TBMM/GCMM/MainModInstaller.cs

using GCMM.Properties;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace GCMM
{
    partial class MainForm
    {
        public async Task InstallMod(ModInfo mod)
        {
            if (mod.DownloadURL == null) return;
            if (CheckNoExe())
                return;
            if (mod.Name != "GamecraftModdingAPI")
                await UpdateAPI();
            var tmp = Directory.CreateDirectory("temp");
            var plugins = Directory.CreateDirectory(GamePath(@"\Plugins"));
            string tmppath = tmp.FullName + Path.DirectorySeparatorChar + mod.Name;
            using (var client = GetClient())
            {
                await client.DownloadFileTaskAsync(mod.DownloadURL, tmppath);
                string disposition = client.ResponseHeaders["Content-Disposition"];
                string filename = disposition.Substring(disposition.IndexOf("filename=") + 10).Replace("\"", "");
                if (filename.EndsWith(".dll"))
                {
                    string name = plugins.FullName + Path.DirectorySeparatorChar + mod.Name + ".dll"; //Force mod name to make uninstalls & identifying easier
                    if (File.Exists(name))
                        File.Delete(name);
                    File.Move(tmppath, name);
                }
                else if (filename.EndsWith(".zip"))
                {
                    bool pluginOnly = true;
                    using (var archive = ZipFile.OpenRead(tmppath))
                    {
                        bool modFound = false;
                        foreach (var entry in archive.Entries)
                        {
                            if (entry.FullName == "Plugins/")
                                pluginOnly = false;
                            if (entry.FullName == "Plugins/" + mod.Name + ".dll")
                            {
                                modFound = true;
                                pluginOnly = false; //The directory-only entry may be missing
                            }
                            else if (pluginOnly && entry.FullName == mod.Name + ".dll")
                                modFound = true;
                            if (!pluginOnly && modFound) break;
                        }
                        if (!modFound)
                            if (MessageBox.Show("The mod was not found in the downloaded archive. It likely means it's using a different name for the dll file. The mod manager will not be able to track this mod if you continue. Do you want to continue?", "Mod not found in archive", MessageBoxButtons.YesNo) == DialogResult.No)
                                return;
                        ExtractMod(archive, pluginOnly ? plugins.FullName : Settings.Default.GamePath, mod);
                    }
                    File.Delete(tmppath);
                }
                else
                {
                    MessageBox.Show("Don't know how to install file: " + filename + "\nThe file remains in the temp folder near the mod manager");
                    return;
                }
                GetInstalledMods(); //Update list
            }
        }

        public void ExtractMod(ZipArchive archive, string destinationDirectoryName, ModInfo mod)
        {
            LoadFileList(mod);
            DirectoryInfo di = Directory.CreateDirectory(destinationDirectoryName);
            string destinationDirectoryFullPath = di.FullName;

            foreach (ZipArchiveEntry file in archive.Entries)
            {
                string completeFileName = Path.GetFullPath(Path.Combine(destinationDirectoryFullPath, file.FullName));

                if (!completeFileName.StartsWith(destinationDirectoryFullPath, StringComparison.OrdinalIgnoreCase))
                {
                    throw new IOException("Trying to extract file outside of destination directory. See this link for more info: https://snyk.io/research/zip-slip-vulnerability");
                }

                Directory.CreateDirectory(Path.GetDirectoryName(completeFileName)); //Sometimes there are no directory-only entries
                if (file.Name == "")
                {// Assuming Empty for Directory
                    continue;
                }

                if ((mod.Version == null || mod.ModFiles.Count != 0)    //Negated: The mod is installed and we don't know about any of its files
                    && File.Exists(completeFileName)                    // OR it's a new file
                    && !mod.ModFiles.Contains(completeFileName)         // OR it's known to be part of the mod already
                    && file.FullName != "Plugins/" + mod.Name + ".dll") // OR it's the plugin's DLL (dll->zip release)
                {
                    if (MessageBox.Show("The mod zip contains a file that exists as part of the game. Do you want to skip this file?\n" + file.FullName + "\nOnly choose No if it's part of a previous installation of the mod.", "File is part of the game", MessageBoxButtons.YesNo) == DialogResult.Yes)
                        continue;
                }

                mod.ModFiles.Add(completeFileName);
                file.ExtractToFile(completeFileName, true);
            }
            SaveFileList(mod);
        }

        public void SaveFileList(ModInfo mod)
        {
            if (mod.ModFiles != null)
                File.WriteAllText(mod.Name + ".json", JsonConvert.SerializeObject(mod.ModFiles));
        }

        public void LoadFileList(ModInfo mod)
        {
            if (File.Exists(mod.Name + ".json"))
                mod.ModFiles = JsonConvert.DeserializeObject<HashSet<string>>(File.ReadAllText(mod.Name + ".json"));
            else
                mod.ModFiles = new HashSet<string>();
        }

        public void UninstallMod(ModInfo mod)
        {
            try
            {
                LoadFileList(mod);
                if (mod.ModFiles.Count == 0) //A single DLL
                    File.Delete(GamePath(@"\Plugins\" + mod.Name + ".dll"));
                else //A ZIP
                {
                    foreach (string file in mod.ModFiles)
                    {
                        File.Delete(file);
                        var parent = Directory.GetParent(file);
                        if (!parent.EnumerateFileSystemInfos().Any())
                            parent.Delete(); //May delete the Plugins dir if empty
                    }
                }
                File.Delete(mod.Name + ".json");
                mod.Version = null; //Not installed
                if (mod.Author != null)
                    AddUpdateModInList(mod); //Update list
                else
                {
                    mods.Remove(mod.Name);
                    modlist.Items[mod.Name].Remove();
                }
            }
            catch (Exception e) when (e is UnauthorizedAccessException || e is IOException)
            {
                MessageBox.Show("Could not remove mod files! Make sure the game isn't running.\n" + e.Message);
            }
        }

        public async Task UpdateAPI()
        {
            if (!mods.ContainsKey("GamecraftModdingAPI"))
                return;
            var gcmapi = mods["GamecraftModdingAPI"];
            if (!gcmapi.Installed || gcmapi.Updatable)
            {
                if (MessageBox.Show(gcmapi.Installed ?
                    "GamecraftModdingAPI will be updated as there's a new version available. It's needed for most mods to function."
                    : "GamecraftModdingAPI will be installed as most mods need it to work. You can uninstall it if you're sure you don't need it.", "API needed",
                    MessageBoxButtons.OKCancel) == DialogResult.OK)
                    await InstallMod(gcmapi);
            }
        }
    }
}