package walk

import (
	"fmt"
	"strings"
	"math"
	"unicode/utf8"
	"bufio"
)

// int or string
type PathSegment interface {}
func stringPathSegment(segment PathSegment) string {
	return fmt.Sprintf("%v", segment)
}
type Path []PathSegment
func (path Path) ToWalkValues() []Value {
	var values []Value
	for _, segment := range path {
		switch s := segment.(type) {
			case int:
				values = append(values, ValueNumber(s))
			case string:
				values = append(values, ValueString(s))
			default:
				panic("Invalid PathSegment")
		}
	}
	return values
}

func PathFromWalkValues(values []Value) Path {
	var segments []PathSegment
	for _, value := range values {
		switch v := value.(type) {
			case ValueNumber:
				segments = append(segments, int(math.Round(float64(v))))
			case ValueString:
				segments = append(segments, string(v))
			default:
				panic("Invalid value in path")
		}
	}
	return segments
}

type WalkItem struct {
	Value []Atom
	Path []Atom
}

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 Atom) {
	state := out.structure[len(out.structure) - 1]
	switch state {
		case JSONOutRoot, JSONOutMap, JSONOutArray:
			switch atom.Typ {
				case AtomNull, AtomBool, 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 AtomStringTerminal:
					out.indent(0)
					if state == JSONOutMap {
						fmt.Fprintf(out.writer, "%q: ", key)
					}
					fmt.Fprint(out.writer, "\"")
					out.structure = append(out.structure, JSONOutString)
				case AtomTerminal:
					switch ValueTerminal(atom.data) {
						case 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 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 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 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 == AtomTerminal && ValueTerminal(atom.data) == 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 == AtomTerminal && ValueTerminal(atom.data) == 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 == 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 Path, values []Atom) {
	var segment PathSegment
	if len(path) > 0 {
		segment = path[len(path) - 1]
	}
	segmentString := stringPathSegment(segment)
	for _, atom := range values {
		out.atomOut(segmentString, atom)
	}
}

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,
	}
}

func ConcatData(first []Atom, second []Atom) []Atom {
	res := make([]Atom, 0, len(first) + len(second))
	res = append(res, first...)
	res = append(res, second...)
	return res
}

func Atomise(in []Value) (out []Atom) {
	numAtoms := 0
	for _, value := range in {
		switch v := value.(type) {
			case ValueTerminal, ValueNull, ValueBool, ValueNumber:
				numAtoms++
			case ValueString:
				numAtoms += utf8.RuneCountInString(string(v)) + 2
			default:
				panic("Invalid WalkValue")
		}
	}
	out = make([]Atom, 0, numAtoms)
	for _, value := range in {
		out = value.Atomise(out)
	}
	return out
}

type CompoundError int

const (
	CompoundRuneOutsideString CompoundError = iota
	CompoundUnknownAtom
	CompoundMissingEnd
	CompoundInvalidStringAtom
)

func (err CompoundError) Error() string {
	switch err {
		case CompoundRuneOutsideString:
			return "Compound Error: Rune Outside String"
		case CompoundUnknownAtom:
			return "Compound Error: Unknown Atom"
		case CompoundMissingEnd:
			return "Compound Error: Missing End"
		case CompoundInvalidStringAtom:
			return "Compound Error: Invalid String Atom"
		default:
			panic("Invalid CompoundError")
	}
}

type CompoundResult struct {
	value Value
	error error
}

func Compound(in []Atom) (out []Value, error error) {
	numValues := 0
	i := 0
	inString := false
	for _, atom := range in {
		switch atom.Typ {
			case AtomNull, AtomBool, AtomNumber, AtomTerminal:
				if !inString {
					numValues++
				}
			case AtomStringTerminal:
				if inString {
					numValues++
				}
				inString = !inString
		}
	}
	i = 0
	out = make([]Value, 0, numValues)
	for {
		if i >= len(in) {
			break
		}
		atom := in[i]
		i++
		switch atom.Typ {
			case AtomNull:
				out = append(out, ValueNull{})
				continue
			case AtomBool:
				out = append(out, ValueBool(atom.data != 0))
				continue
			case AtomNumber:
				out = append(out, ValueNumber(math.Float64frombits(atom.data)))
				continue
			case AtomTerminal:
				out = append(out, ValueTerminal(atom.data))
				continue
			case AtomStringRune:
				return nil, CompoundRuneOutsideString
			case AtomStringTerminal:
			default:
				return nil, CompoundUnknownAtom
		}
		// Handle string start
		var builder strings.Builder
		for {
			if i >= len(in) {
				return nil, CompoundMissingEnd
			}
			atom := in[i]
			i++
			if atom.Typ == AtomStringTerminal {
				break
			}
			builder.WriteString(atom.String())
		}
		out = append(out, ValueString(builder.String()))
	}
	return out, nil
}