Adds the email campaign service layer inside the existing email domain

apps/api/internal/domains/email/campaign_service.go

@@ -0,0 +1,150 @@
+package email
+
+import (
+	"context"
+	"errors"
+	"strings"
+
+	"github.com/rs/zerolog"
+	"github.com/swamphacks/core/apps/api/internal/database/repository"
+	"github.com/swamphacks/core/apps/api/internal/database/sqlc"
+)
+
+var (
+	//Reuses repository-level "not found" error
+	ErrEmailCampaignNotFound = repository.ErrEmailCampaignNotFound
+
+	//validation errors before writing error to db
+	ErrEmailCampaignTitleRequired      = errors.New("email campaign title is required")
+	ErrEmailCampaignSubjectRequired    = errors.New("email campaign subject is required")
+	ErrEmailCampaignBodyRequired       = errors.New("email campaign body is required")
+	ErrEmailCampaignRecipientsRequired = errors.New("email campaign recipients are required")
+
+	ErrEmailCampaignCannotEdit = errors.New("email campaign cannot be edited")
+
+	//status-specific validation errors
+	ErrEmailCampaignScheduledAtRequired = errors.New("scheduled_at is required for scheduled campaigns")
+	ErrEmailCampaignSentAtRequired      = errors.New("sent_at is required for sent campaigns")
+)
+
+// EmailCampaignService owns business rules for saved email campaigns.
+type EmailCampaignService struct {
+	emailCampaignRepo *repository.EmailCampaignRepository
+	logger zerolog.Logger
+}
+
+// NewEmailCampaignService creates the service and stores its dependencies.
+// This will eventually be called from api.go when wiring the app together.
+func NewEmailCampaignService(
+	emailCampaignRepo *repository.EmailCampaignRepository,
+	logger zerolog.Logger,
+) *EmailCampaignService {
+	return &EmailCampaignService{
+		emailCampaignRepo: emailCampaignRepo,
+		logger:            logger.With().Str("service", "EmailCampaignService").Str("domain", "email").Logger(),
+	}
+}
+
+// CreateCampaign validates required campaign fields, then stores a new campaign.
+// The actual INSERT is handled by the repository/sqlc layer.
+func (s *EmailCampaignService) CreateCampaign(
+	ctx context.Context,
+	params sqlc.CreateEmailCampaignParams,
+) (*sqlc.EmailCampaign, error) {
+	if err := validateCampaignContent(params.Title, params.Subject, params.Body, params.RecipientTypes); err != nil {
+		return nil, err
+	}
+
+	return s.emailCampaignRepo.CreateEmailCampaign(ctx, params)
+}
+
+
+// GetCampaignByID fetches one campaign scoped to a hackathon.
+// The hackathon scope prevents one event from reading another event's campaign.
+func (s *EmailCampaignService) GetCampaignByID(
+	ctx context.Context,
+	params sqlc.GetEmailCampaignByIDParams,
+) (*sqlc.EmailCampaign, error) {
+	return s.emailCampaignRepo.GetEmailCampaignByID(ctx, params)
+}
+
+// ListCampaigns fetches all campaigns for one hackathon.
+// Sorting is handled by the SQL query, currently newest first.
+func (s *EmailCampaignService) ListCampaigns(
+	ctx context.Context,
+	hackathonID string,
+) ([]sqlc.EmailCampaign, error) {
+	return s.emailCampaignRepo.ListEmailCampaigns(ctx, hackathonID)
+}
+
+// UpdateCampaign updates editable campaign fields.
+// It first loads the existing campaign so we can enforce status rules before updating.
+func (s *EmailCampaignService) UpdateCampaign(
+	ctx context.Context,
+	params sqlc.UpdateEmailCampaignParams,
+) (*sqlc.EmailCampaign, error) {
+	existingCampaign, err := s.emailCampaignRepo.GetEmailCampaignByID(ctx, sqlc.GetEmailCampaignByIDParams{
+		ID:          params.ID,
+		HackathonID: params.HackathonID,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	if !canEditCampaign(existingCampaign.Status) {
+		return nil, ErrEmailCampaignCannotEdit
+	}
+
+	return s.emailCampaignRepo.UpdateEmailCampaign(ctx, params)
+}
+
+// UpdateCampaignStatus changes lifecycle fields such as draft -> scheduled or sending -> sent.
+// The database also has constraints, but checking here gives cleaner service-level errors.
+func (s *EmailCampaignService) UpdateCampaignStatus(
+	ctx context.Context,
+	params sqlc.UpdateEmailCampaignStatusParams,
+) (*sqlc.EmailCampaign, error) {
+	if params.Status == sqlc.EmailCampaignStatusScheduled && params.ScheduledAt == nil {
+		return nil, ErrEmailCampaignScheduledAtRequired
+	}
+
+	if params.Status == sqlc.EmailCampaignStatusSent && params.SentAt == nil {
+		return nil, ErrEmailCampaignSentAtRequired
+	}
+
+	return s.emailCampaignRepo.UpdateEmailCampaignStatus(ctx, params)
+}
+
+// validateCampaignContent checks fields that every campaign needs before it is saved.
+// strings.TrimSpace prevents values like "   " from passing validation.
+func validateCampaignContent(
+	title string,
+	subject string,
+	body string,
+	recipientTypes []sqlc.EmailRecipientType,
+) error {
+	if strings.TrimSpace(title) == "" {
+		return ErrEmailCampaignTitleRequired
+	}
+
+	if strings.TrimSpace(subject) == "" {
+		return ErrEmailCampaignSubjectRequired
+	}
+
+	if strings.TrimSpace(body) == "" {
+		return ErrEmailCampaignBodyRequired
+	}
+
+	if len(recipientTypes) == 0 {
+		return ErrEmailCampaignRecipientsRequired
+	}
+
+	return nil
+}
+
+// canEditCampaign centralizes edit rules.
+// Drafts are editable, and scheduled campaigns can still be adjusted before sending.
+func canEditCampaign(status sqlc.EmailCampaignStatus) bool {
+	return status == sqlc.EmailCampaignStatusDraft ||
+		status == sqlc.EmailCampaignStatusScheduled
+}