// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
//
// Description: Provides a view port for content of FlowDocument formatted
//              bottomless area.
//
 
using System.Windows;                       // Size
using System.Windows.Controls;              // ScrollViewer
using System.Windows.Controls.Primitives;   // IScrollInfo
using System.Windows.Documents;             // FlowDocument
using System.Windows.Media;                 // Visual
using MS.Internal.PtsHost;                  // FlowDocumentPage
using MS.Internal.Text;                     // TextDpi
 
namespace MS.Internal.Documents
{
    /// <summary>
    /// Provides a view port for content of FlowDocument formatted bottomless area.
    /// </summary>
    internal class FlowDocumentView : FrameworkElement, IScrollInfo, IServiceProvider
    {
        //-------------------------------------------------------------------
        //
        //  Constructors
        //
        //-------------------------------------------------------------------
 
        #region Constructors
 
        /// <summary>
        /// Static Constructor
        /// </summary>
        static FlowDocumentView()
        {
        }
 
        /// <summary>
        /// Constructor
        /// </summary>
        internal FlowDocumentView()
        {
        }
 
        #endregion Constructors
 
        //-------------------------------------------------------------------
        //
        //  Protected Methods
        //
        //-------------------------------------------------------------------
 
        #region Protected Methods
 
        /// <summary>
        /// Content measurement.
        /// </summary>
        /// <param name="constraint">Constraint size.</param>
        /// <returns>Computed desired size.</returns>
        protected sealed override Size MeasureOverride(Size constraint)
        {
            Size desiredSize = new Size();
 
            if (_suspendLayout)
            {
                desiredSize = this.DesiredSize;
            }
            else if (Document != null)
            {
                // Create bottomless formatter, if necessary.
                EnsureFormatter();
 
                // Format bottomless content.
                _formatter.Format(constraint);
 
                // DesiredSize is set to the calculated size of the page.
                // If hosted by ScrollViewer, desired size is limited to constraint.
                if (_scrollData != null)
                {
                    desiredSize.Width = Math.Min(constraint.Width, _formatter.DocumentPage.Size.Width);
                    desiredSize.Height = Math.Min(constraint.Height, _formatter.DocumentPage.Size.Height);
                }
                else
                {
                    desiredSize = _formatter.DocumentPage.Size;
                }
            }
            return desiredSize;
        }
 
        /// <summary>
        /// Content arrangement.
        /// </summary>
        /// <param name="arrangeSize">Size that element should use to arrange itself and its children.</param>
        protected sealed override Size ArrangeOverride(Size arrangeSize)
        {
            Rect viewport = Rect.Empty;
            Vector offset;
            bool invalidateScrollInfo = false;
            Size safeArrangeSize = arrangeSize;
 
            if (!_suspendLayout)
            {
                // Convert to TextDpi and convert back to double, to make sure that we are not
                // getting rounding errors later.
                TextDpi.SnapToTextDpi(ref safeArrangeSize);
 
                if (Document != null)
                {
                    // Create bottomless formatter, if necessary.
                    EnsureFormatter();
 
                    // Arrange bottomless content.
                    if (_scrollData != null)
                    {
                        if (!DoubleUtil.AreClose(_scrollData.Viewport, safeArrangeSize))
                        {
                            _scrollData.Viewport = safeArrangeSize;
                            invalidateScrollInfo = true;
                        }
 
                        if (!DoubleUtil.AreClose(_scrollData.Extent, _formatter.DocumentPage.Size))
                        {
                            _scrollData.Extent = _formatter.DocumentPage.Size;
                            invalidateScrollInfo = true;
                            // DocumentPage Size is calculated by converting double to int and then back to double.
                            // This conversion may produce rounding errors and force us to show scrollbars in cases
                            // when extent is within 1px from viewport. To workaround this issue, snap extent to viewport
                            // if we are within 1px range.
                            if (Math.Abs(_scrollData.ExtentWidth - _scrollData.ViewportWidth) < 1)
                            {
                                _scrollData.ExtentWidth = _scrollData.ViewportWidth;
                            }
                            if (Math.Abs(_scrollData.ExtentHeight - _scrollData.ViewportHeight) < 1)
                            {
                                _scrollData.ExtentHeight = _scrollData.ViewportHeight;
                            }
                        }
                        offset = new Vector(
                            Math.Max(0, Math.Min(_scrollData.ExtentWidth - _scrollData.ViewportWidth, _scrollData.HorizontalOffset)),
                            Math.Max(0, Math.Min(_scrollData.ExtentHeight - _scrollData.ViewportHeight, _scrollData.VerticalOffset)));
                        if (!DoubleUtil.AreClose(offset, _scrollData.Offset))
                        {
                            _scrollData.Offset = offset;
                            invalidateScrollInfo = true;
                        }
                        if (invalidateScrollInfo && _scrollData.ScrollOwner != null)
                        {
                            _scrollData.ScrollOwner.InvalidateScrollInfo();
                        }
                        viewport = new Rect(_scrollData.HorizontalOffset, _scrollData.VerticalOffset, safeArrangeSize.Width, safeArrangeSize.Height);
                    }
                    _formatter.Arrange(safeArrangeSize, viewport);
 
                    // Connect to visual tree.
                    if (_pageVisual != _formatter.DocumentPage.Visual)
                    {
                        _textView?.OnPageConnected();
                        if (_pageVisual != null)
                        {
                            RemoveVisualChild(_pageVisual);
                        }
                        _pageVisual = (PageVisual)_formatter.DocumentPage.Visual;
                        AddVisualChild(_pageVisual);
                    }
 
                    // Set appropriate content offset
                    if (_scrollData != null)
                    {
                        _pageVisual.Offset = new Vector(-_scrollData.HorizontalOffset, -_scrollData.VerticalOffset);
                    }
 
                    // DocumentPage.Visual is always returned in LeftToRight FlowDirection. 
                    // Hence, if the the current FlowDirection is RightToLeft, 
                    // mirroring transform need to be applied to the content.
                    PtsHelper.UpdateMirroringTransform(FlowDirection, FlowDirection.LeftToRight, _pageVisual, safeArrangeSize.Width);
                }
                else
                {
                    if (_pageVisual != null)
                    {
                        _textView?.OnPageDisconnected();
                        RemoveVisualChild(_pageVisual);
                        _pageVisual = null;
                    }
                    // Arrange bottomless content.
                    if (_scrollData != null)
                    {
                        if (!DoubleUtil.AreClose(_scrollData.Viewport, safeArrangeSize))
                        {
                            _scrollData.Viewport = safeArrangeSize;
                            invalidateScrollInfo = true;
                        }
                        if (!DoubleUtil.AreClose(_scrollData.Extent, new Size()))
                        {
                            _scrollData.Extent = new Size();
                            invalidateScrollInfo = true;
                        }
                        if (!DoubleUtil.AreClose(_scrollData.Offset, new Vector()))
                        {
                            _scrollData.Offset = new Vector();
                            invalidateScrollInfo = true;
                        }
                        if (invalidateScrollInfo && _scrollData.ScrollOwner != null)
                        {
                            _scrollData.ScrollOwner.InvalidateScrollInfo();
                        }
                    }
                }
            }
            return arrangeSize;
        }
 
        /// <summary>
        /// Returns visual child at specified index. FlowDocumentView has just one child.
        /// </summary>
        protected override Visual GetVisualChild(int index)
        {
            if (index != 0)
            {
                throw new ArgumentOutOfRangeException(nameof(index), index, SR.Visual_ArgumentOutOfRange);
            }
            return _pageVisual;
        }
 
        #endregion Protected Methods
 
        //-------------------------------------------------------------------
        //
        //  Protected Properties
        //
        //-------------------------------------------------------------------
 
        #region Protected Properties
 
        /// <summary>
        /// Returns number of children. FlowDocumentView has just one child.
        /// </summary>        
        protected override int VisualChildrenCount
        {
            get
            {
                return _pageVisual == null ? 0 : 1;
            }
        }
 
        #endregion Protected Properties
 
        //-------------------------------------------------------------------
        //
        //  Internal Methods
        //
        //-------------------------------------------------------------------
 
        #region Internal Methods
 
        /// <summary>
        /// Suspends page layout.
        /// </summary>
        internal void SuspendLayout()
        {
            _suspendLayout = true;
            _pageVisual?.Opacity = 0.5;
        }
 
        /// <summary>
        /// Resumes page layout.
        /// </summary>
        internal void ResumeLayout()
        {
            _suspendLayout = false;
            _pageVisual?.Opacity = 1.0;
            InvalidateMeasure();
        }
 
        #endregion Internal Methods
 
        //-------------------------------------------------------------------
        //
        //  Internal Properties
        //
        //-------------------------------------------------------------------
 
        #region Internal Properties
 
        /// <summary>
        /// BreakRecordTable.
        /// </summary>
        internal FlowDocument Document
        {
            get
            {
                return _document;
            }
            set
            {
                if (_formatter != null)
                {
                    HandleFormatterSuspended(_formatter, EventArgs.Empty);
                }
                _suspendLayout = false;
                _textView = null;
                _document = value;
                InvalidateMeasure();
                InvalidateVisual(); //ensure re-rendering
            }
        }
 
        /// <summary>
        /// DocumentPage.
        /// </summary>
        internal FlowDocumentPage DocumentPage
        {
            get
            {
                if (_document != null)
                {
                    EnsureFormatter();
                    return _formatter.DocumentPage;
                }
                return null;
            }
        }
 
        #endregion Internal Properties
 
        //-------------------------------------------------------------------
        //
        //  Private Methods
        //
        //-------------------------------------------------------------------
 
        #region Private Methods
 
        /// <summary>
        /// Ensures valid instance of FlowDocumentFormatter.
        /// </summary>
        private void EnsureFormatter()
        {
            Invariant.Assert(_document != null);
            if (_formatter == null)
            {
                _formatter = _document.BottomlessFormatter;
                _formatter.ContentInvalidated += new EventHandler(HandleContentInvalidated);
                _formatter.Suspended += new EventHandler(HandleFormatterSuspended);
            }
            Invariant.Assert(_formatter == _document.BottomlessFormatter);
        }
 
        /// <summary>
        /// Responds to content invalidation.
        /// </summary>
        private void HandleContentInvalidated(object sender, EventArgs e)
        {
            Invariant.Assert(sender == _formatter);
            InvalidateMeasure();
            InvalidateVisual(); //ensure re-rendering
        }
 
        /// <summary>
        /// Responds to formatter suspention.
        /// </summary>
        private void HandleFormatterSuspended(object sender, EventArgs e)
        {
            Invariant.Assert(sender == _formatter);
 
            // Disconnect formatter.
            _formatter.ContentInvalidated -= new EventHandler(HandleContentInvalidated);
            _formatter.Suspended -= new EventHandler(HandleFormatterSuspended);
            _formatter = null;
 
            // Disconnect any content associated with the formatter.
            if (_pageVisual != null && !_suspendLayout)
            {
                _textView?.OnPageDisconnected();
                RemoveVisualChild(_pageVisual);
                _pageVisual = null;
            }
        }
 
        #endregion Private Methods
 
        //-------------------------------------------------------------------
        //
        //  Private Fields
        //
        //-------------------------------------------------------------------
 
        #region Private Fields
 
        private FlowDocument _document;             // Hosted FlowDocument
        private PageVisual _pageVisual;             // Visual representing the content
        private FlowDocumentFormatter _formatter;   // Bottomless formatter associated with FlowDocument
        private ScrollData _scrollData;             // IScrollInfo related data, if hosted by ScrollViewer
        private DocumentPageTextView _textView;     // TextView associated with this element.
        private bool _suspendLayout;                // Layout of the page is suspended.
 
        #endregion Private Fields
 
        //-------------------------------------------------------------------
        //
        //  IScrollInfo Members
        //
        //-------------------------------------------------------------------
 
        #region IScrollInfo Members
 
        /// <summary>
        /// <see cref="IScrollInfo.LineUp"/>
        /// </summary>
        void IScrollInfo.LineUp()
        {
            _scrollData?.LineUp(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.LineDown"/>
        /// </summary>
        void IScrollInfo.LineDown()
        {
            _scrollData?.LineDown(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.LineLeft"/>
        /// </summary>
        void IScrollInfo.LineLeft()
        {
            _scrollData?.LineLeft(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.LineRight"/>
        /// </summary>
        void IScrollInfo.LineRight()
        {
            _scrollData?.LineRight(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.PageUp"/>
        /// </summary>
        void IScrollInfo.PageUp()
        {
            _scrollData?.PageUp(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.PageDown"/>
        /// </summary>
        void IScrollInfo.PageDown()
        {
            _scrollData?.PageDown(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.PageLeft"/>
        /// </summary>
        void IScrollInfo.PageLeft()
        {
            _scrollData?.PageLeft(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.PageRight"/>
        /// </summary>
        void IScrollInfo.PageRight()
        {
            _scrollData?.PageRight(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.MouseWheelUp"/>
        /// </summary>
        void IScrollInfo.MouseWheelUp()
        {
            _scrollData?.MouseWheelUp(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.MouseWheelDown"/>
        /// </summary>
        void IScrollInfo.MouseWheelDown()
        {
            _scrollData?.MouseWheelDown(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.MouseWheelLeft"/>
        /// </summary>
        void IScrollInfo.MouseWheelLeft()
        {
            _scrollData?.MouseWheelLeft(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.MouseWheelRight"/>
        /// </summary>
        void IScrollInfo.MouseWheelRight()
        {
            _scrollData?.MouseWheelRight(this);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.SetHorizontalOffset"/>
        /// </summary>
        void IScrollInfo.SetHorizontalOffset(double offset)
        {
            _scrollData?.SetHorizontalOffset(this, offset);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.SetVerticalOffset"/>
        /// </summary>
        void IScrollInfo.SetVerticalOffset(double offset)
        {
            _scrollData?.SetVerticalOffset(this, offset);
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.MakeVisible"/>
        /// </summary>
        Rect IScrollInfo.MakeVisible(Visual visual, Rect rectangle)
        {
            if (_scrollData == null)
            {
                rectangle = Rect.Empty;
            }
            else
            {
                rectangle = _scrollData.MakeVisible(this, visual, rectangle);
            }
 
            return rectangle;
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.CanVerticallyScroll"/>
        /// </summary>
        bool IScrollInfo.CanVerticallyScroll
        {
            get
            {
                return (_scrollData != null) ? _scrollData.CanVerticallyScroll : false;
            }
            set
            {
                _scrollData?.CanVerticallyScroll = value;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.CanHorizontallyScroll"/>
        /// </summary>
        bool IScrollInfo.CanHorizontallyScroll
        {
            get
            {
                return (_scrollData != null) ? _scrollData.CanHorizontallyScroll : false;
            }
            set
            {
                _scrollData?.CanHorizontallyScroll = value;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.ExtentWidth"/>
        /// </summary>
        double IScrollInfo.ExtentWidth
        {
            get
            {
                return (_scrollData != null) ? _scrollData.ExtentWidth : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.ExtentHeight"/>
        /// </summary>
        double IScrollInfo.ExtentHeight
        {
            get
            {
                return (_scrollData != null) ? _scrollData.ExtentHeight : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.ViewportWidth"/>
        /// </summary>
        double IScrollInfo.ViewportWidth
        {
            get
            {
                return (_scrollData != null) ? _scrollData.ViewportWidth : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.ViewportHeight"/>
        /// </summary>
        double IScrollInfo.ViewportHeight
        {
            get
            {
                return (_scrollData != null) ? _scrollData.ViewportHeight : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.HorizontalOffset"/>
        /// </summary>
        double IScrollInfo.HorizontalOffset
        {
            get
            {
                return (_scrollData != null) ? _scrollData.HorizontalOffset : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.VerticalOffset"/>
        /// </summary>
        double IScrollInfo.VerticalOffset
        {
            get
            {
                return (_scrollData != null) ? _scrollData.VerticalOffset : 0;
            }
        }
 
        /// <summary>
        /// <see cref="IScrollInfo.ScrollOwner"/>
        /// </summary>
        ScrollViewer IScrollInfo.ScrollOwner
        {
            get
            {
                return _scrollData?.ScrollOwner;
            }
 
            set
            {
                if (_scrollData == null)
                {
                    // Create cached scroll info.
                    _scrollData = new ScrollData();
                }
                _scrollData.SetScrollOwner(this, value);
            }
        }
 
        #endregion IScrollInfo Members
 
        //-------------------------------------------------------------------
        //
        //  IServiceProvider Members
        //
        //-------------------------------------------------------------------
 
        #region IServiceProvider Members
 
        /// <summary>
        /// Gets the service object of the specified type.
        /// </summary>
        /// <param name="serviceType">
        /// An object that specifies the type of service object to get.
        /// </param>
        /// <returns>
        /// A service object of type serviceType. A null reference if there is no 
        /// service object of type serviceType.
        /// </returns>
        object IServiceProvider.GetService(Type serviceType)
        {
            object service = null;
 
            if (serviceType == typeof(ITextView))
            {
                if (_textView == null && _document != null)
                {
                    _textView = new DocumentPageTextView(this, _document.StructuralCache.TextContainer);
                }
                service = _textView;
            }
            else if (serviceType == typeof(ITextContainer))
            {
                if (Document != null)
                {
                    service = Document.StructuralCache.TextContainer as TextContainer;
                }
            }
 
            return service;
        }
 
        #endregion IServiceProvider Members
    }
}