/*
*   Copyright (C) 2011 by Daker Fernandes Pinheiro <dakerfp@gmail.com>
*   Copyright (C) 2011 by Mark Gaiser <markg85@gmail.com>
*   Copyright (C) 2011 by Marco Martin <mart@kde.org>
*
*   This program is free software; you can redistribute it and/or modify
*   it under the terms of the GNU Library General Public License as
*   published by the Free Software Foundation; either version 2, or
*   (at your option) any later version.
*
*   This program is distributed in the hope that it will be useful,
*   but WITHOUT ANY WARRANTY; without even the implied warranty of
*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*   GNU Library General Public License for more details
*
*   You should have received a copy of the GNU Library General Public
*   License along with this program; if not, write to the
*   Free Software Foundation, Inc.,
*   51 Franklin Street, Fifth Floor, Boston, MA  2.010-1301, USA.
*/


/**
 * A button with optional label and icon which uses the plasma theme.
 *
 * This button component can also be used as a checkable button by using
 * the checkable and checked properties for that.  Plasma theme is the
 * theme which changes via the systemsetting-workspace appearance -desktop
 * theme.
 */
import QtQuick 2.1
import org.kde.plasma.core 2.0 as PlasmaCore
import "private" as Private


Item {
    id: button


    // Commmon API
    /**
     * This property holds whether this button is checked or not.
     * The button must be in the checkable state to enable users to check or
     * uncheck it.
     *
     * The default value is false.
     *
     * @see checkable
     */
    property bool checked: false

    /**
     * This property holds if the button is acting like a checkable button or
     * not.
     *
     * The default value is false.
     */
    property bool checkable: false

    /**
     * type:bool
     * This property holds if the button is pressed or not.
     * Read-only.
     */
    property alias pressed: mouse.pressed

    /**
     * type:string
     * This property holds the text label for the button.
     */
    property alias text: label.text

    /**
     * type:string
     *
     * This property holds the source url for the Button's icon.
     * It can be any image from any protocol supported by the Image element, or
     * a freedesktop-compatible icon name
     *
     * The default value is an empty url, which displays no icon.
     */
    property alias iconSource: icon.source

    /**
     * type:font
     *
     * This property holds the font used by the button label.
     *
     * See also Qt documentation for font type.
     */
    property alias font: label.font

    //icon + label + left margin + right margin + spacing between icon and text
    /**
     * Smallest width this button can be to show all the contents
     */
    property real minimumWidth: icon.width + label.paintedWidth + surfaceNormal.margins.left + surfaceNormal.margins.right + ((icon.valid) ? surfaceNormal.margins.left : 0)

    /**
     * Smallest height this button can be to show all the contents
     */
    property real minimumHeight: Math.max(units.iconSizes.small, label.paintedHeight) + surfaceNormal.margins.top + surfaceNormal.margins.bottom

    /**
     * This signal is emitted when the button is clicked.
     */
    signal clicked()

    implicitWidth: {
        if (label.text.length == 0) {
            height;
        } else {
            Math.max(theme.mSize(theme.defaultFont).width*12, minimumWidth);
        }
    }

    implicitHeight: Math.max(theme.mSize(theme.defaultFont).height*1.6, minimumHeight)

    // TODO: needs to define if there will be specific graphics for
    //     disabled buttons
    opacity: enabled ? 1.0 : 0.5

    activeFocusOnTab: true


    QtObject {
        id: internal
        property bool userPressed: false

        function belongsToButtonGroup()
        {
            return button.parent
                   && button.parent.hasOwnProperty("checkedButton")
                   && button.parent.exclusive
        }

        function clickButton()
        {
            userPressed = false
            if (!button.enabled) {
                return
            }

            if ((!belongsToButtonGroup() || !button.checked) && button.checkable) {
                button.checked = !button.checked
            }

            button.forceActiveFocus()
            button.clicked()
        }
    }

    Keys.onSpacePressed: internal.userPressed = true
    Keys.onReturnPressed: internal.userPressed = true
    Keys.onReleased: {
        internal.userPressed = false
        if (event.key == Qt.Key_Space ||
            event.key == Qt.Key_Return)
            internal.clickButton();
    }

    Private.ButtonShadow {
        id: shadow
        anchors.fill: parent
        state: {
            if (internal.userPressed || checked) {
                return "hidden"
            } else if (mouse.containsMouse) {
                return "hover"
            } else if (button.activeFocus) {
                return "focus"
            } else {
                return "shadow"
            }
        }
    }

    // The normal button state
    PlasmaCore.FrameSvgItem {
        id: surfaceNormal

        anchors.fill: parent
        imagePath: "widgets/button"
        prefix: "normal"
    }

    // The pressed state
    PlasmaCore.FrameSvgItem {
        id: surfacePressed

        anchors.fill: parent
        imagePath: "widgets/button"
        prefix: "pressed"
        opacity: 0
    }

    Row {
        id: buttonContent
        state: (internal.userPressed || checked) ? "pressed" : "normal"
        spacing: icon.valid ? surfaceNormal.margins.left : 0

        states: [
            State { name: "normal" },
            State { name: "pressed"
                    PropertyChanges {
                        target: surfaceNormal
                        opacity: 0
                    }
                    PropertyChanges {
                        target: surfacePressed
                        opacity: 1
                    }
            }
        ]
        transitions: [
            Transition {
                to: "normal"
                // Cross fade from pressed to normal
                ParallelAnimation {
                    NumberAnimation { target: surfaceNormal; property: "opacity"; to: 1; duration: units.shortDuration * 2 }
                    NumberAnimation { target: surfacePressed; property: "opacity"; to: 0; duration: units.shortDuration * 2 }
                }
            }
        ]

        anchors {
            fill: parent
            leftMargin: surfaceNormal.margins.left
            topMargin: surfaceNormal.margins.top
            rightMargin: surfaceNormal.margins.right
            bottomMargin: surfaceNormal.margins.bottom
        }

        PlasmaCore.IconItem {
            id: icon
            anchors.verticalCenter: parent.verticalCenter
            width: valid? parent.height: 0
            height: width
            active: shadow.hasOverState && mouse.containsMouse
        }

        Label {
            id: label

            width: parent.width - icon.width - parent.spacing
            height: parent.height
            color: theme.buttonTextColor
            horizontalAlignment: icon.valid ? Text.AlignLeft : Text.AlignHCenter
            verticalAlignment: Text.AlignVCenter
        }
    }

    MouseArea {
        id: mouse

        anchors.fill: parent
        hoverEnabled: true
        onPressed: internal.userPressed = true
        onReleased: internal.userPressed = false
        onCanceled: internal.userPressed = false
        onClicked: internal.clickButton()
    }
}
