import QtQuick
import QtQuick.Controls
import QtQuick.Layouts
import qs.Commons

Item {
  id: root

  // Public API
  property var model: []
  property color activeColor: Color.mPrimary
  property color activeOnColor: Color.mOnPrimary
  property color dragHandleColor: Color.mOutline
  property int baseSize: Style.baseWidgetSize * 0.7
  property int spacing: Style.marginM

  signal itemToggled(int index, bool enabled)
  signal itemsReordered(int fromIndex, int toIndex)
  signal dragPotentialStarted
  signal dragPotentialEnded

  implicitHeight: listView.contentHeight

  function toggleItem(index) {
    if (index < 0 || index >= root.model.length)
      return

    var item = root.model[index]
    if (item.required)
      return

    // Create a new array to trigger binding update
    var newModel = root.model.slice()
    newModel[index] = Object.assign({}, item, {
                                      "enabled": !item.enabled
                                    })
    root.model = newModel

    root.itemToggled(index, newModel[index].enabled)
  }

  function moveItem(fromIndex, toIndex) {
    if (fromIndex === toIndex)
      return
    if (fromIndex < 0 || fromIndex >= root.model.length)
      return
    if (toIndex < 0 || toIndex >= root.model.length)
      return

    // Create a new array with item moved
    var newModel = root.model.slice()
    var item = newModel.splice(fromIndex, 1)[0]
    newModel.splice(toIndex, 0, item)
    root.model = newModel

    root.itemsReordered(fromIndex, toIndex)
  }

  ListView {
    id: listView

    anchors.fill: parent
    spacing: root.spacing
    interactive: false
    clip: true
    model: root.model

    delegate: Item {
      id: delegateItem

      width: listView.width
      height: checkboxRow.height

      required property int index
      required property var modelData

      property string text: modelData.text || ""
      property bool enabled: modelData.enabled || false
      property bool required: modelData.required || false
      property bool dragging: false
      property int dragStartY: 0
      property int dragStartIndex: -1
      property int dragTargetIndex: -1
      property int itemSpacing: root.spacing

      RowLayout {
        id: checkboxRow

        width: parent.width
        spacing: Style.marginS

        // Drag handle
        Rectangle {
          id: dragHandle

          Layout.preferredWidth: root.baseSize
          Layout.preferredHeight: root.baseSize
          radius: Style.radiusXS
          color: dragHandleMouseArea.containsMouse ? Color.mSurfaceVariant : Color.transparent

          Behavior on color {
            ColorAnimation {
              duration: Style.animationFast
            }
          }

          ColumnLayout {
            anchors.centerIn: parent
            spacing: Style.marginS

            Repeater {
              model: 3
              Rectangle {
                Layout.preferredWidth: root.baseSize * 0.4
                Layout.preferredHeight: 2
                radius: 1
                color: root.dragHandleColor
              }
            }
          }

          MouseArea {
            id: dragHandleMouseArea

            anchors.fill: parent
            cursorShape: Qt.SizeVerCursor
            hoverEnabled: true
            preventStealing: false
            z: 1000

            onPressed: mouse => {
                         delegateItem.dragStartIndex = delegateItem.index
                         delegateItem.dragTargetIndex = delegateItem.index
                         delegateItem.dragStartY = delegateItem.y
                         delegateItem.dragging = true
                         delegateItem.z = 999

                         // Signal that interaction started (prevents panel close)
                         preventStealing = true
                         root.dragPotentialStarted()
                       }

            onPositionChanged: mouse => {
                                 if (delegateItem.dragging) {
                                   var dy = mouse.y - dragHandle.height / 2
                                   var newY = delegateItem.y + dy

                                   // Constrain within bounds
                                   newY = Math.max(0, Math.min(newY, listView.contentHeight - delegateItem.height))
                                   delegateItem.y = newY

                                   // Calculate target index (but don't apply yet)
                                   var targetIndex = Math.floor((newY + delegateItem.height / 2) / (delegateItem.height + delegateItem.itemSpacing))
                                   targetIndex = Math.max(0, Math.min(targetIndex, listView.count - 1))

                                   delegateItem.dragTargetIndex = targetIndex
                                 }
                               }

            onReleased: {
              // Always signal end of interaction
              preventStealing = false
              root.dragPotentialEnded()

              // Apply the model change now that drag is complete
              if (delegateItem.dragStartIndex !== -1 && delegateItem.dragTargetIndex !== -1 && delegateItem.dragStartIndex !== delegateItem.dragTargetIndex) {
                root.moveItem(delegateItem.dragStartIndex, delegateItem.dragTargetIndex)
              }

              delegateItem.dragging = false
              delegateItem.dragStartIndex = -1
              delegateItem.dragTargetIndex = -1
              delegateItem.z = 0
            }

            onCanceled: {
              // Handle cancel (e.g., ESC key pressed during drag)
              preventStealing = false
              root.dragPotentialEnded()

              delegateItem.dragging = false
              delegateItem.dragStartIndex = -1
              delegateItem.dragTargetIndex = -1
              delegateItem.z = 0
            }
          }
        }

        // Checkbox
        Rectangle {
          id: box

          Layout.preferredWidth: root.baseSize
          Layout.preferredHeight: root.baseSize
          radius: Style.radiusXS
          color: delegateItem.enabled ? root.activeColor : Color.mSurface
          border.color: delegateItem.required ? root.activeColor : Color.mOutline
          border.width: Math.max(1, Style.borderS)
          opacity: delegateItem.required ? 0.7 : 1.0

          Behavior on color {
            ColorAnimation {
              duration: Style.animationFast
            }
          }

          Behavior on border.color {
            ColorAnimation {
              duration: Style.animationFast
            }
          }

          NIcon {
            visible: delegateItem.enabled
            anchors.centerIn: parent
            anchors.horizontalCenterOffset: -1
            icon: "check"
            color: root.activeOnColor
            pointSize: Math.max(Style.fontSizeXS, root.baseSize * 0.5)
          }

          MouseArea {
            anchors.fill: parent
            cursorShape: delegateItem.required ? Qt.ForbiddenCursor : Qt.PointingHandCursor
            enabled: !delegateItem.required

            onClicked: {
              root.toggleItem(delegateItem.index)
            }
          }
        }

        // Label
        NText {
          Layout.fillWidth: true
          text: delegateItem.text
          color: Color.mOnSurface
          verticalAlignment: Text.AlignVCenter
          elide: Text.ElideRight
        }

        // Required indicator
        NText {
          visible: delegateItem.required
          text: "(required)"
          color: Color.mOnSurfaceVariant
          verticalAlignment: Text.AlignVCenter
        }
      }

      // Position binding for non-dragging state
      y: {
        if (delegateItem.dragging) {
          return delegateItem.y
        }

        // Check if any item is being dragged
        var draggedIndex = -1
        var targetIndex = -1
        for (var i = 0; i < listView.count; i++) {
          var item = listView.itemAtIndex(i)
          if (item && item.dragging) {
            draggedIndex = item.dragStartIndex
            targetIndex = item.dragTargetIndex
            break
          }
        }

        // If an item is being dragged, adjust positions
        if (draggedIndex !== -1 && targetIndex !== -1 && draggedIndex !== targetIndex) {
          var currentIndex = delegateItem.index

          if (draggedIndex < targetIndex) {
            // Dragging down: shift items up between draggedIndex and targetIndex
            if (currentIndex > draggedIndex && currentIndex <= targetIndex) {
              return (currentIndex - 1) * (delegateItem.height + delegateItem.itemSpacing)
            }
          } else {
            // Dragging up: shift items down between targetIndex and draggedIndex
            if (currentIndex >= targetIndex && currentIndex < draggedIndex) {
              return (currentIndex + 1) * (delegateItem.height + delegateItem.itemSpacing)
            }
          }
        }

        return delegateItem.index * (delegateItem.height + delegateItem.itemSpacing)
      }

      Behavior on y {
        enabled: !delegateItem.dragging
        NumberAnimation {
          duration: Style.animationNormal
          easing.type: Easing.OutQuad
        }
      }
    }
  }
}