Seen Service (#39)

* Seen Service

* Fixes for model

* Update import

* More fixes

* Complete seen service

seen/domain/domain.go

@@ -0,0 +1,93 @@
+package domain
+
+import (
+	"time"
+
+	"github.com/micro/micro/v3/service/model"
+	"github.com/micro/micro/v3/service/store"
+)
+
+// Seen is the object which represents a user seeing a resource
+type Seen struct {
+	ID           string
+	UserID       string
+	ResourceID   string
+	ResourceType string
+	Timestamp    time.Time
+}
+
+type Domain struct {
+	db model.Model
+}
+
+var (
+	userIDIndex       = model.ByEquality("UserID")
+	resourceIDIndex   = model.ByEquality("ResourceID")
+	resourceTypeIndex = model.ByEquality("ResourceType")
+)
+
+func New(store store.Store) *Domain {
+	db := model.New(store, Seen{}, []model.Index{
+		userIDIndex, resourceIDIndex, resourceTypeIndex,
+	}, &model.ModelOptions{})
+
+	return &Domain{db: db}
+}
+
+// Create a seen object in the store
+func (d *Domain) Create(s Seen) error {
+	return d.db.Create(s)
+}
+
+// Delete a seen object from the store
+func (d *Domain) Delete(s Seen) error {
+	// load all the users objects and then delete only the ones which match the resource, unfortunately
+	// the model doesn't yet support querying by multiple columns
+	var all []Seen
+	if err := d.db.Read(model.Equals("UserID", s.UserID), &all); err != nil {
+		return err
+	}
+	for _, a := range all {
+		if s.ResourceID != a.ResourceID {
+			continue
+		}
+		if s.ResourceType != s.ResourceType {
+			continue
+		}
+
+		q := model.Equals("ID", a.ID)
+		q.Order.Type = model.OrderTypeUnordered
+		if err := d.db.Delete(q); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Read the timestamps from the store
+func (d *Domain) Read(userID, resourceType string, resourceIDs []string) (map[string]time.Time, error) {
+	// load all the users objects and then return only the timestamps for the ones which match the
+	// resource, unfortunately the model doesn't yet support querying by multiple columns
+	var all []Seen
+	if err := d.db.Read(model.Equals("UserID", userID), &all); err != nil {
+		return nil, err
+	}
+
+	result := map[string]time.Time{}
+	for _, a := range all {
+		if a.ResourceType != resourceType {
+			continue
+		}
+
+		for _, id := range resourceIDs {
+			if id != a.ResourceID {
+				continue
+			}
+
+			result[id] = a.Timestamp
+			break
+		}
+	}
+
+	return result, nil
+}