PKHeX/PKHeX.WinForms/Subforms/SAV_Database.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using PKHeX.Core;
using PKHeX.Core.Searching;
using PKHeX.Drawing.PokeSprite;
using PKHeX.WinForms.Controls;
using PKHeX.WinForms.Properties;
using static PKHeX.Core.MessageStrings;

namespace PKHeX.WinForms;

public partial class SAV_Database : Form
{
    private readonly SaveFile SAV;
    private readonly SAVEditor BoxView;
    private readonly PKMEditor PKME_Tabs;
    private readonly EntityInstructionBuilder UC_Builder;

    private const int GridWidth = 6;
    private const int GridHeight = 11;

    private readonly PictureBox[] PKXBOXES;
    private readonly string DatabasePath = Main.DatabasePath;
    private List<SlotCache> Results = [];
    private List<SlotCache> RawDB = [];
    private int slotSelected = -1; // = null;
    private Image? slotColor;
    private const int RES_MIN = GridWidth * 1;
    private const int RES_MAX = GridWidth * GridHeight;
    private readonly string Counter;
    private readonly string Viewed;
    private const int MAXFORMAT = Latest.Generation;
    private readonly SummaryPreviewer ShowSet = new();
    private readonly CancellationTokenSource cts = new();

    public SAV_Database(PKMEditor f1, SAVEditor saveditor)
    {
        InitializeComponent();
        FormClosing += (_, _) => cts.Cancel();

        var settings = new TabPage { Text = "Settings", Name = "Tab_Settings" };
        settings.Controls.Add(new PropertyGrid { Dock = DockStyle.Fill, SelectedObject = Main.Settings.EntityDb });
        TC_SearchSettings.Controls.Add(settings);

        WinFormsUtil.TranslateInterface(this, Main.CurrentLanguage);
        UC_Builder = new EntityInstructionBuilder(() => f1.PreparePKM())
        {
            Anchor = AnchorStyles.Top | AnchorStyles.Left | AnchorStyles.Right,
            Width = Tab_Advanced.Width,
            Dock = DockStyle.Top,
            ReadOnly = true,
        };
        Tab_Advanced.Controls.Add(UC_Builder);
        UC_Builder.SendToBack();
        if (!Directory.Exists(DatabasePath))
            Menu_OpenDB.Visible = false;

        SAV = saveditor.SAV;
        BoxView = saveditor;
        PKME_Tabs = f1;

        // Preset Filters to only show PKM available for loaded save
        UC_EntitySearch.MaxFormat = MAXFORMAT;
        UC_EntitySearch.SaveGeneration = SAV.Generation;
        UC_EntitySearch.FormatComparatorSelectedIndex = 3; // <=

        var grid = DatabasePokeGrid;
        var smallWidth = grid.Width;
        var smallHeight = grid.Height;
        grid.InitializeGrid(GridWidth, GridHeight, SpriteUtil.Spriter);
        grid.SetBackground(Resources.box_wp_clean);
        var newWidth = grid.Width;
        var newHeight = grid.Height;
        var wdelta = newWidth - smallWidth;
        if (wdelta != 0)
            Width += wdelta;
        var hdelta = newHeight - smallHeight;
        if (hdelta != 0)
            Height += hdelta;
        PKXBOXES = [.. grid.Entries];

        // Enable Scrolling when hovered over
        foreach (var slot in PKXBOXES)
        {
            // Enable Click
            slot.MouseClick += (_, e) =>
            {
                switch (ModifierKeys)
                {
                    case Keys.Control: ClickView(slot, e); break;
                    case Keys.Alt: ClickDelete(slot, e); break;
                    case Keys.Shift: ClickSet(slot, e); break;
                }
            };

            slot.ContextMenuStrip = mnu;
            if (Main.Settings.Hover.HoverSlotShowText)
            {
                slot.MouseMove += (_, args) => ShowSet.UpdatePreviewPosition(args.Location);
                slot.MouseEnter += (_, _) => ShowHoverTextForSlot(slot);
                slot.MouseLeave += (_, _) => ShowSet.Clear();
            }
            slot.Enter += (_, _) =>
            {
                var index = PKXBOXES.IndexOf(slot);
                if (index < 0)
                    return;
                index += (SCR_Box.Value * RES_MIN);
                if (index >= Results.Count)
                    return;

                var pk = Results[index];

                var x = Main.Settings;
                var programLanguage = Language.GetLanguageValue(x.Startup.Language);
                var settings = x.BattleTemplate.Hover.GetSettings(programLanguage, pk.Entity.Context);
                slot.AccessibleDescription = ShowdownParsing.GetLocalizedPreviewText(pk.Entity, settings);
            };
        }

        Counter = L_Count.Text;
        Viewed = L_Viewed.Text;
        L_Viewed.Text = string.Empty; // invisible for now
        UC_EntitySearch.PopulateComboBoxes();

        // Load Data
        B_Search.Enabled = false;
        L_Count.Text = "Loading...";
        var token = cts.Token;
        var task = new Task(() => LoadDatabase(token), cts.Token);
        task.ContinueWith(z =>
        {
            if (token.IsCancellationRequested || !z.IsFaulted)
                return;
            Invoke((MethodInvoker)(() => L_Count.Text = "Failed."));
            if (z.Exception is null)
                return;
            WinFormsUtil.Error("Loading database failed.", z.Exception.InnerException ?? z.Exception.GetBaseException());
        });
        task.Start();

        Menu_SearchSettings.DropDown.Closing += (_, e) =>
        {
            if (e.CloseReason == ToolStripDropDownCloseReason.ItemClicked)
                e.Cancel = true;
        };
        UC_EntitySearch.SetFormatAnyText(MsgAny);
        CenterToParent();
        FormClosing += (_, _) => ShowSet.Clear();

        if (Application.IsDarkModeEnabled)
        {
            WinFormsUtil.InvertToolStripIcons(menuStrip1.Items);
            WinFormsUtil.InvertToolStripIcons(mnu.Items);
        }
    }

    protected override void OnShown(EventArgs e)
    {
        base.OnShown(e);
        UC_EntitySearch.ResetComboBoxSelections();
    }

    private void ClickView(object sender, EventArgs e)
    {
        if (!WinFormsUtil.TryGetUnderlying<PictureBox>(sender, out var pb))
            ArgumentNullException.ThrowIfNull(pb);
        int index = PKXBOXES.IndexOf(pb);
        if (!GetShiftedIndex(ref index))
        {
            System.Media.SystemSounds.Exclamation.Play();
            return;
        }

        if (sender == mnu)
            mnu.Hide();

        var slot = Results[index];
        var temp = slot.Entity;
        var pk = EntityConverter.ConvertToType(temp, SAV.PKMType, out var c);
        if (pk is null)
        {
            WinFormsUtil.Error(c.GetDisplayString(temp, SAV.PKMType));
            return;
        }
        SAV.AdaptToSaveFile(pk);
        pk.RefreshChecksum();
        PKME_Tabs.PopulateFields(pk, false);

        slotSelected = index;
        slotColor = SpriteUtil.Spriter.View;
        FillPKXBoxes(SCR_Box.Value);
        L_Viewed.Text = string.Format(Viewed, slot.Identify());
    }

    private void ClickDelete(object sender, EventArgs e)
    {
        if (!WinFormsUtil.TryGetUnderlying<PictureBox>(sender, out var pb))
            ArgumentNullException.ThrowIfNull(pb);
        int index = PKXBOXES.IndexOf(pb);
        if (!GetShiftedIndex(ref index))
        {
            System.Media.SystemSounds.Exclamation.Play();
            return;
        }

        var entry = Results[index];
        var pk = entry.Entity;

        if (entry.Source is SlotInfoFileSingle(var path))
        {
            // Data from Database: Delete file from disk
            if (File.Exists(path))
                File.Delete(path);
        }
        else if (entry.Source is SlotInfoBox b && entry.SAV == SAV)
        {
            // Data from Box: Delete from save file
            var exist = b.Read(SAV);
            if (!exist.DecryptedBoxData.SequenceEqual(pk.DecryptedBoxData)) // data modified already?
            {
                WinFormsUtil.Error(MsgDBDeleteFailModified, MsgDBDeleteFailWarning);
                return;
            }
            BoxView.EditEnv.Slots.Delete(b);
        }
        else
        {
            WinFormsUtil.Error(MsgDBDeleteFailBackup, MsgDBDeleteFailWarning);
            return;
        }
        // Remove from database.
        RawDB.Remove(entry);
        Results.Remove(entry);
        // Refresh database view.
        L_Count.Text = string.Format(Counter, Results.Count);
        slotSelected = -1;
        FillPKXBoxes(SCR_Box.Value);
        System.Media.SystemSounds.Asterisk.Play();
    }

    private void ClickSet(object sender, EventArgs e)
    {
        // Don't care what slot was clicked, just add it to the database
        if (!PKME_Tabs.EditsComplete)
            return;

        PKM pk = PKME_Tabs.PreparePKM();
        Directory.CreateDirectory(DatabasePath);

        string path = Path.Combine(DatabasePath, PathUtil.CleanFileName(pk.FileName));

        if (File.Exists(path))
        {
            WinFormsUtil.Alert(MsgDBAddFailExistsFile);
            return;
        }

        File.WriteAllBytes(path, pk.DecryptedBoxData);

        var info = new SlotInfoFileSingle(path);
        var entry = new SlotCache(info, pk);
        Results.Add(entry);

        // Refresh database view.
        L_Count.Text = string.Format(Counter, Results.Count);
        slotSelected = Results.Count - 1;
        slotColor = SpriteUtil.Spriter.Set;
        if ((SCR_Box.Maximum + 1) * GridWidth < Results.Count)
            SCR_Box.Maximum++;
        SCR_Box.Value = Math.Max(0, SCR_Box.Maximum - (PKXBOXES.Length / GridWidth) + 1);
        FillPKXBoxes(SCR_Box.Value);
        WinFormsUtil.Alert(MsgDBAddFromTabsSuccess);
    }

    private bool GetShiftedIndex(ref int index)
    {
        if ((uint)index >= RES_MAX)
            return false;
        index += SCR_Box.Value * RES_MIN;
        return index < Results.Count;
    }

    private void ResetFilters(object sender, EventArgs e)
    {
        UC_EntitySearch.ResetFilters();
        RTB_Instructions.Clear();

        if (sender != this)
            System.Media.SystemSounds.Asterisk.Play();
    }

    private void GenerateDBReport(object sender, EventArgs e)
    {
        if (WinFormsUtil.Prompt(MessageBoxButtons.YesNo, MsgDBCreateReportPrompt, MsgDBCreateReportWarning) != DialogResult.Yes)
            return;

        if (this.OpenWindowExists<ReportGrid>())
            return;

        ReportGrid reportGrid = new();
        reportGrid.Show();
        var settings = Main.Settings.Report;
        var extra = CollectionsMarshal.AsSpan(settings.ExtraProperties);
        var hide = CollectionsMarshal.AsSpan(settings.HiddenProperties);
        reportGrid.PopulateData(Results, extra, hide);
    }

    private sealed class SearchFolderDetail(string path, bool ignoreBackupFiles)
    {
        public string Path { get; } = path;
        public bool IgnoreBackupFiles { get; } = ignoreBackupFiles;
    }

    private void LoadDatabase(CancellationToken token)
    {
        var settings = Main.Settings;
        var otherPaths = new List<SearchFolderDetail>();
        if (settings.EntityDb.SearchExtraSaves)
            otherPaths.AddRange(settings.Backup.OtherBackupPaths.Where(Directory.Exists).Select(z => new SearchFolderDetail(z, true)));
        if (settings.EntityDb.SearchBackups)
            otherPaths.Add(new SearchFolderDetail(Main.BackupPath, false));

        RawDB = LoadEntitiesFromFolder(DatabasePath, SAV, otherPaths, settings.EntityDb.SearchExtraSavesDeep, token);
        if (token.IsCancellationRequested)
            return;

        // Load stats for pk who do not have any
        foreach (var entry in RawDB)
        {
            var pk = entry.Entity;
            pk.ForcePartyData();
        }

        try
        {
            while (!IsHandleCreated) { }
            if (cts.Token.IsCancellationRequested)
                return;
            BeginInvoke(new MethodInvoker(() => SetResults(RawDB)));
        }
        catch { /* Window Closed? */ }
    }

    private static List<SlotCache> LoadEntitiesFromFolder(string databaseFolder, SaveFile sav, List<SearchFolderDetail> otherPaths, bool otherDeep, CancellationToken token)
    {
        var dbTemp = new ConcurrentBag<SlotCache>();
        var extensions = new HashSet<string>(EntityFileExtension.GetExtensionsAll().Select(z => $".{z}"));

        var files = Directory.EnumerateFiles(databaseFolder, "*", SearchOption.AllDirectories);
        Parallel.ForEach(files, file => SlotInfoLoader.AddFromLocalFile(file, dbTemp, sav, extensions));

        foreach (var folder in otherPaths)
        {
            if (!SaveUtil.GetSavesFromFolder(folder.Path, otherDeep, token, out var paths, folder.IgnoreBackupFiles))
                continue;

            Parallel.ForEach(paths, file => TryAddPKMsFromSaveFilePath(dbTemp, file));
        }

        // Fetch from save file
        SlotInfoLoader.AddFromSaveFile(sav, dbTemp);
        var result = new List<SlotCache>(dbTemp);
        result.RemoveAll(z => !z.IsDataValid());

        if (Main.Settings.EntityDb.FilterUnavailableSpecies)
        {
            var filter = EntityPresenceFilters.GetFilterEntity(sav.Context);
            if (filter is not null)
                result.RemoveAll(z => !filter(z.Entity));
        }

        var sort = Main.Settings.EntityDb.InitialSortMode;
        if (sort is DatabaseSortMode.SlotIdentity)
            result.Sort();
        else if (sort is DatabaseSortMode.SpeciesForm)
            result.Sort((first, second) => first.CompareToSpeciesForm(second));

        // Finalize the Database
        return result;
    }

    private static void TryAddPKMsFromSaveFilePath(ConcurrentBag<SlotCache> dbTemp, string file)
    {
        if (SaveUtil.TryGetSaveFile(file, out var sav))
        {
            SlotInfoLoader.AddFromSaveFile(sav, dbTemp);
            return;
        }

        if (FileUtil.TryGetMemoryCard(file, out var mc))
            TryAddPKMsFromMemoryCard(dbTemp, mc, file);
        else
            Debug.WriteLine($"Unable to load SaveFile: {file}");
    }

    private static void TryAddPKMsFromMemoryCard(ConcurrentBag<SlotCache> dbTemp, SAV3GCMemoryCard mc, string file)
    {
        var state = mc.GetMemoryCardState();
        if (state == MemoryCardSaveStatus.Invalid)
            return;

        if (mc.HasCOLO)
            TryAdd(dbTemp, mc, file, SaveFileType.Colosseum);
        if (mc.HasXD)
            TryAdd(dbTemp, mc, file, SaveFileType.XD);
        if (mc.HasRSBOX)
            TryAdd(dbTemp, mc, file, SaveFileType.RSBox);

        static void TryAdd(ConcurrentBag<SlotCache> dbTemp, SAV3GCMemoryCard mc, string path, SaveFileType game)
        {
            mc.SelectSaveGame(game);
            if (!SaveUtil.TryGetSaveFile(mc, out var sav))
                return;
            sav.Metadata.SetExtraInfo(path);
            SlotInfoLoader.AddFromSaveFile(sav, dbTemp);
        }
    }

    // IO Usage
    private void OpenDB(object sender, EventArgs e)
    {
        if (Directory.Exists(DatabasePath))
            Process.Start("explorer.exe", DatabasePath);
    }

    private void Menu_Export_Click(object sender, EventArgs e)
    {
        if (Results.Count == 0)
        { WinFormsUtil.Alert(MsgDBCreateReportFail); return; }

        if (DialogResult.Yes != WinFormsUtil.Prompt(MessageBoxButtons.YesNo, MsgDBExportResultsPrompt))
            return;

        using var fbd = new FolderBrowserDialog();
        if (DialogResult.OK != fbd.ShowDialog())
            return;

        string path = fbd.SelectedPath;
        Directory.CreateDirectory(path);

        foreach (var pk in Results.Select(z => z.Entity))
            File.WriteAllBytes(Path.Combine(path, PathUtil.CleanFileName(pk.FileName)), pk.DecryptedPartyData);
    }

    private void Menu_Import_Click(object sender, EventArgs e)
    {
        if (!BoxView.GetBulkImportSettings(out var clearAll, out var overwrite, out var settings))
            return;

        int box = BoxView.Box.CurrentBox;
        int ctr = SAV.LoadBoxes(Results.Select(z => z.Entity), out var result, box, clearAll, overwrite, settings);
        if (ctr <= 0)
            return;

        BoxView.SetPKMBoxes();
        BoxView.UpdateBoxViewers();
        WinFormsUtil.Alert(result);
    }

    // View Updates
    private IEnumerable<SlotCache> SearchDatabase()
    {
        var settings = GetSearchSettings();

        IEnumerable<SlotCache> res = RawDB;

        // pre-filter based on the file path (if specified)
        if (!Menu_SearchBoxes.Checked)
            res = res.Where(z => z.SAV != SAV);
        if (!Menu_SearchDatabase.Checked)
            res = res.Where(z => !IsIndividualFilePKMDB(z));
        if (!Menu_SearchBackups.Checked)
            res = res.Where(z => !IsBackupSaveFile(z));

        // return filtered results
        return settings.Search(res);
    }

    private SearchSettings GetSearchSettings()
    {
        var settings = UC_EntitySearch.CreateSearchSettings(RTB_Instructions.Text);

        if (Menu_SearchLegal.Checked != Menu_SearchIllegal.Checked)
            settings.SearchLegal = Menu_SearchLegal.Checked;

        if (Menu_SearchClones.Checked)
        {
            settings.SearchClones = ModifierKeys switch
            {
                Keys.Control => CloneDetectionMethod.HashPID,
                _ => CloneDetectionMethod.HashDetails,
            };
        }

        return settings;
    }

    // ReSharper disable once AsyncVoidMethod
    private async void B_Search_Click(object sender, EventArgs e)
    {
        try
        {
            B_Search.Enabled = false;
            var search = SearchDatabase();

            bool legalSearch = Menu_SearchLegal.Checked ^ Menu_SearchIllegal.Checked;
            bool wordFilter = ParseSettings.Settings.WordFilter.CheckWordFilter;
            if (wordFilter && legalSearch && WinFormsUtil.Prompt(MessageBoxButtons.YesNo, MsgDBSearchLegalityWordfilter) == DialogResult.No)
                ParseSettings.Settings.WordFilter.CheckWordFilter = false;
            var results = await Task.Run(() => search.ToList()).ConfigureAwait(true);
            ParseSettings.Settings.WordFilter.CheckWordFilter = wordFilter;

            if (results.Count == 0)
            {
                if (!Menu_SearchBoxes.Checked && !Menu_SearchDatabase.Checked && !Menu_SearchBackups.Checked)
                    WinFormsUtil.Alert(MsgDBSearchFail, MsgDBSearchNone);
                else
                    WinFormsUtil.Alert(MsgDBSearchNone);
            }
            SetResults(results); // updates Count Label as well.
            System.Media.SystemSounds.Asterisk.Play();
            B_Search.Enabled = true;
        }
        catch
        {
            // Ignore.
        }
    }

    private void UpdateScroll(object sender, ScrollEventArgs e)
    {
        if (e.OldValue == e.NewValue)
            return;
        FillPKXBoxes(e.NewValue);
        ShowSet.Clear();
    }

    private void SetResults(List<SlotCache> res)
    {
        Results = res;
        ShowSet.Clear();

        SCR_Box.Maximum = (int)Math.Ceiling((decimal)Results.Count / RES_MIN);
        if (SCR_Box.Maximum > 0) SCR_Box.Maximum--;

        slotSelected = -1; // reset the slot last viewed
        SCR_Box.Value = 0;
        FillPKXBoxes(0);

        L_Count.Text = string.Format(Counter, Results.Count);
        B_Search.Enabled = true;
    }

    private void FillPKXBoxes(int start)
    {
        if (Results.Count == 0)
        {
            for (int i = 0; i < RES_MAX; i++)
            {
                PKXBOXES[i].Image = null;
                PKXBOXES[i].BackgroundImage = null;
            }
            return;
        }
        int begin = start * RES_MIN;
        int end = Math.Min(RES_MAX, Results.Count - begin);
        for (int i = 0; i < end; i++)
            PKXBOXES[i].Image = Results[i + begin].Entity.Sprite(SAV, flagIllegal: true, storage: Results[i + begin].Source.Type);
        for (int i = end; i < RES_MAX; i++)
            PKXBOXES[i].Image = null;

        for (int i = 0; i < RES_MAX; i++)
            PKXBOXES[i].BackgroundImage = SpriteUtil.Spriter.Transparent;
        if (slotSelected != -1 && slotSelected >= begin && slotSelected < begin + RES_MAX)
            PKXBOXES[slotSelected - begin].BackgroundImage = slotColor ?? SpriteUtil.Spriter.View;
    }

    // Misc Update Methods
    private void Menu_Exit_Click(object sender, EventArgs e) => Close();

    protected override void OnMouseWheel(MouseEventArgs e)
    {
        if (!DatabasePokeGrid.RectangleToScreen(DatabasePokeGrid.ClientRectangle).Contains(MousePosition))
            return;
        int oldval = SCR_Box.Value;
        int newval = oldval + (e.Delta < 0 ? 1 : -1);
        if (newval < SCR_Box.Minimum || SCR_Box.Maximum < newval)
            return;
        FillPKXBoxes(SCR_Box.Value = newval);
        ShowSet.Clear();
    }

    private void Menu_DeleteClones_Click(object sender, EventArgs e)
    {
        var dr = WinFormsUtil.Prompt(MessageBoxButtons.YesNo,
            MsgDBDeleteCloneWarning + Environment.NewLine +
            MsgDBDeleteCloneAdvice, MsgContinue);

        if (dr != DialogResult.Yes)
            return;

        var deleted = 0;
        var db = RawDB.Where(IsIndividualFilePKMDB)
            .OrderByDescending(GetRevisedTime);

        const CloneDetectionMethod method = CloneDetectionMethod.HashDetails;
        var hasher = SearchUtil.GetCloneDetectMethod(method);
        var duplicates = SearchUtil.GetExtraClones(db, z => hasher(z.Entity));
        foreach (var entry in duplicates)
        {
            var src = entry.Source;
            if (src is not SlotInfoFileSingle(var path) || !File.Exists(path))
                continue;

            try { File.Delete(path); ++deleted; }
            catch (Exception ex) { WinFormsUtil.Error(MsgDBDeleteCloneFail + Environment.NewLine + ex.Message + Environment.NewLine + path); }
        }

        var boxClear = new BoxManipClearDuplicate<string>(BoxManipType.DeleteClones, pk => SearchUtil.GetCloneDetectMethod(method)(pk));
        var param = new BoxManipParam(0, SAV.BoxCount - 1);
        int count = boxClear.Execute(SAV, param);
        deleted += count;

        if (deleted == 0)
        { WinFormsUtil.Alert(MsgDBDeleteCloneNone); return; }

        WinFormsUtil.Alert(string.Format(MsgFileDeleteCount, deleted), MsgWindowClose);
        BoxView.ReloadSlots();

        Close();
    }

    private static DateTime GetRevisedTime(SlotCache arg)
    {
        // This isn't displayed to the user, so just return the quickest -- Utc (not local time).
        var src = arg.Source;
        if (src is not SlotInfoFileSingle(var path))
            return DateTime.UtcNow;
        return File.GetLastWriteTimeUtc(path);
    }

    private bool IsBackupSaveFile(SlotCache pk) => pk.SAV is not FakeSaveFile && pk.SAV != SAV;
    private bool IsIndividualFilePKMDB(SlotCache pk) => pk.Source is SlotInfoFileSingle(var path) && path.StartsWith(DatabasePath + Path.DirectorySeparatorChar, StringComparison.Ordinal);

    private void L_Viewed_MouseEnter(object sender, EventArgs e) => hover.SetToolTip(L_Viewed, L_Viewed.Text);

    private void ShowHoverTextForSlot(PictureBox pb)
    {
        int index = PKXBOXES.IndexOf(pb);
        if (!GetShiftedIndex(ref index))
            return;

        var ent = Results[index];
        ShowSet.Show(pb, ent.Entity, ent.Source.Type);
    }

    private void B_Add_Click(object sender, EventArgs e)
    {
        var s = UC_Builder.Create();
        if (s.Length == 0)
        { WinFormsUtil.Alert(MsgBEPropertyInvalid); return; }

        // If we already have text, add a new line (except if the last line is blank).
        var tb = RTB_Instructions;
        var batchText = tb.Text;
        if (batchText.Length != 0 && !batchText.EndsWith('\n'))
            tb.AppendText(Environment.NewLine);
        tb.AppendText(s);
    }
}