Introduce event services and update models

Added the initial implementation of the event service with methods to
retrieve and create events, incorporating user and tag data. Adjusted
the database transaction logic to ensure consistency during event
creation. In the model layer, strengthened the relationship between the
`Cfp` and `Event` by adding an `EventID` to `Cfp` and removing the
redundant `cfp_id` from `Event`, thereby normalizing the database schema
and reducing redundancy. These enhancements prepare for more robust
event handling and querying capabilities.

Resolves #42 - Implement event services
Fixes #56 - Normalize event relationship in models

pkg/event/service_event.go

@@ -0,0 +1,124 @@
+package event
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"time"
+
+	"github.com/lib/pq"
+	"github.com/marcopollivier/techagenda/pkg/user"
+	"github.com/samber/lo"
+	"gorm.io/gorm"
+)
+
+type Service interface {
+	Get(ctx context.Context, name, city string, tags []string, typeOf []EventTypeOf, available bool, page, limit int) (events []Event, err error)
+	Create(ctx context.Context, user user.User, event EventDTO, tags []string) (result Event, err error)
+}
+
+type EventService struct {
+	db *gorm.DB
+}
+
+func NewEventService(db *gorm.DB) Service {
+	return &EventService{
+		db: db,
+	}
+}
+
+func (e *EventService) Get(
+	ctx context.Context,
+	name, city string,
+	tags []string,
+	typeOf []EventTypeOf,
+	available bool,
+	page, limit int,
+) (events []Event, err error) {
+	if limit == 0 || limit > 100 {
+		limit = 50
+	}
+	now := time.Now()
+	base := e.db.Joins("User").
+		Preload("Attendees").
+		Preload("Tags", func(db *gorm.DB) *gorm.DB {
+			if len(tags) > 0 {
+				return db.Where("tag in ?", tags)
+			}
+			return db
+		}).
+		Preload("Venues", func(db *gorm.DB) *gorm.DB {
+			if lo.IsNotEmpty(city) {
+				return db.Where("city in ?", city)
+			}
+			return db
+		}).
+		Offset(page * limit).
+		Limit(limit)
+
+	if lo.IsNotEmpty(name) {
+		base.Where("name like ?", name)
+	}
+	if len(typeOf) > 0 {
+		base.Where("? in ANY(typeOf)", typeOf)
+	}
+	if available {
+		base.Where("begin_date <= ?", now).Where("end_date > ?", now)
+	}
+
+	if err = base.Find(&events).Error; err != nil {
+		slog.ErrorContext(ctx, "Fail to scan events", "error", err.Error())
+	}
+	return
+}
+
+func (e *EventService) Create(ctx context.Context, user user.User, event EventDTO, tags []string) (result Event, err error) {
+	type EventsTag struct {
+		EventID uint
+		TagID   uint
+	}
+	var (
+		tagIDs []uint
+		typeOf = lo.Map(event.TypeOf, func(i EventTypeOf, _ int) string { return i.String() })
+	)
+
+	result = Event{
+		Title:       event.Title,
+		Banner:      event.Banner,
+		Description: event.Description,
+		Href:        event.Href,
+		TypeOf:      append(pq.StringArray{}, typeOf...),
+		BeginDate:   event.BeginDate,
+		EndDate:     event.EndDate,
+		UserID:      user.ID,
+	}
+
+	err = e.db.Transaction(func(tx *gorm.DB) (er error) {
+		if er = tx.Create(&result).Error; er != nil {
+			slog.ErrorContext(ctx, "Fail to create event", "error", er.Error())
+			return er
+		}
+		if er = tx.Table("tags").Select("id").Where("tag in = ?", tags).Find(&tagIDs).Error; er != nil {
+			slog.ErrorContext(ctx, "Fail to find tags", "error", er.Error())
+			return er
+		}
+		if len(tagIDs) != len(tags) {
+			slog.ErrorContext(ctx, "Some tags ware not found in the database", "tags_requested", tags, "ids_found", tagIDs)
+			return errors.New("unable to find a match for all the requested tags")
+		}
+		for _, tagID := range tagIDs {
+			eventTag := EventsTag{
+				EventID: result.ID,
+				TagID:   tagID,
+			}
+			if er = tx.Create(&eventTag).Error; er != nil {
+				slog.ErrorContext(ctx, "Fail to create join of event and tag", "error", er.Error(), "event", result, "tag_id", tagID)
+				return er
+			}
+		}
+
+		return nil
+	})
+
+	return
+}

pkg/event/service_tag.go

@@ -0,0 +1 @@
+package event

ui/src/props/lending.generated.ts

@@ -6,6 +6,7 @@ export interface Cfp {
     CreatedAt: Time;
     UpdatedAt: Time;
     DeletedAt: DeletedAt;
+    EventID: number;
     begin: Time;
     end: Time;
     href: string;
@@ -70,7 +71,6 @@ export interface Event {
     type_of: string[];
     begin: Time;
     end: Time;
-    cfp_id: number;
     user_id: number;
     attendees: Attendee[];
     tags: Tags[];