using System.Text.Json;
using OSMDatastructure;
using OSMDatastructure.Graph;

namespace Pathfinding
{
    public class RegionManager
    {
        private string workingDirectory { get; }
        private readonly Dictionary<ulong, Region> _regions = new();

        public RegionManager(string workingDirectory)
        {
            this.workingDirectory = workingDirectory;
        }

        public Region? GetRegion(Coordinates coordinates)
        {
            return GetRegion(Coordinates.GetRegionHashCode(coordinates));
        }

        public Region? GetRegion(ulong id)
        {
            if(_regions.TryGetValue(id, out Region? value))
                return value;
            else
            {
                Region? loadedRegion = RegionFromId(id);
                if(loadedRegion is not null)
                    _regions.Add(loadedRegion!.regionHash, value: loadedRegion);
                return loadedRegion;
            }
        }

        public Region[] GetAllRegions()
        {
            return this._regions.Values.ToArray();
        }

        private Region? RegionFromFile(string filePath)
        {
            Region? retRegion = null;
            if (File.Exists(filePath))
            {
                FileStream regionFile = new FileStream(filePath, FileMode.Open);
                retRegion = JsonSerializer.Deserialize<Region>(regionFile, Region.serializerOptions)!;
                regionFile.Dispose();
            }
            return retRegion;
        }

        private Region? RegionFromId(ulong regionId)
        {
            string filePath = Path.Join(workingDirectory, $"{regionId}.region");
            return RegionFromFile(filePath);
        }

        public OsmNode? GetNode(ulong nodeId, ulong regionId)
        {
            Region? r = GetRegion(regionId);
            return r?.GetNode(nodeId);
        }

        public bool TestValidConnectionForType(OsmNode node1, OsmNode node2, Tag.SpeedType type)
        {
            foreach (OsmEdge edge in node1.edges)
            {
                if (edge.neighborId.Equals(node2.nodeId))
                    return TestValidConnectionForType(node1, edge, type);
            }

            return false;
        }

        public bool TestValidConnectionForType(OsmNode node1, OsmEdge edge, Tag.SpeedType type)
        {
            if (type == Tag.SpeedType.any)
                return true;
            byte speed = GetSpeedForEdge(node1, edge.wayId, type);
            return (speed is not 0);
        }
        
        public OsmNode? ClosestNodeToCoordinates(Coordinates coordinates, Tag.SpeedType vehicle)
        {
            OsmNode? closest = null;
            double distance = double.MaxValue;
            Region? region = GetRegion(coordinates);
            if (region is null)
                return null;
            foreach (OsmNode node in region.nodes)
            {
                bool hasConnectionUsingVehicle = true;
                if (vehicle is not Tag.SpeedType.any)
                {
                    hasConnectionUsingVehicle = false;
                    foreach (OsmEdge edge in node.edges)
                    {
                        byte speed = GetSpeedForEdge(node, edge.wayId, vehicle);
                        if (speed != 0)
                            hasConnectionUsingVehicle = true;
                    }
                }
                
                double nodeDistance = Utils.DistanceBetween(node, coordinates);
                if (nodeDistance < distance && hasConnectionUsingVehicle)
                {
                    closest = node;
                    distance = nodeDistance;
                }
            }

            return closest;
        }
        
        public byte GetSpeedForEdge(OsmNode node1, ulong wayId, Tag.SpeedType vehicle)
        {
            TagManager tags = GetRegion(node1.coordinates)!.tagManager;
            Tag.WayType wayType = (Tag.WayType)tags.GetTag(wayId, Tag.TagType.highway)!;
            byte speed = 0;
            switch (vehicle)
            {
                case Tag.SpeedType.pedestrian:
                    speed = Tag.defaultSpeedPedestrian[wayType];
                    return speed is not 0 ? speed : (byte)0;
                case Tag.SpeedType.car: 
                    byte? maxSpeed = (byte?)tags.GetTag(wayId, Tag.TagType.maxspeed);
                    speed = Tag.defaultSpeedCar[wayType];
                    return maxSpeed < speed ? (byte)maxSpeed : speed;
                case Tag.SpeedType.any:
                    return 1;
                default:
                    return 0;
            }
        }
    }
}