ElmRuntime.Render.Collage = function() {
'use strict';

var Render = ElmRuntime.use(ElmRuntime.Render.Element);
var Matrix = Elm.Matrix2D({});
var Utils = ElmRuntime.use(ElmRuntime.Render.Utils);
var newElement = Utils.newElement,
    extract = Utils.extract, fromList = Utils.fromList,
    fromString = Utils.fromString, addTransform = Utils.addTransform;

function trace(ctx, path) {
    var points = fromList(path);
    var i = points.length - 1;
    if (i <= 0) return;
    ctx.moveTo(points[i]._0, points[i]._1);
    while (i--) { ctx.lineTo(points[i]._0, points[i]._1); }
    if (path.closed) {
        i = points.length - 1;
        ctx.lineTo(points[i]._0, points[i]._1);
    }
}

function line(ctx,style,path) {
    style.dashing.ctor === 'Nil' ? trace(ctx, path) : customLineHelp(ctx, style, path);
    ctx.stroke();
}

function customLineHelp(ctx, style, path) {
    var points = fromList(path);
    if (path.closed) points.push(points[0]);
    var pattern = fromList(style.dashing);
    var i = points.length - 1;
    if (i <= 0) return;
    var x0 = points[i]._0, y0 = points[i]._1;
    var x1=0, y1=0, dx=0, dy=0, remaining=0, nx=0, ny=0;
    var pindex = 0, plen = pattern.length;
    var draw = true, segmentLength = pattern[0];
    ctx.moveTo(x0,y0);
    while (i--) {
        x1 = points[i]._0; y1 = points[i]._1;
        dx = x1 - x0; dy = y1 - y0;
        remaining = Math.sqrt(dx * dx + dy * dy);
        while (segmentLength <= remaining) {
            x0 += dx * segmentLength / remaining;
            y0 += dy * segmentLength / remaining;
            ctx[draw ? 'lineTo' : 'moveTo'](x0, y0);
            // update starting position
            dx = x1 - x0; dy = y1 - y0;
            remaining = Math.sqrt(dx * dx + dy * dy);
            // update pattern
            draw = !draw;
            pindex = (pindex + 1) % plen;
            segmentLength = pattern[pindex];
        }
        if (remaining > 0) {
            ctx[draw ? 'lineTo' : 'moveTo'](x1, y1);
            segmentLength -= remaining;
        }
        x0 = x1; y0 = y1;
    }
}

function drawLine(ctx, style, path) {
    ctx.lineWidth = style.width;
    ctx.lineCap = style.cap.ctor.toLowerCase();
    var join = style.join.ctor;
    ctx.lineJoin = join === 'Smooth' ? 'round' :
                   join === 'Sharp' ? 'miter' : 'bevel';
    ctx.miterLimit = style.miterLimit;
    ctx.strokeStyle = extract(style.color);
    return line(ctx, style, path);
}

function texture(redo, ctx, src) {
    var img = new Image();
    img.src = fromString(src);
    img.onload = redo;
    return ctx.createPattern(img, 'repeat');
}

function gradient(ctx, grad) {
  var g;
  var stops = [];
  if (grad.ctor === 'Linear') {
    var p0 = grad._0, p1 = grad._1;
    g = ctx.createLinearGradient(p0._0, p0._1, p1._0, p1._1);
    stops = fromList(grad._2);
  } else {
    var p0 = grad._0, p2 = grad._2;
    g = ctx.createRadialGradient(p0._0, p0._1, grad._1, p2._0, p2._1, grad._3);
    stops = fromList(grad._4);
  }
  var len = stops.length;
  for (var i = 0; i < len; ++i) {
    var stop = stops[i];
    g.addColorStop(stop._0, extract(stop._1));
  }
  return g;
}

function drawShape(redo, ctx, style, path) {
    trace(ctx, path);
    var sty = style.ctor;
    ctx.fillStyle =
        sty === 'Solid' ? extract(style._0) :
        sty === 'Texture' ? texture(redo, ctx, style._0) : gradient(ctx, style._0);
    ctx.fill();
}

function drawImage(redo, ctx, form) {
    var img = new Image();
    img.onload = redo;
    img.src = fromString(form._3);
    var w = form._0,
        h = form._1,
        pos = form._2,
        srcX = pos._0,
        srcY = pos._1,
        srcW = w,
        srcH = h,
        destX = -w/2,
        destY = -h/2,
        destW = w,
        destH = h;

    ctx.drawImage(img, srcX, srcY, srcW, srcH, destX, destY, destW, destH);
}

function renderForm(redo, ctx, form) {
    ctx.save();
    var x = form.x, y = form.y, theta = form.theta, scale = form.scale;
    if (x !== 0 || y !== 0) ctx.translate(x, y);
    if (theta !== 0) ctx.rotate(theta);
    ctx.scale(scale,-scale);
    ctx.beginPath();
    var f = form.form;
    switch(f.ctor) {
    case 'FPath' : drawLine(ctx, f._0, f._1); break;
    case 'FImage': drawImage(redo, ctx, f); break;
    case 'FShape':
	if (f._0.ctor === 'Left') {
	    f._1.closed = true;
	    drawLine(ctx, f._0._0, f._1);
	} else {
            drawShape(redo, ctx, f._0._0, f._1);
        }
	break;
    }
    ctx.restore();
}

function formToMatrix(form) {
   var scale = form.scale;
   var matrix = A6( Matrix.matrix, scale, 0, 0, scale, scale * form.x, scale * form.y );

   var theta = form.theta
   if (theta !== 0) matrix = A2( Matrix.rotate, theta, matrix );

   return matrix;
}

function makeTransform(w, h, form, matrices) {
    var props = form.form._0.props;
    var m = A6( Matrix.matrix, 1, 0, 0, 1,
                (w - props.width)/2,
                (h - props.height)/2 );
    var len = matrices.length;
    for (var i = 0; i < len; ++i) { m = A2( Matrix.multiply, m, matrices[i] ); }
    m = A2( Matrix.multiply, m, formToMatrix(form) );

    return 'matrix(' +   m[0]  + ',' +   m[3]  + ',' +
                       (-m[1]) + ',' + (-m[4]) + ',' +
                         m[2]  + ',' +   m[5]  + ')';
}

function stepperHelp(list) {
    var arr = fromList(list);
    var i = 0;
    function peekNext() {
        return i < arr.length ? arr[i].form.ctor : '';
    }
    // assumes that there is a next element
    function next() {
        var out = arr[i];
        ++i;
        return out;
    }
    return { peekNext:peekNext, next:next };
}

function stepper(forms) {
    var ps = [stepperHelp(forms)];
    var matrices = [];
    function peekNext() {
        var len = ps.length;
        var formType = '';
        for (var i = 0; i < len; ++i ) {
            if (formType = ps[i].peekNext()) return formType;
        }
        return '';
    }
    // assumes that there is a next element
    function next(ctx) {
        while (!ps[0].peekNext()) { ps.shift(); matrices.pop(); ctx.restore(); }
        var out = ps[0].next();
        var f = out.form;
        if (f.ctor === 'FGroup') {
            ps.unshift(stepperHelp(f._1));
            var m = A2( Matrix.multiply, f._0, formToMatrix(out));
            ctx.save();
            ctx.transform(m[0], m[3], m[1], m[4], m[2], m[5]);
            matrices.push(m);
        }
        return out;
    }
    function transforms() { return matrices; }
    return { peekNext:peekNext, next:next, transforms:transforms };
}

function makeCanvas(w,h) {
    var canvas = newElement('canvas');
    canvas.style.width  = w + 'px';
    canvas.style.height = h + 'px';
    canvas.style.display = "block";
    canvas.style.position = "absolute";
    canvas.width  = w;
    canvas.height = h;
    return canvas;
}

function render(model) {
    var div = newElement('div');
    update(div, model, model);
    return div;
}

function updateTracker(w,h,div) {
    var kids = div.childNodes;
    var i = 0;
    function transform(transforms, ctx) {
        ctx.translate(w/2, h/2);
        var len = transforms.length;
        for (var i = 0; i < len; ++i) {
            var m = transforms[i];
            ctx.save();
            ctx.transform(m[0], m[3], m[1], m[4], m[2], m[5]);
        }
        return ctx;
    }
    function getContext(transforms) {
        while (i < kids.length) {
            var node = kids[i++];
            if (node.getContext) {
                node.width = w;
                node.height = h;
                node.style.width = w + 'px';
                node.style.height = h + 'px';
                return transform(transforms, node.getContext('2d'));
            }
            div.removeChild(node);
        }
        var canvas = makeCanvas(w,h);
        div.appendChild(canvas);
        // we have added a new node, so we must step our position
        ++i;
        return transform(transforms, canvas.getContext('2d'));
    }
    function element(matrices, form) {
        var container = kids[i];
        if (!container || container.getContext) {
            container = newElement('div');
            container.style.overflow = 'hidden';
            container.style.position = 'absolute';
            addTransform(container.style, 'scaleY(-1)');
            if (!container) {
                div.appendChild(container);
            } else {
                div.insertBefore(container, kids[i]);
            }
        }
        // we have added a new node, so we must step our position
        ++i;

        container.style.width = w + 'px';
        container.style.height = h + 'px';

        var elem = form.form._0;
        var node = container.firstChild;
        if (node) {
            Render.update(node, node.oldElement, elem);
        } else {
            node = Render.render(elem);
            container.appendChild(node);
        }
        node.oldElement = elem;
        addTransform(node.style, makeTransform(w, h, form, matrices));
    }
    return { getContext:getContext, element:element };
}


function update(div, _, model) {
    var w = model.w;
    var h = model.h;
    div.style.width = w + 'px';
    div.style.height = h + 'px';
    if (model.forms.ctor === 'Nil') {
        while (div.hasChildNodes()) {
            div.removeChild(div.lastChild);
        }
    }
    var stpr = stepper(model.forms);
    var tracker = updateTracker(w,h,div);
    var ctx = null;
    var formType = '';

    while (formType = stpr.peekNext()) {
        if (ctx === null && formType !== 'FElement') {
            ctx = tracker.getContext(stpr.transforms());
            ctx.scale(1,-1);
        }
        var form = stpr.next(ctx);
        if (formType === 'FElement') {
            tracker.element(stpr.transforms(), form);
            ctx = null;
        } else if (formType !== 'FGroup') {
            renderForm(function() { update(div, model, model); }, ctx, form);
        }
    }
    return div;
}

return { render:render, update:update };

};