package mw

import "git.smesh.lol/moxie/pkg/mxutil"

type MW struct {
	S string
	I int32
}

func New(s string) (m MW) {
	w := MW{S: s}
	for w.I < len(s) && s[w.I] != '[' {
		w.I++
	}
	if w.I < len(s) {
		w.I++
	}
	return w
}

func (w *MW) Sep() {
	// Declared outside the loop: a declaration in the body of a self-mutating
	// method allocates in the sovereign arena on every iteration.
	var c byte
	for w.I < len(w.S) {
		c = w.S[w.I]
		if c != ' ' && c != '\n' && c != '\r' && c != '\t' && c != ',' {
			break
		}
		w.I++
	}
}

func (w *MW) Str() (s string) {
	w.Sep()
	if w.I >= len(w.S) || w.S[w.I] != '"' {
		return ""
	}
	w.I++
	start := w.I
	for w.I < len(w.S) && w.S[w.I] != '"' {
		if w.S[w.I] == '\\' {
			w.I++
		}
		w.I++
	}
	if w.I >= len(w.S) {
		return ""
	}
	result := w.S[start:w.I]
	w.I++
	return result
}

func (w *MW) Num() (n int64) {
	w.Sep()
	neg := false
	if w.I < len(w.S) && w.S[w.I] == '-' {
		neg = true
		w.I++
	}
	var n int64
	for w.I < len(w.S) && w.S[w.I] >= '0' && w.S[w.I] <= '9' {
		n = n*10 + int64(w.S[w.I]-'0')
		w.I++
	}
	if neg {
		n = -n
	}
	return n
}

func (w *MW) Raw() (s string) {
	w.Sep()
	start := w.I
	w.I = Skipval(w.S, w.I)
	if w.I < 0 {
		w.I = len(w.S)
		return ""
	}
	return w.S[start:w.I]
}

func (w *MW) Strs() (ss []string) {
	w.Sep()
	if w.I >= len(w.S) || w.S[w.I] != '[' {
		return nil
	}
	w.I++
	// Declared outside the loop, as above.
	var out []string
	var s string
	for {
		w.Sep()
		if w.I >= len(w.S) || w.S[w.I] == ']' {
			if w.I < len(w.S) {
				w.I++
			}
			return out
		}
		s = w.Str()
		out = mxutil.Ensure(out, 1)
		out = push(out, s)
	}
}

func Unescape(s string) (sv string) {
	if len(s) == 0 {
		return s
	}
	i := 0
	for i < len(s) {
		if s[i] == '\\' {
			break
		}
		i++
	}
	if i == len(s) {
		return s
	}
	out := []byte{:0:len(s)}
	out = out | s[:i]
	for i < len(s) {
		if s[i] == '\\' && i+1 < len(s) {
			c := s[i+1]
			if c == '"' || c == '\\' || c == '/' {
				out = push(out, c)
			} else if c == 'n' {
				out = out | "\n"
			} else if c == 'r' {
				out = out | "\r"
			} else if c == 't' {
				out = out | "\t"
			} else {
				out = push(out, s[i])
				out = push(out, c)
			}
			i += 2
		} else {
			out = push(out, s[i])
			i++
		}
	}
	return string(out)
}

func Skipval(s string, i int32) (n int32) {
	if i >= len(s) {
		return -1
	}
	c := s[i]
	if c == '"' {
		i++
		for i < len(s) && s[i] != '"' {
			if s[i] == '\\' {
				i++
			}
			i++
		}
		if i >= len(s) {
			return -1
		}
		return i + 1
	}
	if c == '{' || c == '[' {
		open := c
		closeB := byte('}')
		if open == '[' {
			closeB = ']'
		}
		depth := 1
		i++
		for i < len(s) && depth > 0 {
			if s[i] == '"' {
				i++
				for i < len(s) && s[i] != '"' {
					if s[i] == '\\' {
						i++
					}
					i++
				}
				if i >= len(s) {
					return -1
				}
				i++
				continue
			}
			if s[i] == open {
				depth++
			} else if s[i] == closeB {
				depth--
				if depth == 0 {
					return i + 1
				}
			}
			i++
		}
		return -1
	}
	for i < len(s) {
		c = s[i]
		if c == ',' || c == ']' || c == '}' {
			return i
		}
		i++
	}
	return i
}