using Microsoft.Win32;
using System;
using System.Drawing;
using System.IO;
using System.Net;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Linq;

// A program that will periodically download an image from Unsplash and
// change your Windows desktop background to the downloaded image

// Compilation: csc /out:unsplash.exe /t:winexe .\Program.cs /nologo /o

// After compilation, drop the executable in a folder and run it with some command line args
// args[0] = minutes (how often to change the background image
// args[1] = search terms to find your desire type of wallpaper

// Example invocation:
// unsplash.exe 60 nature,scenary
// This will change the wallpaper every hour from category of nature and scenary


namespace Unsplash {

  // Very simple logger implementation with a lock!
  public class FileLogger {
    protected readonly object locker = new object();
    const string LOG_FILE_PATH = "application.log";
    const bool ALSO_LOG_TO_STDOUT = true;

    public void Log(string message) {
      lock (locker) {
        using (var streamWriter = new StreamWriter(LOG_FILE_PATH, append: true)) {
          var line = string.Format("{0} \t {1}", DateTime.Now.ToString("MM/d/yyyy hh:mm:ss tt zzzz"), message);
          streamWriter.WriteLine(line);
          if (ALSO_LOG_TO_STDOUT) Console.WriteLine(line);
        }
      }
    }
  }

  class Program {
    const int ONE_HOUR_MS = 60 * 60 * 1000;
    const int FIFTEEN_MINUTES_MS = ONE_HOUR_MS / 4;
    const string IMAGE_DIR_NAME = "Unsplash";
    const int DEFAULT_SEARCH_INTERVAL_MINUTES = 15;
    const string DEFAULT_SEARCH_CATEGORY = "nature,scenary,landmarks";

    // Arg 0 = width, Arg 1 = height, Arg 2 = search terms (comma separated)
    const string SEARCH_URL_TEMPLATE = "https://source.unsplash.com/{0}x{1}/?{2}";

    static string url;
    static FileLogger logger = new FileLogger();
    static uint timerCallCount = 0;

    static void Main(string[] args) {
      SetAppBasePath();
      logger.Log("Application started");

      if (args.Length < 2) {
        logger.Log(String.Format("Setting default arguments since no arguments were specified. Interval = {0} minutes, search category = {1}",
          DEFAULT_SEARCH_INTERVAL_MINUTES, DEFAULT_SEARCH_CATEGORY));
        args = new string[] { DEFAULT_SEARCH_INTERVAL_MINUTES.ToString(), DEFAULT_SEARCH_CATEGORY };
      }

      var searchTerms = args[1];
      var screenBounds = Screen.AllScreens.Where(x => x.Primary).First().Bounds;
      logger.Log("Primary screen bounds: " + screenBounds.ToString());

      url = string.Format(SEARCH_URL_TEMPLATE, screenBounds.Width, screenBounds.Height, searchTerms);

      if (int.TryParse(args[0], out int interval)) {
        interval *= 60 * 1000; // convert minutes to milliseconds
        if (interval < FIFTEEN_MINUTES_MS) interval = FIFTEEN_MINUTES_MS;
      }
      else {
        interval = ONE_HOUR_MS;
      }

      new System.Threading.Timer(Tick, null, 0, interval);

      while (true) System.Threading.Thread.Sleep(1000);
    }

    private static void SetAppBasePath() {
      string imageDownloadDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, IMAGE_DIR_NAME);
      if (!Directory.Exists(imageDownloadDir)) { Directory.CreateDirectory(imageDownloadDir); }
      Directory.SetCurrentDirectory(imageDownloadDir);
    }

    private static void Tick(object state) {
      string imageFileName = ImageDownloader.Download(url);
      var logMessage = string.Format("Tick count: {0}. Setting wallpaper to {1}", ++timerCallCount, imageFileName);
      logger.Log(logMessage);
      Wallpaper.Set(imageFileName, Wallpaper.Style.Fill);
    }
  }

  class ImageDownloader {
    private static string Extension(string mimeType) {
      switch (mimeType) {
        case "image/jpeg":
          return ".jpg";
        case "image/png":
          return ".png";
        default:
          return "";
      }
    }

    public static string Download(string url) {
      ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
      var request = (HttpWebRequest)WebRequest.Create(url);
      var response = (HttpWebResponse)request.GetResponse();

      var responseUri = response.ResponseUri;
      string imageFileName = new FileInfo(response.ResponseUri.LocalPath).Name + Extension(response.ContentType);

      using (Stream receiveStream = response.GetResponseStream())
      using (Stream outputStream = File.OpenWrite(imageFileName)) {
        byte[] buffer = new byte[4096];
        int bytesRead;

        do {
          bytesRead = receiveStream.Read(buffer, 0, buffer.Length);
          outputStream.Write(buffer, 0, bytesRead);
        } while (bytesRead != 0);

      }
      return imageFileName;
    }
  }

  public sealed class Wallpaper {
    const int SPI_SETDESKWALLPAPER = 20;
    const int SPIF_UPDATEINIFILE = 0x01;
    const int SPIF_SENDWININICHANGE = 0x02;

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    static extern int SystemParametersInfo(int uAction, int uParam, string lpvParam, int fuWinIni);

    public enum Style : int {
      Fill,
      Fit,
      Span,
      Tile,
      Center,
      Stretch
    }

    public static void Set(string filename, Style style) {
      Image img = Image.FromFile(filename);
      string tempPath = Path.Combine(Path.GetTempPath(), "wallpaper.bmp");
      img.Save(tempPath, System.Drawing.Imaging.ImageFormat.Bmp);

      RegistryKey key = Registry.CurrentUser.OpenSubKey(@"Control Panel\Desktop", true);

      if (style == Style.Fill) {
        key.SetValue(@"WallpaperStyle", "10");
        key.SetValue(@"TileWallpaper", "0");
      }
      if (style == Style.Fit) {
        key.SetValue(@"WallpaperStyle", "6");
        key.SetValue(@"TileWallpaper", "0");
      }
      if (style == Style.Span) // Windows 8 or newer only!
      {
        key.SetValue(@"WallpaperStyle", "22");
        key.SetValue(@"TileWallpaper", "0");
      }
      if (style == Style.Stretch) {
        key.SetValue(@"WallpaperStyle", "2");
        key.SetValue(@"TileWallpaper", "0");
      }
      if (style == Style.Tile) {
        key.SetValue(@"WallpaperStyle", "0");
        key.SetValue(@"TileWallpaper", "1");
      }
      if (style == Style.Center) {
        key.SetValue(@"WallpaperStyle", "0");
        key.SetValue(@"TileWallpaper", "0");
      }

      SystemParametersInfo(SPI_SETDESKWALLPAPER,
          0,
          tempPath,
          SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
    }
  }
}