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

   This file is part of the JUCE library.
   Copyright (c) 2020 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

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

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

namespace juce
{

//==============================================================================
/**
    A scrollbar component.

    To use a scrollbar, set up its total range using the setRangeLimits() method - this
    sets the range of values it can represent. Then you can use setCurrentRange() to
    change the position and size of the scrollbar's 'thumb'.

    Registering a ScrollBar::Listener with the scrollbar will allow you to find out when
    the user moves it, and you can use the getCurrentRangeStart() to find out where
    they moved it to.

    The scrollbar will adjust its own visibility according to whether its thumb size
    allows it to actually be scrolled.

    For most purposes, it's probably easier to use a Viewport or ListBox
    instead of handling a scrollbar directly.

    @see ScrollBar::Listener

    @tags{GUI}
*/
class JUCE_API  ScrollBar  : public Component,
                             public AsyncUpdater,
                             private Timer
{
public:
    //==============================================================================
    /** Creates a Scrollbar.
        @param isVertical      specifies whether the bar should be a vertical or horizontal
    */
    ScrollBar (bool isVertical);

    /** Destructor. */
    ~ScrollBar() override;

    //==============================================================================
    /** Returns true if the scrollbar is vertical, false if it's horizontal. */
    bool isVertical() const noexcept                                { return vertical; }

    /** Changes the scrollbar's direction.

        You'll also need to resize the bar appropriately - this just changes its internal
        layout.

        @param shouldBeVertical     true makes it vertical; false makes it horizontal.
    */
    void setOrientation (bool shouldBeVertical);

    /** Tells the scrollbar whether to make itself invisible when not needed.

        The default behaviour is for a scrollbar to become invisible when the thumb
        fills the whole of its range (i.e. when it can't be moved). Setting this
        value to false forces the bar to always be visible.
        @see autoHides()
    */
    void setAutoHide (bool shouldHideWhenFullRange);

    /** Returns true if this scrollbar is set to auto-hide when its thumb is as big
        as its maximum range.
        @see setAutoHide
    */
    bool autoHides() const noexcept;

    //==============================================================================
    /** Sets the minimum and maximum values that the bar will move between.

        The bar's thumb will always be constrained so that the entire thumb lies
        within this range.

        @param newRangeLimit    the new range.
        @param notification     whether to send a notification of the change to listeners.
                                A notification will only be sent if the range has changed.

        @see setCurrentRange
    */
    void setRangeLimits (Range<double> newRangeLimit,
                         NotificationType notification = sendNotificationAsync);

    /** Sets the minimum and maximum values that the bar will move between.

        The bar's thumb will always be constrained so that the entire thumb lies
        within this range.

        @param minimum         the new range minimum.
        @param maximum         the new range maximum.
        @param notification    whether to send a notification of the change to listeners.
                               A notification will only be sent if the range has changed.

        @see setCurrentRange
    */
    void setRangeLimits (double minimum, double maximum,
                         NotificationType notification = sendNotificationAsync);

    /** Returns the current limits on the thumb position.
        @see setRangeLimits
    */
    Range<double> getRangeLimit() const noexcept                    { return totalRange; }

    /** Returns the lower value that the thumb can be set to.

        This is the value set by setRangeLimits().
    */
    double getMinimumRangeLimit() const noexcept                    { return totalRange.getStart(); }

    /** Returns the upper value that the thumb can be set to.

        This is the value set by setRangeLimits().
    */
    double getMaximumRangeLimit() const noexcept                    { return totalRange.getEnd(); }

    //==============================================================================
    /** Changes the position of the scrollbar's 'thumb'.

        This sets both the position and size of the thumb - to just set the position without
        changing the size, you can use setCurrentRangeStart().

        If this method call actually changes the scrollbar's position, it will trigger an
        asynchronous call to ScrollBar::Listener::scrollBarMoved() for all the listeners that
        are registered.

        The notification parameter can be used to optionally send or inhibit a callback to
        any scrollbar listeners.

        @returns true if the range was changed, or false if nothing was changed.
        @see getCurrentRange. setCurrentRangeStart
    */
    bool setCurrentRange (Range<double> newRange,
                          NotificationType notification = sendNotificationAsync);

    /** Changes the position of the scrollbar's 'thumb'.

        This sets both the position and size of the thumb - to just set the position without
        changing the size, you can use setCurrentRangeStart().

        @param newStart     the top (or left) of the thumb, in the range
                            getMinimumRangeLimit() <= newStart <= getMaximumRangeLimit(). If the
                            value is beyond these limits, it will be clipped.
        @param newSize      the size of the thumb, such that
                            getMinimumRangeLimit() <= newStart + newSize <= getMaximumRangeLimit(). If the
                            size is beyond these limits, it will be clipped.
        @param notification specifies if and how a callback should be made to any listeners
                            if the range actually changes
        @see setCurrentRangeStart, getCurrentRangeStart, getCurrentRangeSize
    */
    void setCurrentRange (double newStart, double newSize,
                          NotificationType notification = sendNotificationAsync);

    /** Moves the bar's thumb position.

        This will move the thumb position without changing the thumb size. Note
        that the maximum thumb start position is (getMaximumRangeLimit() - getCurrentRangeSize()).

        If this method call actually changes the scrollbar's position, it will trigger an
        asynchronous call to ScrollBar::Listener::scrollBarMoved() for all the listeners that
        are registered.

        @see setCurrentRange
    */
    void setCurrentRangeStart (double newStart,
                               NotificationType notification = sendNotificationAsync);

    /** Returns the current thumb range.
        @see getCurrentRange, setCurrentRange
    */
    Range<double> getCurrentRange() const noexcept                  { return visibleRange; }

    /** Returns the position of the top of the thumb.
        @see getCurrentRange, setCurrentRangeStart
    */
    double getCurrentRangeStart() const noexcept                    { return visibleRange.getStart(); }

    /** Returns the current size of the thumb.
        @see getCurrentRange, setCurrentRange
    */
    double getCurrentRangeSize() const noexcept                     { return visibleRange.getLength(); }

    //==============================================================================
    /** Sets the amount by which the up and down buttons will move the bar.

        The value here is in terms of the total range, and is added or subtracted
        from the thumb position when the user clicks an up/down (or left/right) button.
    */
    void setSingleStepSize (double newSingleStepSize) noexcept;

    /** Returns the current step size.
        @see setSingleStepSize
    */
    double getSingleStepSize() const noexcept                       { return singleStepSize; }

    /** Moves the scrollbar by a number of single-steps.

        This will move the bar by a multiple of its single-step interval (as
        specified using the setSingleStepSize() method).

        A positive value here will move the bar down or to the right, a negative
        value moves it up or to the left.

        @param howManySteps    the number of steps to move the scrollbar
        @param notification    whether to send a notification of the change to listeners.
                               A notification will only be sent if the position has changed.

        @returns true if the scrollbar's position actually changed.
    */
    bool moveScrollbarInSteps (int howManySteps,
                               NotificationType notification = sendNotificationAsync);

    /** Moves the scroll bar up or down in pages.

        This will move the bar by a multiple of its current thumb size, effectively
        doing a page-up or down.

        A positive value here will move the bar down or to the right, a negative
        value moves it up or to the left.

        @param howManyPages    the number of pages to move the scrollbar
        @param notification    whether to send a notification of the change to listeners.
                               A notification will only be sent if the position has changed.

        @returns true if the scrollbar's position actually changed.
    */
    bool moveScrollbarInPages (int howManyPages,
                               NotificationType notification = sendNotificationAsync);

    /** Scrolls to the top (or left).
        This is the same as calling setCurrentRangeStart (getMinimumRangeLimit());

        @param notification    whether to send a notification of the change to listeners.
                               A notification will only be sent if the position has changed.

        @returns true if the scrollbar's position actually changed.
    */
    bool scrollToTop (NotificationType notification = sendNotificationAsync);

    /** Scrolls to the bottom (or right).
        This is the same as calling setCurrentRangeStart (getMaximumRangeLimit() - getCurrentRangeSize());

        @param notification    whether to send a notification of the change to listeners.
                               A notification will only be sent if the position has changed.

        @returns true if the scrollbar's position actually changed.
    */
    bool scrollToBottom (NotificationType notification = sendNotificationAsync);

    /** Changes the delay before the up and down buttons autorepeat when they are held
        down.

        For an explanation of what the parameters are for, see Button::setRepeatSpeed().

        @see Button::setRepeatSpeed
    */
    void setButtonRepeatSpeed (int initialDelayInMillisecs,
                               int repeatDelayInMillisecs,
                               int minimumDelayInMillisecs = -1);

    //==============================================================================
    /** A set of colour IDs to use to change the colour of various aspects of the component.

        These constants can be used either via the Component::setColour(), or LookAndFeel::setColour()
        methods.

        @see Component::setColour, Component::findColour, LookAndFeel::setColour, LookAndFeel::findColour
    */
    enum ColourIds
    {
        backgroundColourId          = 0x1000300,    /**< The background colour of the scrollbar. */
        thumbColourId               = 0x1000400,    /**< A base colour to use for the thumb. The look and feel will probably use variations on this colour. */
        trackColourId               = 0x1000401     /**< A base colour to use for the slot area of the bar. The look and feel will probably use variations on this colour. */
    };

    //==============================================================================
    /**
        A class for receiving events from a ScrollBar.

        You can register a ScrollBar::Listener with a ScrollBar using the ScrollBar::addListener()
        method, and it will be called when the bar's position changes.

        @see ScrollBar::addListener, ScrollBar::removeListener
    */
    class JUCE_API  Listener
    {
    public:
        /** Destructor. */
        virtual ~Listener() = default;

        /** Called when a ScrollBar is moved.

            @param scrollBarThatHasMoved    the bar that has moved
            @param newRangeStart            the new range start of this bar
        */
        virtual void scrollBarMoved (ScrollBar* scrollBarThatHasMoved,
                                     double newRangeStart) = 0;
    };

    /** Registers a listener that will be called when the scrollbar is moved. */
    void addListener (Listener* listener);

    /** Deregisters a previously-registered listener. */
    void removeListener (Listener* listener);

    //==============================================================================
    /** This abstract base class is implemented by LookAndFeel classes to provide
        scrollbar-drawing functionality.
    */
    struct JUCE_API  LookAndFeelMethods
    {
        virtual ~LookAndFeelMethods() = default;

        virtual bool areScrollbarButtonsVisible() = 0;

        /** Draws one of the buttons on a scrollbar.

            @param g                    the context to draw into
            @param scrollbar            the bar itself
            @param width                the width of the button
            @param height               the height of the button
            @param buttonDirection      the direction of the button, where 0 = up, 1 = right, 2 = down, 3 = left
            @param isScrollbarVertical  true if it's a vertical bar, false if horizontal
            @param isMouseOverButton    whether the mouse is currently over the button (also true if it's held down)
            @param isButtonDown         whether the mouse button's held down
        */
        virtual void drawScrollbarButton (Graphics& g,
                                          ScrollBar& scrollbar,
                                          int width, int height,
                                          int buttonDirection,
                                          bool isScrollbarVertical,
                                          bool isMouseOverButton,
                                          bool isButtonDown) = 0;

        /** Draws the thumb area of a scrollbar.

            @param g                    the context to draw into
            @param scrollbar            the bar itself
            @param x                    the x position of the left edge of the thumb area to draw in
            @param y                    the y position of the top edge of the thumb area to draw in
            @param width                the width of the thumb area to draw in
            @param height               the height of the thumb area to draw in
            @param isScrollbarVertical  true if it's a vertical bar, false if horizontal
            @param thumbStartPosition   for vertical bars, the y coordinate of the top of the
                                        thumb, or its x position for horizontal bars
            @param thumbSize            for vertical bars, the height of the thumb, or its width for
                                        horizontal bars. This may be 0 if the thumb shouldn't be drawn.
            @param isMouseOver          whether the mouse is over the thumb area, also true if the mouse is
                                        currently dragging the thumb
            @param isMouseDown          whether the mouse is currently dragging the scrollbar
        */
        virtual void drawScrollbar (Graphics& g, ScrollBar& scrollbar,
                                    int x, int y, int width, int height,
                                    bool isScrollbarVertical,
                                    int thumbStartPosition,
                                    int thumbSize,
                                    bool isMouseOver,
                                    bool isMouseDown) = 0;

        /** Returns the component effect to use for a scrollbar */
        virtual ImageEffectFilter* getScrollbarEffect() = 0;

        /** Returns the minimum length in pixels to use for a scrollbar thumb. */
        virtual int getMinimumScrollbarThumbSize (ScrollBar&) = 0;

        /** Returns the default thickness to use for a scrollbar. */
        virtual int getDefaultScrollbarWidth() = 0;

        /** Returns the length in pixels to use for a scrollbar button. */
        virtual int getScrollbarButtonSize (ScrollBar&) = 0;
    };

    //==============================================================================
    /** @internal */
    bool keyPressed (const KeyPress&) override;
    /** @internal */
    void mouseWheelMove (const MouseEvent&, const MouseWheelDetails&) override;
    /** @internal */
    void lookAndFeelChanged() override;
    /** @internal */
    void mouseDown (const MouseEvent&) override;
    /** @internal */
    void mouseDrag (const MouseEvent&) override;
    /** @internal */
    void mouseUp   (const MouseEvent&) override;
    /** @internal */
    void paint (Graphics&) override;
    /** @internal */
    void resized() override;
    /** @internal */
    void parentHierarchyChanged() override;
    /** @internal */
    void setVisible (bool) override;

private:
    //==============================================================================
    Range<double> totalRange { 0.0, 1.0 }, visibleRange { 0.0, 1.0 };
    double singleStepSize = 0.1, dragStartRange = 0;
    int thumbAreaStart = 0, thumbAreaSize = 0, thumbStart = 0, thumbSize = 0;
    int dragStartMousePos = 0, lastMousePos = 0;
    int initialDelayInMillisecs = 100, repeatDelayInMillisecs = 50, minimumDelayInMillisecs = 10;
    bool vertical, isDraggingThumb = false, autohides = true, userVisibilityFlag = false;
    class ScrollbarButton;
    std::unique_ptr<ScrollbarButton> upButton, downButton;
    ListenerList<Listener> listeners;

    std::unique_ptr<AccessibilityHandler> createAccessibilityHandler() override;
    void handleAsyncUpdate() override;
    void updateThumbPosition();
    void timerCallback() override;
    bool getVisibility() const noexcept;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ScrollBar)
};


} // namespace juce