;window.addEventListener("load", function () {
    "use strict";

    var v1 = {
        x: document.getElementById("x1"),
        y: document.getElementById("y1"),
        z: document.getElementById("z1"),
        abs: document.getElementById("abs1"),
        xn: document.getElementById("x1n"),
        yn: document.getElementById("y1n"),
        zn: document.getElementById("z1n"),
        absn: document.getElementById("abs1n"),
    };
    var v2 = {
        x: document.getElementById("x2"),
        y: document.getElementById("y2"),
        z: document.getElementById("z2"),
        abs: document.getElementById("abs2"),
        xn: document.getElementById("x2n"),
        yn: document.getElementById("y2n"),
        zn: document.getElementById("z2n"),
        absn: document.getElementById("abs2n"),
    };

    var abs = function (a) {
        return Math.sqrt(a.x*a.x + a.y*a.y + a.z*a.z);
    };
    
    var showAccel = function (v, accel) {
        v.x.value = v.xn.value = accel.x;
        v.y.value = v.yn.value = accel.y;
        v.z.value = v.zn.value = accel.z;
        v.abs.value = v.absn.value = abs(accel);
    };

    // split vertical/horizontal elements of acceleration
    var vhview = {
        v: document.getElementById("v"),
        vn: document.getElementById("vn"),
        h: document.getElementById("h"),
        hn: document.getElementById("hn"),
    };
    var splitVH = function (ev) {
        var acc = ev.acceleration, accg = ev.accelerationIncludingGravity;
        // calc gravity element
        var g = {x: accg.x - acc.x, y: accg.y - acc.y, z: accg.z - acc.z};
        var gl = abs(g);
        var ev = {x: g.x / gl, y: g.y / gl, z: g.z / gl}; // unit vector
        // calc vertical(= gravity direction) part
        var vl = acc.x * ev.x + acc.y * ev.y + acc.z * ev.z;
        var v = {x: ev.x * vl, y: ev.y * vl, z: ev.z * vl};
        // split horizontal(= orthogonal plane of gravity) part
        var h = {x: acc.x - v.x, y: acc.y - v.y, z: acc.z - v.z};
        return {v: v, h: h, ev: ev, vl: vl};
    };
    var showVH = function (vh) {
        vhview.v.value = vhview.vn.value = Math.abs(vh.vl);
        vhview.h.value = vhview.hn.value = abs(vh.h);
    };

    // Simple Walk Counter
    var counter = document.getElementById("counter");
    var vl = 0.0; // noise filtered value
    var count = 0;
    var updown = 0;
    var thresholds = {up: 0.5, down: -0.25};
    var walking = function (vh) {
        vl = 0.9 * vl + 0.1 * vh.vl; //low-pass filtering
        switch (updown) {
        case -1:
            if (vl > thresholds.up) {
                updown = +1;
                count += 1;
            }
            break;
        case +1:
            if (vl < thresholds.down) {
                updown = -1;
            }
            break;
        default:
            if (vl < 0) updown = -1;
            if (vl >= 0) updown = +1;
            break;
        }
        counter.textContent = count;
    };
    var reset = document.getElementById("reset");
    reset.addEventListener("click", function () {
        count = 0;
        updown = 0;
    }, false);
    
    // see: http://www.w3.org/TR/orientation-event/
    window.addEventListener("devicemotion", function (ev) {
        try {
            showAccel(v1, ev.acceleration);
            showAccel(v2, ev.accelerationIncludingGravity);
            var vh = splitVH(ev);
            showVH(vh);
            walking(vh);
        } catch (ex) {
            document.getElementById("log").textContent = ex.toString();
        }
    }, false);
}, false);