using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;

namespace JMonAgent;

public interface IMetricCollector
{
    SystemMetrics Collect();
}

public class LinuxMetricCollector : IMetricCollector
{
    private long _prevJiffy;
    private long _prevIdle;
    private string? _cachedIpAddress;
    private string? _cachedHwId;
    
    public SystemMetrics Collect()
    {
        var memInfo = ParseMemInfo();
        var swapInfo = ParseSwapInfo();
        var diskInfo = ParseDiskInfo();
        
        // Cache IP and HWID on first call
        _cachedIpAddress ??= GetIpAddress();
        _cachedHwId ??= GetHwId();
        
        return new SystemMetrics(
            Environment.MachineName,
            RuntimeInformation.OSDescription,
            GetCpuUsage(),
            memInfo.UsedBytes,
            memInfo.TotalBytes,
            swapInfo.UsedBytes,
            swapInfo.TotalBytes,
            diskInfo.UsedBytes,
            diskInfo.TotalBytes,
            diskInfo.MountPoint,
            DateTime.UtcNow,
            _cachedIpAddress ?? "",
            _cachedHwId ?? "",
            Environment.ProcessId
        );
    }

    private string GetIpAddress()
    {
        try
        {
            var psi = new ProcessStartInfo("hostname", "-I")
            {
                RedirectStandardOutput = true,
                UseShellExecute = false,
                CreateNoWindow = true
            };
            
            using var process = Process.Start(psi);
            if (process == null) return "";
            
            var output = process.StandardOutput.ReadToEnd().Trim();
            var addresses = output.Split(' ', StringSplitOptions.RemoveEmptyEntries);
            return addresses.FirstOrDefault() ?? "";
        }
        catch
        {
            return "";
        }
    }

    private string GetHwId()
    {
        try
        {
            // Try to read machine-id from Linux
            if (File.Exists("/etc/machine-id"))
            {
                return File.ReadAllText("/etc/machine-id").Trim();
            }
            
            // Fallback: use MAC address from first interface
            var interfaces = Directory.GetFiles("/sys/class/net/");
            if (interfaces.Length > 0)
            {
                var firstInterface = Path.GetFileName(interfaces[0]);
                var macPath = $"/sys/class/net/{firstInterface}/address";
                if (File.Exists(macPath))
                {
                    return File.ReadAllText(macPath).Trim();
                }
            }
            
            return "";
        }
        catch
        {
            return "";
        }
    }

    private (long UsedBytes, long TotalBytes) ParseMemInfo()
    {
        try
        {
            var lines = File.ReadAllLines("/proc/meminfo");
            var dict = new Dictionary<string, long>();

            foreach (var line in lines)
            {
                var parts = line.Split(':', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length == 2 && long.TryParse(Regex.Replace(parts[1], @"\D+", ""), out var value))
                {
                    dict[parts[0]] = value * 1024; // Convert from KB to bytes
                }
            }

            long total = dict.TryGetValue("MemTotal", out var t) ? t : 0;
            long available = dict.TryGetValue("MemAvailable", out var a) ? a : 0;
            long used = total - available;

            return (used, total);
        }
        catch
        {
            return (0, 0);
        }
    }

    private (long UsedBytes, long TotalBytes) ParseSwapInfo()
    {
        try
        {
            var lines = File.ReadAllLines("/proc/meminfo");
            var dict = new Dictionary<string, long>();

            foreach (var line in lines)
            {
                var parts = line.Split(':', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length == 2 && long.TryParse(Regex.Replace(parts[1], @"\D+", ""), out var value))
                {
                    dict[parts[0]] = value * 1024; // Convert from KB to bytes
                }
            }

            long total = dict.TryGetValue("SwapTotal", out var st) ? st : 0;
            long free = dict.TryGetValue("SwapFree", out var sf) ? sf : 0;
            long used = total - free;

            return (used, total);
        }
        catch
        {
            return (0, 0);
        }
    }

    private (long UsedBytes, long TotalBytes, string MountPoint) ParseDiskInfo()
    {
        try
        {
            // Use 'df' command to get root filesystem info
            var psi = new ProcessStartInfo("df", "-B1 /")
            {
                RedirectStandardOutput = true,
                UseShellExecute = false,
                CreateNoWindow = true
            };
            
            using var process = Process.Start(psi);
            if (process == null) return (0, 0, "/");
            
            var output = process.StandardOutput.ReadToEnd();
            var lines = output.Split('\n', StringSplitOptions.RemoveEmptyEntries);
            
            // Skip header, parse second line
            if (lines.Length >= 2)
            {
                var parts = lines[1].Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length >= 4 
                    && long.TryParse(parts[1], out var total)
                    && long.TryParse(parts[2], out var used))
                {
                    return (used, total, parts[parts.Length - 1]);
                }
            }

            return (0, 0, "/");
        }
        catch
        {
            return (0, 0, "/");
        }
    }

    private double GetCpuUsage()
    {
        try
        {
            var firstLine = File.ReadLines("/proc/stat").First();
            var parts = firstLine.Split(' ', StringSplitOptions.RemoveEmptyEntries);
            if (parts.Length < 5) return 0.0;

            // /proc/stat format: cpu  user nice system idle iowait irq softirq steal guest guest_nice
            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 totalJiffy = user + nice + system + idle;
            long activeJiffy = user + nice + system;
            
            // First call - initialize baseline
            if (_prevJiffy == 0)
            {
                _prevJiffy = totalJiffy;
                _prevIdle = idle;
                return 0.0;
            }

            // Calculate deltas
            long diffTotal = totalJiffy - _prevJiffy;
            long diffIdle = idle - _prevIdle;

            _prevJiffy = totalJiffy;
            _prevIdle = idle;

            if (diffTotal == 0) return 0.0;
            
            double usage = 100.0 * (1.0 - ((double)diffIdle / diffTotal));
            return Math.Max(0, Math.Min(100, usage));
        }
        catch 
        { 
            return 0.0; 
        }
    }
}

public class WindowsMetricCollector : IMetricCollector
{
    public SystemMetrics Collect()
    {
        // TODO: Use PerformanceCounters or WMI for Windows
        return new SystemMetrics(
            Environment.MachineName,
            RuntimeInformation.OSDescription,
            0.0,
            0,
            0,
            0,
            0,
            0,
            0,
            "C:\\",
            DateTime.UtcNow,
            "",
            "",
            Environment.ProcessId
        );
    }
}

public class MacMetricCollector : IMetricCollector
{
    public SystemMetrics Collect()
    {
        // TODO: Use sysctl for macOS metrics
        return new SystemMetrics(
            Environment.MachineName,
            RuntimeInformation.OSDescription,
            0.0,
            0,
            0,
            0,
            0,
            0,
            0,
            "/",
            DateTime.UtcNow,
            "",
            "",
            Environment.ProcessId
        );
    }
}