using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
using NodaTime;

namespace Foxnouns.Backend.Database;

public readonly struct Snowflake(ulong value)
{
    public const long Epoch = 1_640_995_200_000; // 2022-01-01 at 00:00:00 UTC
    public readonly ulong Value = value;

    /// <summary>
    /// The time this snowflake was created.
    /// </summary>
    public Instant Time => Instant.FromUnixTimeMilliseconds(Timestamp);

    /// <summary>
    /// The Unix timestamp embedded in this snowflake, in milliseconds.
    /// </summary>
    public long Timestamp => (long)((Value >> 22) + Epoch);

    /// <summary>
    /// The process ID embedded in this snowflake.
    /// </summary>
    public byte ProcessId => (byte)((Value & 0x3E0000) >> 17);

    /// <summary>
    /// The thread ID embedded in this snowflake.
    /// </summary>
    public byte ThreadId => (byte)((Value & 0x1F000) >> 12);

    /// <summary>
    /// The increment embedded in this snowflake.
    /// </summary>
    public short Increment => (short)(Value & 0xFFF);

    public static bool operator <(Snowflake arg1, Snowflake arg2) => arg1.Value < arg2.Value;
    public static bool operator >(Snowflake arg1, Snowflake arg2) => arg1.Value > arg2.Value;
    public static bool operator ==(Snowflake arg1, Snowflake arg2) => arg1.Value == arg2.Value;
    public static bool operator !=(Snowflake arg1, Snowflake arg2) => arg1.Value != arg2.Value;

    public static implicit operator ulong(Snowflake s) => s.Value;
    public static implicit operator long(Snowflake s) => (long)s.Value;
    public static implicit operator Snowflake(ulong n) => new(n);
    public static implicit operator Snowflake(long n) => new((ulong)n);

    public override bool Equals(object? obj) => obj is Snowflake other && Value == other.Value;
    public override int GetHashCode() => Value.GetHashCode();

    /// <summary>
    /// An Entity Framework ValueConverter for Snowflakes to longs.
    /// </summary>
    // ReSharper disable once ClassNeverInstantiated.Global
    public class ValueConverter() : ValueConverter<Snowflake, long>(
        convertToProviderExpression: x => x,
        convertFromProviderExpression: x => x
    );
}