using System;
using System.IO;
using System.IO.Pipes;
using System.Text.RegularExpressions;
using CoreHook.BinaryInjection.RemoteInjection;
using CoreHook.BinaryInjection.RemoteInjection.Configuration;
using CoreHook.IPC.Platform;
using Dalamud.Bootstrap.SqexArg;

namespace Dalamud.Bootstrap
{
    public sealed class Bootstrapper
    {
        private readonly BootstrapperOptions m_options;

        public Bootstrapper(BootstrapperOptions options)
        {
            m_options = options;
        }

        public void Launch(string exePath, string? commandLine)
        {
            commandLine = commandLine ?? "";


            //throw new NotImplementedException("TODO");
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="pid"></param>
        /// <exception cref="BootstrapException">
        /// Thrown when it could not relaunch FINAL FANTASY XIV or inject Dalamud.
        /// </exception>
        public void Relaunch(uint pid)
        {
            // TODO
            // 1. Open process `pid` with handle
            // 2. Read command arguments (requires reading PEB)
            // 3. Construct new arguments 
            //   3.1 Decrypt arguments acquired from step.2 (possible key space is very small so it's feasible to do this)
            //   3.2 Manipulate arguments as needed
            //   3.3 Re-encrypt arguments with new timestamp
            // 4 Launch a new process with new argument which was computed from step.3
            //   4.1 Create process with CREATE_SUSPENDED
            //   4.2 Figure out entry-point of ffxiv_dx11.exe
            //   4.3 Insert a hook on entry-point to wait for user-mode process initialization to be finished, but not the code from ffxiv_dx11.exe
            //     - This can be implemented in a such way that constantly checking program counter from `GetThreadContext` returns a value we expect.
            //       Before you might ask: Yes, this is not the cleanest method I could come up with per se, but hey it gives far less headache to actually implement!
            // 5 Attempt to inject into that process.
            // 6. If all succeeded, terminate the old process.
            //
            // delegate Step 3 to 5 to Launch() maybe?

            // Acquire the process handle and read the command line
            using var process = Process.Open(pid);

            var exePath = process.GetImageFilePath();

            var argument = ReadArgumentFromProcess(process);
            
            var newTick = (uint)Environment.TickCount;
            var newKey = newTick & 0xFFFF_0000; // only the high nibble is used

            var newArgument = argument
                .Remove("T")
                .Add("T", $"{newTick}")
                .ToString();

            var encryptedArgument = new EncryptedArgument(newArgument, newKey);
            
            // TODO: launch new exe with the argument from encryptedArgument.ToString()
            // TODO: we also need to figure out where the exe is located
            
            // This is just for poc purpose.
            System.Diagnostics.Process.Start(exePath, encryptedArgument.ToString());

            process.Terminate();
        }

        private static uint RecoverKey(Process gameProcess)
        {
            var createdTime = gameProcess.GetCreationTime();
            
            var currentDt = DateTime.Now;
            var currentTick = Environment.TickCount;

            var delta = currentDt - createdTime;
            var createdTick = (uint)currentTick - (uint)delta.TotalMilliseconds;

            // only the high nibble is used.
            return createdTick & 0xFFFF_0000;
        }

        private static ArgumentBuilder ReadArgumentFromProcess(Process process)
        {
            var arguments = process.ReadArguments();

            if (arguments.Length < 2)
            {
                throw new BootstrapException($"Process id {process.GetPid()} does not have any arguments to parse.");
            }

            var argument = arguments[1];
            
            if (EncryptedArgument.TryParse(argument, out var encryptedArgument))
            {
                var key = RecoverKey(process);   
                argument = encryptedArgument.Decrypt(key);
            }
            
            return ArgumentBuilder.Parse(argument);
        }

        /// <summary>
        /// Injects Dalamud into the process. See remarks for process state prerequisites.
        /// </summary>
        /// <remarks>
        /// TODO: CREATE_SUSPENDED -> entrypoint explainations
        /// </remarks>
        /// <param name="pid">A process id to inject Dalamud into.</param>
        public void Inject(uint pid)
        {
            // Please keep in mind that this config values (especially ClrRootPath) assumes that
            // Dalamud is compiled as self-contained to avoid requiring people to pre-install specific .NET Core version.
            // https://docs.microsoft.com/en-us/dotnet/core/deploying/
            var corehookConfig = new RemoteInjectorConfiguration
            {
                InjectionPipeName = $"Dalamud-{pid}-CoreHook",
                ClrRootPath = m_options.BinaryDirectory, // `dotnet.runtimeconfig.json` is not needed for self-contained app.
                ClrBootstrapLibrary = Path.Combine(m_options.BinaryDirectory, "CoreHook.CoreLoad.dll"),
                DetourLibrary = Path.Combine(m_options.BinaryDirectory, "corehook64.dll"),
                HostLibrary = Path.Combine(m_options.BinaryDirectory, "coreload64.dll"),
                PayloadLibrary = Path.Combine(m_options.BinaryDirectory, "Dalamud.dll"),
                VerboseLog = false,
            };

            try
            {
                RemoteInjector.Inject((int)pid, corehookConfig, new PipePlatform(), m_options.RootDirectory);
            }
            catch (Exception ex)
            {
                var exMessage = $"Failed to inject Dalamud library into the process id {pid}.";

                // Could not inject Dalamud for whatever reason; it could be process is not actually running, insufficient os privilege, or whatever the thing SE put in their game;
                // Therefore there's not much we can do on this side; You have to trobleshoot by yourself somehow.
                throw new BootstrapException(exMessage, ex);
            }
        }
    }

    internal sealed class PipePlatform : IPipePlatform
    {
        public NamedPipeServerStream CreatePipeByName(string pipeName, string serverName = ".")
        {
            return new NamedPipeServerStream(pipeName, PipeDirection.InOut, 1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous, 0x10000, 0x10000);
        }
    }
}