// ==UserScript==
// @name           LinkDragSelectionForChrome
// @description    Opera like link selection for chrome.
// @namespace      http://d.hatena.ne.jp/Griever/
// @author         Griever
// @license        MIT License
// @match          http://*/*
// @match          https://*/*
// @version        0.0.1
// ==/UserScript==

function LinkDragSelection(){
    this.init.apply(this, arguments);
}
LinkDragSelection.prototype = {
    moved_flag: false,
    init: function(event) {
        this.range = document.caretRangeFromPoint(event.pageX - scrollX, event.pageY - scrollY);
        var sel = getSelection();
        if (!sel.isCollapsed && sel.getRangeAt(0).isPointInRange(this.range.startContainer, this.range.startOffset))
            return;
        this.screenX = event.screenX;
        this.screenY = event.screenY;
        addEventListener("mousemove", this, false);
        addEventListener("mouseup", this, false);
    },
    uninit: function() {
        removeEventListener("mousemove", this, false);
        removeEventListener("mouseup", this, false);
        removeEventListener("dragstart", this, false);
        setTimeout(function() {
            removeEventListener("click", this, false);
        }.bind(this), 100);
    },
    handleEvent: function(event) {
        switch(event.type){
            case "mousemove":
                if (this.moved_flag) {
                    var range = document.caretRangeFromPoint(event.pageX - scrollX, event.pageY - scrollY);
                    if (range)
                        getSelection().extend(range.startContainer, range.startOffset);
                } else {
                    this.moveX = event.screenX;
                    this.moveY = event.screenY;
                    this.checkXY();
                }
                break;
            case "mouseup":
                this.uninit();
                break;
            case "dragstart":
                event.currentTarget.removeEventListener(event.type, this, false);
                if (this.moved_flag) {
                    event.preventDefault();
                    event.stopPropagation();
                } else {
                    this.checkXY();
                }
                break;
            case "click":
                event.currentTarget.removeEventListener(event.type, this, false);
                if (!getSelection().isCollapsed) {
                    event.preventDefault();
                    event.stopPropagation();
                }
                break;
        }
    },
    selectionStart: function() {
        this.moved_flag = true;
        getSelection().collapse(this.range.startContainer, this.range.startOffset);
        addEventListener("dragstart", this, false);
        addEventListener("click", this, false);
    },
    checkXY: function() {
        var x = Math.abs(this.screenX - this.moveX);
        var y = Math.abs(this.screenY - this.moveY);
        if (x >= 5 && x > y) {
            this.selectionStart();
        } else if (y >= 5) {
            this.uninit();
        }
    },
};

addEventListener("mousedown", function(event) {
    if (event.button != 0 || event.ctrlKey || event.altKey || event.shiftKey) return;
    if (!event.target.webkitMatchesSelector('a[href], a[href] *')) return;
    new LinkDragSelection(event);
}, false);