;(function(win, lib) {
    var doc = win.document;
    var docel = doc.documentelement;
    var metael = doc.queryselector('meta[name="viewport"]');
    var flexibleel = doc.queryselector('meta[name="flexible"]');
    var dpr = 0;
    var scale = 0;
    var tid;
    var flexible = lib.flexible || (lib.flexible = {});
    
    if (metael) {
        var match = metael.getattribute('content').match(/initial\-scale=([\d\.]+)/);
        if (match) {
            scale = parsefloat(match[1]);
            dpr = parseint(1 / scale);
        }
    } else if (flexibleel) {
        var content = flexibleel.getattribute('content');
        if (content) {
            var initialdpr = content.match(/initial\-dpr=([\d\.]+)/);
            var maximumdpr = content.match(/maximum\-dpr=([\d\.]+)/);
            if (initialdpr) {
                dpr = parsefloat(initialdpr[1]);
                scale = parsefloat((1 / dpr).tofixed(2));    
            }
            if (maximumdpr) {
                dpr = parsefloat(maximumdpr[1]);
                scale = parsefloat((1 / dpr).tofixed(2));    
            }
        }
    }

    if (!dpr && !scale) {
        var isandroid = win.navigator.appversion.match(/android/gi);
        var isiphone = win.navigator.appversion.match(/iphone/gi);
        var devicepixelratio = win.devicepixelratio;
        if (isiphone) {
            // ios下，对于2和3的屏，用2倍的方案，其余的用1倍方案
            if (devicepixelratio >= 3 && (!dpr || dpr >= 3)) {                
                dpr = 3;
            } else if (devicepixelratio >= 2 && (!dpr || dpr >= 2)){
                dpr = 2;
            } else {
                dpr = 1;
            }
        } else {
            // 其他设备下，仍旧使用1倍的方案
            dpr = 1;
        }
        scale = 1 / dpr;
    }

    docel.setattribute('data-dpr', dpr);
    if (!metael) {
        metael = doc.createelement('meta');
        metael.setattribute('name', 'viewport');
        metael.setattribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
        if (docel.firstelementchild) {
            docel.firstelementchild.appendchild(metael);
        } else {
            var wrap = doc.createelement('div');
            wrap.appendchild(metael);
            doc.write(wrap.innerhtml);
        }
    }

    function refreshrem(){
        var width = docel.getboundingclientrect().width;
        if (width / dpr > 1900) {
            width = 1900 * dpr;
        }
        var rem = width / 20;
        docel.style.fontsize = rem + 'px';
        flexible.rem = win.rem = rem;
    }

    win.addeventlistener('resize', function() {
        cleartimeout(tid);
        tid = settimeout(refreshrem, 300);
    }, false);
    win.addeventlistener('pageshow', function(e) {
        if (e.persisted) {
            cleartimeout(tid);
            tid = settimeout(refreshrem, 300);
        }
    }, false);

    if (doc.readystate === 'complete') {
        doc.body.style.fontsize = 12 * dpr + 'px';
    } else {
        doc.addeventlistener('domcontentloaded', function(e) {
            doc.body.style.fontsize = 12 * dpr + 'px';
        }, false);
    }
    

    refreshrem();

    flexible.dpr = win.dpr = dpr;
    flexible.refreshrem = refreshrem;
    flexible.rem2px = function(d) {
        var val = parsefloat(d) * this.rem;
        if (typeof d === 'string' && d.match(/rem$/)) {
            val += 'px';
        }
        return val;
    }
    flexible.px2rem = function(d) {
        var val = parsefloat(d) / this.rem;
        if (typeof d === 'string' && d.match(/px$/)) {
            val += 'rem';
        }
        return val;
    }

})(window, window['lib'] || (window['lib'] = {}));