Rewrite json/read.go to no longer use a path

1 files changed, 159 insertions, 48 deletions

diff --git a/json/read.go b/json/read.go
index 6a68467..8ed7e96 100644
--- a/json/read.go
+++ b/json/read.go
@@ -42,67 +42,77 @@ func NewJSONReader(reader *bufio.Reader) *JSONReader {
 	}
 }
 
+type PathSegment interface {}
+
 type JSONReader struct {
-	path []walk.Value
+	path []PathSegment
 	structure []JSONReaderStructure
 	state JSONReaderState
 	reader *bufio.Reader
+	prevStart bool
 }
 
 func (reader *JSONReader) Read() (walk.WalkItem, error) {
 	switch reader.state {
 	case JSONReaderStateValue:
 		if len(reader.structure) == 0 {
-			path := reader.clonePath()
-			value, err := reader.readValue()
-			if err != nil {
-				panic("Missing JSON input")
-			}
-			return walk.WalkItem {
-				Path: path,
-				Value: []walk.Value{value},
-			}, nil
+			// Before the start of a root JSON value
+			return reader.readValue()
 		}
 		switch reader.structure[len(reader.structure) - 1] {
 		case JSONReaderStructureArray:
+			// Before a value inside an array
 			r, err := reader.nextNonWsRune()
 			if err != nil {
 				panic("Missing rest of array")
 			}
 			if r == ']' {
+				// End of an array
 				reader.structure = reader.structure[:len(reader.structure) - 1]
 				reader.path = reader.path[:len(reader.path) - 1]
 				reader.state = JSONReaderStateValueEnd
-				return reader.Read()
+				item := walk.WalkItem {
+					Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
+					Start: false,
+					PrevStart: reader.prevStart,
+					End: true,
+					NextEnd: reader.isNextEnd(),
+				}
+				reader.prevStart = false
+				return item, nil
 			}
+			// Element in array
 			reader.reader.UnreadRune()
-			prevIndex := reader.path[len(reader.path) - 1].(walk.NumberScalar)
+			prevIndex := reader.path[len(reader.path) - 1].(int)
 			reader.path[len(reader.path) - 1] = prevIndex + 1
-			path := reader.clonePath()
-			value, err := reader.readValue()
-			if err != nil {
-				panic("Missing value in array")
-			}
-			return walk.WalkItem {
-				Path: path,
-				Value: []walk.Value{value},
-			}, nil
+			return reader.readValue()
 		case JSONReaderStructureMap:
+			// Before a value inside a map
 			r, err := reader.nextNonWsRune()
 			if err != nil {
 				panic("Reached EOF inside JSON map")
 			}
 			if r == '}' {
+				// End of a map
 				reader.structure = reader.structure[:len(reader.structure) - 1]
 				reader.path = reader.path[:len(reader.path) - 1]
 				reader.state = JSONReaderStateValueEnd
-				return reader.Read()
+				item := walk.WalkItem {
+					Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
+					Start: false,
+					PrevStart: reader.prevStart,
+					End: true,
+					NextEnd: reader.isNextEnd(),
+				}
+				reader.prevStart = false
+				return item, nil
 			}
+			// Element in map
 			if r != '"' {
 				panic("Expected key in map, found something else")
 			}
 			key := reader.readString()
-			reader.path[len(reader.path) - 1] = walk.StringStructure(key)
+			reader.path[len(reader.path) - 1] = key
 			r, err = reader.nextNonWsRune()
 			if err != nil {
 				panic("Reached EOF after map key")
@@ -110,15 +120,7 @@ func (reader *JSONReader) Read() (walk.WalkItem, error) {
 			if r != ':' {
 				panic("Expected : after map key, found something else")
 			}
-			path := reader.clonePath()
-			value, err := reader.readValue()
-			if err != nil {
-				panic("Missing value in map")
-			}
-			return walk.WalkItem {
-				Path: path,
-				Value: []walk.Value{value},
-			}, nil
+			return reader.readValue()
 		default:
 			panic("Invalid JSONReaderStructure")
 		}
@@ -140,7 +142,15 @@ func (reader *JSONReader) Read() (walk.WalkItem, error) {
 				reader.path = reader.path[:len(reader.path) - 1]
 				reader.structure = reader.structure[:len(reader.structure) - 1]
 				reader.state = JSONReaderStateValueEnd
-				return reader.Read()
+				item := walk.WalkItem {
+					Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
+					Start: false,
+					PrevStart: reader.prevStart,
+					End: true,
+					NextEnd: reader.isNextEnd(),
+				}
+				reader.prevStart = false
+				return item, nil
 			}
 			if r != ',' {
 				panic("Missing , after array value")
@@ -156,7 +166,15 @@ func (reader *JSONReader) Read() (walk.WalkItem, error) {
 				reader.path = reader.path[:len(reader.path) - 1]
 				reader.structure = reader.structure[:len(reader.structure) - 1]
 				reader.state = JSONReaderStateValueEnd
-				return reader.Read()
+				item := walk.WalkItem {
+					Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
+					Start: false,
+					PrevStart: reader.prevStart,
+					End: true,
+					NextEnd: reader.isNextEnd(),
+				}
+				reader.prevStart = false
+				return item, nil
 			}
 			if r != ',' {
 				panic("Missing , after map value")
@@ -171,7 +189,7 @@ func (reader *JSONReader) Read() (walk.WalkItem, error) {
 	}
 }
 
-func (reader *JSONReader) readValue() (walk.Value, error) {
+func (reader *JSONReader) readValue() (walk.WalkItem, error) {
 	r, err := reader.nextNonWsRune()
 	if err != nil {
 		panic("Missing value in JSON")
@@ -180,29 +198,77 @@ func (reader *JSONReader) readValue() (walk.Value, error) {
 		case 'n':
 			reader.requireString("ull")
 			reader.state = JSONReaderStateValueEnd
-			return walk.NullScalar{}, nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.NullValue{}),
+				Start: false,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = false
+			return value, nil
 		case 'f':
 			reader.requireString("alse")
 			reader.state = JSONReaderStateValueEnd
-			return walk.BoolScalar(false), nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.BoolValue(false)),
+				Start: false,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = false
+			return value, nil
 		case 't':
 			reader.requireString("rue")
 			reader.state = JSONReaderStateValueEnd
-			return walk.BoolScalar(true), nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.BoolValue(true)),
+				Start: false,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = false
+			return value, nil
 		case '"':
 			v := reader.readString()
 			reader.state = JSONReaderStateValueEnd
-			return walk.StringStructure(v), nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.StringValue(v)),
+				Start: false,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = false
+			return value, nil
 		case '{':
 			reader.state = JSONReaderStateValue
 			reader.structure = append(reader.structure, JSONReaderStructureMap)
-			reader.path = append(reader.path, walk.StringStructure(""))
-			return walk.MapStructure(make(map[string]walk.Value)), nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
+				Start: true,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = true
+			reader.path = append(reader.path, walk.StringValue(""))
+			return value, nil
 		case '[':
 			reader.state = JSONReaderStateValue
 			reader.structure = append(reader.structure, JSONReaderStructureArray)
-			reader.path = append(reader.path, walk.NumberScalar(-1))
-			return walk.ArrayStructure{}, nil
+			value := walk.WalkItem {
+				Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
+				Start: true,
+				PrevStart: reader.prevStart,
+				End: false,
+				NextEnd: reader.isNextEnd(),
+			}
+			reader.prevStart = true
+			reader.path = append(reader.path, -1)
+			return value, nil
 	}
 	if isNumberRune(r) {
 		var builder strings.Builder
@@ -223,11 +289,43 @@ func (reader *JSONReader) readValue() (walk.Value, error) {
 			panic("Invalid number")
 		}
 		reader.state = JSONReaderStateValueEnd
-		return walk.NumberScalar(number), nil
+		value := walk.WalkItem {
+			Value: reader.buildWalkItemValue(walk.NumberValue(number)),
+			Start: false,
+			PrevStart: reader.prevStart,
+			End: false,
+			NextEnd: reader.isNextEnd(),
+		}
+		reader.prevStart = false
+		return value, nil
 	}
 	panic("Invalid JSON value starting with: " + string(r))
 }
 
+func (reader *JSONReader) buildWalkItemValue(value walk.Value) walk.Value {
+	for i := len(reader.path) - 1; i >= 0; i -= 1 {
+		switch segment := reader.path[i].(type) {
+		case int:
+			value = walk.ArrayValue {
+				walk.ArrayElement {
+					Index: segment,
+					Value: value,
+				},
+			}
+		case string:
+			value = walk.MapValue {
+				walk.MapElement {
+					Key: segment,
+					Value: value,
+				},
+			}
+		default:
+			panic("Invalid segment type")
+		}
+	}
+	return value
+}
+
 func (reader *JSONReader) readString() string {
 	var builder strings.Builder
 	for {
@@ -251,6 +349,23 @@ func (reader *JSONReader) readString() string {
 	return builder.String()
 }
 
+func (reader *JSONReader) isNextEnd() bool {
+	r, err := reader.peekNonWsRune()
+	if err != nil {
+		return false
+	}
+	return r == ']' || r == '}'
+}
+
+func (reader *JSONReader) peekNonWsRune() (rune, error) {
+	r, err := reader.nextNonWsRune()
+	if err != nil {
+		return 0, err
+	}
+	reader.reader.UnreadRune()
+	return r, nil
+}
+
 func (reader *JSONReader) nextNonWsRune() (rune, error) {
 	for {
 		r, _, err := reader.reader.ReadRune()
@@ -279,10 +394,6 @@ func (reader *JSONReader) require(criterion rune) {
 	}
 }
 
-func (reader *JSONReader) clonePath() []walk.Value {
-	return append([]walk.Value{}, reader.path...)
-}
-
 func (reader *JSONReader) AssertDone() {
 	// TODO
 }