using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace AsyncCalcPiWithBackgroundWorkerSample {

  partial class AsyncCalcPiForm : Form {
    public AsyncCalcPiForm() {
      InitializeComponent();
    }

    void ShowProgress(string pi, int totalDigits, int digitsSoFar) {
      // Make sure we're on the UI thread
      Debug.Assert(this.InvokeRequired == false);

      // Display progress in UI
      this.resultsTextBox.Text = pi;
      this.calcToolStripProgressBar.Maximum = totalDigits;
      this.calcToolStripProgressBar.Value = digitsSoFar;
    }

    class CalcPiUserState {
      public readonly string Pi;
      public readonly int TotalDigits;
      public readonly int DigitsSoFar;

      public CalcPiUserState(string pi, int totalDigits, int digitsSoFar) {
        this.Pi = pi;
        this.TotalDigits = totalDigits;
        this.DigitsSoFar = digitsSoFar;
      }
    }

    void CalcPi(int digits) {
      StringBuilder pi = new StringBuilder("3", digits + 2);

      // Report initial progress
      this.backgroundWorker.ReportProgress(0,
        new CalcPiUserState(pi.ToString(), digits, 0));

      if( digits > 0 ) {
        pi.Append(".");

        for( int i = 0; i < digits; i += 9 ) {
          int nineDigits = NineDigitsOfPi.StartingAt(i + 1);
          int digitCount = Math.Min(digits - i, 9);
          string ds = string.Format("{0:D9}", nineDigits);
          pi.Append(ds.Substring(0, digitCount));

          // Report continuing progress
          this.backgroundWorker.ReportProgress(0,
            new CalcPiUserState(pi.ToString(), digits, i + digitCount));

          // Check for cancelation
          if( this.backgroundWorker.CancellationPending ) { return; }
        }
      }
    }

    void calcButton_Click(object sender, EventArgs e) {
      // Don't process if cancel request pending
      // (Should not be called, since we disabled the button...)
      if( this.backgroundWorker.CancellationPending ) { return; }

      // If worker thread currently executing, cancel it
      if( this.backgroundWorker.IsBusy ) {
        this.calcButton.Enabled = false;
        this.backgroundWorker.CancelAsync();
        return;
      }

      // Set calculating UI
      this.calcButton.Text = "Cancel";
      this.calcToolStripProgressBar.Visible = true;
      this.calcToolStripStatusLabel.Text = "Calculating...";

      // Begin calculating pi asynchronously
      this.backgroundWorker.RunWorkerAsync(
        (int)this.decimalPlacesNumericUpDown.Value);
    }

    void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) {
      //throw new Exception("Ooops!");

      // Track start time
      DateTime start = DateTime.Now;

      CalcPi((int)e.Argument);

      // Indicate cancelation
      if( this.backgroundWorker.CancellationPending ) {
        e.Cancel = true;
      }

      // Return elapsed time
      DateTime end = DateTime.Now;
      TimeSpan elapsed = end - start;
      e.Result = elapsed;
    }

    void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) {
      // Show progress
      CalcPiUserState progress = (CalcPiUserState)e.UserState;
      ShowProgress(
        progress.Pi, progress.TotalDigits, progress.DigitsSoFar);
    }

    void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
      // Reset progress UI
      this.calcButton.Text = "Calculate";
      this.calcButton.Enabled = true;
      this.calcToolStripStatusLabel.Text = "Ready";
      this.calcToolStripProgressBar.Visible = false;

      // Was the worker thread cancelled?
      if( e.Cancelled ) {
        this.resultsTextBox.Text = "Canceled";
        return;
      }

      // Show elapsed time
      TimeSpan elapsed = (TimeSpan)e.Result;
      MessageBox.Show("Elapsed: " + elapsed.ToString());
    }

  }
}