using Unosquare.RaspberryIO.Native;
using Unosquare.Swan.Abstractions;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;

namespace Unosquare.RaspberryIO.Computer {
  /// <summary>
  /// http://raspberry-pi-guide.readthedocs.io/en/latest/system.html
  /// </summary>
  public sealed class SystemInfo : SingletonBase<SystemInfo> {
    private const String CpuInfoFilePath = "/proc/cpuinfo";
    private const String MemInfoFilePath = "/proc/meminfo";
    private const String UptimeFilePath = "/proc/uptime";
    private static readonly StringComparer StringComparer = StringComparer.InvariantCultureIgnoreCase;
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Codequalität", "IDE0052:Ungelesene private Member entfernen", Justification = "<Ausstehend>")]
    private static readonly Object SyncRoot = new Object();

    /// <summary>
    /// Prevents a default instance of the <see cref="SystemInfo"/> class from being created.
    /// </summary>
    /// <exception cref="NotSupportedException">Could not initialize the GPIO controller</exception>
    private SystemInfo() {
      #region Obtain and format a property dictionary

      PropertyInfo[] properties =
          typeof(SystemInfo).GetTypeInfo()
              .GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
              .Where(
                  p =>
                      p.CanWrite && p.CanRead &&
                      (p.PropertyType == typeof(String) || p.PropertyType == typeof(String[])))
              .ToArray();
      Dictionary<String, PropertyInfo> propDictionary = new Dictionary<String, PropertyInfo>(StringComparer);

      foreach(PropertyInfo prop in properties) {
        propDictionary[prop.Name.Replace(" ", String.Empty).ToLowerInvariant().Trim()] = prop;
      }

      #endregion

      #region Extract CPU information

      if(File.Exists(CpuInfoFilePath)) {
        String[] cpuInfoLines = File.ReadAllLines(CpuInfoFilePath);

        foreach(String line in cpuInfoLines) {
          String[] lineParts = line.Split(new[] { ':' }, 2);
          if(lineParts.Length != 2) {
            continue;
          }

          String propertyKey = lineParts[0].Trim().Replace(" ", String.Empty);
          String propertyStringValue = lineParts[1].Trim();

          if(!propDictionary.ContainsKey(propertyKey)) {
            continue;
          }

          PropertyInfo property = propDictionary[propertyKey];
          if(property.PropertyType == typeof(String)) {
            property.SetValue(this, propertyStringValue);
          } else if(property.PropertyType == typeof(String[])) {
            String[] propertyArrayAvalue = propertyStringValue.Split(' ');
            property.SetValue(this, propertyArrayAvalue);
          }
        }
      }

      #endregion

      #region Extract Memory Information

      if(File.Exists(MemInfoFilePath)) {
        String[] memInfoLines = File.ReadAllLines(MemInfoFilePath);
        foreach(String line in memInfoLines) {
          String[] lineParts = line.Split(new[] { ':' }, 2);
          if(lineParts.Length != 2) {
            continue;
          }

          if(lineParts[0].ToLowerInvariant().Trim().Equals("memtotal") == false) {
            continue;
          }

          String memKb = lineParts[1].ToLowerInvariant().Trim().Replace("kb", String.Empty).Trim();

          if(Int32.TryParse(memKb, out Int32 parsedMem)) {
            this.InstalledRam = parsedMem * 1024;
            break;
          }
        }
      }

      #endregion

      #region Board Version and Form Factor

      try {
        if(String.IsNullOrWhiteSpace(this.Revision) == false &&
            Int32.TryParse(
                this.Revision.ToUpperInvariant(),
                NumberStyles.HexNumber,
                CultureInfo.InvariantCulture,
                out Int32 boardVersion)) {
          this.RaspberryPiVersion = PiVersion.Unknown;
          if(Enum.GetValues(typeof(PiVersion)).Cast<Int32>().Contains(boardVersion)) {
            this.RaspberryPiVersion = (PiVersion)boardVersion;
          }
        }

        this.WiringPiBoardRevision = WiringPi.PiBoardRev();
      } catch {
        /* Ignore */
      }

      #endregion

      #region Version Information

      {
        String[] libParts = WiringPi.WiringPiLibrary.Split('.');
        Int32 major = Int32.Parse(libParts[libParts.Length - 2]);
        Int32 minor = Int32.Parse(libParts[libParts.Length - 1]);
        Version version = new Version(major, minor);
        this.WiringPiVersion = version;
      }

      #endregion

      #region Extract OS Info

      try {
        _ = Standard.Uname(out SystemName unameInfo);
        this.OperatingSystem = new OsInfo {
          DomainName = unameInfo.DomainName,
          Machine = unameInfo.Machine,
          NodeName = unameInfo.NodeName,
          Release = unameInfo.Release,
          SysName = unameInfo.SysName,
          Version = unameInfo.Version
        };
      } catch {
        this.OperatingSystem = new OsInfo();
      }

      #endregion
    }

    /// <summary>
    /// Gets the wiring pi library version.
    /// </summary>
    public Version WiringPiVersion {
      get;
    }

    /// <summary>
    /// Gets the OS information.
    /// </summary>
    /// <value>
    /// The os information.
    /// </value>
    public OsInfo OperatingSystem {
      get;
    }

    /// <summary>
    /// Gets the Raspberry Pi version.
    /// </summary>
    public PiVersion RaspberryPiVersion {
      get;
    }

    /// <summary>
    /// Gets the Wiring Pi board revision (1 or 2).
    /// </summary>
    /// <value>
    /// The wiring pi board revision.
    /// </value>
    public Int32 WiringPiBoardRevision {
      get;
    }

    /// <summary>
    /// Gets the number of processor cores.
    /// </summary>
    public Int32 ProcessorCount => Int32.TryParse(this.Processor, out Int32 outIndex) ? outIndex + 1 : 0;

    /// <summary>
    /// Gets the installed ram in bytes.
    /// </summary>
    public Int32 InstalledRam {
      get;
    }

    /// <summary>
    /// Gets a value indicating whether this CPU is little endian.
    /// </summary>
    public Boolean IsLittleEndian => BitConverter.IsLittleEndian;

    /// <summary>
    /// Gets the CPU model name.
    /// </summary>
    public String ModelName {
      get; private set;
    }

    /// <summary>
    /// Gets a list of supported CPU features.
    /// </summary>
    public String[] Features {
      get; private set;
    }

    /// <summary>
    /// Gets the CPU implementer hex code.
    /// </summary>
    public String CpuImplementer {
      get; private set;
    }

    /// <summary>
    /// Gets the CPU architecture code.
    /// </summary>
    public String CpuArchitecture {
      get; private set;
    }

    /// <summary>
    /// Gets the CPU variant code.
    /// </summary>
    public String CpuVariant {
      get; private set;
    }

    /// <summary>
    /// Gets the CPU part code.
    /// </summary>
    public String CpuPart {
      get; private set;
    }

    /// <summary>
    /// Gets the CPU revision code.
    /// </summary>
    public String CpuRevision {
      get; private set;
    }

    /// <summary>
    /// Gets the hardware model number.
    /// </summary>
    public String Hardware {
      get; private set;
    }

    /// <summary>
    /// Gets the hardware revision number.
    /// </summary>
    public String Revision {
      get; private set;
    }

    /// <summary>
    /// Gets the serial number.
    /// </summary>
    public String Serial {
      get; private set;
    }

    /// <summary>
    /// Gets the system uptime (in seconds).
    /// </summary>
    public Double Uptime {
      get {
        try {
          if(File.Exists(UptimeFilePath) == false) {
            return 0;
          }

          String[] parts = File.ReadAllText(UptimeFilePath).Trim().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
          if(parts.Length >= 1 && Single.TryParse(parts[0], out Single result)) {
            return result;
          }
        } catch {
          /* Ignore */
        }

        return 0;
      }
    }

    /// <summary>
    /// Gets the uptime in TimeSpan.
    /// </summary>
    public TimeSpan UptimeTimeSpan => TimeSpan.FromSeconds(this.Uptime);

    /// <summary>
    /// Placeholder for processor index
    /// </summary>
    private String Processor {
      get; set;
    }

    /// <summary>
    /// Returns a <see cref="String" /> that represents this instance.
    /// </summary>
    /// <returns>
    /// A <see cref="String" /> that represents this instance.
    /// </returns>
    public override String ToString() {
      PropertyInfo[] properties = typeof(SystemInfo).GetTypeInfo().GetProperties(BindingFlags.Instance | BindingFlags.Public)
          .Where(p => p.CanRead && (
                          p.PropertyType == typeof(String) ||
                          p.PropertyType == typeof(String[]) ||
                          p.PropertyType == typeof(Int32) ||
                          p.PropertyType == typeof(Boolean) ||
                          p.PropertyType == typeof(TimeSpan)))
          .ToArray();

      List<String> properyValues = new List<String>
      {
                "System Information",
                $"\t{nameof(this.WiringPiVersion),-22}: {this.WiringPiVersion}",
                $"\t{nameof(this.RaspberryPiVersion),-22}: {this.RaspberryPiVersion}"
            };

      foreach(PropertyInfo property in properties) {
        if(property.PropertyType != typeof(String[])) {
          properyValues.Add($"\t{property.Name,-22}: {property.GetValue(this)}");
        } else if(property.GetValue(this) is String[] allValues) {
          String concatValues = String.Join(" ", allValues);
          properyValues.Add($"\t{property.Name,-22}: {concatValues}");
        }
      }

      return String.Join(Environment.NewLine, properyValues.ToArray());
    }
  }
}