using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Numerics;
using Godot;
using Vector2 = Godot.Vector2;
using Vector3 = Godot.Vector3;
using GoDotLog;

/// <summary>
/// </summary>
public class NavigationComponent : Node
{
    public class NavigationPoint
    {
        [Flags]
        public enum NavigationFlags
        {
            Position = 1,
            Orientation = 2
        }

        public Vector3 WorldPosition = Vector3.Zero;
        public Quat WorldOrientation = Quat.Identity;
        public NavigationFlags Flags = NavigationFlags.Position | NavigationFlags.Orientation;

        public NavigationPoint(Vector3 worldPosition)
        {
            WorldPosition = worldPosition;
            Flags = NavigationFlags.Position;
        }

        public NavigationPoint(Quat worldOrientation)
        {
            WorldOrientation = worldOrientation;
            Flags = NavigationFlags.Orientation;
        }

        public NavigationPoint(Transform worldTransform)
        {
            WorldPosition = worldTransform.origin;
            WorldOrientation = worldTransform.basis.Quat();
            Flags = NavigationFlags.Position | NavigationFlags.Orientation;
        }

        public bool IsReached(Transform worldTransform)
        {
            bool goalReached = false;
            float positionErrorSquared = (worldTransform.origin - WorldPosition).LengthSquared();
            Quat own_orientation = worldTransform.basis.Quat();
            float orientationError = Mathf.Abs(worldTransform.basis.Quat().AngleTo(WorldOrientation));

            if (Flags.HasFlag(NavigationPoint.NavigationFlags.Position)
                && Flags.HasFlag(NavigationPoint.NavigationFlags.Orientation)
                && positionErrorSquared < Globals.EpsPositionSquared
                && orientationError < Globals.EpsRadians)
            {
                goalReached = true;
            }
            else if (Flags == NavigationPoint.NavigationFlags.Position &&
                     positionErrorSquared < Globals.EpsPositionSquared)
            {
                goalReached = true;
            }
            else if (Flags == NavigationPoint.NavigationFlags.Orientation &&
                     orientationError < Globals.EpsRadians)
            {
                goalReached = true;
            }

            return goalReached;
        }
    }

    public TileWorld TileWorld { set; get; }

    public Vector3 CurrentGoalPositionWorld => _currentGoalPositionWorld;
    public Quat CurrentGoalOrientationWorld => _currentGoalOrientationWorld;

    private NavigationPoint _currentGoal;
    private Vector3 _currentGoalPositionWorld = Vector3.Zero;
    private Quat _currentGoalOrientationWorld = Quat.Identity;
    
    private List<NavigationPoint> _pathWorldNavigationPoints;
    private HexCell[] _path;

    public override void _Ready()
    {
        base._Ready();
        _pathWorldNavigationPoints = new List<NavigationPoint>();
    }

    public override void _Process(float delta)
    {
        Debug.Assert(TileWorld != null);
    }


    public void Plan(Vector3 fromPositionWorld, Vector3 toPositionWorld)
    {
        Vector2 fromPositionOffset = TileWorld.WorldToOffsetCoords(fromPositionWorld);
        Vector2 toPositionOffset = TileWorld.WorldToOffsetCoords(toPositionWorld);

        HexCell fromCell = new HexCell();
        fromCell.OffsetCoords = fromPositionOffset;

        HexCell toCell = new HexCell();
        toCell.OffsetCoords = toPositionOffset;

        _path = fromCell.LineTo(toCell);
        Debug.Assert(_path.Length > 0);

        _pathWorldNavigationPoints = new List<NavigationPoint>();
        foreach (int index in Enumerable.Range(1, _path.Length - 1))
        {
            _pathWorldNavigationPoints.Add(
                new NavigationPoint(TileWorld.GetTileWorldCenterFromOffset(_path[index].OffsetCoords)));
        }

        if ((toPositionWorld - TileWorld.GetTileWorldCenterFromOffset(toCell.OffsetCoords)).LengthSquared() >
            Globals.EpsPositionSquared)
        {
            // Remove the last one, because it is only the position rounded to HexGrid coordinates.
            if (_pathWorldNavigationPoints.Count > 0)
            {
                _pathWorldNavigationPoints.RemoveAt(_pathWorldNavigationPoints.Count - 1);
            }
            _pathWorldNavigationPoints.Add(new NavigationPoint(toPositionWorld));
        }

        UpdateCurrentGoal();
    }


    public void Plan(Vector3 fromPositionWorld, Vector3 toPositionWorld, Quat toWorldOrientation)
    {
        Plan(fromPositionWorld, toPositionWorld);

        _pathWorldNavigationPoints.Add(new NavigationPoint(toWorldOrientation));
    }


    public void Plan(Transform fromTransformWorld, NavigationPoint navigationPoint)
    {
        if (navigationPoint.Flags.HasFlag(NavigationPoint.NavigationFlags.Position)
            && navigationPoint.Flags.HasFlag(NavigationPoint.NavigationFlags.Orientation))
        {
            Plan(fromTransformWorld.origin, navigationPoint.WorldPosition, navigationPoint.WorldOrientation);
        } else if (navigationPoint.Flags.HasFlag(NavigationPoint.NavigationFlags.Position))
        {
            Plan(fromTransformWorld.origin, navigationPoint.WorldPosition);
        } else
        {
            throw new NotImplementedException();
        }
    }


    private void UpdateCurrentGoal()
    {
        if (_pathWorldNavigationPoints.Count == 0)
        {
            return;
        }

        _currentGoal = _pathWorldNavigationPoints[0];
        _currentGoalPositionWorld = _pathWorldNavigationPoints[0].WorldPosition;     
        _currentGoalOrientationWorld = _pathWorldNavigationPoints[0].WorldOrientation;

//        GD.Print("Navigation Goal: pos " + _currentGoal.WorldPosition + " " + " rot: " + _currentGoal.WorldOrientation +
//                 " flags: " + _currentGoal.Flags + " path length: " +
//                 _pathWorldNavigationPoints.Count);
    }

    private void ApplyExistingTransform(Transform worldTransform)
    {
        if (_currentGoal.Flags == NavigationPoint.NavigationFlags.Orientation)
        {
            _currentGoalPositionWorld = worldTransform.origin;
        } else if (_currentGoal.Flags == NavigationPoint.NavigationFlags.Position)
        {
            _currentGoalOrientationWorld = worldTransform.basis.Quat();
        }
    }

    
    public void UpdateCurrentGoal(Transform currentTransformWorld)
    {
        if (_pathWorldNavigationPoints.Count == 0)
        {
            _currentGoalOrientationWorld = currentTransformWorld.basis.Quat();
            _currentGoalPositionWorld = currentTransformWorld.origin;
            return;
        }

        if (_currentGoal.Flags.HasFlag(NavigationPoint.NavigationFlags.Position))
        {
            _currentGoalPositionWorld = _pathWorldNavigationPoints[0].WorldPosition;            
        }
        else
        {
            _currentGoalPositionWorld = currentTransformWorld.origin;
        }

        if (_currentGoal.Flags.HasFlag(NavigationPoint.NavigationFlags.Orientation))
        {
            _currentGoalOrientationWorld = _currentGoal.WorldOrientation;
        }
        else
        {
            _currentGoalOrientationWorld = currentTransformWorld.basis.Quat();
        }

        if (_currentGoal.IsReached(currentTransformWorld))
        {
            _pathWorldNavigationPoints.RemoveAt(0);
            
            UpdateCurrentGoal();
            ApplyExistingTransform(currentTransformWorld);

        }

        if (_pathWorldNavigationPoints.Count == 0)
        {
            _currentGoalOrientationWorld = currentTransformWorld.basis.Quat();
            _currentGoalPositionWorld = currentTransformWorld.origin;
        }
    }
}