var Example = Example || {};

Example.views = function() {
    var Engine = Matter.Engine,
        Render = Matter.Render,
        Runner = Matter.Runner,
        Events = Matter.Events,
        Composites = Matter.Composites,
        Common = Matter.Common,
        MouseConstraint = Matter.MouseConstraint,
        Mouse = Matter.Mouse,
        World = Matter.World,
        Vector = Matter.Vector,
        Bounds = Matter.Bounds,
        Bodies = Matter.Bodies;

    // create engine
    var engine = Engine.create(),
        world = engine.world;

    // create renderer
    var render = Render.create({
        element: document.body,
        engine: engine,
        options: {
            width: 800,
            height: 600,
            hasBounds: true,
            showAngleIndicator: true
        }
    });

    Render.run(render);

    // create runner
    var runner = Runner.create();
    Runner.run(runner, engine);

    // add mouse control
    var mouse = Mouse.create(render.canvas),
        mouseConstraint = MouseConstraint.create(engine, {
            mouse: mouse,
            constraint: {
                stiffness: 0.2,
                render: {
                    visible: false
                }
            }
        });

    World.add(world, mouseConstraint);

    // keep the mouse in sync with rendering
    render.mouse = mouse;

    // add bodies
    var stack = Composites.stack(20, 20, 15, 4, 0, 0, function(x, y) {
        switch (Math.round(Common.random(0, 1))) {

        case 0:
            if (Common.random() < 0.8) {
                return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
            } else {
                return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
            }
        case 1:
            var sides = Math.round(Common.random(1, 8));
            sides = (sides === 3) ? 4 : sides;
            return Bodies.polygon(x, y, sides, Common.random(20, 50));
        }
    });

    World.add(world, [
        stack,
        // walls
        Bodies.rectangle(400, 0, 800, 50, { isStatic: true }),
        Bodies.rectangle(400, 600, 800, 50, { isStatic: true }),
        Bodies.rectangle(800, 300, 50, 600, { isStatic: true }),
        Bodies.rectangle(0, 300, 50, 600, { isStatic: true })
    ]);
    
    // get the centre of the viewport
    var viewportCentre = {
        x: render.options.width * 0.5,
        y: render.options.height * 0.5
    };

    // make the world bounds a little bigger than the render bounds
    world.bounds.min.x = -300;
    world.bounds.min.y = -300;
    world.bounds.max.x = 1100;
    world.bounds.max.y = 900;

    // keep track of current bounds scale (view zoom)
    var boundsScaleTarget = 1,
        boundsScale = {
            x: 1,
            y: 1
        };

    // use the engine tick event to control our view
    Events.on(engine, 'beforeTick', function() {
        var world = engine.world,
            mouse = mouseConstraint.mouse,
            translate;

        // mouse wheel controls zoom
        var scaleFactor = mouse.wheelDelta * -0.1;
        if (scaleFactor !== 0) {
            if ((scaleFactor < 0 && boundsScale.x >= 0.6) || (scaleFactor > 0 && boundsScale.x <= 1.4)) {
                boundsScaleTarget += scaleFactor;
            }
        }

        // if scale has changed
        if (Math.abs(boundsScale.x - boundsScaleTarget) > 0.01) {
            // smoothly tween scale factor
            scaleFactor = (boundsScaleTarget - boundsScale.x) * 0.2;
            boundsScale.x += scaleFactor;
            boundsScale.y += scaleFactor;

            // scale the render bounds
            render.bounds.max.x = render.bounds.min.x + render.options.width * boundsScale.x;
            render.bounds.max.y = render.bounds.min.y + render.options.height * boundsScale.y;

            // translate so zoom is from centre of view
            translate = {
                x: render.options.width * scaleFactor * -0.5,
                y: render.options.height * scaleFactor * -0.5
            };

            Bounds.translate(render.bounds, translate);

            // update mouse
            Mouse.setScale(mouse, boundsScale);
            Mouse.setOffset(mouse, render.bounds.min);
        }

        // get vector from mouse relative to centre of viewport
        var deltaCentre = Vector.sub(mouse.absolute, viewportCentre),
            centreDist = Vector.magnitude(deltaCentre);

        // translate the view if mouse has moved over 50px from the centre of viewport
        if (centreDist > 50) {
            // create a vector to translate the view, allowing the user to control view speed
            var direction = Vector.normalise(deltaCentre),
                speed = Math.min(10, Math.pow(centreDist - 50, 2) * 0.0002);

            translate = Vector.mult(direction, speed);

            // prevent the view moving outside the world bounds
            if (render.bounds.min.x + translate.x < world.bounds.min.x)
                translate.x = world.bounds.min.x - render.bounds.min.x;

            if (render.bounds.max.x + translate.x > world.bounds.max.x)
                translate.x = world.bounds.max.x - render.bounds.max.x;

            if (render.bounds.min.y + translate.y < world.bounds.min.y)
                translate.y = world.bounds.min.y - render.bounds.min.y;

            if (render.bounds.max.y + translate.y > world.bounds.max.y)
                translate.y = world.bounds.max.y - render.bounds.max.y;

            // move the view
            Bounds.translate(render.bounds, translate);

            // we must update the mouse too
            Mouse.setOffset(mouse, render.bounds.min);
        }
    });

    // context for MatterTools.Demo
    return {
        engine: engine,
        runner: runner,
        render: render,
        canvas: render.canvas,
        stop: function() {
            Matter.Render.stop(render);
            Matter.Runner.stop(runner);
        }
    };
};

Example.views.for = '>=0.14.2';

if (typeof module !== 'undefined') {
    module.exports = Example.views;
}