1 files changed, 202 insertions, 0 deletions
diff --git a/json/write.go b/json/write.go
new file mode 100644
index 0000000..d024a56
--- /dev/null
+++ b/json/write.go
@@ -0,0 +1,202 @@
+package json
+
+import (
+	"bufio"
+	"fmt"
+	"main/walk"
+)
+
+func isNumber(value walk.Value) bool {
+	_, isFloat := value.(walk.NumberScalar)
+	return isFloat
+}
+
+func isString(value walk.Value) bool {
+	_, isString := value.(walk.StringStructure)
+	return isString
+}
+
+func segmentEqual(left walk.Value, right walk.Value) bool {
+	switch left := left.(type) {
+	case walk.NumberScalar:
+		_, isNumber := right.(walk.NumberScalar)
+		return isNumber
+	case walk.StringStructure:
+		right, isString := right.(walk.StringStructure)
+		return isString && left == right
+	default:
+		panic("Invalid path segment type")
+	}
+}
+
+type JSONWriterState int
+const (
+	JSONWriterStateBeforeValue JSONWriterState = iota
+	JSONWriterStateAfterValue JSONWriterState = iota
+	JSONWriterStateInArray
+	JSONWriterStateInMap
+)
+
+func NewJSONWriter(writer *bufio.Writer) *JSONWriter {
+	return &JSONWriter {
+		path: nil,
+		writer: writer,
+		state: JSONWriterStateBeforeValue,
+	}
+}
+
+type JSONWriter struct {
+	path []walk.Value
+	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
+		}
+	}
+	return nil
+}
+
+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 {
+	diversionPoint := len(writer.path)
+	for diversionPoint < len(writer.path) && diversionPoint < len(targetPath) && segmentEqual(writer.path[diversionPoint], targetPath[diversionPoint]) {
+		diversionPoint += 1
+	}
+	
+	switch writer.state {
+	case JSONWriterStateBeforeValue:
+		goto beforeValue
+	case JSONWriterStateAfterValue:
+		goto afterValue
+	case JSONWriterStateInMap:
+		goto inMap
+	case JSONWriterStateInArray:
+		goto inArray
+	default:
+		panic("Invalid JSONWriterState")
+	}
+
+	beforeValue: {
+		switch value := value.(type) {
+		case walk.NullScalar:
+			writer.writer.WriteString("null")
+			writer.state = JSONWriterStateAfterValue
+			return nil
+		case walk.BoolScalar:
+			if value {
+				writer.writer.WriteString("true")
+			} else {
+				writer.writer.WriteString("false")
+			}
+			writer.state = JSONWriterStateAfterValue
+			return nil
+		case walk.NumberScalar:
+			writer.writer.WriteString(fmt.Sprintf("%v", value))
+			writer.state = JSONWriterStateAfterValue
+			return nil
+		case walk.StringStructure:
+			writer.writer.WriteString(fmt.Sprintf("%q", value))
+			writer.state = JSONWriterStateAfterValue
+			return nil
+		case walk.ArrayStructure:
+			// TODO: write the contents of the structures
+			writer.writer.WriteString("[\n")
+			writer.state = JSONWriterStateInArray
+			return nil
+		case walk.MapStructure:
+			writer.writer.WriteString("{\n")
+			writer.state = JSONWriterStateInMap
+			return nil
+		default:
+			panic("Invalid value type")
+		}
+	}
+
+	afterValue: {
+		if len(writer.path) == 0 {
+			writer.writer.WriteRune('\n')
+			goto beforeValue
+		}
+		switch writer.path[len(writer.path) - 1].(type) {
+		case walk.NumberScalar:
+			// TODO: second part of this condition might be redundant
+			if len(writer.path) - 1 <= diversionPoint && len(targetPath) >= len(writer.path) && isNumber(targetPath[len(writer.path) - 1]) {
+				writer.writer.WriteString(",\n")
+				writer.path = writer.path[:len(writer.path) - 1]
+				goto inArray
+			} else {
+				writer.writer.WriteString("\n")
+				writer.indent(len(writer.path) - 1)
+				writer.writer.WriteString("]")
+				writer.path = writer.path[:len(writer.path) - 1]
+				goto afterValue
+			}
+		case walk.StringStructure:
+			if len(writer.path) -1 <= diversionPoint && len(targetPath) >= len(writer.path) && isString(targetPath[len(writer.path) - 1]) {
+				writer.writer.WriteString(",\n")
+				writer.path = writer.path[:len(writer.path) - 1]
+				goto inMap
+			} else {
+				writer.writer.WriteString("\n")
+				writer.indent(len(writer.path) - 1)
+				writer.writer.WriteString("}")
+				writer.path = writer.path[:len(writer.path) - 1]
+				goto afterValue
+			}
+		default:
+			panic("Invalid path segment type")
+		}
+	}
+
+	inMap: {
+		if len(writer.path) <= diversionPoint && len(targetPath) > len(writer.path) && isString(targetPath[len(writer.path)]) {
+			writer.indent(len(writer.path) + 1)
+			writer.writer.WriteString(fmt.Sprintf("%q: ", targetPath[len(writer.path)].(walk.StringStructure)))
+			writer.path = append(writer.path, targetPath[len(writer.path)].(walk.StringStructure))
+			goto beforeValue
+		} else {
+			writer.writer.WriteString("\n}")
+			goto afterValue
+		}
+	}
+
+	inArray: {
+		if len(writer.path) <= diversionPoint && len(targetPath) > len(writer.path) && isNumber(targetPath[len(writer.path)]) {
+			writer.indent(len(writer.path) + 1)
+			writer.path = append(writer.path, walk.NumberScalar(0))
+			goto beforeValue
+		} else {
+			writer.writer.WriteString("\n]")
+			goto afterValue
+		}
+	}
+}
+
+func (writer *JSONWriter) AssertDone() {
+	for i := len(writer.path) - 1; i >= 0; i -= 1 {
+		switch writer.path[i].(type) {
+		case walk.NumberScalar:
+			writer.writer.WriteString("\n")
+			writer.indent(i)
+			writer.writer.WriteString("]")
+		case walk.StringStructure:
+			writer.writer.WriteString("\n")
+			writer.indent(i)
+			writer.writer.WriteString("}")
+		default:
+			panic("Invalid path segment type")
+		}
+	}
+	writer.writer.Flush()
+}