Added MongoId struct

Libraries/SPTarkov.Server.Core/Models/Common/MongoId.cs

@@ -0,0 +1,136 @@
+using System.Text.RegularExpressions;
+
+namespace SPTarkov.Server.Core.Models.Common;
+
+public readonly partial struct MongoId : IEquatable<MongoId>
+{
+    private readonly string _stringId;
+
+    public MongoId(string id)
+    {
+        if (string.IsNullOrWhiteSpace(id) || id.Length != 24)
+        {
+            // TODO: Items.json root item has an empty parentId property
+            Console.WriteLine($"Critical MongoId error: Incorrect length. id: {id}");
+        }
+
+        if (!IsValidMongoId(id))
+        {
+            Console.WriteLine(
+                $"Critical MongoId error: Incorrect format. Must be a hexadecimal [a-f0-9] of 24 characters. id: {id}"
+            );
+        }
+
+        _stringId = string.Intern(id);
+    }
+
+    public MongoId()
+    {
+        _stringId = Generate();
+    }
+
+    /// <summary>
+    /// Create a 24 character MongoId
+    /// </summary>
+    /// <returns>24 character objectId</returns>
+    private static string Generate()
+    {
+        // Allocate a span directly onto the stack, will dispose whenever we finished running
+        // Span is recommended to work with stackalloc + we use stackalloc here because we don't do anything with this afterwards
+        Span<byte> objectId = stackalloc byte[12];
+
+        // Time stamp (4 bytes)
+        var timestamp = (int)DateTimeOffset.UtcNow.ToUnixTimeSeconds();
+        // Convert to big-endian
+        objectId[0] = (byte)(timestamp >> 24);
+        objectId[1] = (byte)(timestamp >> 16);
+        objectId[2] = (byte)(timestamp >> 8);
+        objectId[3] = (byte)timestamp;
+
+        // Random value (5 bytes)
+        var rand = new Random();
+        rand.NextBytes(objectId.Slice(4, 5));
+
+        // Incrementing counter (3 bytes)
+        // 24-bit counter
+        var counter = rand.Next(0, 16777215);
+        objectId[9] = (byte)(counter >> 16);
+        objectId[10] = (byte)(counter >> 8);
+        objectId[11] = (byte)counter;
+
+        return Convert.ToHexStringLower(objectId);
+    }
+
+    public override string ToString()
+    {
+        return _stringId ?? string.Empty;
+    }
+
+    public bool Equals(MongoId? other)
+    {
+        if (other is null)
+        {
+            return other == this;
+        }
+
+        return other.ToString().Equals(ToString(), StringComparison.InvariantCultureIgnoreCase);
+    }
+
+    public bool Equals(string? other)
+    {
+        if (other is null)
+        {
+            return other == this;
+        }
+
+        return other.Equals(ToString(), StringComparison.InvariantCultureIgnoreCase);
+    }
+
+    public static bool IsValidMongoId(string stringToCheck)
+    {
+        return MongoIdRegex().IsMatch(stringToCheck);
+    }
+
+    public static implicit operator string(MongoId mongoId)
+    {
+        return mongoId.ToString();
+    }
+
+    public static implicit operator MongoId(string mongoId)
+    {
+        return new MongoId(mongoId);
+    }
+
+    public bool Equals(MongoId other)
+    {
+        return _stringId == other._stringId;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        return obj is MongoId other && Equals(other);
+    }
+
+    public static bool operator ==(MongoId left, MongoId right)
+    {
+        return left.Equals(right);
+    }
+
+    public static bool operator !=(MongoId left, MongoId right)
+    {
+        return !left.Equals(right);
+    }
+
+    public override int GetHashCode()
+    {
+        return _stringId.GetHashCode();
+    }
+
+    public MongoId Empty()
+    {
+        return new MongoId("000000000000000000000000");
+    }
+
+    [GeneratedRegex("^[a-fA-F0-9]{24}$")]
+    private static partial Regex MongoIdRegex();
+}