MainForm.cs

using System.Runtime.InteropServices;

using BreathOfFireSaveEditor.Game;
using BreathOfFireSaveEditor.Ui;

namespace BreathOfFireSaveEditor;

public sealed class MainForm : Form
{
    private const string FileFilter =
        "SNES9x save states (*.000-*.009)|*.000;*.001;*.002;*.003;*.004;*.005;*.006;*.007;*.008;*.009|" +
        "All files (*.*)|*.*";

    private BofSave? _save;
    private BofCharacter? _current;
    private bool _loading;

    private readonly ComboBox _slotPicker = new();
    private readonly SnesPortrait _portrait = new();
    private readonly Label _nameLabel = new();
    private readonly Label _statusLabel = new();
    private readonly Label _addressLabel = new();

    private readonly SnesStatField _atk  = new() { Caption = "ATK",  Maximum = 9999, BoxWidth = 96 };
    private readonly SnesStatField _def  = new() { Caption = "DEF",  Maximum = 9999, BoxWidth = 96 };
    private readonly SnesStatField _act  = new() { Caption = "ACT",  Maximum = 255,  BoxWidth = 96 };
    private readonly SnesStatField _mag  = new() { Caption = "MAG",  Maximum = 255,  BoxWidth = 96 };
    private readonly SnesStatField _int  = new() { Caption = "INT",  Maximum = 255,  BoxWidth = 96 };
    private readonly SnesStatField _fate = new() { Caption = "FATE", Maximum = 255,  BoxWidth = 96 };

    private readonly SnesStatField _level = new() { Caption = "LEVEL", Locked = true };
    private readonly SnesStatField _exp   = new() { Caption = "EXP",   Maximum = 0xFFFFFF, BoxWidth = 150 };
    private readonly SnesStatField _hp    = new() { Caption = "H P",   Maximum = 9999, Paired = true };
    private readonly SnesStatField _ap    = new() { Caption = "A P",   Maximum = 9999, Paired = true };

    // Read only: the game owns equipment, the editor only reports it. The two
    // "Etc." accessory slots have not been found in the record yet, so they stay
    // blank whatever the character is wearing.
    private readonly SnesTextField _wepn = new() { Caption = "Wepn" };
    private readonly SnesTextField _shld = new() { Caption = "Shld" };
    private readonly SnesTextField _armr = new() { Caption = "Armr" };
    private readonly SnesTextField _helm = new() { Caption = "Helm" };
    private readonly SnesTextField _etc1 = new() { Caption = "Etc." };
    private readonly SnesTextField _etc2 = new() { Caption = "Etc." };

    private readonly SnesStatField _str    = new() { Caption = "Str.",   Maximum = 255 };
    private readonly SnesStatField _vigor  = new() { Caption = "Vigor",  Maximum = 255 };
    private readonly SnesStatField _agil   = new() { Caption = "Agil.",  Maximum = 255 };
    private readonly SnesStatField _wisdom = new() { Caption = "Wisdom", Maximum = 255 };
    private readonly SnesStatField _luck   = new() { Caption = "Luck",   Maximum = 255 };

    // Gold belongs to the party rather than to a character, so it sits on the Items
    // tab with the inventory instead of on the per-character Stats tab.
    private readonly SnesStatField _gold = new() { Caption = "GOLD", Maximum = BofSave.MaxGold, BoxWidth = 150 };

    private readonly SnesTabStrip _tabs = new() { Tabs = ["Stats", "Items", "Magic"] };
    private readonly Panel _pageHost = new();
    private IReadOnlyList<Control> _pages = [];
    private TableLayoutPanel _itemGrid = null!;
    private Label _itemEmptyLabel = null!;
    private TableLayoutPanel _spellGrid = null!;
    private Label _spellEmptyLabel = null!;
    private readonly List<(SnesStatField Field, BofItemSlot Slot)> _itemFields = [];

    private ToolStripMenuItem _saveItem = null!;
    private ToolStripMenuItem _saveAsItem = null!;
    private ToolStripMenuItem _reloadItem = null!;

    private IEnumerable<SnesStatField> AllFields =>
    [
        _atk, _def, _act, _mag, _int, _fate,
        _level, _exp, _hp, _ap,
        _str, _vigor, _agil, _wisdom, _luck,
    ];

    public MainForm()
    {
        Text = "Breath of Fire Save State Editor";
        BackColor = SnesTheme.Background;
        ForeColor = SnesTheme.TextLabel;
        Font = SnesTheme.Font(15f);
        ClientSize = new Size(940, 880);
        MinimumSize = new Size(800, 780);
        StartPosition = FormStartPosition.CenterScreen;

        BuildLayout();
        HookFields();
        UpdateEnabledState();

        Shown += (_, _) => TryReopenLastFile();
        FormClosing += OnFormClosing;
    }

    /// <summary>Ask the desktop window manager for a dark title bar to match the theme.</summary>
    protected override void OnHandleCreated(EventArgs e)
    {
        base.OnHandleCreated(e);

        int enabled = 1;
        try
        {
            DwmSetWindowAttribute(Handle, DwmwaUseImmersiveDarkMode, ref enabled, sizeof(int));
        }
        catch (DllNotFoundException)
        {
            // Older Windows: keep the default title bar.
        }
        catch (EntryPointNotFoundException)
        {
        }
    }

    private const int DwmwaUseImmersiveDarkMode = 20;

    [DllImport("dwmapi.dll")]
    private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attribute, ref int value, int size);

    // ---------------------------------------------------------------- layout

    private void BuildLayout()
    {
        var root = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.Background,
            ColumnCount = 1,
            RowCount = 4,
            Padding = new Padding(14, 10, 14, 14),
        };
        root.RowStyles.Add(new RowStyle(SizeType.Absolute, 52));
        root.RowStyles.Add(new RowStyle(SizeType.Absolute, 46));
        root.RowStyles.Add(new RowStyle(SizeType.Percent, 100));
        root.RowStyles.Add(new RowStyle(SizeType.Absolute, 148));

        root.Controls.Add(BuildSlotRow(), 0, 0);
        root.Controls.Add(BuildTabStrip(), 0, 1);
        root.Controls.Add(BuildPages(), 0, 2);
        root.Controls.Add(BuildFooterPanel(), 0, 3);

        Controls.Add(root);
        Controls.Add(BuildMenu());
    }

    private MenuStrip BuildMenu()
    {
        var open = new ToolStripMenuItem("&Open...", null, (_, _) => OpenFile())
            { ShortcutKeys = Keys.Control | Keys.O };
        _saveItem = new ToolStripMenuItem("&Save", null, (_, _) => SaveFile(null))
            { ShortcutKeys = Keys.Control | Keys.S };
        _saveAsItem = new ToolStripMenuItem("Save &As...", null, (_, _) => SaveAs());
        _reloadItem = new ToolStripMenuItem("&Reload from disk", null, (_, _) => Reload())
            { ShortcutKeys = Keys.F5 };
        var exit = new ToolStripMenuItem("E&xit", null, (_, _) => Close());

        var file = new ToolStripMenuItem("&File");
        file.DropDownItems.AddRange(new ToolStripItem[]
        {
            open, _saveItem, _saveAsItem, new ToolStripSeparator(), _reloadItem, new ToolStripSeparator(), exit,
        });

        var help = new ToolStripMenuItem("&Help");
        help.DropDownItems.Add(new ToolStripMenuItem("&About", null, (_, _) => ShowAbout()));

        var menu = new MenuStrip
        {
            BackColor = SnesTheme.PanelFill,
            ForeColor = SnesTheme.TextLabel,
            Renderer = new ToolStripProfessionalRenderer(new SnesMenuColours()),
            Font = SnesTheme.Font(12f),
        };
        menu.Items.AddRange(new ToolStripItem[] { file, help });
        MainMenuStrip = menu;
        return menu;
    }

    private Control BuildSlotRow()
    {
        var host = new Panel { Dock = DockStyle.Fill, BackColor = SnesTheme.Background };

        var caption = new Label
        {
            Text = "CHARACTER",
            AutoSize = false,
            Bounds = new Rectangle(6, 8, 170, 34),
            ForeColor = SnesTheme.TextDim,
            BackColor = SnesTheme.Background,
            TextAlign = ContentAlignment.MiddleLeft,
            Font = SnesTheme.Font(13f),
        };

        _slotPicker.DropDownStyle = ComboBoxStyle.DropDownList;
        _slotPicker.FlatStyle = FlatStyle.Flat;
        _slotPicker.BackColor = SnesTheme.FieldFill;
        _slotPicker.ForeColor = SnesTheme.TextPrimary;
        _slotPicker.Font = SnesTheme.Font(14f);
        _slotPicker.Location = new Point(182, 6);
        // Wide enough for the longest entry: slot, name, level and the reserve note.
        _slotPicker.Width = 470;
        _slotPicker.SelectedIndexChanged += (_, _) => BindCharacter();

        host.Controls.Add(caption);
        host.Controls.Add(_slotPicker);
        return host;
    }

    private Control BuildCombatPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        // A two column table rather than a docked grid with a left margin:
        // DefaultLayout ignores Margin on a Dock.Fill child, which let the stat
        // grid cover the portrait entirely.
        var split = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = 2,
            RowCount = 1,
        };
        split.ColumnStyles.Add(new ColumnStyle(SizeType.Absolute, 152));
        split.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100));
        split.RowStyles.Add(new RowStyle(SizeType.Percent, 100));

        split.Controls.Add(BuildPortraitCell(), 0, 0);

        var grid = NewGrid(columns: 2, rows: 3);
        grid.Controls.Add(_atk, 0, 0);
        grid.Controls.Add(_def, 1, 0);
        grid.Controls.Add(_act, 0, 1);
        grid.Controls.Add(_mag, 1, 1);
        grid.Controls.Add(_int, 0, 2);
        grid.Controls.Add(_fate, 1, 2);
        split.Controls.Add(grid, 1, 0);

        panel.Controls.Add(split);
        return panel;
    }

    private Control BuildPortraitCell()
    {
        var cell = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = 1,
            RowCount = 2,
            Padding = new Padding(0, 14, 0, 0),
        };
        cell.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100));
        cell.RowStyles.Add(new RowStyle(SizeType.Absolute, 112));
        cell.RowStyles.Add(new RowStyle(SizeType.Absolute, 36));

        _portrait.Anchor = AnchorStyles.None;
        _portrait.Size = new Size(104, 104);

        _nameLabel.Dock = DockStyle.Fill;
        _nameLabel.AutoSize = false;
        _nameLabel.TextAlign = ContentAlignment.MiddleCenter;
        _nameLabel.BackColor = SnesTheme.PanelFill;
        _nameLabel.ForeColor = SnesTheme.TextPrimary;
        _nameLabel.Font = SnesTheme.Font(17f);

        cell.Controls.Add(_portrait, 0, 0);
        cell.Controls.Add(_nameLabel, 0, 1);
        return cell;
    }

    private Control BuildVitalsPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        var grid = NewGrid(columns: 2, rows: 5);
        grid.Margin = new Padding(22, 16, 22, 16);
        grid.Controls.Add(_level, 0, 0);
        grid.Controls.Add(_exp, 0, 1);
        grid.Controls.Add(_hp, 0, 2);
        grid.Controls.Add(_ap, 0, 3);

        grid.Controls.Add(_str, 1, 0);
        grid.Controls.Add(_vigor, 1, 1);
        grid.Controls.Add(_agil, 1, 2);
        grid.Controls.Add(_wisdom, 1, 3);
        grid.Controls.Add(_luck, 1, 4);

        panel.Controls.Add(grid);
        return panel;
    }

    private Control BuildTabStrip()
    {
        _tabs.Dock = DockStyle.Fill;
        _tabs.Margin = new Padding(4, 0, 4, 4);
        _tabs.SelectedIndexChanged += (_, _) => ShowPage(_tabs.SelectedIndex);
        return _tabs;
    }

    private Control BuildPages()
    {
        _pageHost.Dock = DockStyle.Fill;
        _pageHost.BackColor = SnesTheme.Background;
        _pageHost.Margin = Padding.Empty;

        _pages = [BuildStatsPage(), BuildItemsPage(), BuildMagicPage()];
        foreach (var page in _pages) _pageHost.Controls.Add(page);
        ShowPage(0);

        return _pageHost;
    }

    private void ShowPage(int index)
    {
        for (int i = 0; i < _pages.Count; i++) _pages[i].Visible = i == index;
        _pages[index].BringToFront();
    }

    private Control BuildStatsPage()
    {
        var page = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.Background,
            ColumnCount = 1,
            RowCount = 3,
            Margin = Padding.Empty,
        };
        page.RowStyles.Add(new RowStyle(SizeType.Absolute, 216));
        page.RowStyles.Add(new RowStyle(SizeType.Percent, 100));
        page.RowStyles.Add(new RowStyle(SizeType.Absolute, 158));

        page.Controls.Add(BuildCombatPanel(), 0, 0);
        page.Controls.Add(BuildVitalsPanel(), 0, 1);
        page.Controls.Add(BuildEquipmentPanel(), 0, 2);
        return page;
    }

    private Control BuildItemsPage()
    {
        var page = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.Background,
            ColumnCount = 1,
            RowCount = 2,
            Margin = Padding.Empty,
        };
        page.RowStyles.Add(new RowStyle(SizeType.Absolute, 72));
        page.RowStyles.Add(new RowStyle(SizeType.Percent, 100));

        page.Controls.Add(BuildGoldPanel(), 0, 0);
        page.Controls.Add(BuildInventoryPanel(), 0, 1);
        return page;
    }

    /// <summary>
    /// The purse. It is party wide, so it lives here beside the inventory rather
    /// than on the Stats tab, where it would read as belonging to one character.
    /// </summary>
    private Control BuildGoldPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        var grid = NewGrid(columns: 1, rows: 1);
        grid.Margin = new Padding(22, 14, 22, 14);
        grid.Controls.Add(_gold, 0, 0);

        panel.Controls.Add(grid);
        return panel;
    }

    private Control BuildInventoryPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        _itemGrid = new TableLayoutPanel
        {
            Dock = DockStyle.Top,
            AutoSize = true,
            AutoSizeMode = AutoSizeMode.GrowAndShrink,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = 2,
            Margin = Padding.Empty,
        };
        _itemGrid.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 50));
        _itemGrid.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 50));

        var itemScroll = NewScrollHost();
        itemScroll.Controls.Add(_itemGrid);

        _itemEmptyLabel = new Label
        {
            Dock = DockStyle.Fill,
            AutoSize = false,
            BackColor = SnesTheme.PanelFill,
            ForeColor = SnesTheme.TextDim,
            Font = SnesTheme.Font(13f, FontStyle.Regular),
            TextAlign = ContentAlignment.MiddleCenter,
            Text = "No save state loaded.",
            Visible = true,
        };

        panel.Controls.Add(itemScroll);
        panel.Controls.Add(_itemEmptyLabel);
        return panel;
    }

    /// <summary>
    /// A scrolling host for a grid that can outgrow the window. AutoScroll has to
    /// sit on the container with the grid docked to its top and sizing itself,
    /// never on the grid: a TableLayoutPanel that both scrolls and carries a
    /// percent row sizes itself to the space it has been given, so it never
    /// reports being taller than its own client area, no scrollbar appears and the
    /// rows past the bottom edge are simply clipped. A 34 item bag lost its last
    /// ten that way.
    /// </summary>
    private static Panel NewScrollHost() => new()
    {
        Dock = DockStyle.Fill,
        AutoScroll = true,
        BackColor = SnesTheme.PanelFill,
        Margin = Padding.Empty,
    };

    /// <summary>
    /// Rebuilds the item rows for the loaded save. Only occupied slots get a row:
    /// quantities are editable but items cannot be added, so an empty slot has
    /// nothing to offer.
    /// </summary>
    private void BuildItemRows()
    {
        _itemGrid.SuspendLayout();
        foreach (var (field, _) in _itemFields) field.Dispose();
        _itemFields.Clear();
        _itemGrid.Controls.Clear();
        _itemGrid.RowStyles.Clear();
        _itemGrid.RowCount = 0;

        var occupied = _save?.Inventory.Occupied.ToList() ?? [];

        int row = 0;
        for (int i = 0; i < occupied.Count; i++)
        {
            var slot = occupied[i];

            // Equipment can sit in the bag, and its second byte is the id's page
            // rather than a count - so there is nothing to spin, and editing it
            // would turn the item into a different one.
            var field = new SnesStatField
            {
                Caption = slot.Name,
                Minimum = 0,
                // A count the game cannot draw is still a count, and clamping a
                // field on binding it would rewrite it on the next save without
                // anyone asking. Whatever is already there sets its own ceiling.
                Maximum = Math.Max(BofInventory.MaxQuantity, slot.Quantity),
                Locked = slot.IsEquipment,
                BoxWidth = 78,
                Dock = DockStyle.Fill,
                Margin = new Padding(10, 3, 10, 3),
                Value = slot.Quantity,
            };

            var captured = slot;
            field.UserEdited += (_, _) =>
            {
                if (_loading || _save is null)
                {
                    return;
                }
                captured.Quantity = field.Value;
                _save.MarkDirty();
                UpdateStatus();
            };

            _itemFields.Add((field, slot));

            int column = i % 2;
            if (column == 0)
            {
                _itemGrid.RowCount = row + 1;
                _itemGrid.RowStyles.Add(new RowStyle(SizeType.Absolute, 40));
            }

            _itemGrid.Controls.Add(field, column, row);

            if (column == 1)
            {
                row++;
            }
        }

        if (occupied.Count % 2 == 1)
        {
            row++;
        }

        // No trailing percent row here. The grid sizes itself to its rows and its
        // host scrolls; a percent row would size it to the host instead and take
        // the scrollbar away with it. See NewScrollHost.
        _itemGrid.RowCount = row;

        bool any = occupied.Count > 0;
        _itemGrid.Visible = any;
        _itemEmptyLabel.Visible = !any;
        _itemEmptyLabel.Text = _save is null ? "No save state loaded." : "The party is not carrying any items.";
        // The scroll host fills the page and sits over the label, so hiding the grid
        // inside it leaves the host's own background covering the message. Lifting
        // the label is what actually puts it on screen. See NewScrollHost.
        if (!any)
        {
            _itemEmptyLabel.BringToFront();
        }

        _itemGrid.ResumeLayout();
    }

    /// <summary>
    /// The magic list, laid out in three columns like the game's own screen.
    /// Read only: spells are not stored in a save at all, so there is nothing
    /// here to change. See <see cref="BofSpells"/>.
    /// </summary>
    private Control BuildMagicPage()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        _spellGrid = new TableLayoutPanel
        {
            Dock = DockStyle.Top,
            AutoSize = true,
            AutoSizeMode = AutoSizeMode.GrowAndShrink,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = 3,
            Margin = Padding.Empty,
            Padding = new Padding(12, 10, 12, 10),
        };

        for (int c = 0; c < 3; c++)
        {
            _spellGrid.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100f / 3));
        }

        _spellEmptyLabel = new Label
        {
            Dock = DockStyle.Fill,
            AutoSize = false,
            BackColor = SnesTheme.PanelFill,
            ForeColor = SnesTheme.TextDim,
            Font = SnesTheme.Font(13f),
            TextAlign = ContentAlignment.MiddleCenter,
            Text = "No save state loaded.",
        };

        var spellScroll = NewScrollHost();
        spellScroll.Controls.Add(_spellGrid);

        panel.Controls.Add(spellScroll);
        panel.Controls.Add(_spellEmptyLabel);
        return panel;
    }

    /// <summary>
    /// Fills the magic page for the picked character. A character with no learn
    /// table says so rather than pretending to know they have no magic.
    /// </summary>
    private void BuildSpellRows()
    {
        _spellGrid.SuspendLayout();
        foreach (Control old in _spellGrid.Controls) old.Dispose();
        _spellGrid.Controls.Clear();
        _spellGrid.RowStyles.Clear();
        _spellGrid.RowCount = 0;

        var spells = _current?.Spells ?? [];

        int row = 0;
        for (int i = 0; i < spells.Count; i++)
        {
            int column = i % 3;
            if (column == 0)
            {
                _spellGrid.RowCount = row + 1;
                _spellGrid.RowStyles.Add(new RowStyle(SizeType.Absolute, 34));
            }

            _spellGrid.Controls.Add(new Label
            {
                Text = spells[i],
                AutoSize = false,
                Dock = DockStyle.Fill,
                BackColor = SnesTheme.PanelFill,
                ForeColor = SnesTheme.TextLocked,
                Font = SnesTheme.Font(15f),
                TextAlign = ContentAlignment.MiddleLeft,
                Margin = new Padding(10, 2, 10, 2),
            }, column, row);

            if (column == 2)
            {
                row++;
            }
        }

        if (spells.Count % 3 != 0)
        {
            row++;
        }

        // The grid sizes itself to its rows and its host scrolls, so the rows keep
        // the height they were given without a percent row to soak up the rest -
        // and Bleu's thirty one spells will have somewhere to go. See NewScrollHost.
        _spellGrid.RowCount = row;

        bool any = spells.Count > 0;
        _spellGrid.Visible = any;
        _spellEmptyLabel.Visible = !any;
        _spellEmptyLabel.Text = SpellEmptyText();
        // Same as the items page: the scroll host covers the label until it is lifted.
        if (!any)
        {
            _spellEmptyLabel.BringToFront();
        }

        _spellGrid.ResumeLayout();
    }

    private string SpellEmptyText()
    {
        if (_save is null)
        {
            return "No save state loaded.";
        }
        if (_current is null)
        {
            return string.Empty;
        }

        if (BofSpells.HasNoMagic(_current.CharacterId))
        {
            return $"{_current.Name} has no magic.";
        }

        // The hero's forms are won from story trials, so an empty list is a place in
        // the story rather than a low level - saying "not learned yet" would misplace
        // the blame onto levelling, which has nothing to do with it.
        if (_current.CharacterId == BofSpells.HeroId)
        {
            return $"{_current.Name} has not won a dragon transformation yet.";
        }

        if (BofSpells.IsKnown(_current.CharacterId))
        {
            return $"{_current.Name} has not learned any spells yet.";
        }

        return _current.IsInParty
            ? $"No spell list is known for {_current.Name}."
            : $"{_current.Name} is not in the party, so there is nothing to look up.";
    }

    private Control BuildEquipmentPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        var grid = NewGrid(columns: 2, rows: 3);
        grid.Margin = new Padding(0);
        grid.Controls.Add(_wepn, 0, 0);
        grid.Controls.Add(_shld, 1, 0);
        grid.Controls.Add(_armr, 0, 1);
        grid.Controls.Add(_helm, 1, 1);
        grid.Controls.Add(_etc1, 0, 2);
        grid.Controls.Add(_etc2, 1, 2);

        foreach (var slot in EquipmentFields)
        {
            slot.Dock = DockStyle.Fill;
            slot.Margin = new Padding(10, 3, 10, 3);
        }

        panel.Controls.Add(grid);
        return panel;
    }

    private IEnumerable<SnesTextField> EquipmentFields =>
        [_wepn, _shld, _armr, _helm, _etc1, _etc2];

    private Control BuildFooterPanel()
    {
        var panel = new SnesPanel { Dock = DockStyle.Fill };

        // Stacked rows rather than absolute bounds, so the wrapped hint cannot
        // spill past the bottom of the box at any window width.
        var rows = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = 1,
            RowCount = 3,
            Padding = new Padding(10, 4, 10, 4),
        };
        rows.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100));
        rows.RowStyles.Add(new RowStyle(SizeType.Absolute, 30));
        rows.RowStyles.Add(new RowStyle(SizeType.Absolute, 26));
        rows.RowStyles.Add(new RowStyle(SizeType.Percent, 100));

        StyleFooterLabel(_statusLabel, SnesTheme.Font(13f), SnesTheme.TextPrimary);
        _statusLabel.Text = "No save state loaded.";

        StyleFooterLabel(_addressLabel, SnesTheme.Font(11f, FontStyle.Regular), SnesTheme.TextDim);

        var hint = new Label();
        StyleFooterLabel(hint, SnesTheme.Font(11f, FontStyle.Regular), SnesTheme.TextDim);
        hint.TextAlign = ContentAlignment.TopLeft;
        hint.Text = "ATK, DEF, ACT, MAG, INT and FATE are derived values: the game recomputes them from the "
                  + "base stats and equipment, so edits to them may not survive a level up or a change of gear.";

        rows.Controls.Add(_statusLabel, 0, 0);
        rows.Controls.Add(_addressLabel, 0, 1);
        rows.Controls.Add(hint, 0, 2);

        panel.Controls.Add(rows);
        return panel;
    }

    private static void StyleFooterLabel(Label label, Font font, Color colour)
    {
        label.Dock = DockStyle.Fill;
        label.AutoSize = false;
        label.BackColor = SnesTheme.PanelFill;
        label.ForeColor = colour;
        label.Font = font;
        label.TextAlign = ContentAlignment.MiddleLeft;
        label.Margin = Padding.Empty;
    }

    private static TableLayoutPanel NewGrid(int columns, int rows)
    {
        var grid = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            BackColor = SnesTheme.PanelFill,
            ColumnCount = columns,
            RowCount = rows,
        };

        for (int c = 0; c < columns; c++)
        {
            grid.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100f / columns));
        }

        for (int r = 0; r < rows; r++)
        {
            grid.RowStyles.Add(new RowStyle(SizeType.Percent, 100f / rows));
        }

        return grid;
    }

    // ----------------------------------------------------------- data wiring

    private void HookFields()
    {
        foreach (var field in AllFields)
        {
            field.Dock = DockStyle.Fill;
            field.Margin = new Padding(10, 3, 10, 3);
            field.UserEdited += (_, _) => PushToModel();
        }

        // Gold is party wide, so it is not part of the per-character push.
        _gold.Dock = DockStyle.Fill;
        _gold.Margin = new Padding(10, 3, 10, 3);
        _gold.UserEdited += (_, _) => PushGold();
    }

    private void PushGold()
    {
        if (_loading || _save is null)
        {
            return;
        }

        _save.Gold = _gold.Value;
        _save.MarkDirty();
        UpdateStatus();
    }

    private void PushToModel()
    {
        if (_loading || _current is null || _save is null)
        {
            return;
        }

        _current.Atk = _atk.Value;
        _current.Def = _def.Value;
        _current.Act = _act.Value;
        _current.Mag = _mag.Value;
        _current.Int = _int.Value;
        _current.Fate = _fate.Value;

        _current.Exp = _exp.Value;
        _current.HpCur = _hp.Value;
        _current.HpMax = _hp.SecondValue;
        _current.ApCur = _ap.Value;
        _current.ApMax = _ap.SecondValue;

        _current.Strength = _str.Value;
        _current.Vigor = _vigor.Value;
        _current.Agility = _agil.Value;
        _current.Wisdom = _wisdom.Value;
        _current.Luck = _luck.Value;

        _save.MarkDirty();
        UpdateStatus();
    }

    /// <summary>Loads the party wide values, which do not depend on the picked character.</summary>
    private void BindSave()
    {
        if (_save is null)
        {
            return;
        }

        _loading = true;
        _gold.Value = _save.Gold;
        _loading = false;
    }

    private void BindCharacter()
    {
        if (_save is null)
        {
            return;
        }

        _current = _slotPicker.SelectedItem is SlotEntry entry ? entry.Character : null;
        if (_current is null)
        {
            return;
        }

        _loading = true;

        _portrait.CharacterName = _current.Name;
        _nameLabel.Text = _current.Name;

        _atk.Value = _current.Atk;
        _def.Value = _current.Def;
        _act.Value = _current.Act;
        _mag.Value = _current.Mag;
        _int.Value = _current.Int;
        _fate.Value = _current.Fate;

        _level.Value = _current.Level;
        _exp.Value = _current.Exp;
        _hp.Value = _current.HpCur;
        _hp.SecondValue = _current.HpMax;
        _ap.Value = _current.ApCur;
        _ap.SecondValue = _current.ApMax;

        _str.Value = _current.Strength;
        _vigor.Value = _current.Vigor;
        _agil.Value = _current.Agility;
        _wisdom.Value = _current.Wisdom;
        _luck.Value = _current.Luck;

        _wepn.Value = _current.Weapon;
        _shld.Value = _current.Shield;
        _armr.Value = _current.Armour;
        _helm.Value = _current.Helmet;
        _etc1.Value = _current.Etc1;
        _etc2.Value = _current.Etc2;

        _loading = false;

        BuildSpellRows();

        // Worth saying out loud when there is no save block copy: those edits stand
        // only until the game writes SRAM from the live record at the next save point.
        string mirror = _current.HasSaveBlockRecord ? string.Empty : "    no save block record";

        _addressLabel.Text =
            $"Slot {_current.Slot}    record at ${_current.Address:X6}    {BofCharacter.RecordSize} bytes{mirror}";
        UpdateStatus();
    }

    private sealed record SlotEntry(BofCharacter Character)
    {
        // Records left behind by characters who have dropped out are still perfectly
        // readable, and still worth editing for when they come back, so they are
        // listed rather than hidden - just marked so the roster is not misread.
        public override string ToString()
        {
            string reserve = Character.IsInParty ? string.Empty : "   (not in party)";
            return $"{Character.Slot}   {Character.DisplayName}   Lv {Character.Level}{reserve}";
        }
    }

    // ------------------------------------------------------------ file verbs

    private void TryReopenLastFile()
    {
        string? last = Settings.LastFile;
        if (!string.IsNullOrWhiteSpace(last) && File.Exists(last))
        {
            LoadFile(last, quiet: true);
        }
    }

    private void OpenFile()
    {
        if (!ConfirmDiscard())
        {
            return;
        }

        using var dialog = new OpenFileDialog
        {
            Title = "Open a SNES9x save state",
            Filter = FileFilter,
            InitialDirectory = InitialDirectory(),
        };

        if (dialog.ShowDialog(this) == DialogResult.OK)
        {
            LoadFile(dialog.FileName, quiet: false);
        }
    }

    private string InitialDirectory()
    {
        string? last = _save?.FilePath ?? Settings.LastFile;
        string? dir = string.IsNullOrWhiteSpace(last) ? null : Path.GetDirectoryName(last);
        return Directory.Exists(dir) ? dir! : Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
    }

    private void LoadFile(string path, bool quiet)
    {
        try
        {
            var save = BofSave.Load(path);
            var present = save.Characters.Where(c => c.IsPresent).ToList();

            if (present.Count == 0)
            {
                if (!quiet)
                {
                    Warn($"No Breath of Fire party data was found in:\n\n{path}\n\n" +
                         "Check that this state is from Breath of Fire and was taken after the game had started.");
                }
                return;
            }

            _save = save;
            Settings.LastFile = path;

            _slotPicker.Items.Clear();
            foreach (var character in present)
                _slotPicker.Items.Add(new SlotEntry(character));
            _slotPicker.SelectedIndex = 0;

            UpdateEnabledState();
            BindSave();
            BuildItemRows();
            BindCharacter();
        }
        catch (Exception ex) when (ex is IOException or InvalidDataException or KeyNotFoundException)
        {
            if (!quiet)
            {
                Warn($"Could not read that save state.\n\n{ex.Message}");
            }
        }
    }

    private void SaveFile(string? path)
    {
        if (_save is null)
        {
            return;
        }

        foreach (var field in AllFields)
        {
            field.CommitPending();
        }

        foreach (var (field, slot) in _itemFields)
        {
            field.CommitPending();
            slot.Quantity = field.Value;
        }

        _gold.CommitPending();

        PushToModel();
        PushGold();

        try
        {
            _save.Save(path ?? _save.FilePath);
            Settings.LastFile = _save.FilePath;
            UpdateStatus();
        }
        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
        {
            Warn($"Could not write the save state.\n\n{ex.Message}");
        }
    }

    private void SaveAs()
    {
        if (_save is null) return;

        using var dialog = new SaveFileDialog
        {
            Title = "Save state as",
            Filter = FileFilter,
            InitialDirectory = InitialDirectory(),
            FileName = Path.GetFileName(_save.FilePath),
        };

        if (dialog.ShowDialog(this) == DialogResult.OK)
        {
            SaveFile(dialog.FileName);
        }
    }

    private void Reload()
    {
        if (_save is null || !ConfirmDiscard())
        {
            return;
        }

        LoadFile(_save.FilePath, quiet: false);
    }

    // ---------------------------------------------------------------- chrome

    private void UpdateEnabledState()
    {
        bool loaded = _save is not null;
        _saveItem.Enabled = loaded;
        _saveAsItem.Enabled = loaded;
        _reloadItem.Enabled = loaded;
        _slotPicker.Enabled = loaded;
        _tabs.Enabled = loaded;
        _gold.Enabled = loaded;
        foreach (var field in AllFields)
        {
            field.Enabled = loaded;
        }
    }

    private void UpdateStatus()
    {
        if (_save is null)
        {
            _statusLabel.Text = "No save state loaded.";
            Text = "Breath of Fire Save State Editor";
            return;
        }

        string marker = _save.IsDirty ? "    * unsaved changes *" : string.Empty;
        _statusLabel.Text = Path.GetFileName(_save.FilePath) + marker;
        Text = $"Breath of Fire Save State Editor - {Path.GetFileName(_save.FilePath)}{marker}";
    }

    private bool ConfirmDiscard()
    {
        if (_save is null || !_save.IsDirty)
        {
            return true;
        }

        var answer = MessageBox.Show(this,
            "There are unsaved changes. Discard them?",
            "Breath of Fire Save State Editor",
            MessageBoxButtons.YesNo, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button2);
        return answer == DialogResult.Yes;
    }

    private void OnFormClosing(object? sender, FormClosingEventArgs e)
    {
        if (!ConfirmDiscard())
        {
            e.Cancel = true;
        }
    }

    private void Warn(string message) =>
        MessageBox.Show(this, message, "Breath of Fire Save State Editor",
            MessageBoxButtons.OK, MessageBoxIcon.Warning);

    private void ShowAbout() =>
        MessageBox.Show(this,
            "Breath of Fire Save State Editor\n\n" +
            "Edits party stats inside SNES9x 1.63 freeze files (*.000 - *.009).\n" +
            "Party data is read from the state's WRAM block at $7E1040.\n\n" +
            "A .bak copy is written next to the file every time you save.",
            "About", MessageBoxButtons.OK, MessageBoxIcon.Information);
}

/// <summary>Dark colours for the menu strip, which does not follow BackColor on its own.</summary>
internal sealed class SnesMenuColours : ProfessionalColorTable
{
    public override Color MenuItemSelected => SnesTheme.FieldBorder;
    public override Color MenuItemSelectedGradientBegin => SnesTheme.FieldBorder;
    public override Color MenuItemSelectedGradientEnd => SnesTheme.FieldBorder;
    public override Color MenuItemBorder => SnesTheme.BorderLight;
    public override Color MenuBorder => SnesTheme.BorderShade;
    public override Color ToolStripDropDownBackground => SnesTheme.PanelFill;
    public override Color ImageMarginGradientBegin => SnesTheme.PanelFill;
    public override Color ImageMarginGradientMiddle => SnesTheme.PanelFill;
    public override Color ImageMarginGradientEnd => SnesTheme.PanelFill;
    public override Color MenuItemPressedGradientBegin => SnesTheme.PanelFill;
    public override Color MenuItemPressedGradientEnd => SnesTheme.PanelFill;
}