Add editor packages

internal/editor/buffer/buffer.go

@@ -0,0 +1,99 @@
+package buffer
+
+import (
+	"bytes"
+	"fmt"
+	"log/slog"
+	"os"
+	"time"
+
+	"code.chimeric.al/dwrz/wen/internal/editor/buffer/line"
+)
+
+type Buffer struct {
+	cursor *Cursor
+	lines  []*line.Line
+	log    *slog.Logger
+	name   string
+	offset *offset
+	saved  time.Time
+}
+
+// offset is the 0-indexed first visible display column (glyph) and row (line)
+// of the buffer viewport.
+type offset struct {
+	glyph int
+	line  int
+}
+
+func (b *Buffer) CursorLine() *line.Line {
+	return b.lines[b.cursor.line]
+}
+
+func (b *Buffer) Name() string {
+	return b.name
+}
+
+type NewBufferParams struct {
+	Name string
+	Log  *slog.Logger
+}
+
+// Create creates or truncates the named file on disk.
+// It returns a Buffer initialized with a single empty line,
+// so CursorLine is always valid.
+func Create(p NewBufferParams) (*Buffer, error) {
+	var b = &Buffer{
+		cursor: &Cursor{},
+		lines:  []*line.Line{{}},
+		log:    p.Log,
+		name:   p.Name,
+		offset: &offset{},
+	}
+
+	// Create the file.
+	f, err := os.Create(b.name)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create file: %w", err)
+	}
+	if err := f.Close(); err != nil {
+		return nil, fmt.Errorf("failed to close file: %w", err)
+	}
+
+	return b, nil
+}
+
+// Open reads the named file into a Buffer. If the file is empty, the Buffer
+// is initialized with a single empty line so CursorLine is always valid.
+func Open(p NewBufferParams) (*Buffer, error) {
+	var b = &Buffer{
+		cursor: &Cursor{},
+		lines:  []*line.Line{},
+		log:    p.Log,
+		name:   p.Name,
+		offset: &offset{},
+	}
+
+	data, err := os.ReadFile(b.name)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open file: %w", err)
+	}
+
+	// Trim a single trailing newline so saving doesn't add an extra blank line.
+	data = bytes.TrimSuffix(data, []byte("\n"))
+	data = bytes.TrimSuffix(data, []byte("\r"))
+
+	if len(data) > 0 {
+		for _, raw := range bytes.Split(data, []byte("\n")) {
+			raw = bytes.TrimSuffix(raw, []byte("\r"))
+			b.lines = append(b.lines, line.New(string(raw)))
+		}
+	}
+
+	// Add a line to write in, if the file is empty.
+	if len(b.lines) == 0 {
+		b.lines = append(b.lines, &line.Line{})
+	}
+
+	return b, nil
+}