1 files changed, 128 insertions, 6 deletions

diff --git a/walk/walk.go b/walk/walk.go
index fc9e9de..e66feff 100644
--- a/walk/walk.go
+++ b/walk/walk.go
@@ -7,7 +7,41 @@ import (
 
 type PathSegment interface {}
 
+type OutputList interface {
+	outputList()
+}
+
+type OutputValueList []Value
+func (_ OutputValueList) outputList() {}
+
+type OutputRuneList []rune
+func (_ OutputRuneList) outputList() {}
+
+// Can be passed to .eat on a state
+type Edible interface {
+	edible()
+}
+
+type RuneEdible rune
+func (_ RuneEdible) edible() {}
+
+type Terminal int
+const (
+	ArrayEnd Terminal = iota
+	MapEnd
+	StringEnd
+)
+func (_ Terminal) edible() {}
+
+// Simple value
+// Has a literal
+type Scalar interface {
+	Value
+	scalar()
+}
+
 type Value interface {
+	Edible
 	value()
 	Debug() string
 }
@@ -17,6 +51,8 @@ func (_ NullValue) value() {}
 func (_ NullValue) Debug() string {
 	return "null"
 }
+func (_ NullValue) edible() {}
+func (_ NullValue) scalar() {}
 
 type BoolValue bool
 func (_ BoolValue) value() {}
@@ -26,24 +62,23 @@ func (b BoolValue) Debug() string {
 	}
 	return "false"
 }
+func (_ BoolValue) edible() {}
+func (_ BoolValue) scalar() {}
 
 type NumberValue float64
 func (_ NumberValue) value() {}
 func (n NumberValue) Debug() string {
 	return fmt.Sprintf("%v", float64(n))
 }
-
-type RuneValue rune
-func (_ RuneValue) value() {}
-func (r RuneValue) Debug() string {
-	return string(r)
-}
+func (_ NumberValue) edible() {}
+func (_ NumberValue) scalar() {}
 
 type StringValue string
 func (_ StringValue) value() {}
 func (s StringValue) Debug() string {
 	return fmt.Sprintf("%q", string(s))
 }
+func (_ StringValue) edible() {}
 
 type ArrayElement struct {
 	Index int
@@ -66,6 +101,7 @@ func (array ArrayValue) Debug() string {
 	builder.WriteRune(']')
 	return builder.String()
 }
+func (_ ArrayValue) edible() {}
 
 type MapElement struct {
 	Key string
@@ -88,6 +124,7 @@ func (m MapValue) Debug() string {
 	builder.WriteRune('}')
 	return builder.String()
 }
+func (_ MapValue) edible() {}
 
 type WalkItem struct {
 	Value Value
@@ -111,3 +148,88 @@ func (item WalkItem) Debug() string {
 	builder.WriteString(item.Value.Debug())
 	return builder.String()
 }
+
+func Merge(first Value, second Value) []Value {
+	switch first := first.(type) {
+	case NullValue:
+		return []Value {first, second}
+	case BoolValue:
+		return []Value {first, second}
+	case NumberValue:
+		return []Value {first, second}
+	case StringValue:
+		return []Value {first, second}
+	case ArrayValue:
+		secondArr, isArr := second.(ArrayValue)
+		if !isArr {
+			return []Value {first, second}
+		}
+
+		if len(first) == 0 {
+			return []Value {second}
+		}
+
+		if len(secondArr) == 0 {
+			return []Value {first}
+		}
+
+		var res ArrayValue
+		for _, el := range first[:len(first) - 1] {
+			res = append(res, el)
+		}
+		midFirst := first[len(first) - 1]
+		midSecond := secondArr[0]
+		if midFirst.Index == midSecond.Index {
+			for _, el := range Merge(midFirst.Value, midSecond.Value) {
+				res = append(res, ArrayElement {
+					Index: midFirst.Index,
+					Value: el,
+				})
+			}
+		} else {
+			res = append(res, midFirst, midSecond)
+		}
+		for _, el := range secondArr[1:] {
+			res = append(res, el)
+		}
+
+		return []Value {res}
+	case MapValue:
+		secondMap, isMap := second.(MapValue)
+		if !isMap {
+			return []Value {first, second}
+		}
+
+		if len(first) == 0 {
+			return []Value {second}
+		}
+
+		if len(secondMap) == 0 {
+			return []Value {first}
+		}
+
+		var res MapValue
+		for _, el := range first[:len(first) - 1] {
+			res = append(res, el)
+		}
+		midFirst := first[len(first) - 1]
+		midSecond := secondMap[0]
+		if midFirst.Key == midSecond.Key {
+			for _, el := range Merge(midFirst.Value, midSecond.Value) {
+				res = append(res, MapElement {
+					Key: midFirst.Key,
+					Value: el,
+				})
+			}
+		} else {
+			res = append(res, midFirst, midSecond)
+		}
+		for _, el := range secondMap[1:] {
+			res = append(res, el)
+		}
+
+		return []Value {res}
+	default:
+		panic("first is invalid value type")
+	}
+}