From 939f8896661a72582149ec35351c517734e3bde8 Mon Sep 17 00:00:00 2001
From: Thomas Pelletier <pelletier.thomas@gmail.com>
Date: Wed, 17 Mar 2021 09:57:50 -0400
Subject: [PATCH] wip: figuring out unmarshaling to interfaces

---
 targets.go          | 56 +++++++++++++++++++++++++++++++++------------
 unmarshaler.go      | 53 +++++++++++++++++++++++++++++-------------
 unmarshaler_test.go |  1 -
 3 files changed, 79 insertions(+), 31 deletions(-)

diff --git a/targets.go b/targets.go
index 417cdb5..b0f9db2 100644
--- a/targets.go
+++ b/targets.go
@@ -196,21 +196,54 @@ func pushNew(t target) (target, error) {
 	}
 }
 
-func scopeTarget(t target, name string) (target, error) {
-	x := t.get()
-	return scope(x, name)
-}
-
 func scopeTableTarget(append bool, t target, name string) (target, error) {
 	x := t.get()
+
+	if x.Kind() == reflect.Interface {
+		t, err := initInterface(append, t)
+		if err != nil {
+			return t, err
+		}
+		x = t.get()
+	}
+
+	if x.Kind() == reflect.Slice {
+		return scopeSlice(t, append)
+	}
+
 	t, err := scope(x, name)
 	if err != nil {
 		return t, err
 	}
-	x = t.get()
-	if x.Kind() == reflect.Slice {
-		return scopeSlice(t, append)
+	return t, nil
+}
+
+// initInterface makes sure that the interface pointed at by the target is not
+// nil.
+// Returns the target to the initialized value of the target.
+func initInterface(append bool, t target) (target, error) {
+	x := t.get()
+
+	if x.Kind() != reflect.Interface {
+		panic("this should only be called on interfaces")
 	}
+
+	if x.IsNil() {
+		var newElement reflect.Value
+		if append {
+			newElement = reflect.MakeSlice(reflect.TypeOf([]interface{}{}), 0, 0)
+		} else {
+			newElement = reflect.MakeMap(reflect.TypeOf(map[string]interface{}{}))
+		}
+		err := t.set(newElement)
+		if err != nil {
+			return t, err
+		}
+		x = t.get()
+	}
+
+	x = x.Elem()
+	t = valueTarget(x)
 	return t, nil
 }
 
@@ -218,12 +251,6 @@ func scope(v reflect.Value, name string) (target, error) {
 	switch v.Kind() {
 	case reflect.Struct:
 		return scopeStruct(v, name)
-	case reflect.Interface:
-		if v.IsNil() {
-			panic("not implemented") // TODO
-		} else {
-			return scope(v.Elem(), name)
-		}
 	case reflect.Map:
 		return scopeMap(v, name)
 	default:
@@ -233,6 +260,7 @@ func scope(v reflect.Value, name string) (target, error) {
 
 func scopeSlice(t target, append bool) (target, error) {
 	v := t.get()
+
 	if append {
 		newElem := reflect.New(v.Type().Elem())
 		newSlice := reflect.Append(v, newElem.Elem())
diff --git a/unmarshaler.go b/unmarshaler.go
index 309fd38..478a127 100644
--- a/unmarshaler.go
+++ b/unmarshaler.go
@@ -42,18 +42,26 @@ func fromAst(tree ast.Root, v interface{}) error {
 // unchanged, except by table and array table.
 func unmarshalTopLevelNode(root target, x target, node *ast.Node) (target, error) {
 	switch node.Kind {
-	case ast.Table:
-		return scopeWithTable(root, node.Key())
-	case ast.ArrayTable:
-		return scopeWithArrayTable(root, node.Key())
 	case ast.KeyValue:
 		return x, unmarshalKeyValue(x, node)
+	case ast.Table:
+		return scopeWithKey(root, node.Key())
+	case ast.ArrayTable:
+		return scopeWithArrayTable(root, node.Key())
 	default:
 		panic(fmt.Errorf("this should not be a top level node type: %s", node.Kind))
 	}
 }
 
-func scopeWithTable(x target, key []ast.Node) (target, error) {
+// scopeWithKey performs target scoping when unmarshaling an ast.KeyValue node.
+//
+// The goal is to hop from target to target recursively using the names in key.
+// Parts of the key should be used to resolve field names for structs, and as
+// keys when targeting maps.
+//
+// When encountering slices, it should always use its last element, and error
+// if the slice does not have any.
+func scopeWithKey(x target, key []ast.Node) (target, error) {
 	var err error
 	for _, n := range key {
 		x, err = scopeTableTarget(false, x, string(n.Data))
@@ -64,6 +72,11 @@ func scopeWithTable(x target, key []ast.Node) (target, error) {
 	return x, nil
 }
 
+// scopeWithArrayTable performs target scoping when unmarshaling an
+// ast.ArrayTable node.
+//
+// It is the same as scopeWithKey, but when scoping the last part of the key
+// it creates a new element in the array instead of using the last one.
 func scopeWithArrayTable(x target, key []ast.Node) (target, error) {
 	var err error
 	if len(key) > 1 {
@@ -74,18 +87,26 @@ func scopeWithArrayTable(x target, key []ast.Node) (target, error) {
 			}
 		}
 	}
-	return scopeTableTarget(true, x, string(key[len(key)-1].Data))
-}
-
-func scopeWithKey(x target, key []ast.Node) (target, error) {
-	var err error
-	for _, n := range key {
-		x, err = scopeTarget(x, string(n.Data))
-		if err != nil {
-			return nil, err
-		}
+	x, err = scopeTableTarget(true, x, string(key[len(key)-1].Data))
+	if err != nil {
+		return x, err
 	}
-	return x, nil
+
+	v := x.get()
+
+	if v.Kind() == reflect.Interface {
+		x, err = initInterface(true, x)
+		if err != nil {
+			return x, err
+		}
+		v = x.get()
+	}
+
+	if v.Kind() == reflect.Slice {
+		return scopeSlice(x, true)
+	}
+
+	return x, err
 }
 
 func unmarshalKeyValue(x target, node *ast.Node) error {
diff --git a/unmarshaler_test.go b/unmarshaler_test.go
index 8c682ed..e748d0c 100644
--- a/unmarshaler_test.go
+++ b/unmarshaler_test.go
@@ -420,7 +420,6 @@ B = "data"`,
 			},
 		},
 		{
-			skip: true, // TODO
 			desc: "one-level multi-element array table to map",
 			input: `[[Products]]
 					Name = "Hammer"