using System;
using System.IO;
using System.Linq;
using System.Xml.Linq;

namespace Unosquare.Swan.Components {
  /// <summary>
  /// Represents a CsProjFile (and FsProjFile) parser.
  /// </summary>
  /// <remarks>
  /// Based on https://github.com/maartenba/dotnetcli-init.
  /// </remarks>
  /// <typeparam name="T">The type of <c>CsProjMetadataBase</c>.</typeparam>
  /// <seealso cref="System.IDisposable" />
  public class CsProjFile<T>
      : IDisposable
      where T : CsProjMetadataBase {
    private readonly Stream _stream;
    private readonly Boolean _leaveOpen;
    private readonly XDocument _xmlDocument;

    /// <summary>
    /// Initializes a new instance of the <see cref="CsProjFile{T}"/> class.
    /// </summary>
    /// <param name="filename">The filename.</param>
    public CsProjFile(String filename = null)
        : this(OpenFile(filename)) {
      // placeholder
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CsProjFile{T}"/> class.
    /// </summary>
    /// <param name="stream">The stream.</param>
    /// <param name="leaveOpen">if set to <c>true</c> [leave open].</param>
    /// <exception cref="ArgumentException">Project file is not of the new .csproj type.</exception>
    public CsProjFile(Stream stream, Boolean leaveOpen = false) {
      this._stream = stream;
      this._leaveOpen = leaveOpen;

      this._xmlDocument = XDocument.Load(stream);

      XElement projectElement = this._xmlDocument.Descendants("Project").FirstOrDefault();
      XAttribute sdkAttribute = projectElement?.Attribute("Sdk");
      String sdk = sdkAttribute?.Value;
      if(sdk != "Microsoft.NET.Sdk" && sdk != "Microsoft.NET.Sdk.Web") {
        throw new ArgumentException("Project file is not of the new .csproj type.");
      }

      this.Metadata = Activator.CreateInstance<T>();
      this.Metadata.SetData(this._xmlDocument);
    }

    /// <summary>
    /// Gets the metadata.
    /// </summary>
    /// <value>
    /// The nu get metadata.
    /// </value>
    public T Metadata {
      get;
    }

    /// <summary>
    /// Saves this instance.
    /// </summary>
    public void Save() {
      this._stream.SetLength(0);
      this._stream.Position = 0;

      this._xmlDocument.Save(this._stream);
    }

    /// <inheritdoc />
    public void Dispose() {
      if(!this._leaveOpen) {
        this._stream?.Dispose();
      }
    }

    private static FileStream OpenFile(String filename) {
      if(filename == null) {
        filename = Directory
            .EnumerateFiles(Directory.GetCurrentDirectory(), "*.csproj", SearchOption.TopDirectoryOnly)
            .FirstOrDefault();
      }

      if(filename == null) {
        filename = Directory
            .EnumerateFiles(Directory.GetCurrentDirectory(), "*.fsproj", SearchOption.TopDirectoryOnly)
            .FirstOrDefault();
      }

      if(String.IsNullOrWhiteSpace(filename)) {
        throw new ArgumentNullException(nameof(filename));
      }

      return File.Open(filename, FileMode.OpenOrCreate, FileAccess.ReadWrite);
    }
  }
}