#include <iostream>
#include <fstream>
#include <cstdint>
#include <vector>
#include <filesystem>
#include <ctime>
#include <algorithm>

static constexpr uint8_t magic[] = {0xf6, 0x76, 0xd8, 0x09};

struct __attribute__((packed)) Frame {
	uint64_t time;
	uint32_t steps;
	uint8_t batteryPercent;
	uint8_t heartRate;
	uint8_t pad[2];
};

bool arrayeq(const uint8_t* a, const uint8_t* b, size_t len)
{
	for(size_t i = 0; i < len; ++i)
	{
		if(a[i] != b[i])
			return false;
	}

	return true;
}

std::vector<Frame> readFile(const std::filesystem::path& path)
{
	std::ifstream file;
	file.open(path, std::ios_base::binary | std::ios_base::in);
	if(!file.is_open())
	{
		std::cout<<"could not open "<<path<<'\n';
		return {};
	}

	uint8_t magicRef[4];
	file.read(reinterpret_cast<char*>(&magicRef), 4);

	if(!arrayeq(magic, magicRef, 4))
	{
		std::cout<<path<<" is not a valid infitime log file\n";
		return {};
	}

	uint8_t versionMajor;
	uint8_t versionMinor;
	file.read(reinterpret_cast<char*>(&versionMajor), 1);
	file.read(reinterpret_cast<char*>(&versionMinor), 1);

	if(versionMajor > 1 || file.bad())
	{
		std::cout<<path<<" is a file of version "<<versionMajor<<'.'<<versionMinor<<" this application supports only versions 1.x and below\n";
		return {};
	}

	uint16_t size;
	file.read(reinterpret_cast<char*>(&size), sizeof(size));

	if(sizeof(Frame) != size)
	{
		std::cout<<path<<" contains frames of an unexpected size\n";
		return {};
	}

	uint32_t length;
	file.read(reinterpret_cast<char*>(&length), sizeof(length));

	std::vector<Frame> frames;
	frames.reserve(length);

	for(size_t i = 0; i < length && !file.bad(); ++i)
	{
		Frame frame = {};
		file.read(reinterpret_cast<char*>(&frame), sizeof(frame));

		if(frame.time != 0)
			frames.push_back(frame);
	}

	std::sort(frames.begin(), frames.end(), [](const Frame& a, const Frame& b){return a.time < b.time;});
	return frames;
}

int main(int argc, char** argv)
{
	if(argc < 2)
	{
		std::cout<<"Usage: "<<(argc > 0 ? argv[0] : "infinilog")<<" [LOG_FILE]\n";
		return 1;
	}

	std::vector<Frame> frames = readFile(argv[1]);

	if(frames.empty())
		return 1;

	std::cout<<"timestamp, steps, battery percent, heart rate\n";
	for(auto& frame : frames) {
		std::time_t time = frame.time;
		std::tm* ptm = std::localtime(&time);
		char timeBuffer[32];
		std::strftime(timeBuffer, 32, "%a, %d.%m.%Y %H:%M:%S", ptm);

		std::cout<<timeBuffer<<", "<<frame.steps<<", "<<static_cast<int>(frame.batteryPercent)<<", "<<static_cast<int>(frame.heartRate)<<'\n';
	}

	return 0;
}