using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
using System.Text.RegularExpressions;
using Hardware.Info;
using Microsoft.Win32;

namespace StabilityMatrix.Core.Helper.HardwareInfo;

public static partial class HardwareHelper
{
    private static IReadOnlyList<GpuInfo>? cachedGpuInfos;

    private static readonly Lazy<IHardwareInfo> HardwareInfoLazy =
        new(() => new Hardware.Info.HardwareInfo());

    public static IHardwareInfo HardwareInfo => HardwareInfoLazy.Value;

    private static string RunBashCommand(string command)
    {
        var processInfo = new ProcessStartInfo("bash", "-c \"" + command + "\"")
        {
            UseShellExecute = false,
            RedirectStandardOutput = true
        };

        var process = Process.Start(processInfo);

        process.WaitForExit();

        var output = process.StandardOutput.ReadToEnd();

        return output;
    }

    [SupportedOSPlatform("windows")]
    private static IEnumerable<GpuInfo> IterGpuInfoWindows()
    {
        const string gpuRegistryKeyPath =
            @"SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}";

        using var baseKey = Registry.LocalMachine.OpenSubKey(gpuRegistryKeyPath);

        if (baseKey == null)
            yield break;

        var gpuIndex = 0;

        foreach (var subKeyName in baseKey.GetSubKeyNames().Where(k => k.StartsWith("0")))
        {
            using var subKey = baseKey.OpenSubKey(subKeyName);
            if (subKey != null)
            {
                yield return new GpuInfo
                {
                    Index = gpuIndex++,
                    Name = subKey.GetValue("DriverDesc")?.ToString(),
                    MemoryBytes = Convert.ToUInt64(
                        subKey.GetValue("HardwareInformation.qwMemorySize")
                    ),
                };
            }
        }
    }

    [SupportedOSPlatform("linux")]
    private static IEnumerable<GpuInfo> IterGpuInfoLinux()
    {
        var output = RunBashCommand("lspci | grep VGA");
        var gpuLines = output.Split("\n");

        var gpuIndex = 0;

        foreach (var line in gpuLines)
        {
            if (string.IsNullOrWhiteSpace(line))
                continue;

            var gpuId = line.Split(' ')[0]; // The GPU ID is the first part of the line
            var gpuOutput = RunBashCommand($"lspci -v -s {gpuId}");

            ulong memoryBytes = 0;
            string? name = null;

            // Parse output with regex
            var match = Regex.Match(gpuOutput, @"VGA compatible controller: ([^\n]*)");
            if (match.Success)
            {
                name = match.Groups[1].Value.Trim();
            }

            match = Regex.Match(gpuOutput, @"prefetchable\) \[size=(\\d+)M\]");
            if (match.Success)
            {
                memoryBytes = ulong.Parse(match.Groups[1].Value) * 1024 * 1024;
            }

            yield return new GpuInfo
            {
                Index = gpuIndex++,
                Name = name,
                MemoryBytes = memoryBytes
            };
        }
    }

    /// <summary>
    /// Yields GpuInfo for each GPU in the system.
    /// </summary>
    public static IEnumerable<GpuInfo> IterGpuInfo()
    {
        if (Compat.IsWindows)
        {
            return IterGpuInfoWindows();
        }
        else if (Compat.IsLinux)
        {
            // Since this requires shell commands, fetch cached value if available.
            if (cachedGpuInfos is not null)
            {
                return cachedGpuInfos;
            }

            // No cache, fetch and cache.
            cachedGpuInfos = IterGpuInfoLinux().ToList();
            return cachedGpuInfos;
        }
        // TODO: Implement for macOS
        return Enumerable.Empty<GpuInfo>();
    }

    /// <summary>
    /// Return true if the system has at least one Nvidia GPU.
    /// </summary>
    public static bool HasNvidiaGpu()
    {
        return IterGpuInfo().Any(gpu => gpu.IsNvidia);
    }

    /// <summary>
    /// Return true if the system has at least one AMD GPU.
    /// </summary>
    public static bool HasAmdGpu()
    {
        return IterGpuInfo().Any(gpu => gpu.IsAmd);
    }

    // Set ROCm for default if AMD and Linux
    public static bool PreferRocm() => !HasNvidiaGpu() && HasAmdGpu() && Compat.IsLinux;

    // Set DirectML for default if AMD and Windows
    public static bool PreferDirectML() => !HasNvidiaGpu() && HasAmdGpu() && Compat.IsWindows;

    /// <summary>
    /// Gets the total and available physical memory in bytes.
    /// </summary>
    public static MemoryInfo GetMemoryInfo() =>
        Compat.IsWindows ? GetMemoryInfoImplWindows() : GetMemoryInfoImplGeneric();

    [SupportedOSPlatform("windows")]
    private static MemoryInfo GetMemoryInfoImplWindows()
    {
        var memoryStatus = new Win32MemoryStatusEx();

        if (!GlobalMemoryStatusEx(ref memoryStatus))
        {
            throw new Win32Exception(Marshal.GetLastWin32Error());
        }

        if (!GetPhysicallyInstalledSystemMemory(out var installedMemoryKb))
        {
            throw new Win32Exception(Marshal.GetLastWin32Error());
        }

        return new MemoryInfo
        {
            TotalInstalledBytes = (ulong)installedMemoryKb * 1024,
            TotalPhysicalBytes = memoryStatus.UllTotalPhys,
            AvailablePhysicalBytes = memoryStatus.UllAvailPhys
        };
    }

    private static MemoryInfo GetMemoryInfoImplGeneric()
    {
        HardwareInfo.RefreshMemoryList();

        return new MemoryInfo
        {
            TotalPhysicalBytes = HardwareInfo.MemoryStatus.TotalPhysical,
            AvailablePhysicalBytes = HardwareInfo.MemoryStatus.AvailablePhysical
        };
    }

    /// <summary>
    /// Gets cpu info
    /// </summary>
    public static Task<CpuInfo> GetCpuInfoAsync() =>
        Compat.IsWindows ? Task.FromResult(GetCpuInfoImplWindows()) : GetCpuInfoImplGenericAsync();

    [SupportedOSPlatform("windows")]
    private static CpuInfo GetCpuInfoImplWindows()
    {
        var info = new CpuInfo();

        using var processorKey = Registry.LocalMachine.OpenSubKey(
            @"Hardware\Description\System\CentralProcessor\0",
            RegistryKeyPermissionCheck.ReadSubTree
        );

        if (processorKey?.GetValue("ProcessorNameString") is string processorName)
        {
            info = info with { ProcessorCaption = processorName.Trim() };
        }

        return info;
    }

    private static Task<CpuInfo> GetCpuInfoImplGenericAsync()
    {
        return Task.Run(() =>
        {
            HardwareInfo.RefreshCPUList();

            return new CpuInfo
            {
                ProcessorCaption = HardwareInfo.CpuList.FirstOrDefault()?.Caption.Trim() ?? ""
            };
        });
    }

    [SupportedOSPlatform("windows")]
    [LibraryImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool GetPhysicallyInstalledSystemMemory(out long totalMemoryInKilobytes);

    [SupportedOSPlatform("windows")]
    [LibraryImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool GlobalMemoryStatusEx(ref Win32MemoryStatusEx lpBuffer);
}