duempelkas/.github/prompts/04-application-services.prompt.md

description, agent

description	agent
Define and implement application service interfaces and implementations for accounts, years, entries, transfers, balance queries, and file operations	agent

Step 4: Application Services

Interfaces (in src/Duempelkas.App/Services/)

IAccountService

• Task<List<AccountSummaryDto>> GetAllAccountsAsync() — returns each account with its current total balance across all years.
• Task<AccountSummaryDto> CreateAccountAsync(string name)
• Task RenameAccountAsync(int accountId, string newName)
• Task DeleteAccountAsync(int accountId)

IAccountYearService

• Task<List<AccountYearDto>> GetYearsForAccountAsync(int accountId)
• Task<AccountYearDto> CreateYearAsync(int accountId, int year, decimal openingBalance)
• Task<decimal> SuggestCarryoverAsync(int accountId, int year) — calculates prior year's closing balance as suggestion.
• Task UpdateOpeningBalanceAsync(int accountYearId, decimal openingBalance)

IEntryService

• Task<List<EntryDto>> GetEntriesAsync(int accountYearId)
• Task<EntryDto> CreateEntryAsync(int accountYearId, EntryType type, DateTime date, string title, decimal amount)
• Task CreateTransferAsync(int sourceAccountYearId, int targetAccountYearId, DateTime date, string title, decimal amount) — atomically creates two entries + TransferLink.
• Task DeleteEntryAsync(int entryId) — if linked transfer, deletes both sides atomically.
• Task UpdateEntryAsync(int entryId, DateTime date, string title, decimal amount)

IBalanceQueryService

• Task<decimal> GetAccountTotalBalanceAsync(int accountId) — OpeningBalance + sum(Income) - sum(Expense) across all years.
• Task<YearlySummaryDto> GetYearlySummaryAsync(int accountYearId) — returns opening balance, total income, total expense, yearly movement, closing balance.

IPdfStatementService

• Task<byte[]> GenerateYearlyStatementAsync(int accountYearId)

IFileSaveService

• Task<string?> SaveFileAsync(byte[] content, string suggestedFileName) — abstracts native file-save dialog.

DTOs (in src/Duempelkas.App/Services/Models/)

• AccountSummaryDto { Id, Name, TotalBalance, CreatedUtc }
• AccountYearDto { Id, AccountId, Year, OpeningBalance }
• EntryDto { Id, AccountYearId, Type, Date, Title, Amount, IsTransfer, TransferLinkId, LinkedAccountName }
• YearlySummaryDto { OpeningBalance, TotalIncome, TotalExpense, YearlyMovement, ClosingBalance }

Implementations (in src/Duempelkas.Infrastructure/Services/)

• Implement each interface using FinanceDbContext.
• All balance calculations use the single formula: OpeningBalance + sum(Income) - sum(Expense).
• Transfer creation must be wrapped in a transaction.
• Entry deletion must check for TransferLink and delete both sides if linked.

DI Registration

• Create src/Duempelkas.Infrastructure/DependencyInjection.cs with AddInfrastructure(this IServiceCollection, string connectionString) extension method that registers DbContext and all services.

Conventions

• File-scoped namespaces.
• Async/await throughout.
• No business logic in entities; all in services.