@inject CatalogApiClient Api
@inject BandLayoutService BandLayoutService

@if (!string.IsNullOrWhiteSpace(errorMessage))
{
    <div class="alert alert-danger" role="alert">@errorMessage</div>
}
else if (!string.IsNullOrWhiteSpace(infoMessage))
{
    <div class="alert alert-success" role="alert">@infoMessage</div>
}

@if (!hasLoaded || isLoading)
{
    <div class="loading-container">
        <div class="spinner-border text-primary" role="status">
            <span class="visually-hidden">Lade...</span>
        </div>
    </div>
}
else if (items.Count == 0)
{
    <p>Keine Einträge vorhanden.</p>
}
else
{
    <div class="band-editor">
        <div class="band-controls">
            <DxButton Text="Band hinzufügen" Click="AddBand" />
            <DxButton Text="Layout speichern" Click="SaveLayoutAsync" Enabled="@CanSaveBandLayout" />
            <DxButton Text="Layout zurücksetzen" Click="ResetLayoutAsync" />
        </div>
        @foreach (var band in bandLayout.Bands)
        {
            <div class="band-row">
                <DxTextBox Text="@band.Caption" TextChanged="@(value => UpdateBandCaption(band, value))" />
                <DxButton Text="Entfernen" Click="@(() => RemoveBand(band))" />
            </div>
        }
        <DxFormLayout CssClass="band-columns" ColCount="2">
            @foreach (var column in columnDefinitions)
            {
                <DxFormLayoutItem Caption="@column.Caption">
                    <DxComboBox Data="@bandOptions"
                                TData="BandOption"
                                TValue="string"
                                TextFieldName="Caption"
                                ValueFieldName="Id"
                                Value="@GetColumnBand(column.FieldName)"
                                ValueChanged="@(value => UpdateColumnBand(column.FieldName, value))"
                                Width="100%" />
                </DxFormLayoutItem>
            }
        </DxFormLayout>
    </div>

    <div class="grid-section">
        <DxGrid Data="@items"
                TItem="CatalogReadDto"
                KeyFieldName="@nameof(CatalogReadDto.Guid)"
                SizeMode="@_sizeMode"
                ShowGroupPanel="true"
                ShowGroupedColumns="true"
                AllowGroup="true"
                FilterMenuButtonDisplayMode="GridFilterMenuButtonDisplayMode.Always"
                AllowColumnResize="true"
                ColumnResizeMode="GridColumnResizeMode.ColumnsContainer"
                AllowColumnReorder="true"
                PageSize="10"
                CssClass="mb-4 catalog-grid"
                EditMode="GridEditMode.PopupEditForm"
                PopupEditFormCssClass="catalog-edit-popup"
                PopupEditFormHeaderText="@popupHeaderText"
                CustomizeEditModel="OnCustomizeEditModel"
                EditModelSaving="OnEditModelSaving"
                DataItemDeleting="OnDataItemDeleting"
                FocusedRowEnabled="true"
                @bind-FocusedRowKey="focusedRowKey"
                @ref="gridRef">
            <ToolbarTemplate>
                <DxToolbar>
                    <DxToolbarItem Alignment="ToolbarItemAlignment.Right">
                        <Template Context="_">
                            <DxDropDownButton Text="@FormatSizeText(_sizeMode)"
                                              RenderStyle="ButtonRenderStyle.Secondary"
                                              RenderStyleMode="ButtonRenderStyleMode.Text"
                                              ItemClick="OnSizeChange">
                                <Items>
                                    @foreach (var size in _sizeModes)
                                    {
                                        <DxDropDownButtonItem Text="@FormatSizeText(size)" Id="@size.ToString()" />
                                    }
                                </Items>
                            </DxDropDownButton>
                        </Template>
                    </DxToolbarItem>
                </DxToolbar>
            </ToolbarTemplate>
            <Columns>
                @RenderColumns()
            </Columns>
            <EditFormTemplate Context="editFormContext">
                @{
                    SetEditContext(editFormContext.EditContext); var editModel = (CatalogEditModel)editFormContext.EditModel; SetPopupHeaderText(editModel.IsNew);
                }
                <DxFormLayout ColCount="2">
                    <DxFormLayoutItem Caption="Titel">
                        <DxTextBox @bind-Text="editModel.CatTitle" Width="100%" />
                    </DxFormLayoutItem>
                    <DxFormLayoutItem Caption="Kennung">
                        <DxTextBox @bind-Text="editModel.CatString" Width="100%" />
                    </DxFormLayoutItem>
                    @if (!editModel.IsNew)
                    {
                        <DxFormLayoutItem Caption="Update-Prozedur">
                            <DxComboBox Data="@procedureOptions"
                                        TData="ProcedureOption"
                                        TValue="int"
                                        TextFieldName="Text"
                                        ValueFieldName="Value"
                                        @bind-Value="editModel.UpdateProcedure"
                                        Width="100%" />
                        </DxFormLayoutItem>
                    }
                    <DxFormLayoutItem ColSpanMd="12">
                        <ValidationSummary />
                    </DxFormLayoutItem>
                </DxFormLayout>
            </EditFormTemplate>
        </DxGrid>
    </div>
}

@code {
    private List<CatalogReadDto> items = new();
    private bool isLoading;
    private bool hasLoaded;
    private string? errorMessage;
    private string? infoMessage;
    private EditContext? editContext;
    private ValidationMessageStore? validationMessageStore;
    private IGrid? gridRef;
    private int? focusedRowKey;
    private string popupHeaderText = "Edit";
    private const string LayoutType = "GRID_BANDS";
    private const string LayoutKey = "CatalogsGrid";
    private string? layoutUser;
    private BandLayout bandLayout = new();
    private Dictionary<string, string> columnBandAssignments = new();
    private List<BandOption> bandOptions = new();
    private Dictionary<string, ColumnDefinition> columnLookup = new();
    private bool gridLayoutApplied;

    private List<ColumnDefinition> columnDefinitions = new()
    {
        new() { FieldName = nameof(CatalogReadDto.Guid), Caption = "Id", Width = "140px", FilterType = ColumnFilterType.Text },
        new() { FieldName = nameof(CatalogReadDto.CatTitle), Caption = "Titel", FilterType = ColumnFilterType.Text },
        new() { FieldName = nameof(CatalogReadDto.CatString), Caption = "String", FilterType = ColumnFilterType.Text },
        new() { FieldName = nameof(CatalogReadDto.AddedWho), Caption = "Angelegt von", ReadOnly = true, FilterType = ColumnFilterType.Text },
        new() { FieldName = nameof(CatalogReadDto.AddedWhen), Caption = "Angelegt am", ReadOnly = true, FilterType = ColumnFilterType.Date },
        new() { FieldName = nameof(CatalogReadDto.ChangedWho), Caption = "Geändert von", ReadOnly = true, FilterType = ColumnFilterType.Text },
        new() { FieldName = nameof(CatalogReadDto.ChangedWhen), Caption = "Geändert am", ReadOnly = true, FilterType = ColumnFilterType.Date }
    };

    private readonly List<ProcedureOption> procedureOptions = new()
    {
        new() { Value = 0, Text = "PRTBMY_CATALOG_UPDATE" },
        new() { Value = 1, Text = "PRTBMY_CATALOG_SAVE" }
    };

    private bool CanSaveBandLayout => !string.IsNullOrWhiteSpace(layoutUser);

    private SizeMode _sizeMode = SizeMode.Medium;
    private static readonly List<SizeMode> _sizeModes = Enum.GetValues<SizeMode>().ToList();

    private string FormatSizeText(SizeMode size) => size switch
    {
        SizeMode.Small => "Klein",
        SizeMode.Medium => "Mittel",
        SizeMode.Large => "Groß",
        _ => size.ToString()
    };

    private void OnSizeChange(DropDownButtonItemClickEventArgs args)
    {
        _sizeMode = Enum.Parse<SizeMode>(args.ItemInfo.Id);
    }

    protected override async Task OnInitializedAsync()
    {
        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
        layoutUser = await BandLayoutService.EnsureLayoutUserAsync();
        bandLayout = await BandLayoutService.LoadBandLayoutAsync(LayoutType, LayoutKey, layoutUser, columnLookup);
        columnBandAssignments = BandLayoutService.BuildAssignmentsFromLayout(bandLayout);
        ApplyColumnLayoutFromStorage();
        _sizeMode = bandLayout.SizeMode;
        UpdateBandOptions();
        await LoadCatalogs();
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (!gridLayoutApplied && gridRef != null && bandLayout.GridLayout != null)
        {
            gridRef.LoadLayout(bandLayout.GridLayout);
            gridLayoutApplied = true;
            await InvokeAsync(StateHasChanged);
        }
    }

    private async Task LoadCatalogs()
    {
        isLoading = true;
        errorMessage = null;
        try
        {
            items = await Api.GetAllAsync();
        }
        catch (Exception ex)
        {
            errorMessage = $"Kataloge konnten nicht geladen werden: {ex.Message}";
        }
        finally
        {
            isLoading = false;
            hasLoaded = true;
            StateHasChanged();
        }
    }

    private async Task SaveLayoutAsync()
    {
        if (string.IsNullOrWhiteSpace(layoutUser))
            return;

        try
        {
            CaptureColumnLayoutFromGrid();
            await BandLayoutService.SaveBandLayoutAsync(LayoutType, LayoutKey, layoutUser, bandLayout);
            infoMessage = "Layout gespeichert.";
            errorMessage = null;
        }
        catch (Exception ex)
        {
            errorMessage = $"Layout konnte nicht gespeichert werden: {ex.Message}";
        }
    }

    private async Task ResetLayoutAsync()
    {
        if (string.IsNullOrWhiteSpace(layoutUser))
            return;

        await BandLayoutService.ResetBandLayoutAsync(LayoutType, LayoutKey, layoutUser);

        bandLayout = new BandLayout();
        columnBandAssignments.Clear();
        UpdateBandOptions();

        foreach (var column in columnDefinitions)
            column.Width = null;
        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);

        _sizeMode = SizeMode.Medium;

        if (gridRef != null)
            gridRef.LoadLayout(new GridPersistentLayout());
        gridLayoutApplied = false;

        infoMessage = "Layout zurückgesetzt.";
        errorMessage = null;
    }

    private void CaptureColumnLayoutFromGrid()
    {
        if (gridRef == null)
            return;

        var layout = gridRef.SaveLayout();
        bandLayout.GridLayout = layout;
        bandLayout.SizeMode = _sizeMode;

        var orderedColumns = layout.Columns
            .Where(c => !string.IsNullOrWhiteSpace(c.FieldName))
            .OrderBy(c => c.VisibleIndex)
            .ToList();

        bandLayout.ColumnOrder = orderedColumns.Select(c => c.FieldName).ToList();
        bandLayout.ColumnWidths = orderedColumns
            .Where(c => !string.IsNullOrWhiteSpace(c.Width))
            .ToDictionary(c => c.FieldName, c => c.Width, StringComparer.OrdinalIgnoreCase);
    }

    private void ApplyColumnLayoutFromStorage()
    {
        foreach (var column in columnDefinitions)
        {
            if (bandLayout.ColumnWidths.TryGetValue(column.FieldName, out var width) && !string.IsNullOrWhiteSpace(width))
                column.Width = width;
        }
        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
    }

    private void AddBand()
    {
        bandLayout.Bands.Add(new BandDefinition { Id = Guid.NewGuid().ToString("N"), Caption = "Band" });
        UpdateBandOptions();
    }

    private void RemoveBand(BandDefinition band)
    {
        bandLayout.Bands.Remove(band);
        foreach (var key in columnBandAssignments.Where(p => p.Value == band.Id).Select(p => p.Key).ToList())
            columnBandAssignments.Remove(key);
        UpdateBandOptions();
        SyncBandsFromAssignments();
    }

    private void UpdateBandCaption(BandDefinition band, string value)
    {
        band.Caption = value;
        UpdateBandOptions();
    }

    private void UpdateColumnBand(string fieldName, string? bandId)
    {
        if (string.IsNullOrWhiteSpace(bandId))
            columnBandAssignments.Remove(fieldName);
        else
            columnBandAssignments[fieldName] = bandId;
        SyncBandsFromAssignments();
    }

    private string GetColumnBand(string fieldName)
        => columnBandAssignments.TryGetValue(fieldName, out var bandId) ? bandId : string.Empty;

    private void SyncBandsFromAssignments()
    {
        foreach (var band in bandLayout.Bands)
        {
            band.Columns = columnDefinitions
                .Where(c => columnBandAssignments.TryGetValue(c.FieldName, out var id) && id == band.Id)
                .Select(c => c.FieldName)
                .ToList();
        }
        StateHasChanged();
    }

    private void UpdateBandOptions()
    {
        bandOptions = new List<BandOption> { new() { Id = string.Empty, Caption = "Ohne Band" } };
        bandOptions.AddRange(bandLayout.Bands.Select(b => new BandOption { Id = b.Id, Caption = b.Caption }));
    }

    private RenderFragment RenderColumns() => builder =>
    {
        var seq = 0;
        builder.OpenComponent<DxGridCommandColumn>(seq++);
        builder.AddAttribute(seq++, "Width", "120px");
        builder.CloseComponent();

        var grouped = bandLayout.Bands.SelectMany(b => b.Columns).ToHashSet(StringComparer.OrdinalIgnoreCase);
        foreach (var column in columnDefinitions.Where(c => !grouped.Contains(c.FieldName)))
            BuildDataColumn(builder, ref seq, column);

        foreach (var band in bandLayout.Bands)
        {
            if (band.Columns.Count == 0) continue;

            builder.OpenComponent<DxGridBandColumn>(seq++);
            builder.AddAttribute(seq++, "Caption", band.Caption);
            builder.AddAttribute(seq++, "Columns", (RenderFragment)(bandBuilder =>
            {
                var bandSeq = 0;
                foreach (var columnName in band.Columns)
                {
                    if (columnLookup.TryGetValue(columnName, out var column))
                        BuildDataColumn(bandBuilder, ref bandSeq, column);
                }
            }));
            builder.CloseComponent();
        }
    };

    private void BuildDataColumn(RenderTreeBuilder builder, ref int seq, ColumnDefinition column)
    {
        builder.OpenComponent<DxGridDataColumn>(seq++);
        builder.AddAttribute(seq++, "FieldName", column.FieldName);
        builder.AddAttribute(seq++, "Caption", column.Caption);
        if (!string.IsNullOrWhiteSpace(column.Width))
            builder.AddAttribute(seq++, "Width", column.Width);
        if (!string.IsNullOrWhiteSpace(column.DisplayFormat))
            builder.AddAttribute(seq++, "DisplayFormat", column.DisplayFormat);
        if (column.ReadOnly)
            builder.AddAttribute(seq++, "ReadOnly", true);
        builder.CloseComponent();
    }

    private void SetEditContext(EditContext context)
    {
        if (editContext == context) return;
        if (editContext != null)
            editContext.OnFieldChanged -= OnEditFieldChanged;
        editContext = context;
        validationMessageStore = new ValidationMessageStore(editContext);
        editContext.OnFieldChanged += OnEditFieldChanged;
    }

    private void OnEditFieldChanged(object? sender, FieldChangedEventArgs e)
    {
        if (validationMessageStore == null || editContext == null) return;

        if (e.FieldIdentifier.FieldName == nameof(CatalogEditModel.UpdateProcedure))
        {
            validationMessageStore.Clear();
            editContext.NotifyValidationStateChanged();
            return;
        }

        if (e.FieldIdentifier.FieldName == nameof(CatalogEditModel.CatTitle))
        {
            validationMessageStore.Clear(new FieldIdentifier(editContext.Model, nameof(CatalogEditModel.CatTitle)));
            editContext.NotifyValidationStateChanged();
        }
    }

    private void SetPopupHeaderText(bool isNew) => popupHeaderText = isNew ? "Neu" : "Edit";

    private void OnCustomizeEditModel(GridCustomizeEditModelEventArgs e)
    {
        popupHeaderText = e.IsNew ? "Neu" : "Edit";
        if (e.IsNew)
        {
            e.EditModel = new CatalogEditModel { IsNew = true };
            return;
        }

        var item = (CatalogReadDto)e.DataItem;
        e.EditModel = new CatalogEditModel
        {
            Guid = item.Guid,
            CatTitle = item.CatTitle,
            CatString = item.CatString,
            UpdateProcedure = 0,
            OriginalCatTitle = item.CatTitle,
            IsNew = false
        };
    }

    private async Task OnEditModelSaving(GridEditModelSavingEventArgs e)
    {
        errorMessage = null;
        infoMessage = null;
        validationMessageStore?.Clear();
        editContext?.NotifyValidationStateChanged();

        var editModel = (CatalogEditModel)e.EditModel;
        if (!ValidateEditModel(editModel, e.IsNew))
        {
            e.Cancel = true;
            return;
        }

        var dto = new CatalogWriteDto
        {
            CatTitle = editModel.CatTitle,
            CatString = editModel.CatString,
            UpdateProcedure = editModel.UpdateProcedure
        };

        try
        {
            if (e.IsNew)
            {
                var created = await Api.CreateAsync(dto);
                if (!created.Success || created.Value == null)
                {
                    if (!string.IsNullOrWhiteSpace(created.Error))
                        AddValidationError(editModel, nameof(CatalogEditModel.CatTitle), created.Error);
                    else
                        errorMessage = "Anlegen fehlgeschlagen.";
                    e.Cancel = true;
                    return;
                }
                infoMessage = "Katalog angelegt.";
                focusedRowKey = created.Value.Guid;
            }
            else
            {
                var updated = await Api.UpdateAsync(editModel.Guid, dto);
                if (!updated.Success)
                {
                    errorMessage = updated.Error ?? "Aktualisierung fehlgeschlagen.";
                    e.Cancel = true;
                    return;
                }
                infoMessage = "Katalog aktualisiert.";
                focusedRowKey = editModel.Guid;
            }

            await LoadCatalogs();
        }
        catch (Exception ex)
        {
            errorMessage = $"Fehler beim Speichern: {ex.Message}";
            e.Cancel = true;
        }
    }

    private void AddValidationError(CatalogEditModel editModel, string fieldName, string message)
    {
        if (editContext == null || validationMessageStore == null) return;
        validationMessageStore.Add(new FieldIdentifier(editModel, fieldName), message);
        editContext.NotifyValidationStateChanged();
    }

    private bool ValidateEditModel(CatalogEditModel editModel, bool isNew)
    {
        if (isNew) return true;
        if (editModel.UpdateProcedure == 0 &&
            !string.Equals(editModel.CatTitle, editModel.OriginalCatTitle, StringComparison.OrdinalIgnoreCase))
        {
            AddValidationError(editModel, nameof(CatalogEditModel.CatTitle), "Titel kann nicht geändert werden.");
            return false;
        }
        return true;
    }

    private async Task OnDataItemDeleting(GridDataItemDeletingEventArgs e)
    {
        errorMessage = null;
        infoMessage = null;
        var item = (CatalogReadDto)e.DataItem;
        try
        {
            var deleted = await Api.DeleteAsync(item.Guid);
            if (!deleted.Success)
            {
                errorMessage = deleted.Error ?? "Löschen fehlgeschlagen.";
                e.Cancel = true;
                return;
            }
            infoMessage = "Katalog gelöscht.";
            await LoadCatalogs();
        }
        catch (Exception ex)
        {
            errorMessage = $"Fehler beim Löschen: {ex.Message}";
            e.Cancel = true;
        }
    }

    private sealed class CatalogEditModel
    {
        public int Guid { get; set; }
        public string CatTitle { get; set; } = string.Empty;
        public string CatString { get; set; } = string.Empty;
        public int UpdateProcedure { get; set; }
        public string OriginalCatTitle { get; set; } = string.Empty;
        public bool IsNew { get; set; }
    }

    private sealed class ProcedureOption
    {
        public int Value { get; set; }
        public string Text { get; set; } = string.Empty;
    }
}