feat: Implement letter service with CRUD operations and message handling

- Added letter service to manage letters, including listing, creating, and editing letters and messages.
- Implemented functionality for sending and receiving messages within letters.
- Introduced pagination for letter listings and message retrieval.
- Added attachment upload capabilities for letters.
- Created detailed responses for letter and message retrieval.

feat: Introduce stats service for user statistics

- Added a service to retrieve user statistics, including newest and online citizens.

feat: Create ticket service for user support tickets

- Implemented ticket management service with functionalities to create, reply, and update tickets.
- Added support for ticket categories and their management.

feat: Add verification service for user account verification

- Implemented functionality to send verification emails for account activation.

feat: Develop warning service for user warnings

- Added service to issue warnings to users, deactivate warnings, and list user warnings.

feat: Create email templates for account status notifications

- Added HTML templates for account ban and disable notifications.

feat: Define request and response types for account, ticket, letter, and warning services

- Created structured request and response types for various services to ensure consistent data handling.

feat: Implement utility functions for authentication and sanitization

- Added functions for validating user hierarchy and sanitizing HTML input.
- Implemented token generation and hashing utilities for secure operations.

1 files changed, 108 insertions, 0 deletions

diff --git a/shrine/services/auth.go b/shrine/services/auth.go
new file mode 100644
index 0000000..28e63c4
--- /dev/null
+++ b/shrine/services/auth.go
@@ -0,0 +1,108 @@
+package services
+
+import (
+	"shrine/enums"
+	"shrine/messages"
+	"shrine/models"
+	"shrine/repositories"
+	"shrine/types/account"
+	"shrine/types/common"
+	"shrine/types/hypertext"
+	"shrine/utils/crypto"
+)
+
+func Register(request account.RegisterRequest) (*common.MessageResponse, *hypertext.ServiceError) {
+	citizen := models.User{
+		Username:    request.Username,
+		Email:       request.Email,
+		DisplayName: request.DisplayName,
+	}
+
+	if err := citizen.SetPassword(request.Password); err != nil {
+		return nil, fail(enums.BadRequest, err.Error())
+	}
+
+	if err := repositories.CreateUser(&citizen); err != nil {
+		return nil, mapRegistrationError(err)
+	}
+
+	if serviceErr := SendVerification(&citizen, enums.Activation); serviceErr != nil {
+		return nil, serviceErr
+	}
+
+	return &common.MessageResponse{Message: messages.AccountCreated}, nil
+}
+
+func Authenticate(request account.LoginRequest) (*models.User, *hypertext.ServiceError) {
+	citizen, err := repositories.FindUserByUsername(request.Username)
+	if err != nil {
+		return nil, fail(enums.Unauthorized, messages.InvalidUsernameOrPassword)
+	}
+
+	if citizen.ClearExpiredDisable() {
+		repositories.UpdateUser(citizen)
+	}
+
+	if !citizen.CanAuthenticate() {
+		return nil, fail(enums.Forbidden, messages.AccountBannedOrDisabled)
+	}
+
+	if !citizen.CheckPassword(request.Password) {
+		return nil, fail(enums.Unauthorized, messages.InvalidUsernameOrPassword)
+	}
+
+	if !citizen.IsVerified() {
+		return nil, fail(enums.Forbidden, messages.EmailNotVerified)
+	}
+
+	return citizen, nil
+}
+
+func VerifyAccount(request account.VerifyRequest) (*common.MessageResponse, *hypertext.ServiceError) {
+	if request.Token == "" {
+		return nil, fail(enums.BadRequest, messages.VerificationTokenRequired)
+	}
+
+	verificationType := enums.VerificationType(request.Type)
+	citizen, err := repositories.FindUserByVerification(crypto.HashToken(request.Token), verificationType)
+	if err != nil {
+		return nil, fail(enums.BadRequest, messages.VerificationLinkInvalid)
+	}
+
+	switch verificationType {
+	case enums.Activation:
+		citizen.VerifyEmail()
+	default:
+		return nil, fail(enums.BadRequest, messages.InvalidVerificationType)
+	}
+
+	if err := repositories.UpdateUser(citizen); err != nil {
+		return nil, fail(enums.Internal, messages.FailedVerifyAccount)
+	}
+
+	return &common.MessageResponse{Message: messages.EmailVerified}, nil
+}
+
+func ResendActivation(request account.ResendActivationRequest) (*common.MessageResponse, *hypertext.ServiceError) {
+	citizen, err := repositories.FindUserByEmail(request.Email)
+	if err != nil {
+		return nil, fail(enums.BadRequest, messages.NoAccountWithEmail)
+	}
+
+	if citizen.IsVerified() {
+		return nil, fail(enums.BadRequest, messages.AccountAlreadyVerified)
+	}
+
+	if serviceErr := SendVerification(citizen, enums.Activation); serviceErr != nil {
+		return nil, serviceErr
+	}
+
+	return &common.MessageResponse{Message: messages.VerificationEmailSent}, nil
+}
+
+func RevokeToken(tokenHash string) (*common.MessageResponse, *hypertext.ServiceError) {
+	if err := repositories.DeleteToken(tokenHash); err != nil {
+		return nil, fail(enums.Internal, messages.FailedEndSession)
+	}
+	return &common.MessageResponse{Message: messages.LoggedOut}, nil
+}
\ No newline at end of file