package csexp

import (
	"bytes"
	"fmt"
	"io"
	"slices"

	"git.codemonkeysoftware.net/b/peachy-go/shortcircuit"
)

type Sexp interface {
	isSexp()
	WriteTo(w io.Writer) (n int64, err error)
	String() string
	Equal(Sexp) bool
	Clone() Sexp
}

type Atom []byte

func (a Atom) isSexp() {}

func (a Atom) WriteTo(w io.Writer) (int64, error) {
	if scw, ok := w.(*shortcircuit.Writer); ok && scw.Failed() {
		return 0, nil
	}

	n, err := fmt.Fprintf(w, "%d:%s", len(a), []byte(a))
	return int64(n), err
}

func (a Atom) String() string {
	var buf bytes.Buffer
	a.WriteTo(&buf)
	return buf.String()
}

func (a Atom) Equal(s Sexp) bool {
	a2, ok := s.(Atom)
	return ok && bytes.Equal([]byte(a), []byte(a2))
}

func (a Atom) Clone() Sexp {
	return Atom(bytes.Clone([]byte(a)))
}

type List []Sexp

func (l List) isSexp() {}

func (l List) WriteTo(w io.Writer) (int64, error) {
	scw := shortcircuit.EnsureWriter(w)
	if scw.Failed() {
		return 0, nil
	}

	io.WriteString(scw, "(")
	for _, child := range l {
		child.WriteTo(scw)
	}
	io.WriteString(scw, ")")
	return scw.Status()
}

func (l List) String() string {
	var buf bytes.Buffer
	l.WriteTo(&buf)
	return buf.String()
}

func (l List) Equal(s Sexp) bool {
	l2, ok := s.(List)
	return ok && slices.EqualFunc(l, l2, Sexp.Equal)
}

func (l List) Clone() Sexp {
	l2 := make(List, len(l))
	for i, child := range l {
		l2[i] = child.Clone()
	}
	return l2
}

func Parse(data []byte) (Sexp, error) {
	return nil, nil
}