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

namespace OSMImporter
{
    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();
        }

        public OsmNode? GetNode(Coordinates coordinates)
        {
            Region? regionWithNode = GetRegion(coordinates);
            if (regionWithNode is not null)
                return regionWithNode.GetNode(coordinates);
            else return null;
        }

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