#region License Information (GPL v3)

/*
    ShareX - A program that allows you to take screenshots and share any file type
    Copyright (c) 2007-2018 ShareX Team

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

    Optionally you can also view the license at <http://www.gnu.org/licenses/>.
*/

#endregion License Information (GPL v3)

using ShareX.HelpersLib;
using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace ShareX.ScreenCaptureLib
{
    internal class ImageEditorScrollbar : DrawableObject
    {
        public Orientation Orientation { get; set; }
        public int Thickness { get; set; } = 10;
        public int Margin { get; set; } = 15;
        public int Padding { get; set; } = 2;
        public Rectangle TrackRectangle { get; set; }
        public Rectangle ThumbRectangle { get; set; }

        public int FadeInTime { get; set; } = 150;
        public int FadeOutDelay { get; set; } = 500;
        public int FadeOutTime { get; set; } = 150;

        private bool shouldDraw = true;
        private bool shouldDrawBefore = true;
        private Stopwatch changeTime;
        private int opacityLast = 255;
        private int opacityCurrent = 255;
        private RegionCaptureForm form;

        public ImageEditorScrollbar(Orientation orientation, RegionCaptureForm form)
        {
            Orientation = orientation;
            this.form = form;

            changeTime = Stopwatch.StartNew();

            if (form.ClientArea.Contains(form.CanvasRectangle))
            {
                opacityLast = 0;
                opacityCurrent = 0;
            }
        }

        public void Update()
        {
            Rectangle imageRectangleVisible = form.CanvasRectangle;
            imageRectangleVisible.Intersect(form.ClientArea);

            if (Orientation == Orientation.Horizontal)
            {
                shouldDraw = form.ShapeManager.IsPanning && (form.CanvasRectangle.Left < form.ClientArea.Left || form.CanvasRectangle.Right > form.ClientArea.Right);

                if (shouldDraw != shouldDrawBefore)
                {
                    changeTime = Stopwatch.StartNew();
                    opacityLast = opacityCurrent;
                }
                shouldDrawBefore = shouldDraw;

                if (shouldDraw)
                {
                    opacityCurrent = opacityLast + OpacityGain(changeTime);
                }
                else
                {
                    opacityCurrent = opacityLast - OpacityLoss(changeTime);
                }
                opacityCurrent = opacityCurrent.Between(0, 255);

                Visible = opacityCurrent > 0;

                if (Visible)
                {
                    int horizontalTrackLength = form.ClientArea.Width - Margin * 2 - Thickness - Padding * 2;
                    int horizontalThumbLength = Math.Max(Thickness, (int)Math.Round((float)imageRectangleVisible.Width / form.CanvasRectangle.Width * horizontalTrackLength));

                    TrackRectangle = new Rectangle(new Point(Margin - Padding, form.ClientArea.Bottom - (Thickness + Margin) - Padding),
                        new Size(horizontalTrackLength + Padding * 2, Thickness + Padding * 2));

                    double limitHorizontal = (horizontalTrackLength - horizontalThumbLength) / 2.0f;
                    double thumbHorizontalPositionX = Math.Round(TrackRectangle.X + TrackRectangle.Width / 2.0f - (horizontalThumbLength / 2.0f) -
                        Math.Min(limitHorizontal, Math.Max(-limitHorizontal, form.CanvasCenterOffset.X / form.CanvasRectangle.Width * horizontalTrackLength)));

                    ThumbRectangle = new Rectangle(new Point((int)thumbHorizontalPositionX, form.ClientArea.Bottom - (Thickness + Margin)),
                        new Size(horizontalThumbLength, Thickness));
                }
            }
            else
            {
                shouldDraw = form.ShapeManager.IsPanning && (form.CanvasRectangle.Top < form.ClientArea.Top || form.CanvasRectangle.Bottom > form.ClientArea.Bottom);

                if (shouldDraw != shouldDrawBefore)
                {
                    changeTime = Stopwatch.StartNew();
                    opacityLast = opacityCurrent;
                }
                shouldDrawBefore = shouldDraw;

                if (shouldDraw)
                {
                    opacityCurrent = opacityLast + OpacityGain(changeTime);
                }
                else
                {
                    opacityCurrent = opacityLast - OpacityLoss(changeTime);
                }
                opacityCurrent = opacityCurrent.Between(0, 255);

                Visible = opacityCurrent > 0;
                if (Visible)
                {
                    int verticalTrackLength = form.ClientArea.Height - Margin * 2 - Thickness - Padding * 2;
                    int verticalThumbLength = Math.Max(Thickness, (int)Math.Round((float)imageRectangleVisible.Height / form.CanvasRectangle.Height * verticalTrackLength));

                    TrackRectangle = new Rectangle(new Point(form.ClientArea.Right - (Thickness + Margin) - Padding, Margin - Padding),
                        new Size(Thickness + Padding * 2, verticalTrackLength + Padding * 2));

                    double limitVertical = (verticalTrackLength - verticalThumbLength) / 2.0f;
                    double thumbVerticalPositionY = Math.Round(TrackRectangle.Y + TrackRectangle.Height / 2.0f - (verticalThumbLength / 2.0f) -
                        Math.Min(limitVertical, Math.Max(-limitVertical, form.CanvasCenterOffset.Y / form.CanvasRectangle.Height * verticalTrackLength)));

                    ThumbRectangle = new Rectangle(new Point(form.ClientArea.Right - (Thickness + Margin), (int)thumbVerticalPositionY),
                        new Size(Thickness, verticalThumbLength));
                }
            }
        }

        public override void OnDraw(Graphics g)
        {
            if (!Visible) return;

            using (Brush trackBrush = new SolidBrush(Color.FromArgb(opacityCurrent, 60, 60, 60)))
            using (Brush thumbBrush = new SolidBrush(Color.FromArgb(opacityCurrent, 130, 130, 130)))
            {
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.DrawCapsule(trackBrush, TrackRectangle);
                g.DrawCapsule(thumbBrush, ThumbRectangle);
                g.SmoothingMode = SmoothingMode.None;
            }
        }

        private int OpacityGain(Stopwatch changeTime)
        {
            return (int)Math.Min(255.0f, 255.0f * changeTime.ElapsedMilliseconds / Math.Max(0, (float)FadeInTime));
        }

        private int OpacityLoss(Stopwatch changeTime)
        {
            int deltaTime = Math.Max(0, (int)changeTime.ElapsedMilliseconds - FadeOutDelay);
            return (int)Math.Min(255.0f, 255.0f * deltaTime / Math.Max(0, (float)FadeOutTime));
        }
    }
}