open System
open System.IO

let convertDataRow(csvLine:string) =
    let cells = List.ofSeq(csvLine.Split(','))
    match cells with
    | title::number::_ ->
        let parsedNumber = Int32.Parse(number)
        (title, parsedNumber)
    | _ -> failwith "Incorrect data format!"

let rec processLines(lines) =
    match lines with
    | [] -> []
    | currentLine::remaining ->
        let parsedLine = convertDataRow(currentLine)
        let parsedRest = processLines(remaining)
        parsedLine :: parsedRest

let rec calculateSum(rows) =
    match rows with
    | [] -> 0
    | (_, value)::tail ->
        let remainingSum = calculateSum(tail)
        value + remainingSum

let lines = List.ofSeq(File.ReadAllLines(@"E:\dane.csv"))
let data = processLines(lines)

open System.Drawing
open System.Windows.Forms
let mainForm = new Form(Width = 620, Height = 450, Text = "Pie Chart")
let menu = new ToolStrip()
let btnOpen = new ToolStripButton("Open")
let btnSave = new ToolStripButton("Save", Enabled = false)
ignore(menu.Items.Add(btnOpen))
ignore(menu.Items.Add(btnSave))
let boxChart = new PictureBox(BackColor = Color.White, Dock =
    DockStyle.Fill, SizeMode = PictureBoxSizeMode.CenterImage)
mainForm.Controls.Add(menu)
mainForm.Controls.Add(boxChart)

let rnd = new Random()
let randomBrush() =
    let r, g, b = rnd.Next(256), rnd.Next(256), rnd.Next(256)
    new SolidBrush(Color.FromArgb(r,g,b))

let fnt = new Font("Times New Roman", 11.0f)
let centerX, centerY = 300.0, 200.0
let labelDistance = 150.0

let drawLabel(gr:Graphics, title, startAngle, angle) =
    let lblAngle = float(startAngle + angle/2)
    let ra = Math.PI * 2.0 * lblAngle / 360.0
    let x = centerX + labelDistance * cos(ra)
    let y = centerY + labelDistance * sin(ra)
    let size = gr.MeasureString(title, fnt)
    let rc = new PointF(float32(x) - size.Width / 2.0f, float32(y) - size.Height / 2.0f)
    gr.DrawString(title, fnt, Brushes.Black, new RectangleF(rc, size))

let drawPieSegment(gr:Graphics, title, startAngle, occupiedAngle) =
    let br = randomBrush()
    gr.FillPie(br, 170, 70, 260, 260, startAngle, occupiedAngle)
    br.Dispose()

let drawStep(drawingFunc, gr:Graphics, sum, data) =
    let rec drawStepUtil(data, angleSoFar) =
        match data with
        | [] -> ()
        | [title, value] ->
            let angle = 360 - angleSoFar
            drawingFunc(gr, title, angleSoFar, angle)
        | (title, value)::tail ->
            let angle = int(float(value) / sum * 360.0)
            drawingFunc(gr, title, angleSoFar, angle)
            drawStepUtil(tail, angleSoFar + angle)
    drawStepUtil(data, 0)

let drawChart(file) =
    let lines = List.ofSeq(File.ReadAllLines(file))
    let data = processLines(lines)
    let sum = float(calculateSum(data))
    let pieChart = new Bitmap(600, 400)
    let gr = Graphics.FromImage(pieChart)
    gr.Clear(Color.White)
    drawStep(drawPieSegment, gr, sum, data)
    drawStep(drawLabel, gr, sum, data)
    gr.Dispose()
    pieChart


let openAndDrawChart(e) =
    let dlg = new OpenFileDialog(Filter="CSV Files|*.csv")
    if (dlg.ShowDialog() = DialogResult.OK) then
        let pieChart = drawChart(dlg.FileName)
        boxChart.Image <- pieChart
        btnSave.Enabled <- true

let saveDrawing(e) =
    let dlg = new SaveFileDialog(Filter="PNG Files|*.png")
    if (dlg.ShowDialog() = DialogResult.OK) then
    boxChart.Image.Save(dlg.FileName)

[<STAThread>]
do
    btnOpen.Click.Add(openAndDrawChart)
    btnSave.Click.Add(saveDrawing)
    Application.Run(mainForm)