using System.Text.Json;
using OSMDatastructure;
using OSMDatastructure.Graph;
using SpeedType = OSMDatastructure.Tag.SpeedType;
using WayType = OSMDatastructure.Tag.WayType;

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.ContainsKey(id))
            {
                Region? loadedRegion = RegionFromId(id);
                if (loadedRegion is not null)
                    _regions.TryAdd(loadedRegion.regionHash, loadedRegion);
                return _regions[id]; //return from _regions instead of loadedRegion for multithreading/pointers
            }
            return _regions[id];
        }

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

        private static Region? RegionFromFile(string filePath)
        {
            if (!File.Exists(filePath))
            {
                //throw new FileNotFoundException(filePath);
                return null;
            }

            FileStream regionFile = new (filePath, FileMode.Open, FileAccess.Read, FileShare.Read, (int)new FileInfo(filePath).Length, FileOptions.SequentialScan);
            Region 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, SpeedType type)
        {
            foreach (OsmEdge edge in node1.edges.Where(edge => edge.neighborId.Equals(node2.nodeId)))
            {
                return TestValidConnectionForType(node1, edge, type);
            }

            return false;
        }

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

            return closest;
        }
        
        public byte GetSpeedForEdge(OsmNode node1, ulong wayId, SpeedType vehicle)
        {
            TagManager tags = GetRegion(node1.coordinates)!.tagManager;
            WayType wayType = (WayType)tags.GetTag(wayId, Tag.TagType.highway)!;
            byte speed = 0;
            switch (vehicle)
            {
                case SpeedType.pedestrian:
                    speed = Tag.defaultSpeedPedestrian[wayType];
                    return speed;
                case SpeedType.car: 
                    byte? maxSpeed = (byte?)tags.GetTag(wayId, Tag.TagType.maxspeed);
                    speed = Tag.defaultSpeedCar[wayType];
                    return maxSpeed < speed ? (byte)maxSpeed : speed;
                case SpeedType.any:
                    return 1;
                default:
                    return 0;
            }
        }
        
        public double GetPriorityForVehicle(SpeedType speedType, OsmEdge edge, OsmNode node)
        {
            if (speedType == SpeedType.any)
                return 1;
            Region region = GetRegion(node.coordinates)!;
            WayType? wayType = (WayType?)region.tagManager.GetTag(edge.wayId, Tag.TagType.highway);
            if(wayType is null)
                return 0;
            if (speedType == SpeedType.car)
            {
                switch (wayType)
                {
                    case WayType.motorway:
                    case WayType.motorway_link:
                    case WayType.motorroad:
                        return 20;
                    case WayType.trunk:
                    case WayType.trunk_link:
                    case WayType.primary:
                    case WayType.primary_link:
                        return 10;
                    case WayType.secondary:
                    case WayType.secondary_link:
                    case WayType.tertiary:
                    case WayType.tertiary_link:
                        return 6;
                    case WayType.unclassified:
                    case WayType.residential:
                    case WayType.road:
                    case WayType.living_street:
                        return 2;
                }
            }
        
            if (speedType == SpeedType.pedestrian)
            {
                switch (wayType)
                {
                    case WayType.pedestrian:
                    case WayType.corridor:
                    case WayType.footway:
                    case WayType.path:
                    case WayType.steps:
                    case WayType.residential: 
                    case WayType.living_street:
                        return 10;
                    case WayType.service:
                    case WayType.cycleway:
                    case WayType.bridleway:
                    case WayType.road:
                    case WayType.track:
                    case WayType.unclassified:
                        return 5;
                    case WayType.tertiary:
                    case WayType.tertiary_link:
                    case WayType.escape:
                        return 2;
                }
            }

            return 0;
        }
    }
}