fluent: add toInterface (#304)

Fixes #178.

fluent/toInterfaceValue.go

@@ -0,0 +1,71 @@
+package fluent
+
+import (
+	"errors"
+
+	"github.com/ipld/go-ipld-prime/datamodel"
+)
+
+var errInvalidKind = errors.New("invalid kind")
+var errUnknownKind = errors.New("unknown kind")
+
+// ToInterface converts an IPLD node to its simplest equivalent Go value.
+//
+// Booleans, integers, floats, strings, bytes, and links are returned as themselves,
+// as per the node's AsT method. Note that nulls are returned as untyped nils.
+//
+// Lists and maps are returned as []interface{} and map[string]interface{}, respectively.
+func ToInterface(node datamodel.Node) (interface{}, error) {
+	switch k := node.Kind(); k {
+	case datamodel.Kind_Invalid:
+		return nil, errInvalidKind
+	case datamodel.Kind_Null:
+		return nil, nil
+	case datamodel.Kind_Bool:
+		return node.AsBool()
+	case datamodel.Kind_Int:
+		return node.AsInt()
+	case datamodel.Kind_Float:
+		return node.AsFloat()
+	case datamodel.Kind_String:
+		return node.AsString()
+	case datamodel.Kind_Bytes:
+		return node.AsBytes()
+	case datamodel.Kind_Link:
+		return node.AsLink()
+	case datamodel.Kind_Map:
+		outMap := make(map[string]interface{}, node.Length())
+		for mi := node.MapIterator(); !mi.Done(); {
+			k, v, err := mi.Next()
+			if err != nil {
+				return nil, err
+			}
+			kVal, err := k.AsString()
+			if err != nil {
+				return nil, err
+			}
+			vVal, err := ToInterface(v)
+			if err != nil {
+				return nil, err
+			}
+			outMap[kVal] = vVal
+		}
+		return outMap, nil
+	case datamodel.Kind_List:
+		outList := make([]interface{}, 0, node.Length())
+		for li := node.ListIterator(); !li.Done(); {
+			_, v, err := li.Next()
+			if err != nil {
+				return nil, err
+			}
+			vVal, err := ToInterface(v)
+			if err != nil {
+				return nil, err
+			}
+			outList = append(outList, vVal)
+		}
+		return outList, nil
+	default:
+		return nil, errUnknownKind
+	}
+}

fluent/toInterfaceValue_test.go

@@ -0,0 +1,47 @@
+package fluent_test
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime/fluent"
+	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+)
+
+var roundTripTestCases = []struct {
+	name  string
+	value interface{}
+}{
+	{name: "Number", value: int64(100)},
+	{name: "String", value: "hi"},
+	{name: "Bool", value: true},
+	{name: "Bytes", value: []byte("hi")},
+	{name: "Map", value: map[string]interface{}{"a": "1", "b": int64(2), "c": 3.14, "d": true}},
+	{name: "Array", value: []interface{}{"a", "b", "c"}},
+	{name: "Nil", value: nil},
+}
+
+func TestRoundTrip(t *testing.T) {
+	for _, testCase := range roundTripTestCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			c := qt.New(t)
+			n, err := fluent.Reflect(basicnode.Prototype.Any, testCase.value)
+			c.Assert(err, qt.IsNil)
+			out, err := fluent.ToInterface(n)
+			c.Assert(err, qt.IsNil)
+			c.Check(out, qt.DeepEquals, testCase.value)
+		})
+	}
+}
+
+func TestLink(t *testing.T) {
+	c := qt.New(t)
+	someCid, err := cid.Parse("bafybeihrqe2hmfauph5yfbd6ucv7njqpiy4tvbewlvhzjl4bhnyiu6h7pm")
+	c.Assert(err, qt.IsNil)
+	link := cidlink.Link{Cid: someCid}
+	v, err := fluent.ToInterface(basicnode.NewLink(link))
+	c.Assert(err, qt.IsNil)
+	c.Assert(v.(cidlink.Link), qt.Equals, link)
+}