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 AsyncCalcPiSample {

  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;

      if( digitsSoFar == totalDigits ) {
        // Reset UI
        this.calcToolStripStatusLabel.Text = "Ready";
        this.calcToolStripProgressBar.Visible = false;
      }

      // No need to force UI update when calculating asynchronously
      //this.Refresh();
    }

    delegate void ShowProgressDelegate(
      string pi, int totalDigits, int digitsSoFar);

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

      // Show progress
      //ShowProgress(pi.ToString(), digits, 0);

      // Get ready to show progress
      ShowProgressDelegate showProgress =
        new ShowProgressDelegate(ShowProgress);

      // Show initial progress asynchronously
      this.BeginInvoke(
        showProgress,
        new object[] { 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));

          // Show continuing progress
          //ShowProgress(pi.ToString(), digits, i + digitCount);

          // Show continuing progress asynchronously
          this.BeginInvoke(
           showProgress,
            new object[] { pi.ToString(), digits, i + digitCount });
        }
      }
    }

    delegate void CalcPiDelegate(int digits);

    void calcButton_Click(object sender, EventArgs e) {
      // Set calculating UI
      this.calcToolStripProgressBar.Visible = true;
      this.calcToolStripStatusLabel.Text = "Calculating...";

      // Start pi calculation on new thread of execution
      //Thread piThread = new Thread(CalcPiThreadStart);
      //piThread.Start((int)this.decimalPlacesNumericUpDown.Value);

      // Begin calculating pi synchronously
      //CalcPiDelegate calcPi = new CalcPiDelegate(CalcPi);
      //calcPi((int)this.decimalPlacesNumericUpDown.Value);

      // Begin calculating pi asynchronously
      CalcPiDelegate calcPi = new CalcPiDelegate(CalcPi);
      calcPi.BeginInvoke(
        (int)this.decimalPlacesNumericUpDown.Value, // CalcPi argument
        EndCalcPi, // Called when CalcPi completes
        calcPi); // EndCalcPi argument (indirectly)
    }

    void EndCalcPi(IAsyncResult ar) {
      // Harvest results, re-thrown exceptions and clean-up resources
      try {
        CalcPiDelegate calcPi = (CalcPiDelegate)ar.AsyncState;
        calcPi.EndInvoke(ar);
      }
      catch( Exception ex ) {
        // EndCalcPi executed on worker thread
        //ShowProgress(ex.Message, 0, 0); // ERR!

        // Show error
        ShowProgressDelegate showProgress =
          new ShowProgressDelegate(ShowProgress);
        this.BeginInvoke(
          showProgress,
          new object[] { ex.Message, 0, 0 });
      }
    }

    //void CalcPiThreadStart(object digits) {
    //  // Convert thread start parameter to int
    //  CalcPi((int)digits);
    //}

  }
}