using FastReport.Utils;
using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace FastReport.Controls
{
    internal class FRScrollablePanel : UserControl
    {
        #region Fields
        private VScrollBar _VScrollBar = null;
        private HScrollBar _HScrollBar = null;
        private Control _Thumb = null;
        private bool _VScrollBarVisible;
        private bool _HScrollBarVisible;
        private bool _ThumbVisible;
        private Point _AutoScrollPosition = Point.Empty;
        private bool _AutoScroll = false;
        private Size _AutoScrollMinSize = Size.Empty;
        #endregion

        #region Properties
        /// <summary>
        /// Gets the reference to internal vertical scroll-bar control if one is created or null if no scrollbar is visible.
        /// </summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public VScrollBar VScrollBar
        {
            get { return _VScrollBar; }
        }

        /// <summary>
        /// Gets the reference to internal horizontal scroll-bar control if one is created or null if no scrollbar is visible.
        /// </summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public HScrollBar HScrollBar
        {
            get { return _HScrollBar; }
        }

        /// <summary>
        /// Gets or sets a value indicating whether the control enables the user to scroll to items placed outside of its visible boundaries.
        /// </summary>
        [Browsable(true), DefaultValue(false)]
        public new bool AutoScroll
        {
            get { return _AutoScroll; }
            set
            {
                if (_AutoScroll != value)
                {
                    _AutoScroll = value;
                    UpdateScrollBars();
                }
            }
        }

        /// <summary>
        /// Gets or sets the minimum size of the auto-scroll. Returns a Size that represents the minimum height and width of the scrolling area in pixels.
        /// This property is managed internally by control and should not be modified.
        /// </summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public new Size AutoScrollMinSize
        {
            get { return _AutoScrollMinSize; }
            set
            {
                _AutoScrollMinSize = value;
                UpdateScrollBars();
            }
        }

        public event EventHandler AutoScrollPositionChanged;

        /// <summary>
        /// Gets or sets the location of the auto-scroll position.
        /// </summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public new Point AutoScrollPosition
        {
            get { return _AutoScrollPosition; }
            set
            {
                if (!HScrollBarVisible)
                    value.X = 0;
                else
                    value.X = -Math.Max(Math.Min(-value.X, _HScrollBar.Maximum - _HScrollBar.LargeChange), _HScrollBar.Minimum);

                if (!VScrollBarVisible)
                    value.Y = 0;
                else
                    value.Y = -Math.Max(Math.Min(-value.Y, _VScrollBar.Maximum - _VScrollBar.LargeChange), _VScrollBar.Minimum);

                if (_AutoScrollPosition != value)
                {
                    _AutoScrollPosition = value;
                    if (_AutoScroll)
                    {
                        if (VScrollBarVisible && _VScrollBar.Value != -_AutoScrollPosition.Y)
                        {
                            _VScrollBar.Value = -_AutoScrollPosition.Y;
                        }
                        if (HScrollBarVisible && _HScrollBar.Value != -_AutoScrollPosition.X)
                        {
                            _HScrollBar.Value = -_AutoScrollPosition.X;
                        }

                        Invalidate();
                    }
                    OnAutoScrollPositionChanged();
                }
            }
        }

        private bool HScrollBarVisible
        {
            get { return _HScrollBarVisible; }
            set
            {
                _HScrollBarVisible = value;
                _HScrollBar.Visible = value;
            }
        }

        private bool VScrollBarVisible
        {
            get { return _VScrollBarVisible; }
            set
            {
                _VScrollBarVisible = value;
                _VScrollBar.Visible = value;
            }
        }

        private bool ThumbVisible
        {
            get { return _ThumbVisible; }
            set
            {
                _ThumbVisible = value;
                _Thumb.Visible = value;
            }
        }
        #endregion

        #region Private Methods
        private void UpdateScrollBars()
        {
            if (!_AutoScroll)
            {
                VScrollBarVisible = false;
                HScrollBarVisible = false;
                ThumbVisible = false;
                return;
            }

            Rectangle innerBounds = this.ClientRectangle;
            // Check do we need vertical scrollbar
            Size scrollSize = _AutoScrollMinSize;
            if (scrollSize.Height > innerBounds.Height)
            {
                VScrollBarVisible = true;
                if (_VScrollBar.Minimum != 0)
                    _VScrollBar.Minimum = 0;
                if (_VScrollBar.LargeChange != innerBounds.Height && innerBounds.Height > 0)
                    _VScrollBar.LargeChange = innerBounds.Height;
                _VScrollBar.SmallChange = 100;
                if (_VScrollBar.Maximum != _AutoScrollMinSize.Height)
                    _VScrollBar.Maximum = _AutoScrollMinSize.Height;
                if (_VScrollBar.Value != -_AutoScrollPosition.Y)
                    _VScrollBar.Value = (Math.Min(_VScrollBar.Maximum, Math.Abs(_AutoScrollPosition.Y)));
            }
            else
            {
                VScrollBarVisible = false;
            }

            // Check horizontal scrollbar
            if (scrollSize.Width > innerBounds.Width)
            {
                HScrollBarVisible = true;
                if (_HScrollBar.Minimum != 0)
                    _HScrollBar.Minimum = 0;
                if (_HScrollBar.LargeChange != innerBounds.Width && innerBounds.Width > 0)
                    _HScrollBar.LargeChange = innerBounds.Width;
                if (_HScrollBar.Maximum != _AutoScrollMinSize.Width)
                    _HScrollBar.Maximum = _AutoScrollMinSize.Width;
                if (_HScrollBar.Value != -_AutoScrollPosition.X)
                    _HScrollBar.Value = (Math.Min(_HScrollBar.Maximum, Math.Abs(_AutoScrollPosition.X)));
                _HScrollBar.SmallChange = 100;
            }
            else
            {
                HScrollBarVisible = false;
            }

            RepositionScrollBars();
        }

        private void VScrollBarScroll(object sender, ScrollEventArgs e)
        {
            if (_AutoScrollPosition.Y != -e.NewValue)
            {
                _AutoScrollPosition.Y = -e.NewValue;
                OnAutoScrollPositionChanged();
                this.OnScroll(e);

                this.Invalidate();
            }
        }

        private void HScrollBarScroll(object sender, ScrollEventArgs e)
        {
            if (_AutoScrollPosition.X != -e.NewValue)
            {
                _AutoScrollPosition.X = -e.NewValue;
                OnAutoScrollPositionChanged();
                this.OnScroll(e);

                this.Invalidate();
            }
        }

        private void RepositionScrollBars()
        {
            Rectangle innerBounds = this.ClientRectangle;

            _VScrollBar.Width = this.LogicalToDevice(SystemInformation.VerticalScrollBarWidth);
            _HScrollBar.Height = this.LogicalToDevice(SystemInformation.HorizontalScrollBarHeight);

            if (HScrollBarVisible)
            {
                int width = innerBounds.Width;
                if (VScrollBarVisible)
                    width -= _VScrollBar.Width - 1;
                _HScrollBar.Bounds = new Rectangle(innerBounds.X, innerBounds.Bottom - _HScrollBar.Height + 1, width, _HScrollBar.Height);
            }

            if (VScrollBarVisible)
            {
                int height = innerBounds.Height;
                if (HScrollBarVisible)
                    height -= _HScrollBar.Height - 1;
                _VScrollBar.Bounds = new Rectangle(innerBounds.Right - _VScrollBar.Width + 1, innerBounds.Y, _VScrollBar.Width, height);
            }

            if (VScrollBarVisible && HScrollBarVisible)
            {
                ThumbVisible = true;
                _Thumb.Bounds = new Rectangle(_HScrollBar.Bounds.Right, _VScrollBar.Bounds.Bottom, _VScrollBar.Width, _HScrollBar.Height);
            }
            else
            {
                ThumbVisible = false;
            }
        }
        #endregion

        #region Protected Methods
        protected virtual void OnAutoScrollPositionChanged()
        {
            if (AutoScrollPositionChanged != null)
                AutoScrollPositionChanged(this, EventArgs.Empty);
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (_VScrollBar != null)
                    _VScrollBar.Dispose();
                _VScrollBar = null;
                if (_HScrollBar != null)
                    _HScrollBar.Dispose();
                _HScrollBar = null;
                if (_Thumb != null)
                    _Thumb.Dispose();
                _Thumb = null;
            }
            base.Dispose(disposing);
        }

        protected override void OnMouseWheel(MouseEventArgs e)
        {
            if (VScrollBarVisible)
            {
                int newValue = _VScrollBar.Value + _VScrollBar.SmallChange * (e.Delta < 0 ? 1 : -1);
                if (newValue < _VScrollBar.Minimum)
                    newValue = _VScrollBar.Minimum;
                if (newValue > _VScrollBar.Maximum - _VScrollBar.LargeChange + 1)
                    newValue = _VScrollBar.Maximum - _VScrollBar.LargeChange + 1;
                ScrollEventType scType = e.Delta < 0 ? ScrollEventType.SmallIncrement : ScrollEventType.SmallDecrement;
                VScrollBarScroll(this, new ScrollEventArgs(scType, _VScrollBar.Value, newValue));
                _VScrollBar.Value = newValue;
            }
            base.OnMouseWheel(e);
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);

            UpdateScrollBars();
            AutoScrollPosition = AutoScrollPosition;
        }

        #endregion

        public FRScrollablePanel()
        {
            _VScrollBar = new VScrollBar();
            _VScrollBar.Width = this.LogicalToDevice(SystemInformation.VerticalScrollBarWidth);
            _VScrollBar.Cursor = Cursors.Default;
            this.Controls.Add(_VScrollBar);
            _VScrollBar.Scroll += new ScrollEventHandler(VScrollBarScroll);
            // CreateControl is needed to avoid error in mdi child mode
            _VScrollBar.CreateControl();

            _HScrollBar = new HScrollBar();
            _HScrollBar.Height = this.LogicalToDevice(SystemInformation.HorizontalScrollBarHeight);
            _HScrollBar.Cursor = Cursors.Default;
            this.Controls.Add(_HScrollBar);
            _HScrollBar.Scroll += new ScrollEventHandler(HScrollBarScroll);
            _HScrollBar.CreateControl();

            _Thumb = new Control();
            _Thumb.BackColor = SystemColors.Control;
            _Thumb.TabStop = false;
            this.Controls.Add(_Thumb);
            _Thumb.CreateControl();

            SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw, true);
        }
    }
}