Introduced consts for every string possible. FML

11 files changed, 135 insertions, 121 deletions

diff --git a/src/Services/DevHive.Services.Tests/UserService.Tests.cs b/src/Services/DevHive.Services.Tests/UserService.Tests.cs
index 7990b32..9d1bca5 100644
--- a/src/Services/DevHive.Services.Tests/UserService.Tests.cs
+++ b/src/Services/DevHive.Services.Tests/UserService.Tests.cs
@@ -344,7 +344,7 @@ namespace DevHive.Services.Tests
 		// 	}
 		// 	else
 		// 	{
-		// 		const string EXCEPTION_MESSAGE = "Unable to edit user!";
+		// 		const string EXCEPTION_MESSAGE = string.Format(ErrorMessages.CannotEdit, ClassesConstants.User.ToLower());
 		//
 		// 		Exception ex = Assert.ThrowsAsync<InvalidOperationException>(() => this._userService.UpdateUser(updateUserServiceModel);
 		//
diff --git a/src/Services/DevHive.Services/Services/CloudinaryService.cs b/src/Services/DevHive.Services/Services/CloudinaryService.cs
index 05600cc..078bb5d 100644
--- a/src/Services/DevHive.Services/Services/CloudinaryService.cs
+++ b/src/Services/DevHive.Services/Services/CloudinaryService.cs
@@ -14,7 +14,7 @@ namespace DevHive.Services.Services
 	{
 		// Regex for getting the filename without (final) filename extension
 		// So, from image.png, it will match image, and from doc.my.txt will match doc.my
-		private static Regex _imageRegex = new Regex(".*(?=\\.)");
+		private static readonly Regex s_imageRegex = new(".*(?=\\.)");
 
 		private readonly Cloudinary _cloudinary;
 
@@ -28,23 +28,21 @@ namespace DevHive.Services.Services
 			List<string> fileUrls = new();
 			foreach (var formFile in formFiles)
 			{
-				string fileName = _imageRegex.Match(formFile.FileName).ToString();
+				string fileName = s_imageRegex.Match(formFile.FileName).ToString();
 
-				using (var ms = new MemoryStream())
+				using var ms = new MemoryStream();
+				formFile.CopyTo(ms);
+				byte[] formBytes = ms.ToArray();
+
+				RawUploadParams rawUploadParams = new()
 				{
-					formFile.CopyTo(ms);
-					byte[] formBytes = ms.ToArray();
-
-					RawUploadParams rawUploadParams = new()
-					{
-						File = new FileDescription(fileName, new MemoryStream(formBytes)),
-						PublicId = fileName,
-						UseFilename = true
-					};
-
-					RawUploadResult rawUploadResult = await this._cloudinary.UploadAsync(rawUploadParams);
-					fileUrls.Add(rawUploadResult.Url.AbsoluteUri);
-				}
+					File = new FileDescription(fileName, new MemoryStream(formBytes)),
+					PublicId = fileName,
+					UseFilename = true
+				};
+
+				RawUploadResult rawUploadResult = await this._cloudinary.UploadAsync(rawUploadParams);
+				fileUrls.Add(rawUploadResult.Url.AbsoluteUri);
 			}
 
 			return fileUrls;
diff --git a/src/Services/DevHive.Services/Services/CommentService.cs b/src/Services/DevHive.Services/Services/CommentService.cs
index b48bac8..1c388f6 100644
--- a/src/Services/DevHive.Services/Services/CommentService.cs
+++ b/src/Services/DevHive.Services/Services/CommentService.cs
@@ -1,14 +1,15 @@
 using System;
 using System.Collections.Generic;
+using System.IdentityModel.Tokens.Jwt;
+using System.Linq;
+using System.Security.Claims;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
+using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
-using DevHive.Services.Models.Comment;
-using System.IdentityModel.Tokens.Jwt;
-using System.Security.Claims;
 using DevHive.Services.Interfaces;
-using DevHive.Data.Interfaces;
-using System.Linq;
+using DevHive.Services.Models.Comment;
 
 namespace DevHive.Services.Services
 {
@@ -31,7 +32,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> AddComment(CreateCommentServiceModel createCommentServiceModel)
 		{
 			if (!await this._postRepository.DoesPostExist(createCommentServiceModel.PostId))
-				throw new ArgumentException("Post does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
 
 			Comment comment = this._postMapper.Map<Comment>(createCommentServiceModel);
 			comment.TimeCreated = DateTime.Now;
@@ -56,10 +57,10 @@ namespace DevHive.Services.Services
 		public async Task<ReadCommentServiceModel> GetCommentById(Guid id)
 		{
 			Comment comment = await this._commentRepository.GetByIdAsync(id) ??
-				throw new ArgumentException("The comment does not exist");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Comment));
 
 			User user = await this._userRepository.GetByIdAsync(comment.Creator.Id) ??
-				throw new ArgumentException("The user does not exist");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			ReadCommentServiceModel readCommentServiceModel = this._postMapper.Map<ReadCommentServiceModel>(comment);
 			readCommentServiceModel.IssuerFirstName = user.FirstName;
@@ -74,7 +75,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> UpdateComment(UpdateCommentServiceModel updateCommentServiceModel)
 		{
 			if (!await this._commentRepository.DoesCommentExist(updateCommentServiceModel.CommentId))
-				throw new ArgumentException("Comment does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Comment));
 
 			Comment comment = this._postMapper.Map<Comment>(updateCommentServiceModel);
 			comment.TimeCreated = DateTime.Now;
@@ -95,7 +96,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteComment(Guid id)
 		{
 			if (!await this._commentRepository.DoesCommentExist(id))
-				throw new ArgumentException("Comment does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Comment));
 
 			Comment comment = await this._commentRepository.GetByIdAsync(id);
 			return await this._commentRepository.DeleteAsync(comment);
@@ -121,7 +122,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> ValidateJwtForComment(Guid commentId, string rawTokenData)
 		{
 			Comment comment = await this._commentRepository.GetByIdAsync(commentId) ??
-				throw new ArgumentException("Comment does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Comment));
 			User user = await this.GetUserForValidation(rawTokenData);
 
 			//If user made the comment
@@ -141,10 +142,10 @@ namespace DevHive.Services.Services
 		{
 			JwtSecurityToken jwt = new JwtSecurityTokenHandler().ReadJwtToken(rawTokenData.Remove(0, 7));
 
-			Guid jwtUserId = Guid.Parse(this.GetClaimTypeValues("ID", jwt.Claims).First());
+			Guid jwtUserId = Guid.Parse(GetClaimTypeValues("ID", jwt.Claims).First());
 
 			User user = await this._userRepository.GetByIdAsync(jwtUserId) ??
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			return user;
 		}
@@ -152,7 +153,7 @@ namespace DevHive.Services.Services
 		/// <summary>
 		/// Returns all values from a given claim type
 		/// </summary>
-		private List<string> GetClaimTypeValues(string type, IEnumerable<Claim> claims)
+		private static List<string> GetClaimTypeValues(string type, IEnumerable<Claim> claims)
 		{
 			List<string> toReturn = new();
 
diff --git a/src/Services/DevHive.Services/Services/FeedService.cs b/src/Services/DevHive.Services/Services/FeedService.cs
index 0af8093..9c622b3 100644
--- a/src/Services/DevHive.Services/Services/FeedService.cs
+++ b/src/Services/DevHive.Services/Services/FeedService.cs
@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -26,10 +28,11 @@ namespace DevHive.Services.Services
 
 		/// <summary>
 		/// This method is used in the feed page.
-		/// See the FeedRepository "GetFriendsPosts" menthod for more information on how it works.
+		/// See the FeedRepository "GetFriendsPosts" method for more information on how it works.
 		/// </summary>
 		public async Task<ReadPageServiceModel> GetPage(GetPageServiceModel getPageServiceModel)
 		{
+			//TODO: Rework the initialization of User
 			User user = null;
 
 			if (getPageServiceModel.UserId != Guid.Empty)
@@ -37,10 +40,10 @@ namespace DevHive.Services.Services
 			else if (!string.IsNullOrEmpty(getPageServiceModel.Username))
 				user = await this._userRepository.GetByUsernameAsync(getPageServiceModel.Username);
 			else
-				throw new ArgumentException("Invalid given data!");
+				throw new InvalidDataException(string.Format(ErrorMessages.InvalidData, ClassesConstants.Data.ToLower()));
 
 			if (user == null)
-				throw new ArgumentException("User doesn't exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			List<Post> posts = await this._feedRepository
 				.GetFriendsPosts(user.Friends.ToList(), getPageServiceModel.FirstRequestIssued, getPageServiceModel.PageNumber, getPageServiceModel.PageSize);
@@ -58,15 +61,16 @@ namespace DevHive.Services.Services
 		/// </summary>
 		public async Task<ReadPageServiceModel> GetUserPage(GetPageServiceModel model)
 		{
+			//TODO: Rework the initialization of User
 			User user = null;
 
 			if (!string.IsNullOrEmpty(model.Username))
 				user = await this._userRepository.GetByUsernameAsync(model.Username);
 			else
-				throw new ArgumentException("Invalid given data!");
+				throw new InvalidDataException(string.Format(ErrorMessages.InvalidData, ClassesConstants.Data.ToLower()));
 
 			if (user == null)
-				throw new ArgumentException("User doesn't exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			List<Post> posts = await this._feedRepository
 				.GetUsersPosts(user, model.FirstRequestIssued, model.PageNumber, model.PageSize);
diff --git a/src/Services/DevHive.Services/Services/LanguageService.cs b/src/Services/DevHive.Services/Services/LanguageService.cs
index 9d2041e..7ee7d9f 100644
--- a/src/Services/DevHive.Services/Services/LanguageService.cs
+++ b/src/Services/DevHive.Services/Services/LanguageService.cs
@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -24,7 +26,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> CreateLanguage(CreateLanguageServiceModel createLanguageServiceModel)
 		{
 			if (await this._languageRepository.DoesLanguageNameExistAsync(createLanguageServiceModel.Name))
-				throw new ArgumentException("Language already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Language));
 
 			Language language = this._languageMapper.Map<Language>(createLanguageServiceModel);
 			bool success = await this._languageRepository.AddAsync(language);
@@ -45,7 +47,7 @@ namespace DevHive.Services.Services
 			Language language = await this._languageRepository.GetByIdAsync(id);
 
 			if (language == null)
-				throw new ArgumentException("The language does not exist");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Language));
 
 			return this._languageMapper.Map<ReadLanguageServiceModel>(language);
 		}
@@ -65,10 +67,10 @@ namespace DevHive.Services.Services
 			bool newLangNameExists = await this._languageRepository.DoesLanguageNameExistAsync(languageServiceModel.Name);
 
 			if (!langExists)
-				throw new ArgumentException("Language does not exist!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Language));
 
 			if (newLangNameExists)
-				throw new ArgumentException("Language name already exists in our data base!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Language));
 
 			Language lang = this._languageMapper.Map<Language>(languageServiceModel);
 			return await this._languageRepository.EditAsync(languageServiceModel.Id, lang);
@@ -79,7 +81,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteLanguage(Guid id)
 		{
 			if (!await this._languageRepository.DoesLanguageExistAsync(id))
-				throw new ArgumentException("Language does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Language));
 
 			Language language = await this._languageRepository.GetByIdAsync(id);
 			return await this._languageRepository.DeleteAsync(language);
diff --git a/src/Services/DevHive.Services/Services/PostService.cs b/src/Services/DevHive.Services/Services/PostService.cs
index a565473..8580e82 100644
--- a/src/Services/DevHive.Services/Services/PostService.cs
+++ b/src/Services/DevHive.Services/Services/PostService.cs
@@ -1,15 +1,16 @@
 using System;
 using System.Collections.Generic;
-using System.Threading.Tasks;
-using AutoMapper;
-using DevHive.Data.Models;
-using DevHive.Services.Models.Post;
 using System.IdentityModel.Tokens.Jwt;
+using System.Linq;
 using System.Security.Claims;
-using DevHive.Services.Interfaces;
+using System.Threading.Tasks;
+using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
-using System.Linq;
+using DevHive.Data.Models;
 using DevHive.Data.Models.Relational;
+using DevHive.Services.Interfaces;
+using DevHive.Services.Models.Post;
 
 namespace DevHive.Services.Services
 {
@@ -34,7 +35,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> CreatePost(CreatePostServiceModel createPostServiceModel)
 		{
 			if (!await this._userRepository.DoesUserExistAsync(createPostServiceModel.CreatorId))
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			Post post = this._postMapper.Map<Post>(createPostServiceModel);
 
@@ -66,7 +67,7 @@ namespace DevHive.Services.Services
 		public async Task<ReadPostServiceModel> GetPostById(Guid id)
 		{
 			Post post = await this._postRepository.GetByIdAsync(id) ??
-				throw new ArgumentException("The post does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
 
 			// This can't happen in repo, because of how time is usually compared
 			post.Comments = post.Comments
@@ -74,7 +75,7 @@ namespace DevHive.Services.Services
 				.ToList();
 
 			User user = await this._userRepository.GetByIdAsync(post.Creator.Id) ??
-				throw new ArgumentException("The user does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			int currentRating = 0;
 			foreach (Rating rating in post.Ratings)
@@ -100,7 +101,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> UpdatePost(UpdatePostServiceModel updatePostServiceModel)
 		{
 			if (!await this._postRepository.DoesPostExist(updatePostServiceModel.PostId))
-				throw new ArgumentException("Post does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
 
 			Post post = this._postMapper.Map<Post>(updatePostServiceModel);
 
@@ -111,11 +112,11 @@ namespace DevHive.Services.Services
 					List<string> fileUrlsToRemove = await this._postRepository.GetFileUrls(updatePostServiceModel.PostId);
 					bool success = await _cloudService.RemoveFilesFromCloud(fileUrlsToRemove);
 					if (!success)
-						throw new InvalidCastException("Could not delete files from the post!");
+						throw new InvalidOperationException(string.Format(ErrorMessages.CannotDelete, ClassesConstants.Files.ToLower()));
 				}
 
 				List<string> fileUrls = await _cloudService.UploadFilesToCloud(updatePostServiceModel.Files) ??
-					throw new ArgumentException("Unable to upload images to cloud!");
+					throw new InvalidOperationException(string.Format(ErrorMessages.CannotUpload, ClassesConstants.Files.ToLower()));
 				post.Attachments = GetPostAttachmentsFromUrls(post, fileUrls);
 			}
 
@@ -136,7 +137,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeletePost(Guid id)
 		{
 			if (!await this._postRepository.DoesPostExist(id))
-				throw new ArgumentException("Post does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
 
 			Post post = await this._postRepository.GetByIdAsync(id);
 
@@ -145,7 +146,7 @@ namespace DevHive.Services.Services
 				List<string> fileUrls = await this._postRepository.GetFileUrls(id);
 				bool success = await _cloudService.RemoveFilesFromCloud(fileUrls);
 				if (!success)
-					throw new InvalidCastException("Could not delete files from the post. Please try again");
+					throw new InvalidOperationException(string.Format(ErrorMessages.CannotDelete, ClassesConstants.Files.ToLower()));
 			}
 
 			return await this._postRepository.DeleteAsync(post);
@@ -158,7 +159,7 @@ namespace DevHive.Services.Services
 		/// </summary>
 		public async Task<bool> ValidateJwtForCreating(Guid userId, string rawTokenData)
 		{
-			User user = await this.GetUserForValidation(rawTokenData);
+			User user = await GetUserForValidation(rawTokenData);
 
 			return user.Id == userId;
 		}
@@ -171,8 +172,8 @@ namespace DevHive.Services.Services
 		public async Task<bool> ValidateJwtForPost(Guid postId, string rawTokenData)
 		{
 			Post post = await this._postRepository.GetByIdAsync(postId) ??
-				throw new ArgumentException("Post does not exist!");
-			User user = await this.GetUserForValidation(rawTokenData);
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
+			User user = await GetUserForValidation(rawTokenData);
 
 			//If user made the post
 			if (post.Creator.Id == user.Id)
@@ -192,8 +193,8 @@ namespace DevHive.Services.Services
 		public async Task<bool> ValidateJwtForComment(Guid commentId, string rawTokenData)
 		{
 			Comment comment = await this._commentRepository.GetByIdAsync(commentId) ??
-				throw new ArgumentException("Comment does not exist!");
-			User user = await this.GetUserForValidation(rawTokenData);
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Comment));
+			User user = await GetUserForValidation(rawTokenData);
 
 			//If user made the comment
 			if (comment.Creator.Id == user.Id)
@@ -215,7 +216,7 @@ namespace DevHive.Services.Services
 			Guid jwtUserId = Guid.Parse(GetClaimTypeValues("ID", jwt.Claims).First());
 
 			User user = await this._userRepository.GetByIdAsync(jwtUserId) ??
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			return user;
 		}
diff --git a/src/Services/DevHive.Services/Services/ProfilePictureService.cs b/src/Services/DevHive.Services/Services/ProfilePictureService.cs
index 1de2114..cafa7cb 100644
--- a/src/Services/DevHive.Services/Services/ProfilePictureService.cs
+++ b/src/Services/DevHive.Services/Services/ProfilePictureService.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -33,14 +34,13 @@ namespace DevHive.Services.Services
 			await ValidateUserExistsAsync(profilePictureServiceModel.UserId);
 
 			User user = await this._userRepository.GetByIdAsync(profilePictureServiceModel.UserId);
-			// if (user.ProfilePicture.PictureURL != ProfilePicture.DefaultURL)
 			if (user.ProfilePicture.Id != Guid.Empty)
 			{
 				List<string> file = new() { user.ProfilePicture.PictureURL };
 				bool removed = await this._cloudinaryService.RemoveFilesFromCloud(file);
 
 				if (!removed)
-					throw new ArgumentException("Cannot delete old picture");
+					throw new InvalidOperationException(string.Format(ErrorMessages.CannotDelete, ClassesConstants.Picture.ToLower()));
 			}
 
 			return await SaveProfilePictureInDatabase(profilePictureServiceModel);
@@ -49,16 +49,16 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteProfilePicture(Guid id)
 		{
 			ProfilePicture profilePic = await this._profilePictureRepository.GetByIdAsync(id) ??
-				throw new ArgumentException("Such picture doesn't exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Picture));
 
 			bool removedFromDb = await this._profilePictureRepository.DeleteAsync(profilePic);
 			if (!removedFromDb)
-				throw new ArgumentException("Cannot delete picture from database!");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotDelete, ClassesConstants.Picture.ToLower()));
 
 			List<string> file = new() { profilePic.PictureURL };
 			bool removedFromCloud = await this._cloudinaryService.RemoveFilesFromCloud(file);
 			if (!removedFromCloud)
-				throw new ArgumentException("Cannot delete picture from cloud!");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotDelete, ClassesConstants.Picture.ToLower()));
 
 			return true;
 		}
@@ -75,13 +75,13 @@ namespace DevHive.Services.Services
 
 			bool success = await this._profilePictureRepository.AddAsync(profilePic);
 			if (!success)
-				throw new ArgumentException("Unable to upload picture!");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotUpload, ClassesConstants.Files.ToLower()));
 
 			user.ProfilePicture = profilePic;
 			bool userProfilePicAlter = await this._userRepository.EditAsync(user.Id, user);
 
 			if (!userProfilePicAlter)
-				throw new ArgumentException("Unable to alter user's profile picture");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotEdit, "user's profile picture"));
 
 			return picUrl;
 		}
@@ -89,13 +89,13 @@ namespace DevHive.Services.Services
 		private static void ValidateProfPic(IFormFile profilePictureFormFile)
 		{
 			if (profilePictureFormFile.Length == 0)
-				throw new ArgumentException("Picture cannot be null");
+				throw new ArgumentNullException(nameof(profilePictureFormFile), string.Format(ErrorMessages.InvalidData, ClassesConstants.Data.ToLower()));
 		}
 
 		private async Task ValidateUserExistsAsync(Guid userId)
 		{
 			if (!await this._userRepository.DoesUserExistAsync(userId))
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 		}
 	}
 }
diff --git a/src/Services/DevHive.Services/Services/RatingService.cs b/src/Services/DevHive.Services/Services/RatingService.cs
index 9d8f4b0..d6b4299 100644
--- a/src/Services/DevHive.Services/Services/RatingService.cs
+++ b/src/Services/DevHive.Services/Services/RatingService.cs
@@ -1,10 +1,7 @@
 using System;
-using System.Collections.Generic;
-using System.IdentityModel.Tokens.Jwt;
-using System.Linq;
-using System.Security.Claims;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -19,6 +16,8 @@ namespace DevHive.Services.Services
 		private readonly IRatingRepository _ratingRepository;
 		private readonly IMapper _mapper;
 
+		private const string NotRated = "{0} has not rated" + ClassesConstants.Post;
+
 		public RatingService(IPostRepository postRepository, IRatingRepository ratingRepository, IUserRepository userRepository, IMapper mapper)
 		{
 			this._postRepository = postRepository;
@@ -31,7 +30,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> RatePost(CreateRatingServiceModel createRatingServiceModel)
 		{
 			if (!await this._postRepository.DoesPostExist(createRatingServiceModel.PostId))
-				throw new ArgumentException("Post does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Post));
 
 			if (await this._ratingRepository.UserRatedPost(createRatingServiceModel.UserId, createRatingServiceModel.PostId))
 				throw new ArgumentException("User already rated the post!");
@@ -84,13 +83,13 @@ namespace DevHive.Services.Services
 		public async Task<ReadRatingServiceModel> UpdateRating(UpdateRatingServiceModel updateRatingServiceModel)
 		{
 			Rating rating = await this._ratingRepository.GetRatingByUserAndPostId(updateRatingServiceModel.UserId, updateRatingServiceModel.PostId) ??
-				throw new ArgumentException("Rating does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Rating));
 
 			User user = await this._userRepository.GetByIdAsync(updateRatingServiceModel.UserId) ??
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			if (!await this._ratingRepository.UserRatedPost(updateRatingServiceModel.UserId, updateRatingServiceModel.PostId))
-				throw new ArgumentException("User has not rated the post!");
+				throw new ArgumentException(string.Format(NotRated, ClassesConstants.User));
 
 			rating.User = user;
 			rating.IsLike = updateRatingServiceModel.IsLike;
@@ -111,7 +110,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteRating(Guid ratingId)
 		{
 			if (!await this._ratingRepository.DoesRatingExist(ratingId))
-				throw new ArgumentException("Rating does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Rating));
 
 			Rating rating = await this._ratingRepository.GetByIdAsync(ratingId);
 			return await this._ratingRepository.DeleteAsync(rating);
diff --git a/src/Services/DevHive.Services/Services/RoleService.cs b/src/Services/DevHive.Services/Services/RoleService.cs
index a5da759..f61181a 100644
--- a/src/Services/DevHive.Services/Services/RoleService.cs
+++ b/src/Services/DevHive.Services/Services/RoleService.cs
@@ -1,6 +1,8 @@
 using System;
+using System.Data;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -22,7 +24,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> CreateRole(CreateRoleServiceModel createRoleServiceModel)
 		{
 			if (await this._roleRepository.DoesNameExist(createRoleServiceModel.Name))
-				throw new ArgumentException("Role already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Role));
 
 			Role role = this._roleMapper.Map<Role>(createRoleServiceModel);
 			bool success = await this._roleRepository.AddAsync(role);
@@ -40,7 +42,7 @@ namespace DevHive.Services.Services
 		public async Task<RoleServiceModel> GetRoleById(Guid id)
 		{
 			Role role = await this._roleRepository.GetByIdAsync(id) ??
-				throw new ArgumentException("Role does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Role));
 
 			return this._roleMapper.Map<RoleServiceModel>(role);
 		}
@@ -48,10 +50,10 @@ namespace DevHive.Services.Services
 		public async Task<bool> UpdateRole(UpdateRoleServiceModel updateRoleServiceModel)
 		{
 			if (!await this._roleRepository.DoesRoleExist(updateRoleServiceModel.Id))
-				throw new ArgumentException("Role does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Role));
 
 			if (await this._roleRepository.DoesNameExist(updateRoleServiceModel.Name))
-				throw new ArgumentException("Role name already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Role));
 
 			Role role = this._roleMapper.Map<Role>(updateRoleServiceModel);
 			return await this._roleRepository.EditAsync(updateRoleServiceModel.Id, role);
@@ -60,7 +62,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteRole(Guid id)
 		{
 			if (!await this._roleRepository.DoesRoleExist(id))
-				throw new ArgumentException("Role does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Role));
 
 			Role role = await this._roleRepository.GetByIdAsync(id);
 			return await this._roleRepository.DeleteAsync(role);
diff --git a/src/Services/DevHive.Services/Services/TechnologyService.cs b/src/Services/DevHive.Services/Services/TechnologyService.cs
index 09c4d20..4cf84c5 100644
--- a/src/Services/DevHive.Services/Services/TechnologyService.cs
+++ b/src/Services/DevHive.Services/Services/TechnologyService.cs
@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Threading.Tasks;
 using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Data.Interfaces;
 using DevHive.Data.Models;
 using DevHive.Services.Interfaces;
@@ -24,7 +26,7 @@ namespace DevHive.Services.Services
 		public async Task<Guid> CreateTechnology(CreateTechnologyServiceModel technologyServiceModel)
 		{
 			if (await this._technologyRepository.DoesTechnologyNameExistAsync(technologyServiceModel.Name))
-				throw new ArgumentException("Technology already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Technology));
 
 			Technology technology = this._technologyMapper.Map<Technology>(technologyServiceModel);
 			bool success = await this._technologyRepository.AddAsync(technology);
@@ -45,7 +47,7 @@ namespace DevHive.Services.Services
 			Technology technology = await this._technologyRepository.GetByIdAsync(id);
 
 			if (technology == null)
-				throw new ArgumentException("The technology does not exist");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Technology));
 
 			return this._technologyMapper.Map<ReadTechnologyServiceModel>(technology);
 		}
@@ -62,10 +64,10 @@ namespace DevHive.Services.Services
 		public async Task<bool> UpdateTechnology(UpdateTechnologyServiceModel updateTechnologyServiceModel)
 		{
 			if (!await this._technologyRepository.DoesTechnologyExistAsync(updateTechnologyServiceModel.Id))
-				throw new ArgumentException("Technology does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Technology));
 
 			if (await this._technologyRepository.DoesTechnologyNameExistAsync(updateTechnologyServiceModel.Name))
-				throw new ArgumentException("Technology name already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Technology));
 
 			Technology technology = this._technologyMapper.Map<Technology>(updateTechnologyServiceModel);
 			bool result = await this._technologyRepository.EditAsync(updateTechnologyServiceModel.Id, technology);
@@ -78,7 +80,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteTechnology(Guid id)
 		{
 			if (!await this._technologyRepository.DoesTechnologyExistAsync(id))
-				throw new ArgumentException("Technology does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Technology));
 
 			Technology technology = await this._technologyRepository.GetByIdAsync(id);
 			bool result = await this._technologyRepository.DeleteAsync(technology);
diff --git a/src/Services/DevHive.Services/Services/UserService.cs b/src/Services/DevHive.Services/Services/UserService.cs
index d487de4..62576d4 100644
--- a/src/Services/DevHive.Services/Services/UserService.cs
+++ b/src/Services/DevHive.Services/Services/UserService.cs
@@ -1,15 +1,17 @@
-using AutoMapper;
-using DevHive.Services.Models.User;
-using System.Threading.Tasks;
-using DevHive.Data.Models;
 using System;
 using System.Collections.Generic;
-using DevHive.Common.Models.Identity;
-using DevHive.Services.Interfaces;
-using DevHive.Data.Interfaces;
+using System.Data;
+using System.IO;
 using System.Linq;
-using Microsoft.AspNetCore.Http;
+using System.Threading.Tasks;
+using AutoMapper;
+using DevHive.Common.Constants;
 using DevHive.Common.Jwt.Interfaces;
+using DevHive.Common.Models.Identity;
+using DevHive.Data.Interfaces;
+using DevHive.Data.Models;
+using DevHive.Services.Interfaces;
+using DevHive.Services.Models.User;
 
 namespace DevHive.Services.Services
 {
@@ -20,15 +22,17 @@ namespace DevHive.Services.Services
 		private readonly ILanguageRepository _languageRepository;
 		private readonly ITechnologyRepository _technologyRepository;
 		private readonly IMapper _userMapper;
-		private readonly ICloudService _cloudService;
 		private readonly IJwtService _jwtService;
 
+		private const string NoYourselfAsFriend = "You cant add yourself as a friend(sry, bro)!";
+		private const string Rant = "Can't promote shit in this country...";
+
+
 		public UserService(IUserRepository userRepository,
 			ILanguageRepository languageRepository,
 			IRoleRepository roleRepository,
 			ITechnologyRepository technologyRepository,
 			IMapper mapper,
-			ICloudService cloudService,
 			IJwtService jwtService)
 		{
 			this._userRepository = userRepository;
@@ -36,7 +40,6 @@ namespace DevHive.Services.Services
 			this._userMapper = mapper;
 			this._languageRepository = languageRepository;
 			this._technologyRepository = technologyRepository;
-			this._cloudService = cloudService;
 			this._jwtService = jwtService;
 		}
 
@@ -44,12 +47,12 @@ namespace DevHive.Services.Services
 		public async Task<TokenModel> LoginUser(LoginServiceModel loginModel)
 		{
 			if (!await this._userRepository.DoesUsernameExistAsync(loginModel.UserName))
-				throw new ArgumentException("Invalid username!");
+				throw new InvalidDataException(string.Format(ErrorMessages.InvalidData, ClassesConstants.Username));
 
 			User user = await this._userRepository.GetByUsernameAsync(loginModel.UserName);
 
 			if (!await this._userRepository.VerifyPassword(user, loginModel.Password))
-				throw new ArgumentException("Incorrect password!");
+				throw new InvalidDataException(string.Format(ErrorMessages.IncorrectData, ClassesConstants.Password.ToLower()));
 
 			List<string> roleNames = user.Roles.Select(x => x.Name).ToList();
 			return new TokenModel(this._jwtService.GenerateJwtToken(user.Id, user.UserName, roleNames));
@@ -58,10 +61,11 @@ namespace DevHive.Services.Services
 		public async Task<TokenModel> RegisterUser(RegisterServiceModel registerModel)
 		{
 			if (await this._userRepository.DoesUsernameExistAsync(registerModel.UserName))
-				throw new ArgumentException("Username already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Username));
 
 			if (await this._userRepository.DoesEmailExistAsync(registerModel.Email))
-				throw new ArgumentException("Email already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Email));
+
 
 			User user = this._userMapper.Map<User>(registerModel);
 
@@ -69,9 +73,9 @@ namespace DevHive.Services.Services
 			bool roleResult = await this._userRepository.AddRoleToUser(user, Role.DefaultRole);
 
 			if (!userResult)
-				throw new ArgumentException("Unable to create a user");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotCreate, ClassesConstants.User.ToLower()));
 			if (!roleResult)
-				throw new ArgumentException("Unable to add role to user");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotAdd, ClassesConstants.Role.ToLower()));
 
 			User createdUser = await this._userRepository.GetByUsernameAsync(registerModel.UserName);
 
@@ -84,7 +88,7 @@ namespace DevHive.Services.Services
 		public async Task<UserServiceModel> GetUserById(Guid id)
 		{
 			User user = await this._userRepository.GetByIdAsync(id) ??
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			return this._userMapper.Map<UserServiceModel>(user);
 		}
@@ -92,7 +96,7 @@ namespace DevHive.Services.Services
 		public async Task<UserServiceModel> GetUserByUsername(string username)
 		{
 			User user = await this._userRepository.GetByUsernameAsync(username) ??
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			return this._userMapper.Map<UserServiceModel>(user);
 		}
@@ -101,20 +105,20 @@ namespace DevHive.Services.Services
 		#region Update
 		public async Task<UserServiceModel> UpdateUser(UpdateUserServiceModel updateUserServiceModel)
 		{
-			await this.ValidateUserOnUpdate(updateUserServiceModel);
+			await ValidateUserOnUpdate(updateUserServiceModel);
 
 			User user = await this._userRepository.GetByIdAsync(updateUserServiceModel.Id);
-			await this.PopulateUserModel(user, updateUserServiceModel);
+			await PopulateUserModel(user, updateUserServiceModel);
 
 			if (updateUserServiceModel.Friends.Count > 0)
-				await this.CreateRelationToFriends(user, updateUserServiceModel.Friends.ToList());
+				await CreateRelationToFriends(user, updateUserServiceModel.Friends.ToList());
 			else
 				user.Friends.Clear();
 
 			bool result = await this._userRepository.EditAsync(user.Id, user);
 
 			if (!result)
-				throw new InvalidOperationException("Unable to edit user!");
+				throw new InvalidOperationException(string.Format(ErrorMessages.CannotEdit, ClassesConstants.User.ToLower()));
 
 			User newUser = await this._userRepository.GetByIdAsync(user.Id);
 			return this._userMapper.Map<UserServiceModel>(newUser);
@@ -125,7 +129,7 @@ namespace DevHive.Services.Services
 		public async Task<bool> DeleteUser(Guid id)
 		{
 			if (!await this._userRepository.DoesUserExistAsync(id))
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			User user = await this._userRepository.GetByIdAsync(id);
 			return await this._userRepository.DeleteAsync(user);
@@ -140,21 +144,21 @@ namespace DevHive.Services.Services
 		private async Task ValidateUserOnUpdate(UpdateUserServiceModel updateUserServiceModel)
 		{
 			if (!await this._userRepository.DoesUserExistAsync(updateUserServiceModel.Id))
-				throw new ArgumentException("User does not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User));
 
 			if (updateUserServiceModel.Friends.Any(x => x.UserName == updateUserServiceModel.UserName))
-				throw new ArgumentException("You cant add yourself as a friend(sry, bro)!");
+				throw new InvalidOperationException(NoYourselfAsFriend);
 
 			if (!await this._userRepository.DoesUserHaveThisUsernameAsync(updateUserServiceModel.Id, updateUserServiceModel.UserName)
 					&& await this._userRepository.DoesUsernameExistAsync(updateUserServiceModel.UserName))
-				throw new ArgumentException("Username already exists!");
+				throw new DuplicateNameException(string.Format(ErrorMessages.AlreadyExists, ClassesConstants.Username.ToLower()));
 
 			List<string> usernames = new();
 			foreach (var friend in updateUserServiceModel.Friends)
 				usernames.Add(friend.UserName);
 
 			if (!await this._userRepository.ValidateFriendsCollectionAsync(usernames))
-				throw new ArgumentException("One or more friends do not exist!");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.OneOrMoreFriends));
 		}
 		#endregion
 
@@ -162,7 +166,7 @@ namespace DevHive.Services.Services
 		public async Task<TokenModel> SuperSecretPromotionToAdmin(Guid userId)
 		{
 			User user = await this._userRepository.GetByIdAsync(userId) ??
-				throw new ArgumentException("User does not exist! Can't promote shit in this country...");
+				throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.User) + " " + Rant);
 
 			if (!await this._roleRepository.DoesNameExist(Role.AdminRole))
 			{
@@ -202,7 +206,7 @@ namespace DevHive.Services.Services
 				foreach (var role in updateUserServiceModel.Roles)
 				{
 					Role returnedRole = await this._roleRepository.GetByNameAsync(role.Name) ??
-						throw new ArgumentException($"Role {role.Name} does not exist!");
+						throw new ArgumentNullException(string.Format(ErrorMessages.DoesNotExist, ClassesConstants.Role));
 
 					roles.Add(returnedRole);
 				}
@@ -214,7 +218,7 @@ namespace DevHive.Services.Services
 			for (int i = 0; i < languagesCount; i++)
 			{
 				Language language = await this._languageRepository.GetByNameAsync(updateUserServiceModel.Languages.ElementAt(i).Name) ??
-					throw new ArgumentException("Invalid language name!");
+					throw new InvalidDataException(string.Format(ErrorMessages.InvalidData, nameof(Language)));
 
 				languages.Add(language);
 			}
@@ -226,7 +230,8 @@ namespace DevHive.Services.Services
 			for (int i = 0; i < technologiesCount; i++)
 			{
 				Technology technology = await this._technologyRepository.GetByNameAsync(updateUserServiceModel.Technologies.ElementAt(i).Name) ??
-					throw new ArgumentException("Invalid technology name!");
+					throw new InvalidDataException(string.Format(ErrorMessages.InvalidData, nameof(Technology)));
+
 
 				technologies.Add(technology);
 			}