Add editor packages

internal/editor/prompt/prompt.go

@@ -0,0 +1,165 @@
+package prompt
+
+import (
+	"fmt"
+	"log/slog"
+	"unicode"
+	"unicode/utf8"
+
+	"code.chimeric.al/dwrz/wen/internal/editor/buffer/glyph"
+	"code.chimeric.al/dwrz/wen/internal/editor/buffer/line"
+)
+
+type Prompt struct {
+	log *slog.Logger
+
+	err    error
+	cb     CB
+	cursor cursor
+	line   *line.Line
+	text   string
+}
+
+type CB func(l line.Line) error
+
+// cursor tracks the position in the prompt input line.
+// glyph is the 0-indexed terminal display column.
+// index is the 0-indexed byte offset in line's UTF-8 string.
+type cursor struct {
+	glyph int
+	index int
+}
+
+type Parameters struct {
+	Log *slog.Logger
+}
+
+func New(p Parameters) *Prompt {
+	return &Prompt{log: p.Log}
+}
+
+// Complete runs the prompt callback with the current input line.
+// If the callback returns an error, the prompt stays active and displays the
+// error; otherwise the prompt state is cleared.
+func (p *Prompt) Complete() {
+	if err := p.cb(*p.line); err != nil {
+		p.log.Error("callback error", slog.Any("error", err))
+		p.err = err
+
+		return
+	}
+
+	// No error -- we should be done.
+	p.cb = nil
+	p.err = nil
+	p.line = nil
+	p.text = ""
+	p.cursor = cursor{}
+}
+
+func (p *Prompt) Cursor() int {
+	return p.cursor.glyph
+}
+
+func (p *Prompt) Escape() {
+	p.cb = nil
+	p.err = nil
+	p.line = nil
+	p.text = ""
+	p.cursor = cursor{}
+}
+
+// IsPrompt reports whether an interactive prompt is active (as opposed to a
+// passive status message).
+func (p *Prompt) IsPrompt() bool {
+	return p.line != nil
+}
+
+func (p *Prompt) Prompt(s string, cb CB) {
+	p.text = s
+	p.line = &line.Line{}
+	p.cb = cb
+
+	p.log.Debug("new prompt", slog.Any("prompt", p))
+}
+
+func (p *Prompt) SetText(s string) {
+	p.text = s
+}
+
+func (p *Prompt) Text() string {
+	if p.err != nil {
+		return fmt.Sprintf("[%v] %s", p.err, p.text)
+	}
+
+	return p.text
+}
+
+func (p *Prompt) Line(offset, width int) string {
+	if p.line == nil {
+		return ""
+	}
+
+	return p.line.Render(offset, width)
+}
+
+func (p *Prompt) CursorLeft() {
+	if p.cursor.index > 0 {
+		var (
+			r    rune
+			size int
+		)
+		// Reverse until we hit the start of a rune.
+		for i := p.cursor.index - 1; i >= 0; i-- {
+			r, size = p.line.DecodeRune(i)
+			if r != utf8.RuneError {
+				p.cursor.index -= size
+				p.cursor.glyph -= glyph.Width(r)
+				break
+			}
+		}
+	}
+}
+
+func (p *Prompt) CursorRight() {
+	if p.cursor.index < p.line.Length() {
+		r, size := p.line.DecodeRune(p.cursor.index)
+		if r == utf8.RuneError {
+			p.cursor.index++
+			p.cursor.glyph += glyph.Width(r)
+		} else {
+			p.cursor.index += size
+			p.cursor.glyph += glyph.Width(r)
+		}
+	}
+}
+
+func (p *Prompt) CursorHome() {
+	p.cursor.glyph = 0
+	p.cursor.index = 0
+}
+
+func (p *Prompt) CursorEnd() {
+	p.cursor.index = p.line.Length()
+	p.cursor.glyph = p.line.Width()
+}
+
+func (p *Prompt) Backspace() {
+	if p.cursor.index > 0 {
+		p.CursorLeft()
+		p.line.DeleteRune(p.cursor.index)
+	}
+}
+
+func (p *Prompt) Insert(r rune) {
+	switch {
+	// Ignore all other non-printable characters.
+	case !unicode.IsPrint(r):
+		return
+
+	default:
+		p.line.Insert(p.cursor.index, r)
+		p.cursor.index += utf8.RuneLen(r)
+		p.cursor.glyph += glyph.Width(r)
+	}
+}