add Count function to Model

begin work on tracking populated/unpopulated fields

document.go

@@ -7,12 +7,13 @@ import (
 
 type Document struct {
 	// Created time. updated/added automatically.
-	Created time.Time `bson:"createdAt" json:"createdAt"`
+	Created time.Time `bson:"createdAt" json:"createdAt" tstype:"Date"`
 	// Modified time. updated/added automatically.
-	Modified time.Time `bson:"updatedAt" json:"updatedAt"`
-	model    *Model    `bson:"-"`
-	exists   bool      `bson:"-"`
-	self     any       `bson:"-"`
+	Modified        time.Time       `bson:"updatedAt" json:"updatedAt" tstype:"Date"`
+	model           *Model          `bson:"-"`
+	exists          bool            `bson:"-"`
+	self            any             `bson:"-"`
+	populatedFields map[string]bool `bson:"-"`
 }
 type IDocument interface {
 	Append(field string, a ...interface{}) error
@@ -32,6 +33,8 @@ type IDocument interface {
 	serializeToStore() any
 	getModel() *Model
 	setModel(m Model)
+	markPopulated(field string)
+	markDepopulated(field string)
 }
 
 type SaveOptions struct {

document_internals.go

@@ -266,3 +266,11 @@ func incrementAll(item interface{}) {
 	default:
 	}
 }
+
+func (d *Document) markPopulated(field string) {
+	d.populatedFields[field] = true
+}
+
+func (d *Document) markDepopulated(field string) {
+	d.populatedFields[field] = false
+}

model.go

@@ -193,6 +193,11 @@ func (m *Model) FindOne(query interface{}, options *options.FindOneOptionsBuilde
 	return qq, err
 }
 
+func (m *Model) Count(query interface{}, options *options.CountOptionsBuilder) (int64, error) {
+	coll := m.getColl()
+	return coll.CountDocuments(context.TODO(), query, options)
+}
+
 func createBase(d any) (reflect.Value, int, string) {
 	var n string
 	var ri *Model