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src/PowderCoating.Application/Interfaces/IAccountBalanceService.cs

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+namespace PowderCoating.Application.Interfaces;
+
+/// <summary>
+/// Keeps Account.CurrentBalance in sync with double-entry transactions.
+/// DebitAsync / CreditAsync update the balance in the normal-balance direction
+/// for each account sub-type, but do NOT call CompleteAsync — the caller must
+/// persist by calling IUnitOfWork.CompleteAsync / CommitTransactionAsync.
+/// RecalculateAllAsync is the exception: it saves internally and is safe to call standalone.
+/// </summary>
+public interface IAccountBalanceService
+{
+    /// <summary>
+    /// Applies a debit to the account.
+    /// Debit-normal accounts (Asset / Expense / COGS): balance increases.
+    /// Credit-normal accounts (Liability / Equity / Revenue): balance decreases.
+    /// No-op when accountId is null or amount is zero.
+    /// </summary>
+    Task DebitAsync(int? accountId, decimal amount);
+
+    /// <summary>
+    /// Applies a credit to the account.
+    /// Debit-normal accounts: balance decreases.
+    /// Credit-normal accounts: balance increases.
+    /// No-op when accountId is null or amount is zero.
+    /// </summary>
+    Task CreditAsync(int? accountId, decimal amount);
+
+    /// <summary>
+    /// Recomputes CurrentBalance for every active account in the company by replaying all
+    /// transactions through LedgerService. Saves internally. Use after import or to fix drift.
+    /// </summary>
+    Task RecalculateAllAsync(int companyId);
+}