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Classes/DBs/AgeVerificationDB.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using LiteDB;
+
+namespace Mocha2023.Classes.DBs
+{
+
+    public static class AgeVerificationDB
+    {
+        private static readonly LiteDatabase Database =
+            new(Path.Combine(Program.dataDir, "DBs", "AgeVerification.db"));
+
+        private static readonly ILiteCollection<AgeVerificationRequest> Requests =
+            Database.GetCollection<AgeVerificationRequest>("Requests");
+
+        private const string CodeAlphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
+        private static readonly Random Rng = new();
+        private static readonly object Sync = new();
+
+        static AgeVerificationDB()
+        {
+            LiteDbMaintenance.StartPeriodicCheckpoint("AgeVerification.db", Database);
+            Requests.EnsureIndex(value => value.AccountId);
+            Requests.EnsureIndex(value => value.Status);
+        }
+
+        public sealed class AgeVerificationRequest
+        {
+            [BsonId]
+            public string Code { get; set; } = string.Empty;
+            public long AccountId { get; set; }
+
+            public string Method { get; set; } = string.Empty;
+
+            public string Status { get; set; } = "Pending";
+
+            public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+            public DateTime? SubmittedAt { get; set; }
+            public DateTime? ReviewedAt { get; set; }
+            public long? ReviewedByAccountId { get; set; }
+            public string? RejectionReason { get; set; }
+        }
+
+        public static string GenerateCode(long accountId)
+        {
+            lock (Sync)
+            {
+
+                foreach (AgeVerificationRequest stale in Requests
+                             .Find(value => value.AccountId == accountId &&
+                                 (value.Status == "Pending" || value.Status == "UnderReview"))
+                             .ToList())
+                {
+                    Requests.Delete(stale.Code);
+                }
+
+                string code;
+                do
+                {
+                    code = NewCode();
+                } while (Requests.Exists(value => value.Code == code));
+
+                Requests.Insert(new AgeVerificationRequest
+                {
+                    Code = code,
+                    AccountId = accountId,
+                    Status = "Pending"
+                });
+
+                return code;
+            }
+        }
+
+        private static string NewCode()
+        {
+            char[] buffer = new char[6];
+            for (int i = 0; i < buffer.Length; i++)
+                buffer[i] = CodeAlphabet[Rng.Next(CodeAlphabet.Length)];
+            return new string(buffer);
+        }
+
+        public static AgeVerificationRequest? GetByCode(string? code)
+        {
+            string normalized = (code ?? string.Empty).Trim().ToUpperInvariant();
+            return normalized.Length == 0 ? null : Requests.FindById(normalized);
+        }
+
+        public static AgeVerificationRequest? GetActiveForAccount(long accountId)
+        {
+            return Requests.FindAll()
+                .Where(value => value.AccountId == accountId &&
+                    (value.Status == "Pending" || value.Status == "UnderReview"))
+                .OrderByDescending(value => value.CreatedAt)
+                .FirstOrDefault();
+        }
+
+        public static bool MarkUnderReview(string code, long accountId, string method)
+        {
+            lock (Sync)
+            {
+                AgeVerificationRequest? request = GetByCode(code);
+                if (request == null ||
+                    request.AccountId != accountId ||
+                    request.Status != "Pending")
+                {
+                    return false;
+                }
+
+                request.Method = method;
+                request.Status = "UnderReview";
+                request.SubmittedAt = DateTime.UtcNow;
+                return Requests.Update(request);
+            }
+        }
+
+        public static List<AgeVerificationRequest> GetForReview()
+        {
+            return Requests.Find(value => value.Status == "UnderReview")
+                .OrderBy(value => value.SubmittedAt)
+                .ToList();
+        }
+
+        public static bool Review(string code, bool approve, long reviewerId, string? reason)
+        {
+            lock (Sync)
+            {
+                AgeVerificationRequest? request = GetByCode(code);
+                if (request == null || request.Status != "UnderReview")
+                    return false;
+
+                request.Status = approve ? "Approved" : "Rejected";
+                request.ReviewedAt = DateTime.UtcNow;
+                request.ReviewedByAccountId = reviewerId;
+                request.RejectionReason = reason;
+                return Requests.Update(request);
+            }
+        }
+    }
+}