using System.Security.Cryptography;
using System.Text;
using EventFlow.Core;

namespace Books.Api.Domain.Accounts;

public class AccountId(string value) : Identity<AccountId>(value)
{
    /// <summary>
    /// Creates a deterministic AccountId based on company and account number.
    /// This prevents duplicate accounts even with race conditions.
    /// Uses SHA256 to generate a deterministic GUID from the input.
    /// </summary>
    public static AccountId FromCompanyAndNumber(string companyId, string accountNumber)
    {
        // Create a deterministic GUID from the company ID and account number
        var input = $"{companyId}:{accountNumber}";
        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(input));

        // Use the first 16 bytes of the hash to create a GUID
        var guidBytes = new byte[16];
        Array.Copy(hash, guidBytes, 16);

        // Set version (4) and variant bits to make it a valid UUID
        guidBytes[6] = (byte)((guidBytes[6] & 0x0F) | 0x40); // Version 4
        guidBytes[8] = (byte)((guidBytes[8] & 0x3F) | 0x80); // Variant 1

        var deterministicGuid = new Guid(guidBytes);
        return new AccountId($"account-{deterministicGuid:D}");
    }
}
