Path: Use concrete types instead of path.Value where possible.

Change-Id: I8f41a57b00e9875ba518f9ca214456cad00e5457

9 files changed, 84 insertions, 57 deletions

diff --git a/service/path/array_index.go b/service/path/array_index.go
index d2542ed1c..479309f1e 100644
--- a/service/path/array_index.go
+++ b/service/path/array_index.go
@@ -23,7 +23,7 @@ import (
 // ArrayIndex is a path that refers to a single element of an array.
 type ArrayIndex struct {
 	binary.Generate
-	Array Value  // The path to the array.
+	Array Path   // The path to the array.
 	Index uint64 // The index of the element in the array.
 }
 
@@ -42,20 +42,29 @@ func (n *ArrayIndex) Base() Path {
 
 // Clone implements the Path interface, returning a deep-copy of this path.
 func (n *ArrayIndex) Clone() Path {
-	return &ArrayIndex{Array: n.Array.Clone().(Value), Index: n.Index}
+	return &ArrayIndex{Array: n.Array.Clone(), Index: n.Index}
 }
 
-// Field implements the Value interface.
-func (n *ArrayIndex) Field(name string) Value {
+// Field returns the path to the field value with the specified name on the
+// struct object represented by this path.
+// The represented value type must be of type struct, otherwise the returned
+// path is invalid.
+func (n *ArrayIndex) Field(name string) *Field {
 	return &Field{Struct: n, Name: name}
 }
 
-// ArrayIndex implements the Value interface.
-func (n *ArrayIndex) ArrayIndex(index uint64) Value {
+// ArrayIndex returns the path to the i'th element on the array or slice
+// represented by this path.
+// The represented value type must be of type array or slice, otherwise the
+// returned path is invalid.
+func (n *ArrayIndex) ArrayIndex(index uint64) *ArrayIndex {
 	return &ArrayIndex{Array: n, Index: index}
 }
 
-// MapIndex implements the Value interface.
-func (n *ArrayIndex) MapIndex(key interface{}) Value {
+// MapIndex returns the path to the map element with key k on the map object
+// represented by this path.
+// The represented value type must be of type map, otherwise the returned path
+// is invalid.
+func (n *ArrayIndex) MapIndex(key interface{}) *MapIndex {
 	return &MapIndex{Map: n, Key: key}
 }
diff --git a/service/path/atom.go b/service/path/atom.go
index d31f8020d..b81cbf521 100644
--- a/service/path/atom.go
+++ b/service/path/atom.go
@@ -45,21 +45,12 @@ func (n *Atom) Clone() Path {
 	return &Atom{Atoms: n.Atoms.Clone().(*Atoms), Index: n.Index}
 }
 
-// Field implements the Value interface.
-func (n *Atom) Field(name string) Value {
+// Field returns the path to the field value with the specified name on the
+// atom represented by this path.
+func (n *Atom) Field(name string) *Field {
 	return &Field{Struct: n, Name: name}
 }
 
-// ArrayIndex implements the Value interface.
-func (n *Atom) ArrayIndex(index uint64) Value {
-	return &ArrayIndex{Array: n, Index: index}
-}
-
-// MapIndex implements the Value interface.
-func (n *Atom) MapIndex(key interface{}) Value {
-	return &MapIndex{Map: n, Key: key}
-}
-
 // StateAfter returns the path to the state immediately following this atom.
 func (n *Atom) StateAfter() *State {
 	return &State{After: n}
diff --git a/service/path/capture.go b/service/path/capture.go
index b2799cfc8..69d44aec0 100644
--- a/service/path/capture.go
+++ b/service/path/capture.go
@@ -50,6 +50,6 @@ func (c *Capture) Atoms() *Atoms {
 }
 
 // Report returns the path to the capture's report.
-func (c *Capture) Report() Path {
+func (c *Capture) Report() *Report {
 	return &Report{Capture: c}
 }
diff --git a/service/path/field.go b/service/path/field.go
index 689fceb27..ad3723f40 100644
--- a/service/path/field.go
+++ b/service/path/field.go
@@ -23,7 +23,7 @@ import (
 // Field is a path that refers to a single field of a struct object.
 type Field struct {
 	binary.Generate
-	Struct Value  // The path to the structure holding the field.
+	Struct Path   // The path to the structure holding the field.
 	Name   string // The name of the field.
 }
 
@@ -42,20 +42,29 @@ func (n *Field) Base() Path {
 
 // Clone implements the Path interface, returning a deep-copy of this path.
 func (n *Field) Clone() Path {
-	return &Field{Struct: n.Struct.Clone().(Value), Name: n.Name}
+	return &Field{Struct: n.Struct.Clone(), Name: n.Name}
 }
 
-// Field implements the Value interface.
-func (n *Field) Field(name string) Value {
+// Field returns the path to the field value with the specified name on the
+// struct object represented by this path.
+// The represented value type must be of type struct, otherwise the returned
+// path is invalid.
+func (n *Field) Field(name string) *Field {
 	return &Field{Struct: n, Name: name}
 }
 
-// ArrayIndex implements the Value interface.
-func (n *Field) ArrayIndex(index uint64) Value {
+// ArrayIndex returns the path to the i'th element on the array or slice
+// represented by this path.
+// The represented value type must be of type array or slice, otherwise the
+// returned path is invalid.
+func (n *Field) ArrayIndex(index uint64) *ArrayIndex {
 	return &ArrayIndex{Array: n, Index: index}
 }
 
-// MapIndex implements the Value interface.
-func (n *Field) MapIndex(key interface{}) Value {
+// MapIndex returns the path to the map element with key k on the map object
+// represented by this path.
+// The represented value type must be of type map, otherwise the returned path
+// is invalid.
+func (n *Field) MapIndex(key interface{}) *MapIndex {
 	return &MapIndex{Map: n, Key: key}
 }
diff --git a/service/path/map_index.go b/service/path/map_index.go
index b2a5d7848..ac4a7eec6 100644
--- a/service/path/map_index.go
+++ b/service/path/map_index.go
@@ -23,7 +23,7 @@ import (
 // MapIndex is a path that refers to a single value in a map.
 type MapIndex struct {
 	binary.Generate
-	Map Value       // The path to the map containing the value.
+	Map Path        // The path to the map containing the value.
 	Key interface{} // The key to the value in the map.
 }
 
@@ -42,20 +42,29 @@ func (n *MapIndex) Base() Path {
 
 // Clone implements the Path interface, returning a deep-copy of this path.
 func (n *MapIndex) Clone() Path {
-	return &MapIndex{Map: n.Map.Clone().(Value), Key: n.Key}
+	return &MapIndex{Map: n.Map.Clone(), Key: n.Key}
 }
 
-// Field implements the Value interface.
-func (n *MapIndex) Field(name string) Value {
+// Field returns the path to the field value with the specified name on the
+// struct object represented by this path.
+// The represented value type must be of type struct, otherwise the returned
+// path is invalid.
+func (n *MapIndex) Field(name string) *Field {
 	return &Field{Struct: n, Name: name}
 }
 
-// ArrayIndex implements the Value interface.
-func (n *MapIndex) ArrayIndex(index uint64) Value {
+// ArrayIndex returns the path to the i'th element on the array or slice
+// represented by this path.
+// The represented value type must be of type array or slice, otherwise the
+// returned path is invalid.
+func (n *MapIndex) ArrayIndex(index uint64) *ArrayIndex {
 	return &ArrayIndex{Array: n, Index: index}
 }
 
-// MapIndex implements the Value interface.
-func (n *MapIndex) MapIndex(key interface{}) Value {
+// MapIndex returns the path to the map element with key k on the map object
+// represented by this path.
+// The represented value type must be of type map, otherwise the returned path
+// is invalid.
+func (n *MapIndex) MapIndex(key interface{}) *MapIndex {
 	return &MapIndex{Map: n, Key: key}
 }
diff --git a/service/path/path.go b/service/path/path.go
index 30ce83dff..fd305e5b4 100644
--- a/service/path/path.go
+++ b/service/path/path.go
@@ -53,17 +53,17 @@ type Value interface {
 	// struct object represented by this path.
 	// The represented value type must be of type struct, otherwise the returned
 	// path is invalid.
-	Field(name string) Value
+	Field(name string) *Field
 
-	// ArrayIndex returns the path to the i'th array element on the array object
+	// ArrayIndex returns the path to the i'th element on the array or slice
 	// represented by this path.
 	// The represented value type must be of type array or slice, otherwise the
 	// returned path is invalid.
-	ArrayIndex(i uint64) Value
+	ArrayIndex(i uint64) *ArrayIndex
 
 	// MapIndex returns the path to the map element with key k on the map object
 	// represented by this path.
 	// The represented value type must be of type map, otherwise the returned path
 	// is invalid.
-	MapIndex(k interface{}) Value
+	MapIndex(k interface{}) *MapIndex
 }
diff --git a/service/path/path_binary.go b/service/path/path_binary.go
index 3ea96436d..c30617ba8 100644
--- a/service/path/path_binary.go
+++ b/service/path/path_binary.go
@@ -27,12 +27,12 @@ func init() {
 }
 
 var (
-	binaryIDArrayIndex = binary.ID{0x48, 0x23, 0xb9, 0xfb, 0x5c, 0x3c, 0xd8, 0x21, 0x0a, 0xe7, 0xca, 0x09, 0xc7, 0xb9, 0x4b, 0xc9, 0x7d, 0xd2, 0x48, 0x69}
+	binaryIDArrayIndex = binary.ID{0x70, 0x45, 0xaf, 0xd6, 0x00, 0x20, 0x4c, 0x2c, 0x72, 0x36, 0x74, 0xc3, 0x2e, 0x1e, 0xb9, 0xf5, 0x4b, 0xe6, 0x68, 0xfb}
 	binaryIDCapture    = binary.ID{0x0e, 0x9b, 0xe3, 0x62, 0x7b, 0x67, 0x5b, 0xe0, 0x44, 0x7b, 0x7b, 0x21, 0xa1, 0x50, 0x6d, 0x1b, 0xfb, 0xc7, 0x47, 0xe6}
 	binaryIDAtoms      = binary.ID{0x17, 0x6b, 0x7c, 0x08, 0xc2, 0x36, 0x2c, 0xe3, 0x1b, 0x17, 0xd5, 0x3a, 0x0a, 0x98, 0x5b, 0x76, 0xc5, 0x1d, 0x01, 0xa7}
 	binaryIDAtom       = binary.ID{0x58, 0x11, 0xbe, 0x6d, 0xfc, 0xe2, 0xe0, 0x12, 0x6c, 0x42, 0x55, 0x2d, 0xf3, 0x5e, 0x11, 0x1a, 0xc1, 0x6b, 0xfe, 0x3b}
-	binaryIDField      = binary.ID{0xd0, 0x6a, 0xce, 0x53, 0xcf, 0xc3, 0x4c, 0x2a, 0x51, 0xa7, 0xaf, 0xf1, 0xb5, 0x91, 0x67, 0xdd, 0xe0, 0x21, 0x7b, 0x02}
-	binaryIDMapIndex   = binary.ID{0xf1, 0xfd, 0x8e, 0x5c, 0x70, 0x49, 0x7f, 0xbd, 0x40, 0xbc, 0x54, 0x04, 0xff, 0x46, 0x76, 0xec, 0x4c, 0x4c, 0xc0, 0x01}
+	binaryIDField      = binary.ID{0xd2, 0x4f, 0x7f, 0x64, 0xec, 0x81, 0x92, 0x06, 0x6c, 0x25, 0x60, 0xfa, 0x5a, 0x0b, 0x9c, 0x6e, 0x73, 0xf7, 0x4b, 0x4c}
+	binaryIDMapIndex   = binary.ID{0x0d, 0x46, 0x56, 0xf3, 0x1d, 0xba, 0xf9, 0xd8, 0x5e, 0xcf, 0xcc, 0x0e, 0x84, 0x93, 0x38, 0x5b, 0xbb, 0xd2, 0xec, 0xde}
 	binaryIDReport     = binary.ID{0xc3, 0x15, 0x30, 0x12, 0xb4, 0xa6, 0x7e, 0x71, 0x3a, 0xa3, 0xec, 0xb5, 0x93, 0x21, 0xf6, 0x2f, 0xd2, 0xf1, 0x4f, 0xa9}
 	binaryIDState      = binary.ID{0xf1, 0xa4, 0x19, 0x51, 0x01, 0xc4, 0xe2, 0x90, 0xc2, 0xca, 0x28, 0x00, 0x17, 0x08, 0x72, 0xb9, 0x46, 0x3a, 0xd1, 0x7b}
 )
@@ -59,7 +59,7 @@ func doDecodeArrayIndex(d binary.Decoder, o *ArrayIndex) error {
 	if obj, err := d.Object(); err != nil {
 		return err
 	} else if obj != nil {
-		o.Array = obj.(Value)
+		o.Array = obj.(Path)
 	} else {
 		o.Array = nil
 	}
@@ -99,7 +99,7 @@ var schemaArrayIndex = &schema.Class{
 	Package: "path",
 	Name:    "ArrayIndex",
 	Fields: []schema.Field{
-		{Declared: "Array", Type: &schema.Interface{Name: "Value"}},
+		{Declared: "Array", Type: &schema.Interface{Name: "Path"}},
 		{Declared: "Index", Type: &schema.Primitive{Name: "uint64", Method: schema.Uint64}},
 	},
 }
@@ -297,7 +297,7 @@ func doDecodeField(d binary.Decoder, o *Field) error {
 	if obj, err := d.Object(); err != nil {
 		return err
 	} else if obj != nil {
-		o.Struct = obj.(Value)
+		o.Struct = obj.(Path)
 	} else {
 		o.Struct = nil
 	}
@@ -337,7 +337,7 @@ var schemaField = &schema.Class{
 	Package: "path",
 	Name:    "Field",
 	Fields: []schema.Field{
-		{Declared: "Struct", Type: &schema.Interface{Name: "Value"}},
+		{Declared: "Struct", Type: &schema.Interface{Name: "Path"}},
 		{Declared: "Name", Type: &schema.Primitive{Name: "string", Method: schema.String}},
 	},
 }
@@ -373,7 +373,7 @@ func doDecodeMapIndex(d binary.Decoder, o *MapIndex) error {
 	if obj, err := d.Object(); err != nil {
 		return err
 	} else if obj != nil {
-		o.Map = obj.(Value)
+		o.Map = obj.(Path)
 	} else {
 		o.Map = nil
 	}
@@ -417,7 +417,7 @@ var schemaMapIndex = &schema.Class{
 	Package: "path",
 	Name:    "MapIndex",
 	Fields: []schema.Field{
-		{Declared: "Map", Type: &schema.Interface{Name: "Value"}},
+		{Declared: "Map", Type: &schema.Interface{Name: "Path"}},
 		{Declared: "Key", Type: &any.Any{}},
 	},
 }
diff --git a/service/path/report.go b/service/path/report.go
index 16eba87aa..4a1b38297 100644
--- a/service/path/report.go
+++ b/service/path/report.go
@@ -23,7 +23,7 @@ import (
 // Report is a path that refers to a capture's report.
 type Report struct {
 	binary.Generate
-	Capture *Capture // The path to the capture containing the atoms.
+	Capture *Capture // The path to the capture containing the report.
 }
 
 // String returns the string representation of the path.
diff --git a/service/path/state.go b/service/path/state.go
index 04f9f3567..530d3051c 100644
--- a/service/path/state.go
+++ b/service/path/state.go
@@ -45,17 +45,26 @@ func (n *State) Clone() Path {
 	return &State{After: n.After.Clone().(*Atom)}
 }
 
-// Field implements the Value interface.
-func (n *State) Field(name string) Value {
+// Field returns the path to the field value with the specified name on the
+// struct object represented by this path.
+// The represented value type must be of type struct, otherwise the returned
+// path is invalid.
+func (n *State) Field(name string) *Field {
 	return &Field{Struct: n, Name: name}
 }
 
-// ArrayIndex implements the Value interface.
-func (n *State) ArrayIndex(index uint64) Value {
+// ArrayIndex returns the path to the i'th element on the array or slice
+// represented by this path.
+// The represented value type must be of type array or slice, otherwise the
+// returned path is invalid.
+func (n *State) ArrayIndex(index uint64) *ArrayIndex {
 	return &ArrayIndex{Array: n, Index: index}
 }
 
-// MapIndex implements the Value interface.
-func (n *State) MapIndex(key interface{}) Value {
+// MapIndex returns the path to the map element with key k on the map object
+// represented by this path.
+// The represented value type must be of type map, otherwise the returned path
+// is invalid.
+func (n *State) MapIndex(key interface{}) *MapIndex {
 	return &MapIndex{Map: n, Key: key}
 }