using System.Text;

namespace OSMDatastructure;

public static class ByteConverter
{
    #region Region
    /*
     * |   regionHash  |     Nodes     |
     * |---------------+---------------+
     * |    8 bytes    | 
     * |     ulong     | 
     */
    public static byte[] GetBytes(Region region)
    {
        int totalNodeBytes = 0;
        HashSet<byte[]> nodes = new();
        foreach (OsmNode node in region.nodes)
        {
            byte[] nodeBytes = GetBytes(node);
            totalNodeBytes += nodeBytes.Length;
            nodes.Add(nodeBytes);
        }

        byte[] retBytes = new byte[sizeof(ulong) + totalNodeBytes];
        Array.Copy(BitConverter.GetBytes(region.regionHash), 0, retBytes, 0, sizeof(ulong));
        int offset = sizeof(ulong);
        foreach (byte[] node in nodes)
        {
            Array.Copy(node, 0, retBytes, offset, node.Length);
            offset += node.Length;
        }

        return retBytes;
    }

    public static Region ToRegion(byte[] bytes)
    {
        Region retRegion = new Region(BitConverter.ToUInt64(bytes, 0));
        int offset = sizeof(ulong);
        while (offset < bytes.Length)
        {
            int size = BitConverter.ToInt32(bytes, offset);
            byte[] nodeBytes = new byte[size];
            Array.Copy(bytes, offset, nodeBytes, 0, size);
            offset += size;
            retRegion.nodes.Add(ToNode(nodeBytes));
        }

        return retRegion;
    }

    #endregion
    
    #region Coordinates

    /*
     * |    Latitude   |   Longitude   |
     * |---------------+---------------+
     * |    4 bytes    |    4 bytes    |
     * |     float     |     float     |
     */

    public static byte[] GetBytes(Coordinates coordinates)
    {
        byte[] retBytes = new byte[8];
        Array.Copy(BitConverter.GetBytes(coordinates.latitude), 0, retBytes, 0, sizeof(float));
        Array.Copy(BitConverter.GetBytes(coordinates.longitude), 0, retBytes, sizeof(float), sizeof(float));
        return retBytes;
    }

    public static Coordinates ToCoordinates(byte[] bytes)
    {
        if (bytes.Length != 8)
            throw new ArgumentException("Needs exactly 8 bytes", nameof(bytes));
        float latitude = BitConverter.ToSingle(bytes, 0);
        float longitude = BitConverter.ToSingle(bytes, sizeof(float));
        return new Coordinates(latitude, longitude);
    }

    #endregion

    #region OsmNode

    /*
     * |     Size      |  Coordinates  |     Edges
     * |---------------+---------------+---------------+
     * |    4 bytes    |    8 bytes    |
     * |      int      |     byte[]    |
     */

    public static byte[] GetBytes(OsmNode node)
    {
        int totalBytes = 4 + 8; //size + Coordinates
        HashSet<byte[]> edges = new();
        foreach (OsmEdge edge in node.edges)
        {
            edges.Add(GetBytes(edge));
        }

        byte[] retBytes = new byte[totalBytes];
        Array.Copy(BitConverter.GetBytes(totalBytes), retBytes, 4);
        Array.Copy(GetBytes(node.coordinates), 0, retBytes, 4, 8);
        int offset = 4 + 8;
        foreach (byte[] edgeBytes in edges)
        {
            Array.Copy(edgeBytes, 0, retBytes, offset, edgeBytes.Length);
            offset += edgeBytes.Length;
        }

        return retBytes;
    }

    public static OsmNode ToNode(byte[] bytes)
    {
        byte[] coordinateBytes = new byte[8];
        Array.Copy(bytes, 4, coordinateBytes, 0, 8);
        Coordinates coordinates = ToCoordinates(coordinateBytes);

        OsmNode retNode = new OsmNode(coordinates);

        int offset = sizeof(int) + 8;
        while (offset < bytes.Length)
        {
            int tagsSize = BitConverter.ToInt32(bytes, offset);
            byte[] edgeBytes = new byte[sizeof(int) + 8 + tagsSize];
            Array.Copy(bytes, offset, edgeBytes, 0, edgeBytes.Length);
            offset += edgeBytes.Length;
            retNode.edges.Add(ToEdge(edgeBytes));
        }

        return retNode;
    }

    #endregion

    #region OsmEdge

    /* Edge:
     * |    tagsSize   | neighborCoord |     tags
     * |---------------+---------------+--------------
     * |    4 bytes    |    8 bytes    |
     * |      int      |     byte[]    |
     *
     */

    public static byte[] GetBytes(OsmEdge edge)
    {
        int totalBytes = sizeof(int) + 8; //size + Coordinates
        int offset = totalBytes;

        int tagsSize = 0;
        HashSet<byte[]> tags = new();
        foreach (KeyValuePair<OsmEdge.tagType, object> kv in edge.tags)
        {
            byte[] tagBytes = GetBytes(kv);
            tags.Add(tagBytes);
            tagsSize += tagBytes.Length;
        }

        byte[] retBytes = new byte[totalBytes];
        Array.Copy(BitConverter.GetBytes(tagsSize), retBytes, 4);
        Array.Copy(GetBytes(edge.neighborCoordinates), 0, retBytes, sizeof(int), 8);

        foreach (byte[] tag in tags)
        {
            Array.Copy(tag, 0, retBytes, offset, tag.Length);
            offset += tag.Length;
        }

        return retBytes;
    }

    public static OsmEdge ToEdge(byte[] bytes)
    {
        byte[] coordinateBytes = new byte[8];
        Array.Copy(bytes, 4, coordinateBytes, 0, 8);
        Coordinates coordinates = ToCoordinates(coordinateBytes);

        OsmEdge retEdge = new OsmEdge(coordinates);

        int offset = sizeof(int) + 8;
        while (offset < bytes.Length)
        {
            int tagContentSize = BitConverter.ToInt32(bytes, offset);
            byte[] tagBytes = new byte[sizeof(int) + 1 + tagContentSize];
            Array.Copy(bytes, offset, tagBytes, 0, tagBytes.Length);
            offset += tagBytes.Length;
            KeyValuePair<OsmEdge.tagType, object> tag = ToTag(tagBytes);
            retEdge.tags.Add(tag.Key, tag.Value);
        }

        return retEdge;
    }

    #endregion

    #region OsmEdge.Tag
    /*
     * Tag:
     * |  contentSize  |    tagType    |   tagContent
     * |---------------+---------------+---------------
     * |    4 bytes    |     1 byte    |
     * |      int      |      byte     |
     */

    public static byte[] GetBytes(KeyValuePair<OsmEdge.tagType, object> tag)
    {
        byte[] objectBytes = Array.Empty<byte>();
        if (tag.Value.GetType() == Type.GetType("string"))
        {
            objectBytes = Encoding.ASCII.GetBytes((string)tag.Value);
        }
        else if (tag.Value.GetType() == Type.GetType("bool"))
        {
            objectBytes = BitConverter.GetBytes((bool)tag.Value);
        }
        else if (tag.Value.GetType() == Type.GetType("int"))
        {
            objectBytes = BitConverter.GetBytes((int)tag.Value);
        }
        else if (tag.Value.GetType() == Type.GetType("ulong"))
        {
            objectBytes = BitConverter.GetBytes((ulong)tag.Value);
        }
        else if (tag.Value.GetType() == Type.GetType("byte"))
        {
            objectBytes = new[] { (byte)tag.Value };
        }

        byte[] retBytes = new byte[sizeof(int) + 1 + objectBytes.Length];
        Array.Copy(BitConverter.GetBytes(objectBytes.Length), 0, retBytes, 0, sizeof(int));
        retBytes[sizeof(int)] = (byte)tag.Key;
        Array.Copy(objectBytes, 0, retBytes, sizeof(int) + 1, retBytes.Length);
        return retBytes;
    }

    public static KeyValuePair<OsmEdge.tagType, object> ToTag(byte[] bytes)
    {
        OsmEdge.tagType tagType = (OsmEdge.tagType)bytes[sizeof(int)];
        int contentSize = BitConverter.ToInt32(bytes, 0);
        byte[] content = new byte[contentSize];
        Array.Copy(bytes, sizeof(int) + 1, content, 0, contentSize);

        switch (tagType)
        {
            case OsmEdge.tagType.highway:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, (OsmEdge.wayType)content[0]);
            case OsmEdge.tagType.maxspeed:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, content[0]);
            case OsmEdge.tagType.oneway:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, BitConverter.ToBoolean(content));
            case OsmEdge.tagType.forward:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, BitConverter.ToBoolean(content));
            case OsmEdge.tagType.id:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, BitConverter.ToUInt64(content));
            default:
                return new KeyValuePair<OsmEdge.tagType, object>(tagType, content);
        }
    }
    #endregion
}