Implement the Sorting Logic

Francesco.Recipes.World/Services/Instruction/IInstructionService.cs

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+namespace Francesco.Recipes.World.Services.Instruction
+{
+    public interface IInstructionService
+    {
+        Task MoveInstructionUpAsync(Guid instructionId);
+
+        Task MoveInstructionDownAsync(Guid instructionId);
+    }
+}

Francesco.Recipes.World/Services/Instruction/InstructionService.cs

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+using Francesco.Recipes.World.Repositories.Instruction;
+
+namespace Francesco.Recipes.World.Services.Instruction
+{
+    public class InstructionService : IInstructionService
+    {
+        private readonly IInstructionRepository _instructionRepository;
+
+        public InstructionService(IInstructionRepository instructionRepository)
+        {
+            _instructionRepository = instructionRepository;
+        }
+
+        public async Task MoveInstructionDownAsync(Guid instructionId)
+        {
+            var instruction = await _instructionRepository.GetInstructionWithRecipeAsync(instructionId);
+
+            var instructions = await _instructionRepository.GetInstructionsByRecipeIdAsync(instruction.Recipe.Id);
+
+            var maxStep = instructions.Max(i => i.Number);
+
+            if (instruction.Number >= maxStep)
+            {
+                return;
+            }
+
+            var neighbor = instructions.FirstOrDefault(i => i.Number == instruction.Number + 1);
+
+            if (neighbor != null)
+            {
+                await _instructionRepository.SwapInstructionOrderAsync(instruction, neighbor);
+            }
+        }
+
+        public async Task MoveInstructionUpAsync(Guid instructionId)
+        {
+            var instruction = await _instructionRepository.GetInstructionWithRecipeAsync(instructionId);
+
+            if (instruction.Number == 1)
+            {
+                return;
+            }
+
+            var instructions = await _instructionRepository.GetInstructionsByRecipeIdAsync(instruction.Recipe.Id);
+
+            var neighbor = instructions.FirstOrDefault(i => i.Number == instruction.Number - 1);
+
+            if (neighbor != null)
+            {
+                await _instructionRepository.SwapInstructionOrderAsync(instruction, neighbor);
+            }
+        }
+    }
+}