// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Drawing;
using Windows.Win32.System.Variant;
using Windows.Win32.UI.Accessibility;
 
namespace System.Windows.Forms;
 
public partial class DataGridView
{
    protected class DataGridViewTopRowAccessibleObject : AccessibleObject
    {
        private int[]? _runtimeId;
        private DataGridView? _ownerDataGridView;
 
        public DataGridViewTopRowAccessibleObject()
        {
        }
 
        public DataGridViewTopRowAccessibleObject(DataGridView owner) : base()
        {
            _ownerDataGridView = owner;
        }
 
        public override Rectangle Bounds
        {
            get
            {
                if (_ownerDataGridView is null)
                {
                    throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
                }
 
                if (_ownerDataGridView.IsHandleCreated && _ownerDataGridView.ColumnHeadersVisible)
                {
                    Rectangle rect = Rectangle.Union(_ownerDataGridView._layout.ColumnHeaders, _ownerDataGridView._layout.TopLeftHeader);
                    return _ownerDataGridView.RectangleToScreen(rect);
                }
 
                return Rectangle.Empty;
            }
        }
 
        public override string Name => SR.DataGridView_AccTopRow;
 
        internal override bool CanGetNameInternal => false;
 
        public DataGridView? Owner
        {
            get
            {
                return _ownerDataGridView;
            }
            set
            {
                if (_ownerDataGridView is not null)
                {
                    throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerAlreadySet);
                }
 
                _ownerDataGridView = value;
            }
        }
 
        public override AccessibleObject Parent
        {
            get
            {
                if (_ownerDataGridView is null)
                {
                    throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
                }
 
                return _ownerDataGridView.AccessibilityObject;
            }
        }
 
        public override AccessibleRole Role
        {
            get
            {
                return AccessibleRole.Row;
            }
        }
 
        internal override int[] RuntimeId => _runtimeId ??=
        [
            RuntimeIDFirstItem,
            Parent.GetHashCode(),
            GetHashCode()
        ];
 
        public override string Value => Name;
 
        internal override bool CanGetValueInternal => false;
 
        public override AccessibleObject? GetChild(int index)
        {
            if (_ownerDataGridView is null)
            {
                throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
            }
 
            ArgumentOutOfRangeException.ThrowIfNegative(index);
 
            if (index > GetChildCount() - 1)
            {
                return null;
            }
 
            if (index == 0 && _ownerDataGridView.RowHeadersVisible)
            {
                return _ownerDataGridView.TopLeftHeaderCell.AccessibilityObject;
            }
 
            if (_ownerDataGridView.RowHeadersVisible)
            {
                // decrement the index because the first child is the top left header cell
                index--;
            }
 
            Debug.Assert(index >= 0);
 
            if (index < _ownerDataGridView.Columns.GetColumnCount(DataGridViewElementStates.Visible))
            {
                int actualColumnIndex = _ownerDataGridView.Columns.ActualDisplayIndexToColumnIndex(index, DataGridViewElementStates.Visible);
                return _ownerDataGridView.Columns[actualColumnIndex].HeaderCell.AccessibilityObject;
            }
            else
            {
                return null;
            }
        }
 
        public override int GetChildCount()
        {
            if (_ownerDataGridView is null)
            {
                throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
            }
 
            int result = _ownerDataGridView.Columns.GetColumnCount(DataGridViewElementStates.Visible);
            if (_ownerDataGridView.RowHeadersVisible)
            {
                // + 1 is the top left header cell accessibility object
                result++;
            }
 
            return result;
        }
 
        public override AccessibleObject? Navigate(AccessibleNavigation navigationDirection)
        {
            if (_ownerDataGridView is null)
            {
                throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
            }
 
            switch (navigationDirection)
            {
                case AccessibleNavigation.Down:
                case AccessibleNavigation.Next:
                    if (_ownerDataGridView.AccessibilityObject.GetChildCount() > 1)
                    {
                        return _ownerDataGridView.AccessibilityObject.GetChild(1);
                    }
                    else
                    {
                        return null;
                    }
 
                case AccessibleNavigation.FirstChild:
                    return GetChildCount() > 0
                        ? GetChild(0)
                        : null;
                case AccessibleNavigation.LastChild:
                    int childCount = GetChildCount();
                    return childCount > 0
                        ? GetChild(childCount - 1)
                        : null;
                default:
                    return null;
            }
        }
 
        #region IRawElementProviderFragment Implementation
 
        internal override IRawElementProviderFragmentRoot.Interface FragmentRoot =>
            _ownerDataGridView is null
                ? throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet)
                : (IRawElementProviderFragmentRoot.Interface)_ownerDataGridView.AccessibilityObject;
 
        internal override IRawElementProviderFragment.Interface? FragmentNavigate(NavigateDirection direction)
        {
            switch (direction)
            {
                case NavigateDirection.NavigateDirection_Parent:
                    return Parent;
                case NavigateDirection.NavigateDirection_NextSibling:
                    if (Parent.GetChildCount() > 1)
                    {
                        if (_ownerDataGridView is null)
                        {
                            throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet);
                        }
 
                        return _ownerDataGridView.Rows.Count == 0 ? null : Parent.GetChild(1);
                    }
 
                    break;
                case NavigateDirection.NavigateDirection_FirstChild:
                    if (GetChildCount() > 0)
                    {
                        return GetChild(0);
                    }
 
                    break;
                case NavigateDirection.NavigateDirection_LastChild:
                    if (GetChildCount() > 0)
                    {
                        return GetChild(GetChildCount() - 1);
                    }
 
                    break;
            }
 
            return null;
        }
 
        #endregion
 
        #region IRawElementProviderSimple Implementation
 
        internal override bool IsPatternSupported(UIA_PATTERN_ID patternId)
        {
            if (patternId.Equals(UIA_PATTERN_ID.UIA_LegacyIAccessiblePatternId))
            {
                return true;
            }
 
            return base.IsPatternSupported(patternId);
        }
 
        internal override VARIANT GetPropertyValue(UIA_PROPERTY_ID propertyId) =>
            propertyId switch
            {
                UIA_PROPERTY_ID.UIA_HasKeyboardFocusPropertyId => VARIANT.False,
                UIA_PROPERTY_ID.UIA_IsContentElementPropertyId => VARIANT.True,
                UIA_PROPERTY_ID.UIA_IsEnabledPropertyId => _ownerDataGridView is null
                    ? throw new InvalidOperationException(SR.DataGridViewTopRowAccessibleObject_OwnerNotSet)
                    : (VARIANT)_ownerDataGridView.Enabled,
                UIA_PROPERTY_ID.UIA_IsKeyboardFocusablePropertyId => VARIANT.False,
                UIA_PROPERTY_ID.UIA_IsOffscreenPropertyId => VARIANT.False,
                _ => base.GetPropertyValue(propertyId)
            };
 
        #endregion
    }
}