MainForm.cs

using System.Text;

namespace TextEditor;

/// <summary>
/// Editor di testo semplice in stile Notepad, con schede multiple.
/// </summary>
public class MainForm : Form
{
    private readonly TabControl _tabs = new();
    private readonly StatusStrip _status = new();
    private readonly ToolStripStatusLabel _posLabel = new();
    private readonly ToolStripStatusLabel _infoLabel = new();
    private ToolStripMenuItem _wordWrapItem = null!;
    private ToolStripMenuItem _lineNumbersItem = null!;

    private Font _editorFont = new("Consolas", 11f);
    private bool _wordWrap = true;
    private bool _showLineNumbers = true;
    private int _untitledCounter = 1;

    /// <summary>Se impostato, alla comparsa la finestra si cattura in questo PNG e si chiude (solo test).</summary>
    public string? ScreenshotPath { get; set; }

    public MainForm(string[] args)
    {
        Text = "Mio Editor";
        Width = 1000;
        Height = 700;
        StartPosition = FormStartPosition.CenterScreen;
        KeyPreview = true;
        AllowDrop = true;
        try { Icon = Icon.ExtractAssociatedIcon(Application.ExecutablePath); } catch { }

        BuildTabs();
        BuildStatusBar();

        // L'ordine conta: il docking processa i controlli dall'ultimo aggiunto al primo.
        // Aggiungendo i tab (Fill) per primi, poi la status bar (Bottom) e il menu (Top)
        // per ultimi, le barre superiore/inferiore riservano il loro spazio e i tab
        // riempiono il resto SENZA che il menu copra la striscia delle linguette.
        Controls.Add(_tabs);
        Controls.Add(_status);
        BuildMenu(); // aggiunge il MenuStrip per ultimo (Dock = Top)

        DragEnter += (s, e) =>
            e.Effect = e.Data!.GetDataPresent(DataFormats.FileDrop) ? DragDropEffect_Copy() : DragDropEffects.None;
        DragDrop += (s, e) =>
        {
            if (e.Data!.GetData(DataFormats.FileDrop) is string[] files)
                foreach (var f in files) OpenFile(f);
        };

        FormClosing += (s, e) =>
        {
            if (!ConfirmCloseAll()) e.Cancel = true;
        };

        // Apri i file passati da riga di comando, altrimenti una scheda vuota.
        var opened = 0;
        foreach (var a in args)
            if (File.Exists(a)) { OpenFile(a); opened++; }
        if (opened == 0) NewTab();
    }

    private static DragDropEffects DragDropEffect_Copy() => DragDropEffects.Copy;

    protected override void OnShown(EventArgs e)
    {
        base.OnShown(e);
        if (ScreenshotPath == null) return;
        var t = new System.Windows.Forms.Timer { Interval = 500 };
        t.Tick += (s, ev) =>
        {
            t.Stop();
            try
            {
                using var bmp = new Bitmap(Width, Height);
                using (var g = Graphics.FromImage(bmp))
                    g.CopyFromScreen(Location, Point.Empty, new Size(Width, Height));
                bmp.Save(ScreenshotPath, System.Drawing.Imaging.ImageFormat.Png);
            }
            catch { }
            Close();
        };
        t.Start();
    }

    // ---------- Costruzione UI ----------

    private void BuildMenu()
    {
        var menu = new MenuStrip();

        // File
        var file = new ToolStripMenuItem("&File");
        file.DropDownItems.Add(Item("&Nuovo", Keys.Control | Keys.N, (s, e) => NewTab()));
        file.DropDownItems.Add(Item("&Apri...", Keys.Control | Keys.O, (s, e) => OpenDialog()));
        file.DropDownItems.Add(Item("&Salva", Keys.Control | Keys.S, (s, e) => Save(Current)));
        file.DropDownItems.Add(Item("Salva con &nome...", Keys.Control | Keys.Shift | Keys.S, (s, e) => SaveAs(Current)));
        file.DropDownItems.Add(new ToolStripSeparator());
        file.DropDownItems.Add(Item("&Chiudi scheda", Keys.Control | Keys.W, (s, e) => CloseTab(_tabs.SelectedTab)));
        file.DropDownItems.Add(Item("&Esci", Keys.Alt | Keys.F4, (s, e) => Close()));
        menu.Items.Add(file);

        // Modifica
        var edit = new ToolStripMenuItem("&Modifica");
        edit.DropDownItems.Add(Item("&Annulla", Keys.Control | Keys.Z, (s, e) => Editor?.Undo()));
        edit.DropDownItems.Add(Item("&Ripeti", Keys.Control | Keys.Y, (s, e) => Editor?.Redo()));
        edit.DropDownItems.Add(new ToolStripSeparator());
        edit.DropDownItems.Add(Item("Ta&glia", Keys.Control | Keys.X, (s, e) => Editor?.Cut()));
        edit.DropDownItems.Add(Item("&Copia", Keys.Control | Keys.C, (s, e) => Editor?.Copy()));
        edit.DropDownItems.Add(Item("&Incolla", Keys.Control | Keys.V, (s, e) => Editor?.Paste()));
        edit.DropDownItems.Add(new ToolStripSeparator());
        edit.DropDownItems.Add(Item("Seleziona &tutto", Keys.Control | Keys.A, (s, e) => Editor?.SelectAll()));
        edit.DropDownItems.Add(new ToolStripSeparator());
        edit.DropDownItems.Add(Item("&Trova...", Keys.Control | Keys.F, (s, e) => ShowFindReplace(false)));
        edit.DropDownItems.Add(Item("&Sostituisci...", Keys.Control | Keys.H, (s, e) => ShowFindReplace(true)));
        edit.DropDownItems.Add(Item("&Vai alla riga...", Keys.Control | Keys.G, (s, e) => GoToLine()));
        menu.Items.Add(edit);

        // Formato
        var format = new ToolStripMenuItem("F&ormato");
        _wordWrapItem = new ToolStripMenuItem("&A capo automatico", null, (s, e) => ToggleWordWrap()) { Checked = _wordWrap };
        format.DropDownItems.Add(_wordWrapItem);
        _lineNumbersItem = new ToolStripMenuItem("&Numeri di riga", null, (s, e) => ToggleLineNumbers()) { Checked = _showLineNumbers };
        format.DropDownItems.Add(_lineNumbersItem);
        format.DropDownItems.Add(Item("&Carattere...", Keys.None, (s, e) => ChooseFont()));
        menu.Items.Add(format);

        // ?
        var help = new ToolStripMenuItem("&?");
        help.DropDownItems.Add(Item("&Informazioni", Keys.None, (s, e) =>
            MessageBox.Show("Mio Editor 1.0\nEditor di testo semplice con schede.", "Informazioni",
                MessageBoxButtons.OK, MessageBoxIcon.Information)));
        menu.Items.Add(help);

        MainMenuStrip = menu;
        Controls.Add(menu);
    }

    private static ToolStripMenuItem Item(string text, Keys shortcut, EventHandler handler)
    {
        var i = new ToolStripMenuItem(text, null, handler);
        if (shortcut != Keys.None) i.ShortcutKeys = shortcut;
        return i;
    }

    private void BuildTabs()
    {
        _tabs.Dock = DockStyle.Fill;
        _tabs.DrawMode = TabDrawMode.OwnerDrawFixed;
        _tabs.SizeMode = TabSizeMode.Normal;
        _tabs.Padding = new Point(18, 4); // spazio extra a destra per la "x"
        _tabs.DrawItem += Tabs_DrawItem;
        _tabs.MouseDown += Tabs_MouseDown;
        _tabs.SelectedIndexChanged += (s, e) => UpdateStatus();
    }

    private void BuildStatusBar()
    {
        _posLabel.Text = "Riga 1, Col 1";
        _infoLabel.Spring = true;
        _infoLabel.TextAlign = ContentAlignment.MiddleRight;
        _infoLabel.Text = "UTF-8";
        _status.Items.Add(_posLabel);
        _status.Items.Add(_infoLabel);
    }

    // ---------- Gestione documenti ----------

    private TabPage? Current => _tabs.SelectedTab;
    private RichTextBox? Editor => Current?.Tag is Doc d ? d.Box : null;

    private TabPage NewTab(string? path = null, string? content = null)
    {
        var box = new CodeBox
        {
            Dock = DockStyle.Fill,
            BorderStyle = BorderStyle.None,
            Font = _editorFont,
            WordWrap = _wordWrap,
            AcceptsTab = true,
            DetectUrls = false,
            HideSelection = false,
            MaxLength = 0,
            ScrollBars = RichTextBoxScrollBars.Both,
        };
        if (content != null) box.Text = content;

        var gutter = new LineNumberGutter(box) { Font = _editorFont, Visible = _showLineNumbers };

        var doc = new Doc { Box = box, Gutter = gutter, Path = path };
        var page = new TabPage { Tag = doc, UseVisualStyleBackColor = true };
        // Ordine: prima il box (Fill), poi il gutter (Left), così il gutter occupa
        // la colonna sinistra e il testo riempie lo spazio restante.
        page.Controls.Add(box);
        page.Controls.Add(gutter);

        box.Modified = false;
        box.TextChanged += (s, e) => { doc.Dirty = box.Modified; UpdateTabTitle(page); gutter.Invalidate(); };
        box.SelectionChanged += (s, e) => UpdateStatus();
        box.MouseUp += (s, e) => UpdateStatus();
        box.KeyUp += (s, e) => UpdateStatus();
        box.ContentScrolled += (s, e) => gutter.Invalidate();
        box.FontChanged += (s, e) => { gutter.Font = box.Font; gutter.Invalidate(); };

        page.Text = path == null ? $"Senza nome {_untitledCounter++}" : Path.GetFileName(path);
        _tabs.TabPages.Add(page);
        _tabs.SelectedTab = page;
        box.Select();
        UpdateStatus();
        return page;
    }

    private void OpenDialog()
    {
        using var dlg = new OpenFileDialog
        {
            Filter = "File di testo (*.txt)|*.txt|Tutti i file (*.*)|*.*",
            Multiselect = true,
        };
        if (dlg.ShowDialog(this) == DialogResult.OK)
            foreach (var f in dlg.FileNames) OpenFile(f);
    }

    private void OpenFile(string path)
    {
        // Se già aperto, porta in primo piano quella scheda.
        foreach (TabPage p in _tabs.TabPages)
            if (p.Tag is Doc d && string.Equals(d.Path, path, StringComparison.OrdinalIgnoreCase))
            {
                _tabs.SelectedTab = p;
                return;
            }
        try
        {
            var text = File.ReadAllText(path);
            NewTab(path, text);
        }
        catch (Exception ex)
        {
            MessageBox.Show($"Impossibile aprire il file:\n{ex.Message}", "Errore",
                MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

    private bool Save(TabPage? page)
    {
        if (page?.Tag is not Doc doc) return false;
        if (doc.Path == null) return SaveAs(page);
        return WriteFile(page, doc, doc.Path);
    }

    private bool SaveAs(TabPage? page)
    {
        if (page?.Tag is not Doc doc) return false;
        using var dlg = new SaveFileDialog
        {
            Filter = "File di testo (*.txt)|*.txt|Tutti i file (*.*)|*.*",
            FileName = doc.Path != null ? Path.GetFileName(doc.Path) : page.Text.Trim('●', ' ') + ".txt",
        };
        if (dlg.ShowDialog(this) != DialogResult.OK) return false;
        return WriteFile(page, doc, dlg.FileName);
    }

    private bool WriteFile(TabPage page, Doc doc, string path)
    {
        try
        {
            File.WriteAllText(path, doc.Box.Text, new UTF8Encoding(false));
            doc.Path = path;
            doc.Box.Modified = false;
            doc.Dirty = false;
            page.Text = Path.GetFileName(path);
            UpdateTabTitle(page);
            UpdateStatus();
            return true;
        }
        catch (Exception ex)
        {
            MessageBox.Show($"Impossibile salvare il file:\n{ex.Message}", "Errore",
                MessageBoxButtons.OK, MessageBoxIcon.Error);
            return false;
        }
    }

    private void CloseTab(TabPage? page)
    {
        if (page?.Tag is not Doc doc) return;
        if (doc.Dirty && !ConfirmSave(page)) return;
        _tabs.TabPages.Remove(page);
        page.Dispose();
        if (_tabs.TabPages.Count == 0) NewTab();
    }

    private bool ConfirmSave(TabPage page)
    {
        _tabs.SelectedTab = page;
        var name = page.Text.TrimStart('●', ' ');
        var r = MessageBox.Show($"Salvare le modifiche a \"{name}\"?", "Mio Editor",
            MessageBoxButtons.YesNoCancel, MessageBoxIcon.Warning);
        return r switch
        {
            DialogResult.Yes => Save(page),
            DialogResult.No => true,
            _ => false,
        };
    }

    private bool ConfirmCloseAll()
    {
        foreach (TabPage p in _tabs.TabPages)
            if (p.Tag is Doc { Dirty: true } && !ConfirmSave(p))
                return false;
        return true;
    }

    // ---------- Schede: disegno + click sulla "x" ----------

    private void Tabs_DrawItem(object? sender, DrawItemEventArgs e)
    {
        var page = _tabs.TabPages[e.Index];
        var rect = _tabs.GetTabRect(e.Index);
        var selected = e.Index == _tabs.SelectedIndex;

        using (var bg = new SolidBrush(selected ? SystemColors.Window : SystemColors.Control))
            e.Graphics.FillRectangle(bg, rect);

        // Testo della scheda.
        var textRect = new Rectangle(rect.X + 6, rect.Y + 3, rect.Width - 26, rect.Height - 4);
        TextRenderer.DrawText(e.Graphics, page.Text, _tabs.Font, textRect,
            SystemColors.ControlText, TextFormatFlags.Left | TextFormatFlags.EndEllipsis);

        // Pulsante "x".
        var x = CloseButtonRect(rect);
        TextRenderer.DrawText(e.Graphics, "✕", _tabs.Font, x, SystemColors.GrayText,
            TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter);
    }

    private static Rectangle CloseButtonRect(Rectangle tab) =>
        new(tab.Right - 20, tab.Y + (tab.Height - 16) / 2, 16, 16);

    private void Tabs_MouseDown(object? sender, MouseEventArgs e)
    {
        for (int i = 0; i < _tabs.TabPages.Count; i++)
        {
            var rect = _tabs.GetTabRect(i);
            if (!rect.Contains(e.Location)) continue;

            // Click sulla "x" oppure click con rotellina = chiudi.
            if (e.Button == MouseButtons.Middle || CloseButtonRect(rect).Contains(e.Location))
                CloseTab(_tabs.TabPages[i]);
            return;
        }
    }

    private void UpdateTabTitle(TabPage page)
    {
        if (page.Tag is not Doc doc) return;
        var baseName = doc.Path != null ? Path.GetFileName(doc.Path) : page.Text.TrimStart('●', ' ');
        var title = doc.Dirty ? "● " + baseName : baseName;
        if (page.Text != title) page.Text = title;
        Text = (doc.Dirty ? "● " : "") + baseName + " - Mio Editor";
    }

    // ---------- Funzioni varie ----------

    private void ToggleWordWrap()
    {
        _wordWrap = !_wordWrap;
        _wordWrapItem.Checked = _wordWrap;
        foreach (TabPage p in _tabs.TabPages)
            if (p.Tag is Doc d) d.Box.WordWrap = _wordWrap;
    }

    private void ToggleLineNumbers()
    {
        _showLineNumbers = !_showLineNumbers;
        _lineNumbersItem.Checked = _showLineNumbers;
        foreach (TabPage p in _tabs.TabPages)
            if (p.Tag is Doc d) { d.Gutter.Visible = _showLineNumbers; d.Gutter.Invalidate(); }
    }

    private void ChooseFont()
    {
        using var dlg = new FontDialog { Font = _editorFont };
        if (dlg.ShowDialog(this) != DialogResult.OK) return;
        _editorFont = dlg.Font;
        foreach (TabPage p in _tabs.TabPages)
            if (p.Tag is Doc d) d.Box.Font = _editorFont;
    }

    private void GoToLine()
    {
        if (Editor is not { } box) return;
        var input = Microsoft.VisualBasic.Interaction.InputBox("Numero di riga:", "Vai alla riga", "1");
        if (int.TryParse(input, out var line) && line >= 1)
        {
            line = Math.Min(line, box.Lines.Length);
            var idx = box.GetFirstCharIndexFromLine(line - 1);
            if (idx >= 0) { box.SelectionStart = idx; box.SelectionLength = 0; box.ScrollToCaret(); box.Focus(); }
        }
    }

    private FindReplaceForm? _findForm;

    /// <summary>Editor della scheda attiva (usato dalla finestra Trova/Sostituisci).</summary>
    public RichTextBox? CurrentEditor => Editor;

    private void ShowFindReplace(bool replaceMode)
    {
        if (Editor is null) return;
        if (_findForm == null || _findForm.IsDisposed)
        {
            _findForm = new FindReplaceForm(this);
            _findForm.FormClosed += (s, e) => _findForm = null;
        }
        _findForm.ShowReplace(replaceMode);
        if (!_findForm.Visible) _findForm.Show(this);
        _findForm.Activate();
        _findForm.FocusSearch(Editor.SelectedText);
    }

    private void UpdateStatus()
    {
        if (Editor is not { } box) { _posLabel.Text = ""; _infoLabel.Text = ""; return; }
        var line = box.GetLineFromCharIndex(box.SelectionStart);
        var col = box.SelectionStart - box.GetFirstCharIndexFromLine(line);
        _posLabel.Text = $"Riga {line + 1}, Col {col + 1}";
        _infoLabel.Text = $"{box.TextLength} caratteri    UTF-8";
    }

    private sealed class Doc
    {
        public required RichTextBox Box;
        public required LineNumberGutter Gutter;
        public string? Path;
        public bool Dirty;
    }
}