path: root/json/write.go

package json

import (
	"bufio"
	"fmt"
	"main/walk"
	// "text/scanner"
)

func isInt(segment walk.PathSegment) bool {
	_, isInt := segment.(int)
	return isInt
}

func isString(segment walk.PathSegment) bool {
	_, isString := segment.(string)
	return isString
}

func segmentEqual(left walk.PathSegment, right walk.PathSegment) bool {
	switch left := left.(type) {
	case int:
		_, isInt := right.(int)
		return isInt
	case string:
		right, isString := right.(string)
		return isString && left == right
	default:
		panic("Invalid path segment type")
	}
}

type JSONWriterState int
const (
	JSONWriterStateBeforeValue JSONWriterState = iota
	JSONWriterStateAfterValue
	JSONWriterStateInArray
	JSONWriterStateInMap
)

func NewJSONWriter(writer *bufio.Writer) *JSONWriter {
	return &JSONWriter {
		path: nil,
		writer: writer,
		state: JSONWriterStateBeforeValue,
	}
}

type JSONWriter struct {
	path []walk.PathSegment
	writer *bufio.Writer
	state JSONWriterState
}

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.PathSegment, value walk.Value) error {
	diversionPoint := 0
	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 JSONWriterStateInArray:
		goto inArray
	case JSONWriterStateInMap:
		goto inMap
	}

	beforeValue: {
		if diversionPoint < len(writer.path) {
			panic("Writing a value before doing a necessary leave")
		}
		if diversionPoint < len(targetPath) {
			segment := targetPath[diversionPoint]
			switch segment.(type) {
			case int:
				writer.writer.WriteString("[\n")
				goto inArray
			case string:
				writer.writer.WriteString("{\n")
				goto inMap
			default:
				panic("Invalid path segment")
			}
		}

		switch value := value.(type) {
		case walk.NullValue:
			writer.writer.WriteString("null")
			writer.state = JSONWriterStateAfterValue
			return nil
		case walk.BoolValue:
			if value {
				writer.writer.WriteString("true")
			} else {
				writer.writer.WriteString("false")
			}
			writer.state = JSONWriterStateAfterValue
			return nil
		case walk.NumberValue:
			writer.writer.WriteString(fmt.Sprintf("%v", value))
			writer.state = JSONWriterStateAfterValue
			return nil
		case walk.StringValue:
			writer.writer.WriteString(fmt.Sprintf("%q", value))
			writer.state = JSONWriterStateAfterValue
			return nil
		case walk.ArrayValue:
			// TODO: write the contents of the structures
			writer.writer.WriteString("[\n")
			writer.state = JSONWriterStateInArray
			return nil
		case walk.MapValue:
			writer.writer.WriteString("{\n")
			writer.state = JSONWriterStateInMap
			return nil
		default:
			panic("Invalid value type")
		}
	}

	afterValue: {
		if diversionPoint < len(writer.path) {
			if diversionPoint == len(writer.path) - 1 && diversionPoint < len(targetPath) {
				segment := writer.path[diversionPoint]
				switch segment.(type) {
				case int:
					_, isNumber := targetPath[diversionPoint].(walk.NumberValue)
					if isNumber {
						writer.writer.WriteString(",\n")
						writer.path = writer.path[:diversionPoint]
						goto inArray
					}
				case string:
					_, isString := targetPath[diversionPoint].(walk.StringValue)
					if isString {
						writer.writer.WriteString(",\n")
						writer.path = writer.path[:diversionPoint]
						goto inMap
					}
				default:
					panic("Invalid segment type")
				}
			}

			writer.writer.WriteString("\n")
			switch writer.path[len(writer.path) - 1].(type) {
			case int:
				writer.path = writer.path[:len(writer.path) - 1]
				goto inArray
			case string:
				writer.path = writer.path[:len(writer.path) - 1]
				goto inMap
			default:
				panic("Invalid segment type")
			}
		}

		// TODO: handle len(writer.path) == 0
		if diversionPoint < len(targetPath) {
			if len(writer.path) == 0 {
				writer.writer.WriteString("\n")
				goto beforeValue
			}
			segment := writer.path[diversionPoint - 1]
			writer.writer.WriteString(",")
			diversionPoint--
			writer.path = writer.path[:diversionPoint]
			switch segment.(type) {
			case int:
				goto inArray
			case string:
				goto inMap
			default:
				panic("Invalid segment type")
			}
		}

		if len(writer.path) == 0 {
			writer.writer.WriteString("\n")
			goto beforeValue
		}
		segment := writer.path[diversionPoint - 1]
		writer.writer.WriteString(",\n")
		diversionPoint--
		writer.path = writer.path[:diversionPoint]
		switch segment.(type) {
		case int:
			goto inArray
		case string:
			goto inMap
		default:
			panic("Invalid segment type")
		}
	}

	inArray: {
		if diversionPoint < len(writer.path) {
			writer.indent(len(writer.path))
			writer.writer.WriteString("]")
			goto afterValue
		}

		if diversionPoint < len(targetPath) {
			switch s := targetPath[diversionPoint].(type) {
			case int:
				writer.path = append(writer.path, s)
				diversionPoint++
				writer.indent(len(writer.path))
				goto beforeValue
			case string:
				writer.indent(len(writer.path))
				writer.writer.WriteString("]")
				goto afterValue
			default:
				panic("Invalid segment type")
			}
		}

		writer.indent(len(writer.path))
		writer.writer.WriteString("]")
		goto afterValue
	}

	inMap: {
		if diversionPoint < len(writer.path) {
			writer.indent(len(writer.path))
			writer.writer.WriteString("}")
			goto afterValue
		}

		if diversionPoint < len(targetPath) {
			switch s := targetPath[diversionPoint].(type) {
			case int:
				writer.indent(len(writer.path))
				writer.writer.WriteString("}")
				goto afterValue
			case string:
				writer.path = append(writer.path, s)
				diversionPoint++
				writer.indent(len(writer.path))
				writer.writer.WriteString(fmt.Sprintf("%q: ", s))
				goto beforeValue
			}
		}

		writer.indent(len(writer.path))
		writer.writer.WriteString("}")
		goto afterValue
	}
}

func (writer *JSONWriter) AssertDone() {
	switch writer.state {
	case JSONWriterStateInArray:
		writer.writer.WriteString("]")
	case JSONWriterStateInMap:
		writer.writer.WriteString("}")
	}
	for i := len(writer.path) - 1; i >= 0; i -= 1 {
		switch writer.path[i].(type) {
		case int:
			writer.writer.WriteString("\n")
			writer.indent(i)
			writer.writer.WriteString("]")
		case string:
			writer.writer.WriteString("\n")
			writer.indent(i)
			writer.writer.WriteString("}")
		default:
			panic("Invalid path segment type")
		}
	}
	writer.writer.Flush()
}