MainForm.cs

using System.Diagnostics;
using System.Drawing.Printing;

namespace FMPReceiptPrinter;

public sealed class MainForm : Form
{
    private readonly AppState _state;
    private readonly List<ReceiptTemplate> _templates;
    private readonly ReceiptPreviewControl _preview = new() { Dock = DockStyle.Fill };
    private readonly NumericUpDown _receiptNo = new() { Minimum = 1, Maximum = 99999, Width = 90 };
    private readonly DateTimePicker _date = new() { Format = DateTimePickerFormat.Short, Width = 120 };
    private readonly TextBox _customer = new() { Width = 260 };
    private readonly TextBox _address = new() { Width = 260 };
    private readonly ComboBox _terms = new() { DropDownStyle = ComboBoxStyle.DropDownList, Width = 120 };
    private readonly DateTimePicker _due = new() { Format = DateTimePickerFormat.Short, Width = 120 };
    private readonly NumericUpDown _deliveryFee = new() { DecimalPlaces = 2, Maximum = 1000000, ThousandsSeparator = true, Width = 110 };
    private readonly TextBox _preparedBy = new() { Width = 160 };
    private readonly Label _subtotal = new() { AutoSize = true, Font = new Font("Segoe UI", 10, FontStyle.Bold) };
    private readonly Label _total = new() { AutoSize = true, Font = new Font("Segoe UI", 12, FontStyle.Bold), ForeColor = Color.FromArgb(8,126,175) };
    private readonly DataGridView _items = new() { AllowUserToAddRows = false, AllowUserToDeleteRows = false, RowHeadersVisible = false, AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill, Width = 420, Height = 245 };
    private readonly ComboBox _templateCombo = new() { DropDownStyle = ComboBoxStyle.DropDownList, Width = 220 };
    private readonly ComboBox _printerCombo = new() { DropDownStyle = ComboBoxStyle.DropDownList, Width = 245 };
    private readonly Label _printerStatus = new() { AutoSize = true, Padding = new Padding(0,6,0,0) };
    private readonly TextBox _signaturePath = new() { Width = 250, ReadOnly = true };
    private readonly CheckBox _useSignature = new() { Text = "Place uploaded signature on receipt", AutoSize = true };
    private readonly Dictionary<ReceiptSlot, CheckBox> _slotChecks = new();
    private Button _printPreviewButton = null!;
    private Button _printButton = null!;
    private ReceiptTemplate CurrentTemplate => (ReceiptTemplate?)_templateCombo.SelectedItem ?? _templates[0];

    public MainForm()
    {
        Storage.Initialize();
        _state = Storage.LoadState();
        _templates = Storage.LoadTemplates();
        if (_templates.Count == 0) _templates.Add(new());
        Text = "ARCWorks Simple Receipt Printer";
        MinimumSize = new Size(1120, 720);
        Size = new Size(1280, 820);
        StartPosition = FormStartPosition.CenterScreen;
        Font = new Font("Segoe UI", 9f);
        Icon = System.Drawing.Icon.ExtractAssociatedIcon(Application.ExecutablePath);
        BuildUi();
        NewReceipt();
    }

    private void BuildUi()
    {
        var toolbar = new FlowLayoutPanel { Dock = DockStyle.Top, Height = 48, Padding = new Padding(10,8,10,6), BackColor = Color.FromArgb(245,247,249), WrapContents = false };
        if (Icon is not null)
        {
            toolbar.Controls.Add(new PictureBox
            {
                Image = Icon.ToBitmap(),
                Size = new Size(32, 32),
                SizeMode = PictureBoxSizeMode.Zoom,
                Margin = new Padding(0, 0, 8, 0)
            });
        }
        toolbar.Controls.Add(MakeButton("New Receipt", (_,_) => NewReceipt()));
        toolbar.Controls.Add(MakeButton("Save JSON", (_,_) => SaveReceipt(true)));
        _printPreviewButton = MakeButton("Print Preview", (_,_) => ShowPrintPreview());
        _printButton = MakeButton("Print", (_,_) => PrintReceipt());
        toolbar.Controls.Add(_printPreviewButton);
        toolbar.Controls.Add(_printButton);
        toolbar.Controls.Add(MakeButton("Open Receipts", (_,_) => OpenFolder(Storage.ReceiptFolder)));
        toolbar.Controls.Add(MakeButton("Import Template", (_,_) => ImportTemplate()));
        toolbar.Controls.Add(MakeButton("Open Templates", (_,_) => OpenFolder(Storage.TemplateFolder)));
        Controls.Add(toolbar);

        var split = new SplitContainer { Dock = DockStyle.Fill, SplitterDistance = 500, FixedPanel = FixedPanel.Panel1, Panel1MinSize = 470 };
        Controls.Add(split);
        split.BringToFront();
        var editor = new Panel { Dock = DockStyle.Fill, AutoScroll = true, Padding = new Padding(14) };
        split.Panel1.Controls.Add(editor);
        split.Panel2.Controls.Add(_preview);

        var flow = new FlowLayoutPanel { Dock = DockStyle.Top, AutoSize = true, FlowDirection = FlowDirection.TopDown, WrapContents = false };
        editor.Controls.Add(flow);
        flow.Controls.Add(Section("Receipt template", FieldRow(("Template", _templateCombo))));
        _templateCombo.DataSource = _templates;
        _templateCombo.DisplayMember = nameof(ReceiptTemplate.Name);
        var lastTemplate = _templates.FindIndex(x => string.Equals(x.Name, _state.LastTemplate, StringComparison.OrdinalIgnoreCase));
        if (lastTemplate >= 0) _templateCombo.SelectedIndex = lastTemplate;
        _templateCombo.SelectedIndexChanged += (_,_) =>
        {
            _state.LastTemplate = CurrentTemplate.Name;
            Storage.SaveState(_state);
            ConfigureRows();
            RefreshPreview();
        };
        var printerRow = new FlowLayoutPanel { AutoSize=true, Width=430, WrapContents=false };
        printerRow.Controls.Add(_printerCombo); printerRow.Controls.Add(MakeSmallButton("Refresh", (_,_) => RefreshPrinters())); printerRow.Controls.Add(_printerStatus);
        flow.Controls.Add(Section("Printer connection", printerRow));
        _printerCombo.SelectedIndexChanged += (_,_) => UpdatePrinterStatus();
        RefreshPrinters();
        flow.Controls.Add(Section("Receipt details",
            FieldRow(("Receipt no.", _receiptNo), ("Date", _date)),
            FieldRow(("Customer", _customer)),
            FieldRow(("Address", _address)),
            FieldRow(("Terms", _terms), ("Due date", _due))));
        _terms.Items.AddRange(["Cash", "7 Days", "14 Days", "Custom"]);
        _terms.SelectedIndexChanged += (_,_) => UpdateDueDate();

        ConfigureGrid();
        var itemSection = Section("Items", _items);
        itemSection.Width = 455;
        flow.Controls.Add(itemSection);
        var signatureButtons = new FlowLayoutPanel { AutoSize=true, Width=430, WrapContents=false };
        signatureButtons.Controls.Add(_signaturePath);
        signatureButtons.Controls.Add(MakeSmallButton("Upload signature", (_,_) => UploadSignature()));
        flow.Controls.Add(Section("Totals and e-signature",
            FieldRow(("Delivery fee", _deliveryFee), ("Prepared by", _preparedBy)),
            signatureButtons, _useSignature,
            FieldRow(("Subtotal", _subtotal), ("Total", _total))));
        _useSignature.CheckedChanged += (_,_) => RefreshPreview();

        var slots = new FlowLayoutPanel { AutoSize = true, WrapContents = true, Width = 430 };
        foreach (var slot in Enum.GetValues<ReceiptSlot>())
        {
            var cb = new CheckBox { Text = SlotName(slot), AutoSize = true, Margin = new Padding(4,4,14,4), Checked = slot == ReceiptSlot.TopLeft };
            cb.CheckedChanged += (_,_) => RefreshPreview();
            _slotChecks[slot] = cb; slots.Controls.Add(cb);
        }
        slots.Controls.Add(MakeSmallButton("All", (_,_) => SetAllSlots(true)));
        slots.Controls.Add(MakeSmallButton("Clear", (_,_) => SetAllSlots(false)));
        flow.Controls.Add(Section("Print positions", slots));

        foreach (var control in new Control[] { _receiptNo, _date, _customer, _address, _due, _deliveryFee, _preparedBy })
        {
            if (control is TextBox tb) tb.TextChanged += (_,_) => RefreshPreview();
            else if (control is NumericUpDown nud) nud.ValueChanged += (_,_) => { Recalculate(); RefreshPreview(); };
            else if (control is DateTimePicker dt) dt.ValueChanged += (_,_) => RefreshPreview();
        }
        Shown += (_,_) =>
        {
            split.SplitterDistance = Math.Min(500, Math.Max(split.Panel1MinSize, ClientSize.Width - 620));
            flow.Width = 455;
            flow.Height = flow.PreferredSize.Height + 12;
            editor.AutoScrollMinSize = new Size(0, flow.Height + 28);
            flow.PerformLayout(); editor.PerformLayout();
        };
    }

    private void ConfigureGrid()
    {
        _items.Columns.Add(new DataGridViewTextBoxColumn { Name="Quantity", HeaderText="Qty", FillWeight=18 });
        _items.Columns.Add(new DataGridViewTextBoxColumn { Name="Description", HeaderText="Description", FillWeight=47 });
        _items.Columns.Add(new DataGridViewTextBoxColumn { Name="UnitPrice", HeaderText="Unit Price", FillWeight=22, DefaultCellStyle = new DataGridViewCellStyle { Format="N2" } });
        _items.Columns.Add(new DataGridViewTextBoxColumn { Name="Amount", HeaderText="Amount", FillWeight=23, ReadOnly=true, DefaultCellStyle = new DataGridViewCellStyle { Format="N2", BackColor=Color.FromArgb(245,247,249) } });
        _items.CellEndEdit += (_,e) => { UpdateAmount(e.RowIndex); Recalculate(); RefreshPreview(); };
        _items.RowsAdded += (_,_) => Recalculate();
    }

    private void ConfigureRows()
    {
        if (_items.Columns.Count == 0) return;
        var existing = ReadItems().ToList();
        _items.Rows.Clear();
        var count = Math.Max(4, CurrentTemplate.ItemRows);
        _items.Rows.Add(count);
        for (var i=0; i<Math.Min(count, existing.Count); i++)
        {
            _items.Rows[i].Cells[0].Value = existing[i].Quantity == 0 ? null : existing[i].Quantity;
            _items.Rows[i].Cells[1].Value = existing[i].Description;
            _items.Rows[i].Cells[2].Value = existing[i].UnitPrice == 0 ? null : existing[i].UnitPrice;
            UpdateAmount(i);
        }
    }

    private void NewReceipt()
    {
        _receiptNo.Value = Math.Max(1, _state.LastReceiptNumber + 1);
        _date.Value = DateTime.Today;
        _customer.Clear(); _address.Clear(); _preparedBy.Clear(); _deliveryFee.Value = 0;
        _terms.SelectedItem = "7 Days"; _due.Value = DateTime.Today.AddDays(7);
        ConfigureRows(); Recalculate(); RefreshPreview();
    }

    private ReceiptData ReadReceipt() => new()
    {
        ReceiptNumber = (int)_receiptNo.Value, Date = _date.Value.Date, Customer = _customer.Text.Trim(), Address = _address.Text.Trim(),
        Terms = _terms.Text, DueDate = _due.Value.Date, DeliveryFee = _deliveryFee.Value, PreparedBy = _preparedBy.Text.Trim(),
        UseESignature = _useSignature.Checked, SignatureFile = _signaturePath.Text, Items = ReadItems().ToList()
    };

    private IEnumerable<ReceiptItem> ReadItems()
    {
        foreach (DataGridViewRow row in _items.Rows)
        {
            var qty = DecimalValue(row.Cells[0].Value); var description = Convert.ToString(row.Cells[1].Value)?.Trim() ?? ""; var price = DecimalValue(row.Cells[2].Value);
            if (qty != 0 || price != 0 || description.Length > 0) yield return new ReceiptItem { Quantity=qty, Description=description, UnitPrice=price };
        }
    }

    private void UpdateAmount(int rowIndex)
    {
        if (rowIndex < 0 || rowIndex >= _items.Rows.Count) return;
        var row = _items.Rows[rowIndex]; row.Cells[3].Value = DecimalValue(row.Cells[0].Value) * DecimalValue(row.Cells[2].Value);
    }

    private void Recalculate()
    {
        var receipt = ReadReceipt(); _subtotal.Text = receipt.Subtotal.ToString("N2"); _total.Text = receipt.Total.ToString("N2");
    }

    private void RefreshPreview()
    {
        if (_templates.Count == 0 || _items.Columns.Count == 0) return;
        Recalculate(); _preview.Receipt = ReadReceipt(); _preview.Template = CurrentTemplate; _preview.Slots = SelectedSlots(); _preview.Invalidate();
    }

    private HashSet<ReceiptSlot> SelectedSlots() => _slotChecks.Where(x => x.Value.Checked).Select(x => x.Key).ToHashSet();
    private bool ValidatePrint()
    {
        if (SelectedSlots().Count == 0) { MessageBox.Show("Select at least one print position.", Text, MessageBoxButtons.OK, MessageBoxIcon.Information); return false; }
        if (string.IsNullOrWhiteSpace(_customer.Text) && MessageBox.Show("Customer is blank. Continue?", Text, MessageBoxButtons.YesNo, MessageBoxIcon.Question) != DialogResult.Yes) return false;
        if (_printerCombo.SelectedItem is null) { MessageBox.Show("No installed printer is available. Connect or install a printer, then click Refresh.", Text, MessageBoxButtons.OK, MessageBoxIcon.Warning); return false; }
        return true;
    }

    private string SaveReceipt(bool notify)
    {
        var receipt = ReadReceipt(); var path = Storage.SaveReceipt(receipt);
        _state.LastReceiptNumber = Math.Max(_state.LastReceiptNumber, receipt.ReceiptNumber); _state.LastTemplate = CurrentTemplate.Name; Storage.SaveState(_state);
        if (notify) MessageBox.Show($"Saved to:\n{path}", Text, MessageBoxButtons.OK, MessageBoxIcon.Information);
        return path;
    }

    private PrintDocument CreatePrintDocument()
    {
        var receipt = ReadReceipt(); var template = CurrentTemplate; var slots = SelectedSlots();
        var doc = new PrintDocument { DocumentName = $"Delivery Receipt {receipt.ReceiptNumber:00000}", OriginAtMargins = false };
        doc.PrinterSettings.PrinterName = Convert.ToString(_printerCombo.SelectedItem) ?? "";
        doc.DefaultPageSettings.Landscape = false;
        doc.DefaultPageSettings.PaperSize = new PaperSize("216 x 279 mm", (int)Math.Round(ReceiptRenderer.PageWidth), (int)Math.Round(ReceiptRenderer.PageHeight));
        doc.DefaultPageSettings.Margins = new Margins(0,0,0,0);
        doc.PrintPage += (_,e) =>
        {
            if (e.Graphics is not null)
            {
                // GDI starts at the printer's printable origin. Move back to the
                // physical page origin so left/right hardware margins stay balanced.
                var state = e.Graphics.Save();
                e.Graphics.TranslateTransform(-e.PageSettings.HardMarginX, -e.PageSettings.HardMarginY);
                ReceiptRenderer.DrawPage(
                    e.Graphics,
                    new RectangleF(0, 0, ReceiptRenderer.PageWidth, ReceiptRenderer.PageHeight),
                    receipt,
                    template,
                    slots,
                    showCutGuides: false);
                e.Graphics.Restore(state);
            }
            e.HasMorePages=false;
        };
        return doc;
    }

    private void ShowPrintPreview()
    {
        if (!ValidatePrint()) return;
        using var doc = CreatePrintDocument(); using var dialog = new PrintPreviewDialog { Document=doc, Width=1100, Height=800, StartPosition=FormStartPosition.CenterParent };
        dialog.ShowDialog(this);
    }

    private void PrintReceipt()
    {
        if (!ValidatePrint()) return;
        using var doc = CreatePrintDocument(); using var dialog = new PrintDialog { Document=doc, UseEXDialog=true };
        if (dialog.ShowDialog(this) == DialogResult.OK) { SaveReceipt(false); doc.Print(); MessageBox.Show("Receipt sent to the printer and saved as JSON.", Text, MessageBoxButtons.OK, MessageBoxIcon.Information); }
    }

    private void UpdateDueDate()
    {
        if (_terms.Text == "Cash") _due.Value = _date.Value.Date;
        else if (_terms.Text == "7 Days") _due.Value = _date.Value.Date.AddDays(7);
        else if (_terms.Text == "14 Days") _due.Value = _date.Value.Date.AddDays(14);
        RefreshPreview();
    }

    private void SetAllSlots(bool value) { foreach (var cb in _slotChecks.Values) cb.Checked=value; RefreshPreview(); }
    private void RefreshPrinters()
    {
        var selected = Convert.ToString(_printerCombo.SelectedItem);
        _printerCombo.Items.Clear();
        foreach (string printer in PrinterSettings.InstalledPrinters) _printerCombo.Items.Add(printer);
        if (!string.IsNullOrWhiteSpace(selected) && _printerCombo.Items.Contains(selected)) _printerCombo.SelectedItem = selected;
        else if (_printerCombo.Items.Count > 0) _printerCombo.SelectedIndex = 0;
        UpdatePrinterStatus();
    }

    private void UpdatePrinterStatus()
    {
        var isReady = false;
        if (_printerCombo.SelectedItem is not null)
        {
            var settings = new PrinterSettings { PrinterName = Convert.ToString(_printerCombo.SelectedItem) ?? "" };
            isReady = settings.IsValid;
        }
        _printerStatus.Text = isReady ? "Ready" : "Not available";
        _printerStatus.ForeColor = isReady ? Color.ForestGreen : Color.Firebrick;
        _printPreviewButton.Enabled = isReady;
        _printButton.Enabled = isReady;
    }

    private void UploadSignature()
    {
        using var dialog = new OpenFileDialog { Title="Upload signature image", Filter="Image files|*.png;*.jpg;*.jpeg;*.bmp" };
        if (dialog.ShowDialog(this) != DialogResult.OK) return;
        try { _signaturePath.Text = Storage.ImportSignature(dialog.FileName); _useSignature.Checked=true; RefreshPreview(); }
        catch (Exception ex) { MessageBox.Show(ex.Message, Text, MessageBoxButtons.OK, MessageBoxIcon.Error); }
    }

    private void ImportTemplate()
    {
        using var dialog = new OpenFileDialog { Title="Import receipt template", Filter="Receipt template JSON|*.json" };
        if (dialog.ShowDialog(this) != DialogResult.OK) return;
        try
        {
            Storage.ImportTemplate(dialog.FileName);
            var updated = Storage.LoadTemplates();
            _templates.Clear();
            _templates.AddRange(updated);
            if (_templates.Count == 0) _templates.Add(new());
            _templateCombo.DataSource = null; _templateCombo.DataSource = _templates; _templateCombo.DisplayMember = nameof(ReceiptTemplate.Name);
            MessageBox.Show("Template imported.", Text, MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
        catch (Exception ex) { MessageBox.Show($"Could not import template:\n{ex.Message}", Text, MessageBoxButtons.OK, MessageBoxIcon.Error); }
    }
    private static decimal DecimalValue(object? value) => decimal.TryParse(Convert.ToString(value), out var result) ? result : 0;
    private static string SlotName(ReceiptSlot slot) => slot switch { ReceiptSlot.TopLeft=>"Top left", ReceiptSlot.TopRight=>"Top right", ReceiptSlot.BottomLeft=>"Bottom left", _=>"Bottom right" };
    private static Button MakeButton(string text, EventHandler click) { var b=new Button{Text=text,AutoSize=true,Height=30,Margin=new Padding(3)}; b.Click+=click; return b; }
    private static Button MakeSmallButton(string text, EventHandler click) { var b=new Button{Text=text,AutoSize=true,Height=26,Margin=new Padding(3,1,3,1)}; b.Click+=click; return b; }
    private static void OpenFolder(string path) { Directory.CreateDirectory(path); Process.Start(new ProcessStartInfo("explorer.exe", path) { UseShellExecute=true }); }

    private static FlowLayoutPanel FieldRow(params (string Label, Control Control)[] fields)
    {
        var row = new FlowLayoutPanel { AutoSize=true, Width=430, WrapContents=false, Margin=new Padding(0,2,0,2) };
        foreach (var field in fields) { row.Controls.Add(new Label { Text=field.Label, AutoSize=true, Width=78, TextAlign=ContentAlignment.MiddleLeft, Padding=new Padding(0,6,0,0) }); row.Controls.Add(field.Control); }
        return row;
    }

    private static GroupBox Section(string title, params Control[] controls)
    {
        var box = new GroupBox { Text=title, AutoSize=false, Width=455, Padding=new Padding(10), Margin=new Padding(0,0,0,8) };
        var flow = new FlowLayoutPanel { AutoSize=true, Width=430, FlowDirection=FlowDirection.TopDown, WrapContents=false, Location=new Point(10,22) };
        flow.Controls.AddRange(controls);
        flow.Height = flow.PreferredSize.Height;
        box.Height = flow.Height + 34;
        box.Controls.Add(flow);
        return box;
    }
}