Merge pull request #28 from fogfish/object-id-at-gen-interface

add object id to gen representation

core.go

@@ -170,6 +170,7 @@ type FMap func(Gen) (Thing, error)
 //
 // Gen is a generic representation of storage type
 type Gen interface {
+	ID() (*ID, error)
 	To(Thing) error
 }
 

ddb.go

@@ -228,6 +228,21 @@ func (dynamo DB) Update(entity Thing, config ...Config) (err error) {
 // dbGen is type alias for generic representation
 type dbGen map[string]*dynamodb.AttributeValue
 
+// ID lifts generic representation to its Identity
+func (gen dbGen) ID() (*ID, error) {
+	prefix, isPrefix := gen["prefix"]
+	suffix, isSuffix := gen["suffix"]
+	if !isPrefix || !isSuffix {
+		return nil, errors.New("Invalid DDB schema")
+	}
+
+	pf := aws.StringValue(prefix.S)
+	sf := aws.StringValue(suffix.S)
+	id := MkID(curie.New(pf).Join(sf))
+
+	return &id, nil
+}
+
 // To lifts generic representation to Thing
 func (gen dbGen) To(thing Thing) error {
 	item, err := unmarshal(gen)

ddb_test.go

@@ -111,6 +111,16 @@ func TestDdbMatchWithFMap(t *testing.T) {
 		If(pseq).Should().Equal(persons{thing, thing})
 }
 
+func TestDdbMatchIDsWithFMap(t *testing.T) {
+	seq := dynamo.IDs{}
+	_, err := apiDB().Match(dynamo.NewID("dead:")).FMap(seq.Join)
+
+	thing := entity().ID
+	it.Ok(t).
+		If(err).Should().Equal(nil).
+		If(seq).Should().Equal(dynamo.IDs{thing, thing})
+}
+
 //-----------------------------------------------------------------------------
 //
 // Mock Dynamo DB

id.go

@@ -112,6 +112,28 @@ func (id ID) Unwrap() *IRI {
 
 /*
 
+IDs sequence of Identities
+*/
+type IDs []ID
+
+/*
+
+Join lifts sequence of matched objects to seq of IDs
+	seq := dynamo.IDs{}
+	dynamo.Match(...).FMap(seq.Join)
+*/
+func (seq *IDs) Join(gen Gen) (Thing, error) {
+	id, err := gen.ID()
+	if err != nil {
+		return nil, err
+	}
+
+	*seq = append(*seq, *id)
+	return id, nil
+}
+
+/*
+
 
 Thing is the most generic type of item. The interfaces declares anything with
 unique identifier. Embedding CURIE ID into struct makes it Thing compatible.

s3.go

@@ -3,11 +3,13 @@ package dynamo
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net"
 	"net/http"
 	"reflect"
+	"strings"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
@@ -136,6 +138,24 @@ type s3Gen struct {
 	key *string
 }
 
+// ID lifts generic representation to its Identity
+func (gen s3Gen) ID() (*ID, error) {
+	if gen.key == nil {
+		return nil, errors.New("End Of Stream")
+	}
+
+	var id ID
+	seq := strings.SplitN(*gen.key, "/", 2)
+	switch {
+	case len(seq) == 2:
+		id = MkID(curie.New(strings.Join(seq, ":")))
+	default:
+		id = MkID(curie.New(*gen.key))
+	}
+
+	return &id, nil
+}
+
 // Lifts generic representation to Thing
 func (gen s3Gen) To(thing Thing) error {
 	req := &s3.GetObjectInput{

s3_test.go

@@ -84,6 +84,16 @@ func TestS3MatchWithFMap(t *testing.T) {
 		If(pseq).Should().Equal(persons{thing, thing})
 }
 
+func TestS3MatchIDsWithFMap(t *testing.T) {
+	seq := dynamo.IDs{}
+	_, err := apiS3().Match(dynamo.NewID("dead:")).FMap(seq.Join)
+
+	thing := entity().ID
+	it.Ok(t).
+		If(err).Should().Equal(nil).
+		If(seq).Should().Equal(dynamo.IDs{thing, thing})
+}
+
 //-----------------------------------------------------------------------------
 //
 // Mock S3