Add skill management system: implement Skill and PetSkill models, create SkillController, and update ApplicationDbContext for skills

Services/SkillService.cs

@@ -0,0 +1,76 @@
+using PetCompanion.Models;
+using PetCompanion.Data;
+using Microsoft.EntityFrameworkCore;
+using PetCompanion.Repositories;
+
+namespace PetCompanion.Services
+{
+    public class SkillService
+    {
+        private readonly ApplicationDbContext context;
+        private readonly PetRepository petRepository;
+
+        public SkillService(ApplicationDbContext context, PetRepository petRepository)
+        {
+            this.context = context;
+            this.petRepository = petRepository;
+        }
+
+        public async Task<PetSkill> AllocateSkillPoint(string petId, string userId, int skillId)
+        {
+            var pet = await context.Pets
+                .Include(p => p.Skills)
+                .FirstOrDefaultAsync(p => p.Id == petId && p.UserId == userId);
+
+            if (pet == null)
+                throw new Exception("Pet not found");
+
+            if (pet.SkillPoints <= 0)
+                throw new Exception("No skill points available");
+
+            var skill = await context.Skills
+                .Include(s => s.Effects)
+                .FirstOrDefaultAsync(s => s.Id == skillId);
+
+            if (skill == null)
+                throw new Exception("Skill not found");
+
+            var existingSkill = pet.Skills.FirstOrDefault(ps => ps.SkillId == skillId);
+            if (existingSkill != null)
+            {
+                if (existingSkill.CurrentTier == SkillTier.III)
+                    throw new Exception("Skill already at maximum tier");
+
+                existingSkill.CurrentTier++;
+                var effect = skill.Effects.FirstOrDefault(e => e.Tier == existingSkill.CurrentTier);
+                if (effect != null)
+                    effect.PetSkillUpgrade(ref pet);
+            }
+            else
+            {
+                var newSkill = new PetSkill
+                {
+                    PetId = petId,
+                    SkillId = skillId,
+                    CurrentTier = SkillTier.I
+                };
+                pet.Skills.Add(newSkill);
+                var effect = skill.Effects.FirstOrDefault(e => e.Tier == SkillTier.I);
+                if (effect != null)
+                    effect.PetSkillUpgrade(ref pet);
+            }
+
+            pet.SkillPoints--;
+            await context.SaveChangesAsync();
+
+            return pet.Skills.First(ps => ps.SkillId == skillId);
+        }
+
+        public async Task<IEnumerable<Skill>> GetAvailableSkills()
+        {
+            return await context.Skills
+                .Include(s => s.Effects)
+                .ToListAsync();
+        }
+    }
+}