// 
//     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/>.
// 
 
namespace KerbalEngineer.Flight.Readouts.Vessel
{
    using System;
 
    public class SuicideBurnProcessor : IUpdatable, IUpdateRequest
    {
        private static readonly SuicideBurnProcessor s_Instance = new SuicideBurnProcessor();
        private double m_Acceleration;
        private double m_Gravity;
        private double m_RadarAltitude;
 
        public static double Altitude { get; private set; }
 
        public static double DeltaV { get; private set; }
 
        public static double Distance { get; private set; }
 
        public static SuicideBurnProcessor Instance
        {
            get
            {
                return s_Instance;
            }
        }
 
        public static bool ShowDetails { get; set; }
 
        public void Update()
        {
            if (FlightGlobals.currentMainBody == null || FlightGlobals.ActiveVessel == null || SimulationProcessor.LastStage == null ||
                FlightGlobals.ship_orbit.PeA >= 0.0 || !SimulationProcessor.ShowDetails)
            {
                ShowDetails = false;
                return;
            }
 
            m_Gravity = FlightGlobals.currentMainBody.gravParameter / Math.Pow(FlightGlobals.currentMainBody.Radius, 2.0);
            m_Acceleration = SimulationProcessor.LastStage.thrust / SimulationProcessor.LastStage.totalMass;
            m_RadarAltitude = FlightGlobals.ActiveVessel.terrainAltitude > 0.0
                ? FlightGlobals.ship_altitude - FlightGlobals.ActiveVessel.terrainAltitude
                : FlightGlobals.ship_altitude;
 
            DeltaV = Math.Sqrt((2 * m_Gravity * m_RadarAltitude) + Math.Pow(FlightGlobals.ship_verticalSpeed, 2.0));
            Altitude = Math.Pow(DeltaV, 2.0) / (2.0 * m_Acceleration);
            Distance = m_RadarAltitude - Altitude;
 
            ShowDetails = !double.IsInfinity(Distance);
        }
 
        public bool UpdateRequested { get; set; }
 
        public static void RequestUpdate()
        {
            s_Instance.UpdateRequested = true;
            SimulationProcessor.RequestUpdate();
        }
 
        public static void Reset()
        {
            FlightEngineerCore.Instance.AddUpdatable(SimulationProcessor.Instance);
            FlightEngineerCore.Instance.AddUpdatable(s_Instance);
        }
    }
}