Move reading and writing of tokens into a separate package to prepare for other input and output formats

1 files changed, 151 insertions, 0 deletions

diff --git a/json_tokens/write.go b/json_tokens/write.go
new file mode 100644
index 0000000..813f2f3
--- /dev/null
+++ b/json_tokens/write.go
@@ -0,0 +1,151 @@
+package json_tokens
+
+import (
+	"fmt"
+	"strings"
+	"bufio"
+	"main/walk"
+)
+
+func stringPathSegment(segment walk.PathSegment) string {
+	return fmt.Sprintf("%v", segment)
+}
+
+type JSONOutStructure int
+const (
+	JSONOutRoot JSONOutStructure = iota
+	JSONOutMap
+	JSONOutArray
+	JSONOutString
+	JSONOutValueEnd
+)
+
+type JSONOut struct {
+	structure []JSONOutStructure
+	writer *bufio.Writer
+}
+
+func (out *JSONOut) indent(adjust int) {
+	fmt.Fprint(out.writer, strings.Repeat("\t", len(out.structure) - 1 + adjust))
+}
+
+func (out *JSONOut) atomOut(key string, atom walk.Atom) {
+	state := out.structure[len(out.structure) - 1]
+	switch state {
+		case JSONOutRoot, JSONOutMap, JSONOutArray:
+			switch atom.Typ {
+				case walk.AtomNull, walk.AtomBool, walk.AtomNumber:
+					out.indent(0)
+					if state == JSONOutMap {
+						fmt.Fprintf(out.writer, "%q: ", key)
+					}
+					fmt.Fprint(out.writer, atom.String())
+					out.structure = append(out.structure, JSONOutValueEnd)
+				case walk.AtomStringTerminal:
+					out.indent(0)
+					if state == JSONOutMap {
+						fmt.Fprintf(out.writer, "%q: ", key)
+					}
+					fmt.Fprint(out.writer, "\"")
+					out.structure = append(out.structure, JSONOutString)
+				case walk.AtomTerminal:
+					switch atom.Terminal() {
+						case walk.MapBegin:
+							out.indent(0)
+							if state == JSONOutMap {
+								fmt.Fprintf(out.writer, "%q: ", key)
+							}
+							fmt.Fprint(out.writer, "{\n")
+							out.structure = append(out.structure, JSONOutMap)
+						case walk.ArrayBegin:
+							out.indent(0)
+							if state == JSONOutMap {
+								fmt.Fprintf(out.writer, "%q: ", key)
+							}
+							fmt.Fprint(out.writer, "[\n")
+							out.structure = append(out.structure, JSONOutArray)
+						case walk.MapEnd:
+							out.indent(-1)
+							if state != JSONOutMap {
+								panic("Map ended while not inside a map")
+							}
+							fmt.Fprint(out.writer, "}")
+							out.structure[len(out.structure) - 1] = JSONOutValueEnd
+						case walk.ArrayEnd:
+							out.indent(-1)
+							if state != JSONOutArray {
+								panic("Array ended while not inside a array")
+							}
+							fmt.Fprint(out.writer, "]")
+							out.structure[len(out.structure) - 1] = JSONOutValueEnd
+						default:
+							panic("Invalid TerminalValue")
+					}
+				default:
+					panic("Invalid AtomType in root value")
+			}
+		case JSONOutValueEnd:
+			out.structure = out.structure[:len(out.structure) - 1]
+			underState := out.structure[len(out.structure) - 1]
+			if underState == JSONOutMap && atom.Typ == walk.AtomTerminal && atom.Terminal() == walk.MapEnd {
+				fmt.Fprint(out.writer, "\n")
+				out.indent(-1)
+				fmt.Fprint(out.writer, "}")
+				out.structure[len(out.structure) - 1] = JSONOutValueEnd
+			} else if underState == JSONOutArray && atom.Typ == walk.AtomTerminal && atom.Terminal() == walk.ArrayEnd {
+				fmt.Fprint(out.writer, "\n")
+				out.indent(-1)
+				fmt.Fprint(out.writer, "]")
+				out.structure[len(out.structure) - 1] = JSONOutValueEnd
+			} else if underState == JSONOutRoot {
+				panic("Tried to output JSON after root value has concluded")
+			} else {
+				fmt.Fprint(out.writer, ",\n")
+				out.atomOut(key, atom)
+			}
+		case JSONOutString:
+			if atom.Typ == walk.AtomStringTerminal {
+				fmt.Fprint(out.writer, "\"")
+				out.structure[len(out.structure) - 1] = JSONOutValueEnd
+			} else {
+				fmt.Fprint(out.writer, atom.String())
+			}
+		default:
+			panic("Invalid JSONOutState")
+	}
+}
+
+func (out *JSONOut) Print(path walk.Path, values []walk.Atom) {
+	var segment walk.PathSegment
+	if len(path) > 0 {
+		segment = path[len(path) - 1]
+	}
+	segmentString := stringPathSegment(segment)
+	for _, atom := range values {
+		out.atomOut(segmentString, atom)
+	}
+}
+
+func (out *JSONOut) Write(item walk.WalkItem) error {
+	pathValues, err := walk.Compound(item.Path)
+	if err != nil {
+		return err
+	}
+	path := walk.PathFromWalkValues(pathValues)
+	out.Print(path, item.Value)
+	return nil
+}
+
+func (out *JSONOut) AssertDone() {
+	out.writer.Flush()
+	if len(out.structure) != 2 || out.structure[0] != JSONOutRoot || out.structure[1] != JSONOutValueEnd {
+		panic("Program ended with incomplete JSON output")
+	}
+}
+
+func NewJSONOut(writer *bufio.Writer) *JSONOut {
+	return &JSONOut {
+		structure: []JSONOutStructure{JSONOutRoot},
+		writer: writer,
+	}
+}