Implements helper function navigateTo in json/write.go

3 files changed, 348 insertions, 213 deletions

diff --git a/json/read.go b/json/read.go
index 8ed7e96..f3a0a65 100644
--- a/json/read.go
+++ b/json/read.go
@@ -42,10 +42,8 @@ func NewJSONReader(reader *bufio.Reader) *JSONReader {
 	}
 }
 
-type PathSegment interface {}
-
 type JSONReader struct {
-	path []PathSegment
+	path []walk.PathSegment
 	structure []JSONReaderStructure
 	state JSONReaderState
 	reader *bufio.Reader
diff --git a/json/write.go b/json/write.go
index 9e349be..97b3f4e 100644
--- a/json/write.go
+++ b/json/write.go
@@ -4,25 +4,26 @@ import (
 	"bufio"
 	"fmt"
 	"main/walk"
+	// "text/scanner"
 )
 
-func isNumber(value walk.Value) bool {
-	_, isFloat := value.(walk.NumberScalar)
-	return isFloat
+func isInt(segment walk.PathSegment) bool {
+	_, isInt := segment.(int)
+	return isInt
 }
 
-func isString(value walk.Value) bool {
-	_, isString := value.(walk.StringStructure)
+func isString(segment walk.PathSegment) bool {
+	_, isString := segment.(string)
 	return isString
 }
 
-func segmentEqual(left walk.Value, right walk.Value) bool {
+func segmentEqual(left walk.PathSegment, right walk.PathSegment) bool {
 	switch left := left.(type) {
-	case walk.NumberScalar:
-		_, isNumber := right.(walk.NumberScalar)
-		return isNumber
-	case walk.StringStructure:
-		right, isString := right.(walk.StringStructure)
+	case int:
+		_, isInt := right.(int)
+		return isInt
+	case string:
+		right, isString := right.(string)
 		return isString && left == right
 	default:
 		panic("Invalid path segment type")
@@ -32,7 +33,7 @@ func segmentEqual(left walk.Value, right walk.Value) bool {
 type JSONWriterState int
 const (
 	JSONWriterStateBeforeValue JSONWriterState = iota
-	JSONWriterStateAfterValue JSONWriterState = iota
+	JSONWriterStateAfterValue
 	JSONWriterStateInArray
 	JSONWriterStateInMap
 )
@@ -46,29 +47,243 @@ func NewJSONWriter(writer *bufio.Writer) *JSONWriter {
 }
 
 type JSONWriter struct {
-	path []walk.Value
+	path []walk.PathSegment
 	writer *bufio.Writer
 	state JSONWriterState
 }
 
-func (writer *JSONWriter) Write(item walk.WalkItem) error {
-	path := item.Path
-	for _, value := range item.Value {
-		err := writer.write(path, value)
-		if err != nil {
-			return err
+func (writer *JSONWriter) navigateTo(keepLen int, path []walk.PathSegment, state JSONWriterState) {
+	for {
+		if keepLen > len(writer.path) {
+			panic("keepLen > len(writer.path)")
+		} else if len(writer.path) == keepLen {
+			if len(path) == 0 {
+				switch writer.state {
+				case JSONWriterStateBeforeValue:
+					switch state {
+					case JSONWriterStateBeforeValue:
+						return
+					case JSONWriterStateAfterValue:
+						panic("Cannot go from BeforeValue to AfterValue in navigateTo")
+					case JSONWriterStateInArray:
+						writer.writer.WriteRune('[')
+						writer.state = JSONWriterStateInArray
+					case JSONWriterStateInMap:
+						writer.writer.WriteRune('{')
+						writer.state = JSONWriterStateInMap
+					}
+				case JSONWriterStateAfterValue:
+					if state == JSONWriterStateAfterValue {
+						return
+					} else {
+						if keepLen == 0 {
+							writer.writer.WriteRune('\n')
+							writer.state = JSONWriterStateBeforeValue
+						} else {
+							writer.writer.WriteRune(',')
+							path = writer.path[len(writer.path) - 1:]
+							writer.path = writer.path[:len(writer.path) - 1]
+							keepLen -= 1
+							switch path[0].(type) {
+							case string:
+								writer.state = JSONWriterStateInMap
+							case int:
+								writer.state = JSONWriterStateInArray
+							}
+						}
+					}
+				case JSONWriterStateInArray:
+					if state == JSONWriterStateInArray {
+						return
+					} else {
+						writer.writer.WriteRune(']')
+						writer.state = JSONWriterStateAfterValue
+					}
+				case JSONWriterStateInMap:
+					if state == JSONWriterStateInMap {
+						return
+					} else {
+						writer.writer.WriteRune('}')
+						writer.state = JSONWriterStateAfterValue
+					}
+				}
+			} else {
+				// len(path) > 0
+				switch writer.state {
+				case JSONWriterStateBeforeValue:
+					switch path[0].(type) {
+					case string:
+						writer.writer.WriteRune('{')
+						writer.state = JSONWriterStateInMap
+					case int:
+						writer.writer.WriteRune('[')
+						writer.state = JSONWriterStateInArray
+					}
+				case JSONWriterStateAfterValue:
+					if keepLen == 0 {
+						writer.writer.WriteRune('\n')
+						writer.state = JSONWriterStateBeforeValue
+					} else {
+						writer.writer.WriteRune(',')
+						path = append(writer.path[len(writer.path) - 1:], path...)
+						writer.path = writer.path[:len(writer.path) - 1]
+						keepLen -= 1
+						switch path[0].(type) {
+						case string:
+							writer.state = JSONWriterStateInMap
+						case int:
+							writer.state = JSONWriterStateInArray
+						}
+					}
+				case JSONWriterStateInArray:
+					switch path[0].(type) {
+					case string:
+						writer.writer.WriteRune(']')
+						writer.state = JSONWriterStateAfterValue
+					case int:
+						writer.path = append(writer.path, path[0])
+						path = path[1:]
+						keepLen += 1
+						writer.state = JSONWriterStateBeforeValue
+					}
+				case JSONWriterStateInMap:
+					switch p := path[0].(type) {
+					case string:
+						fmt.Fprintf(writer.writer, "%q:", p)
+						writer.path = append(writer.path, p)
+						path = path[1:]
+						keepLen += 1
+						writer.state = JSONWriterStateBeforeValue
+					case int:
+						writer.writer.WriteRune('}')
+						writer.state = JSONWriterStateAfterValue
+					}
+				}
+			}
+		} else {
+			switch writer.state {
+			case JSONWriterStateBeforeValue:
+				panic("Cannot close structures from BeforeValue in navigateTo")
+			case JSONWriterStateAfterValue:
+				if len(writer.path) == keepLen + 1 {
+					if len(path) == 0 {
+						switch writer.path[len(writer.path) - 1].(type) {
+						case string:
+							if state == JSONWriterStateInMap {
+								writer.writer.WriteRune(',')
+								writer.path = writer.path[:len(writer.path) - 1]
+								writer.state = JSONWriterStateInMap
+							} else {
+								writer.writer.WriteRune('}')
+								writer.path = writer.path[:len(writer.path) - 1]
+							}
+						case int:
+							if state == JSONWriterStateInArray {
+								writer.writer.WriteRune(',')
+								writer.path = writer.path[:len(writer.path) - 1]
+								writer.state = JSONWriterStateInArray
+							} else {
+								writer.writer.WriteRune(']')
+								writer.path = writer.path[:len(writer.path) - 1]
+							}
+						}
+					} else {
+						switch writer.path[len(writer.path) - 1].(type) {
+						case string:
+							switch path[0].(type) {
+							case string:
+								writer.writer.WriteRune(',')
+								writer.path = writer.path[:len(writer.path) - 1]
+								writer.state = JSONWriterStateInMap
+							case int:
+								writer.writer.WriteRune('}')
+								writer.path = writer.path[:len(writer.path) - 1]
+							}
+						case int:
+							switch path[0].(type) {
+							case string:
+								writer.writer.WriteRune(']')
+								writer.path = writer.path[:len(writer.path) - 1]
+							case int:
+								writer.writer.WriteRune(',')
+								writer.path = writer.path[:len(writer.path) - 1]
+								writer.state = JSONWriterStateInArray
+							}
+						}
+					}
+				} else {
+					switch writer.path[len(writer.path) - 1].(type) {
+					case string:
+						writer.writer.WriteRune('}')
+						writer.path = writer.path[:len(writer.path) - 1]
+					case int:
+						writer.writer.WriteRune(']')
+						writer.path = writer.path[:len(writer.path) - 1]
+					}
+				}
+			case JSONWriterStateInArray:
+				writer.writer.WriteRune(']')
+				writer.state = JSONWriterStateAfterValue
+			case JSONWriterStateInMap:
+				writer.writer.WriteRune('}')
+				writer.state = JSONWriterStateAfterValue
+			}
 		}
 	}
+}
+
+func (writer *JSONWriter) Write(value walk.Value) error {
 	return nil
 }
 
+func (writer *JSONWriter) pathWrite(value walk.Value, path []walk.PathSegment) error {
+	switch value := value.(type) {
+	case walk.NullValue:
+		return writer.write(path, value)
+	case walk.BoolValue:
+		return writer.write(path, value)
+	case walk.NumberValue:
+		return writer.write(path, value)
+	case walk.StringValue:
+		return writer.write(path, value)
+	case walk.ArrayValue:
+		if len(value) == 0 {
+			return writer.write(path, value)
+		} else {
+			for _, element := range value {
+				err := writer.pathWrite(element.Value, append(path, element.Index))
+				if err != nil {
+					return err
+				}
+			}
+			return nil
+		}
+	case walk.MapValue:
+		if len(value) == 0 {
+			return writer.write(path, value)
+		} else {
+			for _, element := range value {
+				err := writer.pathWrite(element.Value, append(path, element.Key))
+				if err != nil {
+					return err
+				}
+			}
+			return nil
+		}
+	case walk.RuneValue:
+		panic("Cannot write rune value")
+	default:
+		panic("Unrecognised value type")
+	}
+}
+
 func (writer *JSONWriter) indent(level int) {
 	for i := 0; i < level; i += 1 {
 		writer.writer.WriteRune('\t')
 	}
 }
 
-func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error {
+func (writer *JSONWriter) write(targetPath []walk.PathSegment, value walk.Value) error {
 	diversionPoint := 0
 	for diversionPoint < len(writer.path) && diversionPoint < len(targetPath) && segmentEqual(writer.path[diversionPoint], targetPath[diversionPoint]) {
 		diversionPoint += 1
@@ -92,10 +307,10 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 		if diversionPoint < len(targetPath) {
 			segment := targetPath[diversionPoint]
 			switch segment.(type) {
-			case walk.NumberScalar:
+			case int:
 				writer.writer.WriteString("[\n")
 				goto inArray
-			case walk.StringStructure:
+			case string:
 				writer.writer.WriteString("{\n")
 				goto inMap
 			default:
@@ -104,11 +319,11 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 		}
 
 		switch value := value.(type) {
-		case walk.NullScalar:
+		case walk.NullValue:
 			writer.writer.WriteString("null")
 			writer.state = JSONWriterStateAfterValue
 			return nil
-		case walk.BoolScalar:
+		case walk.BoolValue:
 			if value {
 				writer.writer.WriteString("true")
 			} else {
@@ -116,20 +331,20 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 			}
 			writer.state = JSONWriterStateAfterValue
 			return nil
-		case walk.NumberScalar:
+		case walk.NumberValue:
 			writer.writer.WriteString(fmt.Sprintf("%v", value))
 			writer.state = JSONWriterStateAfterValue
 			return nil
-		case walk.StringStructure:
+		case walk.StringValue:
 			writer.writer.WriteString(fmt.Sprintf("%q", value))
 			writer.state = JSONWriterStateAfterValue
 			return nil
-		case walk.ArrayStructure:
+		case walk.ArrayValue:
 			// TODO: write the contents of the structures
 			writer.writer.WriteString("[\n")
 			writer.state = JSONWriterStateInArray
 			return nil
-		case walk.MapStructure:
+		case walk.MapValue:
 			writer.writer.WriteString("{\n")
 			writer.state = JSONWriterStateInMap
 			return nil
@@ -143,15 +358,15 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 			if diversionPoint == len(writer.path) - 1 && diversionPoint < len(targetPath) {
 				segment := writer.path[diversionPoint]
 				switch segment.(type) {
-				case walk.NumberScalar:
-					_, isNumber := targetPath[diversionPoint].(walk.NumberScalar)
+				case int:
+					_, isNumber := targetPath[diversionPoint].(walk.NumberValue)
 					if isNumber {
 						writer.writer.WriteString(",\n")
 						writer.path = writer.path[:diversionPoint]
 						goto inArray
 					}
-				case walk.StringStructure:
-					_, isString := targetPath[diversionPoint].(walk.StringStructure)
+				case string:
+					_, isString := targetPath[diversionPoint].(walk.StringValue)
 					if isString {
 						writer.writer.WriteString(",\n")
 						writer.path = writer.path[:diversionPoint]
@@ -164,10 +379,10 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 
 			writer.writer.WriteString("\n")
 			switch writer.path[len(writer.path) - 1].(type) {
-			case walk.NumberScalar:
+			case int:
 				writer.path = writer.path[:len(writer.path) - 1]
 				goto inArray
-			case walk.StringStructure:
+			case string:
 				writer.path = writer.path[:len(writer.path) - 1]
 				goto inMap
 			default:
@@ -186,9 +401,9 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 			diversionPoint--
 			writer.path = writer.path[:diversionPoint]
 			switch segment.(type) {
-			case walk.NumberScalar:
+			case int:
 				goto inArray
-			case walk.StringStructure:
+			case string:
 				goto inMap
 			default:
 				panic("Invalid segment type")
@@ -204,9 +419,9 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 		diversionPoint--
 		writer.path = writer.path[:diversionPoint]
 		switch segment.(type) {
-		case walk.NumberScalar:
+		case int:
 			goto inArray
-		case walk.StringStructure:
+		case string:
 			goto inMap
 		default:
 			panic("Invalid segment type")
@@ -222,12 +437,12 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 
 		if diversionPoint < len(targetPath) {
 			switch s := targetPath[diversionPoint].(type) {
-			case walk.NumberScalar:
+			case int:
 				writer.path = append(writer.path, s)
 				diversionPoint++
 				writer.indent(len(writer.path))
 				goto beforeValue
-			case walk.StringStructure:
+			case string:
 				writer.indent(len(writer.path))
 				writer.writer.WriteString("]")
 				goto afterValue
@@ -250,11 +465,11 @@ func (writer *JSONWriter) write(targetPath []walk.Value, value walk.Value) error
 
 		if diversionPoint < len(targetPath) {
 			switch s := targetPath[diversionPoint].(type) {
-			case walk.NumberScalar:
+			case int:
 				writer.indent(len(writer.path))
 				writer.writer.WriteString("}")
 				goto afterValue
-			case walk.StringStructure:
+			case string:
 				writer.path = append(writer.path, s)
 				diversionPoint++
 				writer.indent(len(writer.path))
@@ -278,11 +493,11 @@ func (writer *JSONWriter) AssertDone() {
 	}
 	for i := len(writer.path) - 1; i >= 0; i -= 1 {
 		switch writer.path[i].(type) {
-		case walk.NumberScalar:
+		case int:
 			writer.writer.WriteString("\n")
 			writer.indent(i)
 			writer.writer.WriteString("]")
-		case walk.StringStructure:
+		case string:
 			writer.writer.WriteString("\n")
 			writer.indent(i)
 			writer.writer.WriteString("}")
diff --git a/json/write_test.go b/json/write_test.go
index 60ad609..508ccfa 100644
--- a/json/write_test.go
+++ b/json/write_test.go
@@ -5,179 +5,101 @@ import (
 	"main/walk"
 	"strings"
 	"testing"
-	"encoding/json"
 )
 
-type writeTester struct {
-	writer *JSONWriter
-	output *strings.Builder
-	t *testing.T
-}
-
-func (t writeTester) write(value walk.Value, path ...interface{}) writeTester {
-	var pathValues []walk.Value
-	for _, segment := range path {
-		switch s := segment.(type) {
-		case int:
-			pathValues = append(pathValues, walk.NumberScalar(s))
-		case string:
-			pathValues = append(pathValues, walk.StringStructure(s))
-		default:
-			panic("Invalid path segment type")
-		}
-	}
-
-	t.writer.Write(walk.WalkItem {
-		Value: []walk.Value{value},
-		Path: pathValues,
-	})
-
-	return t
-}
-
-func (t writeTester) expect(expected interface{}) writeTester {
-	t.writer.AssertDone()
-	output := t.output.String()
-	var actual interface{}
-	err := json.Unmarshal([]byte(output), &actual)
-	if err != nil {
-		t.t.Log("Produced invalid JSON:")
-		t.t.Log(output)
-		t.t.FailNow()
-	}
-
-	expectedBytes, err1 := json.Marshal(expected)
-	actualBytes, err2 := json.Marshal(actual)
-
-	if err1 != nil || err2 != nil {
-		panic("Error marshalling")
-	}
-
-	expectedString := string(expectedBytes)
-	actualString := string(actualBytes)
-
-	if expectedString != actualString {
-		t.t.Log("Expected:")
-		t.t.Log(expectedString)
-		t.t.Log("Found:")
-		t.t.Log(actualString)
-		t.t.FailNow()
+func TestNavigateTo(t *testing.T) {
+	type testCase struct {
+		fromPath []walk.PathSegment
+		fromState JSONWriterState
+		toKeep int
+		toPath []walk.PathSegment
+		toState JSONWriterState
+		expected string
 	}
 
-	return t
-}
-
-func tester(t *testing.T) writeTester {
-	var output strings.Builder
-	return writeTester {
-		writer: NewJSONWriter(bufio.NewWriter(&output)),
-		output: &output,
-		t: t,
-	}
-}
-
-func TestImplicitStructures(t *testing.T) {
-	tester(t).write(
-		walk.NullScalar{},
-		0, "test", 0,
-	).expect(
-		[]interface{}{
-			map[string]interface{}{
-				"test": []interface{}{
-					nil,
-				},
-			},
+	tests := []testCase {
+		{
+			fromPath: []walk.PathSegment{},
+			fromState: JSONWriterStateBeforeValue,
+			toKeep: 0,
+			toPath: []walk.PathSegment{"a", "b", "c"},
+			toState: JSONWriterStateBeforeValue,
+			expected: `{"a":{"b":{"c":`,
 		},
-	)
-}
-
-func TestExplicitMap(t *testing.T) {
-	tester(t).write(
-		make(walk.MapStructure),
-	).write(
-		walk.NullScalar{},
-		"test",
-	).expect(
-		map[string]interface{}{
-			"test": nil,
+		{
+			fromPath: []walk.PathSegment{},
+			fromState: JSONWriterStateBeforeValue,
+			toKeep: 0,
+			toPath: []walk.PathSegment{0, "a", "a", 0, 1},
+			toState: JSONWriterStateInMap,
+			expected: `[{"a":{"a":[[{`,
 		},
-	)
-}
-
-func TestExplicitNested(t *testing.T) {
-	tester(t).write(
-		make(walk.MapStructure),
-	).write(
-		make(walk.MapStructure),
-		"first",
-	).write(
-		make(walk.MapStructure),
-		"first", "second",
-	).write(
-		walk.StringStructure("test"),
-		"first", "second", "third",
-	).expect(
-		map[string]interface{}{
-			"first": map[string]interface{}{
-				"second": map[string]interface{}{
-					"third": "test",
-				},
-			},
+		{
+			fromPath: []walk.PathSegment{},
+			fromState: JSONWriterStateInMap,
+			toKeep: 0,
+			toPath: []walk.PathSegment{},
+			toState: JSONWriterStateInArray,
+			expected: "}\n[",
 		},
-	)
-}
-
-func TestArrayOfMaps(t *testing.T) {
-	tester(t).write(
-		walk.ArrayStructure{},
-	).write(
-		make(walk.MapStructure),
-		0,
-	).write(
-		walk.NumberScalar(0),
-		0, "number",
-	).write(
-		make(walk.MapStructure),
-		1,
-	).write(
-		walk.NumberScalar(1),
-		1, "nested", "number",
-	).write(
-		make(walk.MapStructure),
-		2,
-	).write(
-		walk.NumberScalar(2),
-		2, "number",
-	).expect(
-		[]interface{}{
-			map[string]interface{}{
-				"number": 0,
-			},
-			map[string]interface{}{
-				"nested": map[string]interface{}{
-					"number": 1,
-				},
-			},
-			map[string]interface{}{
-				"number": 2,
-			},
+		{
+			fromPath: []walk.PathSegment{0, 0},
+			fromState: JSONWriterStateBeforeValue,
+			toKeep: 2,
+			toPath: []walk.PathSegment{"a"},
+			toState: JSONWriterStateInArray,
+			expected: `{"a":[`,
 		},
-	)
-}
-
-func TestStructures1(t *testing.T) {
-	tester(t).write(
-		make(walk.MapStructure),
-	).write(
-		make(walk.MapStructure),
-		"map",
-	).write(
-		walk.ArrayStructure{},
-		"array",
-	).expect(
-		map[string]interface{}{
-			"map": map[string]interface{}{},
-			"array": []interface{}{},
+		{
+			fromPath: []walk.PathSegment{"a", "b"},
+			fromState: JSONWriterStateAfterValue,
+			toKeep: 1,
+			toPath: []walk.PathSegment{"c"},
+			toState: JSONWriterStateBeforeValue,
+			expected: `,"c":`,
 		},
-	)
+		{
+			fromPath: []walk.PathSegment{0, "a"},
+			fromState: JSONWriterStateInArray,
+			toKeep: 0,
+			toPath: []walk.PathSegment{"b", 1},
+			toState: JSONWriterStateInMap,
+			expected: `]}]` + "\n" + `{"b":[{`,
+		},
+		{
+			fromPath: []walk.PathSegment{"a", "b", "c", "d", "e"},
+			fromState: JSONWriterStateAfterValue,
+			toKeep: 2,
+			toPath: []walk.PathSegment{"f", "g", "h"},
+			toState: JSONWriterStateBeforeValue,
+			expected: `}},"f":{"g":{"h":`,
+		},
+		{
+			fromPath: []walk.PathSegment{"a", 0, "b"},
+			fromState: JSONWriterStateAfterValue,
+			toKeep: 2,
+			toPath: []walk.PathSegment{0},
+			toState: JSONWriterStateBeforeValue,
+			expected: `},[`,
+		},
+	}
+
+	for i, test := range tests {
+		var writer strings.Builder
+		jsonWriter := &JSONWriter {
+			path: test.fromPath,
+			writer: bufio.NewWriter(&writer),
+			state: test.fromState,
+		}
+		jsonWriter.navigateTo(
+			test.toKeep,
+			test.toPath,
+			test.toState,
+		)
+		jsonWriter.writer.Flush()
+		res := writer.String()
+		if res != test.expected {
+			t.Errorf(`Test %d: Expected '%s' found '%s'`, i, test.expected, res)
+		}
+	}
 }