Refactor. Add data layer

BudgetApp.Data/Repositories/SalaryRepository.cs

@@ -0,0 +1,116 @@
+using BudgetApp.Data.Entities;
+using BudgetApp.Data.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace BudgetApp.Data.Repositories;
+
+public class SalaryRepository(ApplicationDbContext db) : ISalaryRepository
+{
+    public async Task<List<Salary>> GetSalariesAsync(string userId)
+    {
+        return await db.Salaries
+            .Include(s => s.Account)
+            .Include(s => s.Category)
+            .Where(s => s.UserId == userId)
+            .OrderBy(s => s.Name)
+            .ToListAsync();
+    }
+
+    public async Task CreateSalaryAsync(Salary salary, DateTime windowEnd)
+    {
+        var salaryCategoryId = await db.Categories
+            .Where(c => c.UserId == salary.UserId && c.Name == "Salary")
+            .Select(c => (int?)c.Id)
+            .FirstOrDefaultAsync();
+        salary.CategoryId = salaryCategoryId;
+
+        db.Salaries.Add(salary);
+        await db.SaveChangesAsync();
+        await MaterializeSalaryTransactionsAsync(salary.UserId, windowEnd);
+    }
+
+    public async Task DeleteSalaryAsync(int id, string userId)
+    {
+        var exists = await db.Salaries.AnyAsync(s => s.Id == id && s.UserId == userId);
+        if (!exists) return;
+
+        await using var transaction = await db.Database.BeginTransactionAsync();
+
+        // Delete future unpaid transactions generated by this salary
+        await db.Transactions
+            .Where(t => t.SalaryId == id && t.Date.Date > DateTime.Today && !t.IsPaid)
+            .ExecuteDeleteAsync();
+
+        // Unlink past / paid transactions so they stay in history without the salary reference
+        await db.Transactions
+            .Where(t => t.SalaryId == id)
+            .ExecuteUpdateAsync(s => s.SetProperty(t => t.SalaryId, (int?)null));
+
+        await db.Salaries
+            .Where(s => s.Id == id && s.UserId == userId)
+            .ExecuteDeleteAsync();
+
+        await transaction.CommitAsync();
+    }
+
+    public async Task MaterializeSalaryTransactionsAsync(string userId, DateTime windowEnd)
+    {
+        var salaries = await db.Salaries
+            .Where(s => s.UserId == userId)
+            .ToListAsync();
+
+        var newTransactions = new List<Transaction>();
+
+        foreach (var salary in salaries)
+        {
+            var latestDate = await db.Transactions
+                .Where(t => t.SalaryId == salary.Id)
+                .OrderByDescending(t => t.Date)
+                .Select(t => (DateTime?)t.Date)
+                .FirstOrDefaultAsync();
+
+            var nextDate = latestDate.HasValue
+                ? GetNextDate(latestDate.Value, salary)
+                : salary.StartDate.Date;
+
+            while (nextDate <= windowEnd)
+            {
+                newTransactions.Add(new Transaction
+                {
+                    Description = salary.Name,
+                    Amount = salary.Amount,
+                    Date = nextDate,
+                    Type = TransactionType.Income,
+                    AccountId = salary.AccountId,
+                    CategoryId = salary.CategoryId,
+                    RecurrenceType = RecurrenceType.None,
+                    SalaryId = salary.Id
+                });
+                nextDate = GetNextDate(nextDate, salary);
+            }
+        }
+
+        if (newTransactions.Count > 0)
+        {
+            db.Transactions.AddRange(newTransactions);
+            await db.SaveChangesAsync();
+        }
+    }
+
+    public async Task<DateTime?> GetNextPaydateAsync(int salaryId)
+    {
+        return await db.Transactions
+            .Where(t => t.SalaryId == salaryId && t.Date.Date >= DateTime.Today)
+            .OrderBy(t => t.Date)
+            .Select(t => (DateTime?)t.Date)
+            .FirstOrDefaultAsync();
+    }
+
+    private static DateTime GetNextDate(DateTime from, Salary salary) => salary.RecurrenceType switch
+    {
+        RecurrenceType.Weekly  => from.AddDays(7),
+        RecurrenceType.Monthly => from.AddMonths(1),
+        RecurrenceType.Yearly  => from.AddYears(1),
+        _                      => from.AddMonths(1)
+    };
+}