service backend

api/pkg/db/internal/mongo/repositoryimp/builderimp/projection.go

@@ -0,0 +1,97 @@
+package builderimp
+
+import (
+	"github.com/tech/sendico/pkg/db/repository/builder"
+	"go.mongodb.org/mongo-driver/bson"
+)
+
+// projectionExprImp is a concrete implementation of builder.Projection
+// that projects a field using a custom expression.
+type projectionExprImp struct {
+	expr  builder.Expression // The expression for this projection.
+	field builder.Field      // The field name for the projected field.
+}
+
+// Field returns the field being projected.
+func (p *projectionExprImp) Field() builder.Field {
+	return p.field
+}
+
+// Expression returns the expression for the projection.
+func (p *projectionExprImp) Expression() builder.Expression {
+	return p.expr
+}
+
+// Build returns the built expression. If no expression is provided, returns 1.
+func (p *projectionExprImp) Build() bson.D {
+	if p.expr == nil {
+		return bson.D{{Key: p.field.Build(), Value: 1}}
+	}
+	return bson.D{{Key: p.field.Build(), Value: p.expr.Build()}}
+}
+
+// NewProjectionExpr creates a new Projection for a given field and expression.
+func NewProjectionExpr(field builder.Field, expr builder.Expression) builder.Projection {
+	return &projectionExprImp{field: field, expr: expr}
+}
+
+// aliasProjectionImp is a concrete implementation of builder.Projection
+// that projects an alias (renaming a field or expression).
+type aliasProjectionImp struct {
+	alias builder.Alias // The alias for this projection.
+}
+
+// Field returns the field being projected (via the alias).
+func (p *aliasProjectionImp) Field() builder.Field {
+	return p.alias.Field()
+}
+
+// Expression returns no additional expression for an alias projection.
+func (p *aliasProjectionImp) Expression() builder.Expression {
+	return nil
+}
+
+// Build returns the built alias expression.
+func (p *aliasProjectionImp) Build() bson.D {
+	return p.alias.Build()
+}
+
+// NewAliasProjection creates a new Projection that renames or wraps an existing field or expression.
+func NewAliasProjection(alias builder.Alias) builder.Projection {
+	return &aliasProjectionImp{alias: alias}
+}
+
+// sinkProjectionImp is a simple include/exclude projection (0 or 1).
+type sinkProjectionImp struct {
+	field builder.Field // The field name for the projected field.
+	val   int           // 1 to include, 0 to exclude.
+}
+
+// Expression returns no expression for a sink projection.
+func (p *sinkProjectionImp) Expression() builder.Expression {
+	return nil
+}
+
+// Build returns the include/exclude projection.
+func (p *sinkProjectionImp) Build() bson.D {
+	return bson.D{{Key: p.field.Build(), Value: p.val}}
+}
+
+// NewSinkProjection creates a new Projection that includes (true) or excludes (false) a field.
+func NewSinkProjection(field builder.Field, include bool) builder.Projection {
+	val := 0
+	if include {
+		val = 1
+	}
+	return &sinkProjectionImp{field: field, val: val}
+}
+
+// IncludeField returns a projection including the given field.
+func IncludeField(field builder.Field) builder.Projection {
+	return NewSinkProjection(field, true)
+}
+
+// ExcludeField returns a projection excluding the given field.
+func ExcludeField(field builder.Field) builder.Projection {
+	return NewSinkProjection(field, false)
+}