elm axes

main : Element
main = plotAxis 580 300 "time - minutes" "events"

plotAxis w h xLabel yLabel =
    let lineWidth = 2
        labelHeight = 10
        arrowSize = 6
        ylen = toFloat (h-lineWidth-2*arrowSize-4*labelHeight)
        xlen = toFloat (w-lineWidth-2*arrowSize-4*labelHeight)
        maxX = 100
        maxY = 30
        xscale = (xlen - labelHeight) / toFloat maxX
        yscale = (ylen - labelHeight) / toFloat maxY

        axesStyle = { defaultLine | width <- lineWidth, join <- Smooth, cap <- Round }
        axeLines = group <| map (traced axesStyle << path) <| [[(0,0),(0,ylen)], [(0,0),(xlen,0)]]
        
        arrowPoint = scale arrowSize <| filled black <| polygon [(0,0.7), (0.6,-0.3), (0,-0), (-0.6,-0.3)]
        axeArrows = group [move (0, ylen) arrowPoint, move (xlen, 0) <| rotate (degrees 270) arrowPoint]
        
        xLabelForm = move (xlen/2,-2*labelHeight) <| toForm <| plainText xLabel
        yLabelForm = move (-3*labelHeight,ylen/2) <| rotate (degrees 90) <| toForm <| plainText yLabel
        
        xTick i = move (toFloat i * xscale,-lineWidth/2) <| filled black <| rect (lineWidth/2) (lineWidth*2)
        xLabelTicks = group <| map xTick [0..maxX]
        xTickLabel i = scale 0.5 <| move (toFloat i * xscale, -labelHeight) <| toForm <| plainText (show i)
        xTickLabels = group <| map xTickLabel <| map ((*) 4) [0..(maxX // 4)]
        
        yTick i = move (-lineWidth/2, toFloat i * yTickScale) <| filled black <| rect (lineWidth*2) (lineWidth/2) 
        noYTicks = floor (ylen / labelHeight)
        yTickScale = ylen / toFloat noYTicks
        yLabelTicks = group <| map yTick [0..noYTicks-1]
        yTickLabel i = scale 0.5 <| move (-labelHeight, toFloat i * yTickScale*2)
            <| toForm <| plainText <| show <| round <| yTickScale*2 * toFloat i / yscale
        yTickLabels = group <| map yTickLabel <| [0..(noYTicks // 2) - 1]

        axes = group [axeLines, axeArrows, xLabelForm, yLabelForm, xLabelTicks, xTickLabels, yLabelTicks, yTickLabels]

        
        moveOrigin = move (-xlen/2 + lineWidth + 2*labelHeight, -ylen/2 + lineWidth + 2*labelHeight)

    in collage w h [moveOrigin axes]