Openlayers ol.interaction.Draw stroke style - reactjs

Question

I have the this jsfiddle, it has the ability to draw a polygon on a map which works perfectly. What I can't figure out is how to style the .Draw interaction.
Currently I have a dashed line for the sections of the polygon that the users has already draw and another dashed line connecting the first drawn point to the last drawn point.
When I write styles it seems to effect both lines.
What I need to have is a dashed black line joining points the user has already drawn, and no line (fully transparent) for the line connecting the last drawn point back to the first drawn point.
This is my current style object:
style: new ol.style.Style({
stroke: new ol.style.Stroke({
color: 'rgba(0, 0, 0, 0.5)',
lineDash: [10, 10],
width: 3
}),
image: new ol.style.Circle({
fill: new ol.style.Fill({ color: [0, 0, 0, 0.2] }),
stroke: new ol.style.Stroke({
color: [0, 0, 0, 0.5],
width: 1
}),
radius: 4
})
})
I have tried adding arrays of colours and styles but can't seem to get it working.
Has anyone come across this and found a fix?

Answer 1

Ok I have cracked this one, I had to take a dive into the library's source to figure it out, so I'm gonna post the answer here in the hope it helps somebody else in the future, so here goes:
What I could see looking as the source code was that when you are using ol.interaction.Draw to draw a polygon there are multiple pieces of geometry being used. There is the underlying Polygon, this is the bit that has a stroke and fill and shows the connecting line (based on it's stroke style). There is a LineString which shows a line for the points the user has drawn only (no fill and no connecting line). And there is a point, which is attached to the mouse pointer. I have left a `console.log()' in the jsfiddle to show all this.
I have created this working jsfiddle. What I have done is, rather than set the styles directly inside ol.interaction.Draw I have used a styleFunction (see code below). I detect each geometry by type and set a specific style for it.
const styleFunction = feature => {
var geometry = feature.getGeometry();
console.log('geometry', geometry.getType());
if (geometry.getType() === 'LineString') {
var styles = [
new ol.style.Style({
stroke: new ol.style.Stroke({
color: 'rgba(255, 102, 0, 1)',
width: 3
})
})
];
return styles;
}
if (geometry.getType() === 'Polygon') {
var styles = [
new ol.style.Style({
stroke: new ol.style.Stroke({
color: 'rgba(255, 102, 0, 0)',
width: 3
}),
fill: new ol.style.Fill({
color: 'rgba(255, 102, 0, 0.3)'
})
})
];
return styles;
}
return false;
};
Hope this helps 🤓