/**
 * ButtonElement is often mixed into other classes to generate a button, which is a clickable
 * interface element that can be configured with access keys for accessibility.
 * See the [OOjs UI documentation on MediaWiki] [1] for examples.
 *
 * [1]: https://www.mediawiki.org/wiki/OOjs_UI/Widgets/Buttons_and_Switches#Buttons
 * @abstract
 * @class
 *
 * @constructor
 * @param {Object} [config] Configuration options
 * @cfg {jQuery} [$button] The button element created by the class.
 *  If this configuration is omitted, the button element will use a generated `<a>`.
 * @cfg {boolean} [framed=true] Render the button with a frame
 * @cfg {string} [accessKey] Button's access key
 */
OO.ui.ButtonElement = function OoUiButtonElement( config ) {
	// Configuration initialization
	config = config || {};

	// Properties
	this.$button = null;
	this.framed = null;
	this.accessKey = null;
	this.active = false;
	this.onMouseUpHandler = this.onMouseUp.bind( this );
	this.onMouseDownHandler = this.onMouseDown.bind( this );
	this.onKeyDownHandler = this.onKeyDown.bind( this );
	this.onKeyUpHandler = this.onKeyUp.bind( this );
	this.onClickHandler = this.onClick.bind( this );
	this.onKeyPressHandler = this.onKeyPress.bind( this );

	// Initialization
	this.$element.addClass( 'oo-ui-buttonElement' );
	this.toggleFramed( config.framed === undefined || config.framed );
	this.setAccessKey( config.accessKey );
	this.setButtonElement( config.$button || $( '<a>' ) );
};

/* Setup */

OO.initClass( OO.ui.ButtonElement );

/* Static Properties */

/**
 * Cancel mouse down events.
 *
 * This property is usually set to `true` to prevent the focus from changing when the button is clicked.
 * Classes such as {@link OO.ui.DraggableElement DraggableElement} and {@link OO.ui.ButtonOptionWidget ButtonOptionWidget}
 * use a value of `false` so that dragging behavior is possible and mousedown events can be handled by a
 * parent widget.
 *
 * @static
 * @inheritable
 * @property {boolean}
 */
OO.ui.ButtonElement.static.cancelButtonMouseDownEvents = true;

/* Events */

/**
 * A 'click' event is emitted when the button element is clicked.
 *
 * @event click
 */

/* Methods */

/**
 * Set the button element.
 *
 * This method is used to retarget a button mixin so that its functionality applies to
 * the specified button element instead of the one created by the class. If a button element
 * is already set, the method will remove the mixin’s effect on that element.
 *
 * @param {jQuery} $button Element to use as button
 */
OO.ui.ButtonElement.prototype.setButtonElement = function ( $button ) {
	if ( this.$button ) {
		this.$button
			.removeClass( 'oo-ui-buttonElement-button' )
			.removeAttr( 'role accesskey' )
			.off( {
				mousedown: this.onMouseDownHandler,
				keydown: this.onKeyDownHandler,
				click: this.onClickHandler,
				keypress: this.onKeyPressHandler
			} );
	}

	this.$button = $button
		.addClass( 'oo-ui-buttonElement-button' )
		.attr( { role: 'button', accesskey: this.accessKey } )
		.on( {
			mousedown: this.onMouseDownHandler,
			keydown: this.onKeyDownHandler,
			click: this.onClickHandler,
			keypress: this.onKeyPressHandler
		} );
};

/**
 * Handles mouse down events.
 *
 * @protected
 * @param {jQuery.Event} e Mouse down event
 */
OO.ui.ButtonElement.prototype.onMouseDown = function ( e ) {
	if ( this.isDisabled() || e.which !== 1 ) {
		return;
	}
	this.$element.addClass( 'oo-ui-buttonElement-pressed' );
	// Run the mouseup handler no matter where the mouse is when the button is let go, so we can
	// reliably remove the pressed class
	this.getElementDocument().addEventListener( 'mouseup', this.onMouseUpHandler, true );
	// Prevent change of focus unless specifically configured otherwise
	if ( this.constructor.static.cancelButtonMouseDownEvents ) {
		return false;
	}
};

/**
 * Handles mouse up events.
 *
 * @protected
 * @param {jQuery.Event} e Mouse up event
 */
OO.ui.ButtonElement.prototype.onMouseUp = function ( e ) {
	if ( this.isDisabled() || e.which !== 1 ) {
		return;
	}
	this.$element.removeClass( 'oo-ui-buttonElement-pressed' );
	// Stop listening for mouseup, since we only needed this once
	this.getElementDocument().removeEventListener( 'mouseup', this.onMouseUpHandler, true );
};

/**
 * Handles mouse click events.
 *
 * @protected
 * @param {jQuery.Event} e Mouse click event
 * @fires click
 */
OO.ui.ButtonElement.prototype.onClick = function ( e ) {
	if ( !this.isDisabled() && e.which === 1 ) {
		if ( this.emit( 'click' ) ) {
			return false;
		}
	}
};

/**
 * Handles key down events.
 *
 * @protected
 * @param {jQuery.Event} e Key down event
 */
OO.ui.ButtonElement.prototype.onKeyDown = function ( e ) {
	if ( this.isDisabled() || ( e.which !== OO.ui.Keys.SPACE && e.which !== OO.ui.Keys.ENTER ) ) {
		return;
	}
	this.$element.addClass( 'oo-ui-buttonElement-pressed' );
	// Run the keyup handler no matter where the key is when the button is let go, so we can
	// reliably remove the pressed class
	this.getElementDocument().addEventListener( 'keyup', this.onKeyUpHandler, true );
};

/**
 * Handles key up events.
 *
 * @protected
 * @param {jQuery.Event} e Key up event
 */
OO.ui.ButtonElement.prototype.onKeyUp = function ( e ) {
	if ( this.isDisabled() || ( e.which !== OO.ui.Keys.SPACE && e.which !== OO.ui.Keys.ENTER ) ) {
		return;
	}
	this.$element.removeClass( 'oo-ui-buttonElement-pressed' );
	// Stop listening for keyup, since we only needed this once
	this.getElementDocument().removeEventListener( 'keyup', this.onKeyUpHandler, true );
};

/**
 * Handles key press events.
 *
 * @protected
 * @param {jQuery.Event} e Key press event
 * @fires click
 */
OO.ui.ButtonElement.prototype.onKeyPress = function ( e ) {
	if ( !this.isDisabled() && ( e.which === OO.ui.Keys.SPACE || e.which === OO.ui.Keys.ENTER ) ) {
		if ( this.emit( 'click' ) ) {
			return false;
		}
	}
};

/**
 * Check if button has a frame.
 *
 * @return {boolean} Button is framed
 */
OO.ui.ButtonElement.prototype.isFramed = function () {
	return this.framed;
};

/**
 * Render the button with or without a frame. Omit the `framed` parameter to toggle the button frame on and off.
 *
 * @param {boolean} [framed] Make button framed, omit to toggle
 * @chainable
 */
OO.ui.ButtonElement.prototype.toggleFramed = function ( framed ) {
	framed = framed === undefined ? !this.framed : !!framed;
	if ( framed !== this.framed ) {
		this.framed = framed;
		this.$element
			.toggleClass( 'oo-ui-buttonElement-frameless', !framed )
			.toggleClass( 'oo-ui-buttonElement-framed', framed );
		this.updateThemeClasses();
	}

	return this;
};

/**
 * Set the button's access key.
 *
 * @param {string} accessKey Button's access key, use empty string to remove
 * @chainable
 */
OO.ui.ButtonElement.prototype.setAccessKey = function ( accessKey ) {
	accessKey = typeof accessKey === 'string' && accessKey.length ? accessKey : null;

	if ( this.accessKey !== accessKey ) {
		if ( this.$button ) {
			if ( accessKey !== null ) {
				this.$button.attr( 'accesskey', accessKey );
			} else {
				this.$button.removeAttr( 'accesskey' );
			}
		}
		this.accessKey = accessKey;
	}

	return this;
};

/**
 * Set the button to its 'active' state.
 *
 * The active state occurs when a {@link OO.ui.ButtonOptionWidget ButtonOptionWidget} or
 * a {@link OO.ui.ToggleButtonWidget ToggleButtonWidget} is pressed. This method does nothing
 * for other button types.
 *
 * @param {boolean} [value] Make button active
 * @chainable
 */
OO.ui.ButtonElement.prototype.setActive = function ( value ) {
	this.$element.toggleClass( 'oo-ui-buttonElement-active', !!value );
	return this;
};