// 
//     Kerbal Engineer Redux
// 
//     Copyright (C) 2014 CYBUTEK
// 
//     This program is free software: you can redistribute it and/or modify
//     it under the terms of the GNU General Public License as published by
//     the Free Software Foundation, either version 3 of the License, or
//     (at your option) any later version.
// 
//     This program is distributed in the hope that it will be useful,
//     but WITHOUT ANY WARRANTY; without even the implied warranty of
//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//     GNU General Public License for more details.
// 
//     You should have received a copy of the GNU General Public License
//     along with this program.  If not, see <http://www.gnu.org/licenses/>.
// 
 
#region Using Directives
 
using System;
using KerbalEngineer.Flight.Sections;
using KerbalEngineer.Helpers;
using KerbalEngineer.Extensions;
 
#endregion
 
namespace KerbalEngineer.Flight.Readouts.Orbital
{
    public class SpeedAtPeriapsis : ReadoutModule
    {
        #region Constructors
 
        public SpeedAtPeriapsis()
        {
            this.Name = "Speed at Periapsis";
            this.Category = ReadoutCategory.GetCategory("Orbital");
            this.HelpString = "Shows the orbital speed of the vessel when at periapsis, the lowest point of the orbit.";
            this.IsDefault = false;
        }
 
        #endregion
 
        #region Methods: public
 
        public override void Draw(SectionModule section)
        {
            // Vis-viva: v^2 = GM(2/r - 1/a)
            // All this is easily got from the ships orbit (and reference body)
            String str;
            Orbit orbit = FlightGlobals.ship_orbit;
            double oneovera = (orbit.eccentricity == 1) ? 0 : (1 / orbit.semiMajorAxis);
            double speedsqr = orbit.referenceBody.gravParameter * ((2 / orbit.PeR) - oneovera);
            if (Double.IsNaN(speedsqr) || speedsqr < 0)
                str = "---m/s";
            else
                str = Math.Sqrt(speedsqr).ToSpeed();
            this.DrawLine(str, section.IsHud);
        }
 
        #endregion
    }
}