# Calendar Layout Algorithm

This algorithm will calculate top, left, width and height for each event from a list of events so that they can be drawn on a canvas such that none of them overlap visually.

## Algorithm

The most complex bit in the algorithm is `CalLayout.insertEventTree` and `CalLayout.insertEventForest`, which, inserts an event into a tree or forest such that every parent overlaps the children. Afterwards given a list of events, `CalLayout.mkIntersectionsForest` will convert them to a forest by using the two functions above. This will produce a similar forest to:

```
> putStr $ drawForest $ map (fmap show) forest
"P&P Leg Training"
|
`- "Gym Tour"

"12 days of Christmas workout"

"12 days of Christmas workout"
|
`- "12 days of Christmas workout"
```

Now that we have this structure, we need to calculate the `depth` and `maxDepth` of each node. `CalLayout.populateDepths` does exactly that. Viewed as a forest, it looks something like:

```
("P&P Leg Training", 1, 1)
|
`- ("Gym Tour", 1, 0)

("12 days of Christmas workout", 0, 0)

("12 days of Christmas workout", 1, 1)
|
`- ("12 days of Christmas workout", 1, 0)
```

Once we have this data, calculations are straight-forward:

```
top    = start e
left   = width * depth
width  = 100 / (1 + maxDepth)
height = end e - start e
```

As we can see, all this calculation is just for figuring out `left` and `width`, whereas `top` and `height` were easy.

## Prerequisites

Make sure you have [`stack`](https://haskellstack.org/) installed.

## Running

1. Run `stack init`
1. Run `stack run`

For playground, you can use `stack repl`.

Example:

```
$ stack run
("P&P Leg Training",Dimension {top = 600.0, left = 50.0, width = 50.0, height = 60.0})
("Gym Tour",Dimension {top = 600.0, left = 0.0, width = 50.0, height = 15.0})
("12 days of Christmas workout",Dimension {top = 720.0, left = 0.0, width = 100.0, height = 120.0})
("12 days of Christmas workout",Dimension {top = 840.0, left = 50.0, width = 50.0, height = 360.0})
("12 days of Christmas workout",Dimension {top = 1020.0, left = 0.0, width = 50.0, height = 120.0})
```

Copyright 2019, Boro Sitnikovski. All rights reserved.