using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace BetaVersionLauncher
{
    /// <summary>
    /// Replicates a directory to a target directory.
    /// </summary>
    public class RoboCopy
    {
        public static void ReplicateDirectory(string source, string destination)
        {
            var sourceFiles = GetRelativeFilesRecursive(source);
            var destinationFiles = GetRelativeFilesRecursive(destination);

            // Copy new files.
            foreach (var file in sourceFiles)
            {
                ReplicateFile(Path.Combine(source, file), Path.Combine(destination, file));
            }

            // Remove old files.
            foreach (var destinationFile in destinationFiles)
            {
                if (!sourceFiles.Contains(destinationFile))
                {
                    string file = Path.Combine(destination, destinationFile);
                    File.SetAttributes(file, FileAttributes.Normal);
                    File.Delete(file);
                }
            }
        }

        private static HashSet<string> GetRelativeFilesRecursive(string folder)
        {
            if (!Directory.Exists(folder))
            {
                return new HashSet<string>();
            }

            return new HashSet<string>(Directory.GetFiles(folder, "*.*", SearchOption.AllDirectories).Select(file => ToRelative(folder, file)));
        }

        private static void ReplicateFile(string source, string destination)
        {
            CreateDirectory(Path.GetDirectoryName(destination));
            var sourceFileInfo = new FileInfo(source);
            var destinationFileInfo = new FileInfo(destination);
            if (!destinationFileInfo.Exists || sourceFileInfo.Length != destinationFileInfo.Length ||
                sourceFileInfo.LastWriteTimeUtc != destinationFileInfo.LastWriteTimeUtc)
            {
                if (destinationFileInfo.Exists && destinationFileInfo.IsReadOnly)
                {
                    File.SetAttributes(destination, FileAttributes.Normal);
                }
                File.Copy(source, destination, true);
            }
        }

        private static void CreateDirectory(string directory)
        {
            if (!Directory.Exists(directory))
            {
                CreateDirectory(Path.GetDirectoryName(directory));
                Directory.CreateDirectory(directory);
            }
        }

        private static string ToRelative(string folder, string file)
        {
            return file.Substring(folder.Length).Replace('/', '\\').TrimStart('\\');
        }
    }
}