textedit/lib.go

package textedit

import "io"

type Editor interface {
	Edit(r rune, state any) ([]rune, any)
	ReleaseState(state any) []rune
}

type editorFunc[S any] struct {
	edit         func(rune, S) ([]rune, S)
	releaseState func(S) []rune
}

type Writer struct {
	out    io.Writer
	editor Editor
	state  any
	err    error
}

func (e editorFunc[S]) Edit(r rune, state any) ([]rune, any) {
	s, _ := state.(S)
	return e.edit(r, s)
}

func (e editorFunc[S]) ReleaseState(state any) []rune {
	s, _ := state.(S)
	r := e.releaseState(s)
	return r
}

func Func[S any](edit func(r rune, state S) ([]rune, S), releaseState func(S) []rune) Editor {
	if edit == nil {
		edit = func(r rune, s S) ([]rune, S) { return []rune{r}, s }
	}

	if releaseState == nil {
		releaseState = func(S) []rune { return nil }
	}

	return editorFunc[S]{edit: edit, releaseState: releaseState}
}

func Replace(a ...string) Editor {
	return replace(a...)
}

func Escape(esc rune, chars ...rune) Editor {
	return escape(esc, chars...)
}

func Indent(first, rest string) Editor {
	return wrapIndent([]rune(first), []rune(rest), 0, 0)
}

func Wrap(firstWidth, restWidth int) Editor {
	return wrapIndent(nil, nil, firstWidth, restWidth)
}

func WrapIndent(firstIndent, restIndent string, firstWidth, restWidth int) Editor {
	return wrapIndent([]rune(firstIndent), []rune(restIndent), firstWidth, restWidth)
}

func SingleLine() Editor {
	return sequence(
		replace("\n", " "),
		wrapIndent(nil, nil, 0, 0),
	)
}

func New(out io.Writer, e ...Editor) *Writer {
	return &Writer{
		out:    out,
		editor: sequence(e...),
	}
}

func (w *Writer) write(r []rune) error {
	if w.err != nil {
		return w.err
	}

	for _, ri := range r {
		rr, s := w.editor.Edit(ri, w.state)
		if _, err := w.out.Write([]byte(string(rr))); err != nil {
			w.err = err
			return w.err
		}

		w.state = s
	}

	return nil
}

func (w *Writer) flush() error {
	if w.err != nil {
		return w.err
	}

	r := w.editor.ReleaseState(w.state)
	w.state = nil
	if _, err := w.out.Write([]byte(string(r))); err != nil {
		w.err = err
		return w.err
	}

	return nil
}

func (w *Writer) Write(p []byte) (int, error) {
	return len(p), w.write([]rune(string(p)))
}

func (w *Writer) WriteRune(r rune) (int, error) {
	return len([]byte(string(r))), w.write([]rune{r})
}

func (w *Writer) Flush() error {
	return w.flush()
}