using System.Globalization;

using GSS2.Core.Extentions;

using Microsoft.Extensions.Logging;

namespace GSS2.Core.Hardware;

public class ComputeResourcesService
{
    public record CpuUsage(double AllUsagePercent, List<double> CoreUsagePercents);
    public record CpuTemperature(double Current, double Critical);
    public record MemoryUsage(
        long TotalB, long UsedB, long AvailableB,
        double TotalkB, double UsedkB, double AvailablekB,
        double TotalMB, double UsedMB, double AvailableMB,
        double TotalGB, double UsedGB, double AvailableGB)
    {
        public MemoryUsage(long totalB, long usedB, long availableB) :
        this(
            TotalB: totalB, UsedB: usedB, AvailableB: availableB,
            TotalkB: totalB / 1000, UsedkB: usedB / 1000, AvailablekB: availableB / 1000,
            TotalMB: totalB / Math.Pow(1000.0, 2), UsedMB: usedB / Math.Pow(1000.0, 2), AvailableMB: availableB / Math.Pow(1000.0, 2),
            TotalGB: totalB / Math.Pow(1000.0, 3), UsedGB: usedB / Math.Pow(1000.0, 3), AvailableGB: availableB / Math.Pow(1000.0, 3)
        )
        { }
    }
    public record ComputeResourcesSnapshot(CpuUsage CpuUsage, MemoryUsage MemoryUsage, CpuTemperature CpuTemperature, DateTime Timestamp);
    private readonly ILogger<ComputeResourcesService> _logger;

    private (long idle, long total)? _prevAll = null;
    private Dictionary<int, (long idle, long total)?>? _prevCores = null;

    public ComputeResourcesService(ILogger<ComputeResourcesService> logger)
    {
        _logger = logger;
        _logger.LogInformation("Initialization");
        _logger.LogInformation("Initialized");
    }

    public ComputeResourcesSnapshot GetSnapshot()
    {
        return new ComputeResourcesSnapshot(
            CpuUsage: GetCpuUsage(),
            CpuTemperature: GetCpuTemperature(),
            MemoryUsage: GetMemoryUsage(),
            Timestamp: DateTime.UtcNow
        );
    }
    private CpuUsage GetCpuUsage()
    {
        static (double usage, long idle, long total) ParceLines(string line, (long idle, long total)? prev)
        {
            var parts = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);
            long user = long.Parse(parts[1]);
            long nice = long.Parse(parts[2]);
            long system = long.Parse(parts[3]);
            long idle = long.Parse(parts[4]);
            long iowait = line.Length > 5 ? long.Parse(parts[5]) : 0;
            long irq = line.Length > 6 ? long.Parse(parts[6]) : 0;
            long softirq = line.Length > 7 ? long.Parse(parts[7]) : 0;

            long idleTime = idle + iowait;
            long totalTime = idleTime + user + nice + system + irq + softirq;

            double usage = 0;

            if (prev is not null)
            {
                long totalDiff = totalTime - prev.Value.total;
                long idleDiff = idleTime - prev.Value.idle;


                if (totalDiff > 0)
                    usage = (double)(totalDiff - idleDiff) / totalDiff * 100.0;
            }

            return (usage, idleTime, totalTime);
        }

        var lines = File.ReadLines("/proc/stat").Where(l => l.StartsWith("cpu"));
        if (lines.Count() == 0)
            return new CpuUsage(0, new List<double>());

        var (allUsage, allIdle, allTotal) = ParceLines(lines.First(), _prevAll);
        _prevAll = (allIdle, allTotal);

        var coreUsages = new List<double>();

        foreach (var (i, line) in lines.Skip(1).Enumerate())
        {
            if (_prevCores is null)
                _prevCores = new Dictionary<int, (long idle, long total)?>();
            if (!_prevCores.ContainsKey(i))
                _prevCores.Add(i, null);
            var (coreUsage, coreIdle, coreTotal) = ParceLines(line, _prevCores[i]);
            _prevCores[i] = (coreIdle, coreTotal);
            coreUsages.Add(coreUsage);
        }

        return new CpuUsage(
            AllUsagePercent: allUsage,
            CoreUsagePercents: coreUsages
        );
    }
    private CpuTemperature GetCpuTemperature()
    {
        var currentStr = File.ReadAllText("/sys/class/thermal/thermal_zone0/temp").Trim();
        var current = int.Parse(currentStr) / 1000.0;

        var criticalFile = Directory.GetFiles("/sys/class/thermal/thermal_zone0/", "trip_point_*_type")
            .FirstOrDefault(f => File.ReadAllText(f).Trim() == "critical")?
            .Replace("_type", "_temp");

        double critical = 100.0;
        if (criticalFile is not null)
        {
            var criticalStr = File.ReadAllText(criticalFile).Trim();
            critical = int.Parse(criticalStr) / 1000.0;
        }

        return new CpuTemperature(
            Current: current,
            Critical: critical
        );
    }
    private MemoryUsage GetMemoryUsage()
    {
        var memInfo = File.ReadAllLines("/proc/meminfo")
            .Select(l => l.Split(':', 2))
            .ToDictionary(
                p => p[0],
                p => long.Parse(p[1].Trim().Split(' ')[0], CultureInfo.InvariantCulture) * 1024
            );

        long total = memInfo["MemTotal"];
        long available = memInfo.ContainsKey("MemAvailable") ? memInfo["MemAvailable"] : memInfo["MemFree"];

        long used = total - available;

        return new MemoryUsage(totalB: total, usedB: used, availableB: available);
    }
}