using System;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;

namespace mklinker
{
    /// <summary>
    /// A msbuild friendly application that creates hard link between files.
    /// </summary>
    class Program
    {
        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);

        static int Main(string[] args)
        {
            if (args.Length % 2 != 0)
            {
                Console.WriteLine("Invalid arguments, please specify [target name] and [source file name] for each hard link to create.");
                return -2;
            }

            for (int i = 0; i < args.Length; i += 2)
            {
                var toCreate = args[i];
                var existing = args[i + 1];

                try
                {
                    if (!File.Exists(existing))
                    {
                        Console.WriteLine("error: File {0} does not exist", toCreate);
                        return -3;
                    }

                    if (!File.Exists(toCreate))
                    {
                        if (!Directory.Exists(Path.GetDirectoryName(toCreate)))
                        {
                            Directory.CreateDirectory(Path.GetDirectoryName(toCreate));
                        }

                        if (!CreateHardLink(toCreate, existing, new IntPtr()))
                        {
                            Console.WriteLine("error: Could not create hard link {0} from {1}", toCreate, existing);
                            return -4;
                        }
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine("error: Unhandled exception creating hard link {0} from {1}. Details {2}", toCreate, existing, ex.Message);
                    return -5;
                }
            }
            return 0;
        }
    }
}