using System.Collections.Generic;
using OpenBveApi.Runtime;

namespace OpenbveFcmbTrainPlugin
{
    internal class Route
    {
        /// <summary>Represents the state of the current station.</summary>
        internal enum StationStates
        {
            /// <summary>The train has not arrived at the station yet.</summary>
            Pending = 0,
            /// <summary>The train has arrived at the station.</summary>
            Arrived = 1,
            /// <summary>The train is ready to depart.</summary>
            Completed = 2,
        }

        /// <summary>The state of the current station.</summary>
        internal StationStates StationState { get; private set; } = StationStates.Arrived;

        /// <summary>The list of stations in the route.</summary>
        internal List<Station> Stations;

        /// <summary>The current station in the route.</summary>
        internal Station CurrentStation;

        /// <summary>The next station in the route.</summary>
        internal Station NextStation;

        /// <summary>The current state of the train doors.</summary>
        private DoorStates DoorState;

        /// <summary>The previous state of the train doors.</summary>
        private DoorStates PreviousDoorState;

        /// <summary>Is called every frame.</summary>
        /// <param name="data">The data passed to the plugin.</param>
        internal void Elapse(ElapseData data)
        {
            if (OpenbveFcmbTrainPlugin.Initializing)
            {
                // Get the list of stations and set the current station
                Stations = data.Stations;
                UpdateStationData(data.Vehicle.Location);
            }

            if (StationState == StationStates.Completed && data.Vehicle.Location > CurrentStation.StopPosition + CurrentStation.ForwardTolerance)
            {
                // The train is heading for the next station
                StationState = StationStates.Pending;
                UpdateStationData(data.Vehicle.Location);
            }

            if (StationState == StationStates.Pending && data.Vehicle.Location > CurrentStation.StopPosition + CurrentStation.ForwardTolerance + 100)
            {
                // The train has passed the station without stopping
                UpdateStationData(data.Vehicle.Location);
            }

            // Update station status after closing the doors
            if (StationState == StationStates.Arrived && DoorState == DoorStates.None)
            {
                // The train is ready to leave the station
                StationState = StationStates.Completed;
            }

            // Check if the train is at a station where the doors should open
            bool ArrivedDoorStop = (PreviousDoorState == DoorStates.None && DoorState != DoorStates.None && (CurrentStation.OpenLeftDoors || CurrentStation.OpenRightDoors));
            // Check if the train is at a station where the doors should not open
            bool ArrivedNoDoorStop = (DoorState == DoorStates.None && !CurrentStation.OpenLeftDoors && !CurrentStation.OpenRightDoors);
            if (StationState == StationStates.Pending && (ArrivedDoorStop || ArrivedNoDoorStop) && data.Vehicle.Speed.KilometersPerHour < 0.05 && data.Vehicle.Location >= CurrentStation.DefaultTrackPosition)
            {
                // The train has arrived at the station
                StationState = StationStates.Arrived;
            }
        }

        /// <summary>Is called when the state of the doors changes.</summary>
        /// <param name="oldState">The old state of the doors.</param>
        /// <param name="newState">The new state of the doors.</param>
        internal void DoorChange(DoorStates oldState, DoorStates newState)
        {
            PreviousDoorState = oldState;
            DoorState = newState;
        }

        /// <summary>Updates the data for the current and next station.</summary>
        /// <param name="location">The current location of the train.</param>
        internal void UpdateStationData(double location)
        {
            // Calculate the index of the current station
            double position = location;
            int currentIndex = 0;
            if (Stations.Count > 1)
            {
                while (currentIndex > 0 && (Stations[currentIndex].StopPosition + Stations[currentIndex].ForwardTolerance > position || !Stations[currentIndex].PlayerStops()))
                {
                    // Detects the station index when driving or jumping backwards
                    currentIndex--;
                }
                while (currentIndex < Stations.Count - 1 && (Stations[currentIndex].StopPosition + Stations[currentIndex].ForwardTolerance <= position || !Stations[currentIndex].PlayerStops()))
                {
                    // Detects the station index when driving or jumping forwards
                    currentIndex++;
                }
            }
            CurrentStation = Stations[currentIndex];
            NextStation = currentIndex < Stations.Count - 1 ? Stations[currentIndex + 1] : null;
        }
    }
}