/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-9-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

//==============================================================================
/** Contains classes for different types of physics behaviours - these classes
    are used as template parameters for the AnimatedPosition class.
*/
namespace juce::AnimatedPositionBehaviours
{

    /** A non-snapping behaviour that allows the content to be freely flicked in
        either direction, with momentum based on the velocity at which it was
        released, and variable friction to make it come to a halt.

        This class is intended to be used as a template parameter to the
        AnimatedPosition class.

        @see AnimatedPosition

        @tags{GUI}
    */
    struct ContinuousWithMomentum
    {
        ContinuousWithMomentum() = default;

        /** Sets the friction that damps the movement of the value.
            A typical value is 0.08; higher values indicate more friction.
        */
        void setFriction (double newFriction) noexcept
        {
            damping = 1.0 - newFriction;
        }

        /** Sets the minimum velocity of the movement. Any velocity that's slower than
            this will stop the animation. The default is 0.05. */
        void setMinimumVelocity (double newMinimumVelocityToUse) noexcept
        {
            minimumVelocity = newMinimumVelocityToUse;
        }

        /** Called by the AnimatedPosition class. This tells us the position and
            velocity at which the user is about to release the object.
            The velocity is measured in units/second.
        */
        void releasedWithVelocity (double /*position*/, double releaseVelocity) noexcept
        {
            velocity = releaseVelocity;
        }

        /** Called by the AnimatedPosition class to get the new position, after
            the given time has elapsed.
        */
        double getNextPosition (double oldPos, double elapsedSeconds) noexcept
        {
            velocity *= damping;

            if (std::abs (velocity) < minimumVelocity)
                velocity = 0;

            return oldPos + velocity * elapsedSeconds;
        }

        /** Called by the AnimatedPosition class to check whether the object
            is now stationary.
        */
        bool isStopped (double /*position*/) const noexcept
        {
            return approximatelyEqual (velocity, 0.0);
        }

    private:
        double velocity = 0, damping = 0.92, minimumVelocity = 0.05;
    };

    //==============================================================================
    /** A behaviour that gravitates an AnimatedPosition object towards the nearest
        integer position when released.

        This class is intended to be used as a template parameter to the
        AnimatedPosition class. It's handy when using an AnimatedPosition to show a
        series of pages, because it allows the pages can be scrolled smoothly, but when
        released, snaps back to show a whole page.

        @see AnimatedPosition

        @tags{GUI}
    */
    struct SnapToPageBoundaries
    {
        SnapToPageBoundaries() = default;

        /** Called by the AnimatedPosition class. This tells us the position and
            velocity at which the user is about to release the object.
            The velocity is measured in units/second.
        */
        void releasedWithVelocity (double position, double releaseVelocity) noexcept
        {
            targetSnapPosition = std::floor (position + 0.5);

            if (releaseVelocity >  1.0 && targetSnapPosition < position)  ++targetSnapPosition;
            if (releaseVelocity < -1.0 && targetSnapPosition > position)  --targetSnapPosition;
        }

        /** Called by the AnimatedPosition class to get the new position, after
            the given time has elapsed.
        */
        double getNextPosition (double oldPos, double elapsedSeconds) const noexcept
        {
            if (isStopped (oldPos))
                return targetSnapPosition;

            const double snapSpeed = 10.0;
            const double velocity = (targetSnapPosition - oldPos) * snapSpeed;
            const double newPos = oldPos + velocity * elapsedSeconds;

            return isStopped (newPos) ? targetSnapPosition : newPos;
        }

        /** Called by the AnimatedPosition class to check whether the object
            is now stationary.
        */
        bool isStopped (double position) const noexcept
        {
            return std::abs (targetSnapPosition - position) < 0.001;
        }

    private:
        double targetSnapPosition = 0.0;
    };

} // namespace juce::AnimatedPositionBehaviours
