import QtQuick
import QtQuick.Controls
import qs.Common

Flickable {
    id: flickable

    property real mouseWheelSpeed: 12
    property real momentumVelocity: 0
    property bool isMomentumActive: false
    property real friction: 0.95
    property real minMomentumVelocity: 50
    property real maxMomentumVelocity: 2500
    // Internal: controls transient scrollbar visibility
    property bool _scrollBarActive: false

    flickDeceleration: 1500
    maximumFlickVelocity: 2000
    boundsBehavior: Flickable.StopAtBounds
    boundsMovement: Flickable.FollowBoundsBehavior
    pressDelay: 0
    flickableDirection: Flickable.VerticalFlick

    WheelHandler {
        id: wheelHandler

        property real touchpadSpeed: 1.8
        property real momentumRetention: 0.92
        property real lastWheelTime: 0
        property real momentum: 0
        property var velocitySamples: []

        function startMomentum() {
            flickable.isMomentumActive = true;
            momentumTimer.start();
        }

        acceptedDevices: PointerDevice.Mouse | PointerDevice.TouchPad
        
        onWheel: (event) => {
            // Activate scrollbar on any wheel interaction
            flickable._scrollBarActive = true;
            hideScrollBarTimer.restart();
            let currentTime = Date.now();
            let timeDelta = currentTime - lastWheelTime;
            lastWheelTime = currentTime;
            
            const deltaY = event.angleDelta.y;
            const isMouseWheel = Math.abs(deltaY) >= 120 && (Math.abs(deltaY) % 120) === 0;
            
            if (isMouseWheel) {
                momentumTimer.stop();
                flickable.isMomentumActive = false;
                velocitySamples = [];
                momentum = 0;
                
                const lines = Math.floor(Math.abs(deltaY) / 120);
                const scrollAmount = (deltaY > 0 ? -lines : lines) * flickable.mouseWheelSpeed; 
                let newY = flickable.contentY + scrollAmount;
                newY = Math.max(0, Math.min(flickable.contentHeight - flickable.height, newY));
                
                if (flickable.flicking)
                    flickable.cancelFlick();
                
                flickable.contentY = newY;
            } else {
                momentumTimer.stop();
                flickable.isMomentumActive = false;
                
                let delta = 0;
                if (event.pixelDelta.y !== 0) {
                    delta = event.pixelDelta.y * touchpadSpeed;
                } else {
                    delta = event.angleDelta.y / 8 * touchpadSpeed;
                }
                    
                velocitySamples.push({
                    "delta": delta,
                    "time": currentTime
                });
                velocitySamples = velocitySamples.filter((s) => {
                    return currentTime - s.time < 100;
                });
                
                if (velocitySamples.length > 1) {
                    let totalDelta = velocitySamples.reduce((sum, s) => {
                        return sum + s.delta;
                    }, 0);
                    let timeSpan = currentTime - velocitySamples[0].time;
                    if (timeSpan > 0)
                        flickable.momentumVelocity = Math.max(-flickable.maxMomentumVelocity, 
                                         Math.min(flickable.maxMomentumVelocity, 
                                                totalDelta / timeSpan * 1000));
                }
                
                if (event.pixelDelta.y !== 0 && timeDelta < 50) {
                    momentum = momentum * momentumRetention + delta * 0.15;
                    delta += momentum;
                } else {
                    momentum = 0;
                }
                
                let newY = flickable.contentY - delta;
                newY = Math.max(0, Math.min(flickable.contentHeight - flickable.height, newY));
                
                if (flickable.flicking)
                    flickable.cancelFlick();

                flickable.contentY = newY;
            }
            
            event.accepted = true;
        }
        
        onActiveChanged: {
            if (!active) {
                if (Math.abs(flickable.momentumVelocity) >= flickable.minMomentumVelocity) {
                    startMomentum();
                } else {
                    velocitySamples = [];
                    flickable.momentumVelocity = 0;
                }
            }
        }
    }

    // Show scrollbar while flicking / momentum
    onMovementStarted: {
        _scrollBarActive = true;
        hideScrollBarTimer.stop();
    }
    onMovementEnded: hideScrollBarTimer.restart()

    Timer {
        id: momentumTimer
        interval: 16
        repeat: true
        
        onTriggered: {
            let newY = flickable.contentY - flickable.momentumVelocity * 0.016;
            let maxY = Math.max(0, flickable.contentHeight - flickable.height);
            
            if (newY < 0) {
                flickable.contentY = 0;
                stop();
                flickable.isMomentumActive = false;
                flickable.momentumVelocity = 0;
                return;
            } else if (newY > maxY) {
                flickable.contentY = maxY;
                stop();
                flickable.isMomentumActive = false;
                flickable.momentumVelocity = 0;
                return;
            }
            
            flickable.contentY = newY;
            
            flickable.momentumVelocity *= flickable.friction;
            
            if (Math.abs(flickable.momentumVelocity) < 5) {
                stop();
                flickable.isMomentumActive = false;
                flickable.momentumVelocity = 0;
            }
        }
    }

    NumberAnimation {
        id: returnToBoundsAnimation
        target: flickable
        property: "contentY"
        duration: 300
        easing.type: Easing.OutQuad
    }

    // Styled vertical scrollbar (auto-hide, no track)
    ScrollBar.vertical: ScrollBar {
        id: vbar
        policy: flickable.contentHeight > flickable.height ? ScrollBar.AsNeeded : ScrollBar.AlwaysOff
        minimumSize: 0.08
        implicitWidth: 10
        interactive: true
        hoverEnabled: true
        z: 1000
        opacity: (policy !== ScrollBar.AlwaysOff) && (vbar.pressed || vbar.hovered || vbar.active || flickable.moving || flickable.flicking || flickable.isMomentumActive || flickable._scrollBarActive) ? 1 : 0
        visible: policy !== ScrollBar.AlwaysOff
        Behavior on opacity { NumberAnimation { duration: 160; easing.type: Easing.OutQuad } }

        contentItem: Rectangle {
            implicitWidth: 6
            radius: width / 2
            color: vbar.pressed ? Theme.primary
                  : (vbar.hovered || vbar.active || flickable.moving || flickable.flicking || flickable.isMomentumActive || flickable._scrollBarActive ? Theme.outline : Theme.outlineMedium)
            opacity: vbar.pressed ? 1 : (vbar.hovered || vbar.active || flickable.moving || flickable.flicking || flickable.isMomentumActive || flickable._scrollBarActive ? 1 : 0.6)
        }

        background: Item {}
    }

    Timer {
        id: hideScrollBarTimer
        interval: 1200
        onTriggered: flickable._scrollBarActive = false
    }
}