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import QtQuick 2.1
import "private/TabGroup.js" as Engine

import "." 2.0 as PlasmaComponents

/**
 * Provides a set of pages for a tab-based interface.
 *
 * A tabbed interface is made up of tab buttons plus content for each button. A
 * TabGroup component has, as its children, each page of content in the
 * interface. These pages can be any QML items but are typically Page
 * components for a single page of content or PageStack components when a
 * hierarchical navigation system is required for the tab content.
 *
 * If you use Page components for your tab content, the status property of each
 * page is updated appropriately when the current tab is changed: the current
 * page has status PageStatus.Active and other pages have the status
 * PageStatus.Inactive. During page transitions, PageStatus.Activating (for the
 * page that is becoming the current page) and PageStatus.Deactivating (for the
 * page that was the current page) statuses are also set.
 */
Item {
    id: root

    /**
     * The tab that is currently active and visible to the user.
     *
     * The currentTab property is initialized to null and is automatically set
     * to point to the first tab when content is added. You can set the
     * currentTab at any time to activate a particular tab.
     */
    property Item currentTab

    property list<Item> privateContents
    // Qt defect: cannot have list as default property
    default property alias privateContentsDefault: root.privateContents

    onChildrenChanged: {
        //  [0] is containerHost
        if (children.length > 1)
            Engine.addTab(children[1])
    }

    onPrivateContentsChanged: {
        Engine.ensureContainers()
    }

    Component.onCompleted: {
        // Set first tabs as current if currentTab is not set by application
        if (currentTab == null && containerHost.children[0] && containerHost.children[0].children[0])
            currentTab = containerHost.children[0].children[0]
        priv.complete = true;
    }

    Item {
        id: containerHost
        objectName: "containerHost"
        anchors.fill: parent
    }

    Component {
        id: tabContainerComponent
        Item {
            id: tabContainerItem

            onChildrenChanged: {
                if (children.length == 0)
                    Engine.removeContainer(tabContainerItem)

                else if (children.length == 1) {
                    children[0].width = width
                    children[0].height = height
                    // tab content created. set the first tab as current (if not set before, and if
                    // child is added after TabGroup has completed)
                    if (priv.complete && root.currentTab == null)
                        root.currentTab = children[0]
                }
            }

            onWidthChanged: {
                if (children.length > 0)
                    children[0].width = width
            }

            onHeightChanged: {
                if (children.length > 0)
                    children[0].height = height
            }

            Component.onDestruction: {
                if (typeof(root) != "undefined" && !root.currentTab) {
                    // selected one deleted. try to activate the neighbour
                    var removedIndex = -1
                    for (var i = 0; i < containerHost.children.length; i++) {
                        if (containerHost.children[i] == tabContainerItem) {
                            removedIndex = i
                            break
                        }
                    }
                    var newIndex = -1
                    if (removedIndex != -1) {
                        if (removedIndex != containerHost.children.length - 1)
                            newIndex = removedIndex + 1
                        else if (removedIndex != 0)
                            newIndex = removedIndex - 1
                    }

                    if (newIndex != -1)
                        root.currentTab = containerHost.children[newIndex].children[0]
                    else
                        root.currentTab = null
                }
            }

            function incomingDone() {
                state = ""
                if (priv.incomingPage) {
                    if (priv.incomingPage.status != undefined) {
                        priv.incomingPage.status = PlasmaComponents.PageStatus.Active
                    }
                    priv.incomingPage = null
                }
            }

            function outgoingDone() {
                if (priv.outgoingPage) {
                    if (priv.outgoingPage.status != undefined) {
                        priv.outgoingPage.status = PlasmaComponents.PageStatus.Active
                    }
                    priv.outgoingPage.visible = false
                    priv.outgoingPage = null
                }
                state = "HiddenLeft"
            }

            width: parent ? parent.width : 0
            height: parent ? parent.height : 0
            state: "HiddenLeft"

            states: [
                State { name: ""; PropertyChanges { target: tabContainerItem; opacity: 1.0; x: 0 } },
                State { name: "Incoming"; PropertyChanges { target: tabContainerItem; opacity: 1.0; x: 0 } },

                State {
                    name: "OutgoingLeft"
                    PropertyChanges {
                        target: tabContainerItem
                        opacity: 0.0
                        x: -root.width
                    }
                },
                State {
                    name: "OutgoingRight"
                    PropertyChanges {
                        target: tabContainerItem
                        opacity: 0.0
                        x: root.width
                    }
                },

                State { name: "HiddenLeft"; PropertyChanges { target: tabContainerItem; opacity: 0.0; x: root.width } },
                State { name: "HiddenRight"; PropertyChanges { target: tabContainerItem; opacity: 0.0; x: -root.width } }
            ]

            transitions:  [
                Transition {
                    to: "Incoming"
                    SequentialAnimation {
                        ScriptAction { script: root.clip = true }
                        PropertyAnimation { properties: "opacity,x"; easing.type: Easing.InQuad; duration: units.longDuration }
                        ScriptAction { script: {incomingDone(); root.clip = false} }
                    }
                },
                Transition {
                    to: "OutgoingLeft,OutgoingRight"
                    SequentialAnimation {
                        PropertyAnimation { properties: "opacity,x"; easing.type: Easing.InQuad; duration: units.longDuration }
                        ScriptAction { script: outgoingDone() }
                    }
                }
            ]
        }
    }

    QtObject {
        id: priv
        property bool reparenting: false
        property bool complete: false
        property Item currentTabContainer: root.currentTab ? root.currentTab.parent : null
        property int currentIndex: 0
        property Item incomingPage
        property Item outgoingPage
        property bool animate: true

        onCurrentTabContainerChanged: {
            var newCurrentIndex = 0
            for (var i = 0; i < containerHost.children.length; i++) {
                if (containerHost.children[i] == currentTabContainer) {
                    newCurrentIndex = i
                    break
                }
            }

            currentTabContainer.visible = true
            incomingPage = currentTabContainer.children[0]
            incomingPage.visible = true
            if (incomingPage.status != undefined) {
                incomingPage.status = PlasmaComponents.PageStatus.Activating
            }
            if (currentIndex < newCurrentIndex) {
                currentTabContainer.state = "HiddenLeft"
            } else {
                currentTabContainer.state = "HiddenRight"
            }
            if (animate) {
                currentTabContainer.state = "Incoming"
            } else {
                currentTabContainer.incomingDone()
            }

            if (newCurrentIndex == currentIndex) {
                return
            }

            var oldPage = containerHost.children[currentIndex]
            outgoingPage = oldPage.children[0]
            if (animate) {
                if (currentIndex < newCurrentIndex) {
                    oldPage.state = "OutgoingLeft"
                } else {
                    oldPage.state = "OutgoingRight"
                }
            } else {
                oldPage.outgoingDone()
            }
            currentIndex = newCurrentIndex
        }
    }
}
