private async void ListView2_SelectedIndexChanged()

in Tools/MultiplayerSessionHistoryViewer/Form1.cs [360:444]
71 lines of code
12 McCabe index (conditional complexity)

        private async void ListView2_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (this.listView2.SelectedIndices.Count > 2)
            {
                return;
            }

            this.rtbSnapshotLeft.Text = string.Empty;
            this.rtbSnapshotRight.Text = string.Empty;
            this.lblChangeLeft.Text = string.Empty;
            this.lblChangeRight.Text = string.Empty;

            if (this.listView2.SelectedIndices.Count > 0)
            {
                int index = 0;
                if (this.listView1.SelectedItems.Count > 0)
                {
                    index = this.listView1.SelectedIndices[0];
                }
                
                var leftIndex = this.listView2.SelectedIndices[0];
                long changeLeft;

                string errMsg = null;

                string leftSnapshot = string.Empty;
                string rightSnapshot = string.Empty;

                if (long.TryParse(this.listView2.Items[leftIndex].SubItems[0].Text, out changeLeft))
                {
                    Tuple<string, string> getSnapshotResponse = await this.QueryForDocSessionHistoryChangeAsync(
                        this.listView1.Items[index].SubItems[0].Text,
                        this.listView1.Items[index].SubItems[1].Text,
                        changeLeft).ConfigureAwait(true);

                    if (getSnapshotResponse.Item1 != null)
                    {
                        this.lblChangeLeft.Text = string.Format("Change #{0}", changeLeft);
                        leftSnapshot = getSnapshotResponse.Item1;
                    }
                    else
                    {
                        errMsg = getSnapshotResponse.Item2;
                    }
                }

                if (errMsg == null && this.listView2.SelectedIndices.Count > 1)
                {
                    long changeRight;
                    var rightIndex = this.listView2.SelectedIndices[1];

                    if (long.TryParse(this.listView2.Items[rightIndex].SubItems[0].Text, out changeRight))
                    {
                        if (!this.showingOfflineSession)
                        {
                            this.lblExplanation.Text = string.Format("Downloading change #{0}", changeRight);
                        }

                        Tuple<string, string> getSnapshotResponse = await this.QueryForDocSessionHistoryChangeAsync(
                            this.listView1.Items[index].SubItems[0].Text,
                            this.listView1.Items[index].SubItems[1].Text,
                            changeRight).ConfigureAwait(true);

                        if (getSnapshotResponse.Item1 != null)
                        {
                            rightSnapshot = getSnapshotResponse.Item1;
                            this.lblChangeRight.Text = string.Format("Change #{0}", changeRight);
                        }
                        else
                        {
                            errMsg = getSnapshotResponse.Item2;
                        }
                    }
                }

                this.ShowDiffs(leftSnapshot, rightSnapshot);

                this.downloadPanel.Hide();

                if (errMsg != null)
                {
                    MessageBox.Show(string.Format("{0}\n\nThe server is busy.\nPlease try again.", errMsg), QueryFailure);
                }
            }
        }