Version::DecodeVersionInformation(versionBits);
		// TODO: why care for the contents of the version bits if we know the dimension already?
		if (theParsedVersion != nullptr && theParsedVersion->dimensionForVersion() == dimension)
			return theParsedVersion;
	}

	return nullptr;
}

FormatInformation ReadFormatInformation(const BitMatrix& bitMatrix, bool isMicro)
{
	if (!hasValidDimension(bitMatrix, isMicro))
		return {};

	if (isMicro) {
		// Read top-left format info bits
		int formatInfoBits = 0;
		for (int x = 1; x < 9; x++)
			AppendBit(formatInfoBits, getBit(bitMatrix, x, 8));
		for (int y = 7; y >= 1; y--)
			AppendBit(formatInfoBits, getBit(bitMatrix, 8, y));

		return FormatInformation::DecodeMQR(formatInfoBits);
	}

	// Read top-left format info bits
	int formatInfoBits1 = 0;
	for (int x = 0; x < 6; x++)
		AppendBit(formatInfoBits1, getBit(bitMatrix, x, 8));
	// .. and skip a bit in the timing pattern ...
	AppendBit(formatInfoBits1, getBit(bitMatrix, 7, 8));
	AppendBit(formatInfoBits1, getBit(bitMatrix, 8, 8));
	AppendBit(formatInfoBits1, getBit(bitMatrix, 8, 7));
	// .. and skip a bit in the timing pattern ...
	for (int y = 5; y >= 0; y--)
		AppendBit(formatInfoBits1, getBit(bitMatrix, 8, y));

	// Read the top-right/bottom-left pattern including the 'Dark Module' from the bottom-left
	// part that has to be considered separately when looking for mirrored symbols.
	// See also FormatInformation::DecodeQR
	int dimension = bitMatrix.height();
	int formatInfoBits2 = 0;
	for (int y = dimension - 1; y >= dimension - 8; y--)
		AppendBit(formatInfoBits2, getBit(bitMatrix, 8, y));
	for (int x = dimension - 8; x < dimension; x++)
		AppendBit(formatInfoBits2, getBit(bitMatrix, x, 8));

	return FormatInformation::DecodeQR(formatInfoBits1, formatInfoBits2);
}

static ByteArray ReadQRCodewords(const BitMatrix& bitMatrix, const Version& version, const FormatInformation& formatInfo)
{
	BitMatrix functionPattern = version.buildFunctionPattern();

	ByteArray result;
	result.reserve(version.totalCodewords());
	uint8_t currentByte = 0;
	bool readingUp = true;
	int bitsRead = 0;
	int dimension = bitMatrix.height();
	// Read columns in pairs, from right to left
	for (int x = dimension - 1; x > 0; x -= 2) {
		// Skip whole column with vertical timing pattern.
		if (x == 6)
			x--;
		// Read alternatingly from bottom to top then top to bottom
		for (int row = 0; row < dimension; row++) {
			int y = readingUp ? dimension - 1 - row : row;
			for (int col = 0; col < 2; col++) {
				int xx = x - col;
				// Ignore bits covered by the function pattern
				if (!functionPattern.get(xx, y)) {
					// Read a bit
					AppendBit(currentByte,
							  GetDataMaskBit(formatInfo.dataMask, xx, y) != getBit(bitMatrix, xx, y, formatInfo.isMirrored));
					// If we've made a whole byte, save it off
					if (++bitsRead % 8 == 0)
						result.push_back(std::exchange(currentByte, 0));
				}
			}
		}
		readingUp = !readingUp; // switch directions
	}
	if (Size(result) != version.totalCodewords())
		return {};

	return result;
}

static ByteArray ReadMQRCodewords(const BitMatrix& bitMatrix, const QRCode::Version& version, const FormatInformation& formatInfo)
{
	BitMatrix functionPattern = version.buildFunctionPattern();

	// D3 in a Version M1 symbol, D11 in a Version M3-L symbol and D9
	// in a Version M3-M symbol is a 2x2 square 4-module block.
	// See ISO 18004:2006 6.7.3.
	bool hasD4mBlock = version.versionNumber() % 2 == 1;
	int d4mBlockIndex =
		version.versionNumber() == 1 ? 3 : (formatInfo.ecLevel == QRCode::ErrorCorrectionLevel::Low ? 11 : 9);

	ByteArray result;
	result.reserve(version.totalCodewords());
	uint8_t currentByte = 0;
	bool readingUp = true;
	int bitsRead = 0;
	int dimension = bitMatrix.height();
	// Read columns in pairs, from right to left
	for (int x = dimension - 1; x > 0; x -= 2) {
		// Read alternatingly from bottom to top then top to bottom
		for (int row = 0; row < dimension; row++) {
			int y = readingUp ? dimension - 1 - row : row;
			for (int col = 0; col < 2; col++) {
				int xx = x - col;
				// Ignore bits covered by the function pattern
				if (!functionPattern.get(xx, y)) {
					// Read a bit
					AppendBit(currentByte,
							  GetDataMaskBit(formatInfo.dataMask, xx, y, true) != getBit(bitMatrix, xx, y, formatInfo.isMirrored));
					++bitsRead;
					// If we've made a whole byte, save it off; save early if 2x2 data block.
					if (bitsRead == 8 || (bitsRead == 4 && hasD4mBlock && Size(result) == d4mBlockIndex - 1)) {
						result.push_back(std::exchange(currentByte, 0));
						bitsRead = 0;
					}
				}
			}
		}
		readingUp = !readingUp; // switch directions
	}
	if (Size(result) != version.totalCodewords())
		return {};

	return result;
}

ByteArray ReadCodewords(const BitMatrix& bitMatrix, const Version& version, const FormatInformation& formatInfo)
{
	if (!hasValidDimension(bitMatrix, version.isMicroQRCode()))
		return {};

	return version.isMicroQRCode() ? ReadMQRCodewords(bitMatrix, version, formatInfo)
								   : ReadQRCodewords(bitMatrix, version, formatInfo);
}

} // namespace ZXing::QRCode
