quintodrome/conf/dir.go

package conf

import (
	"fmt"
	"os"
	"sync"
)

// Dir wraps a directory path and lazily creates the directory on first use.
// The directory is created at most once; if creation fails, the error is
// permanently cached (sync.Once semantics). Dir is not safe for mutation
// after Path() has been called.
type Dir struct {
	path string
	perm os.FileMode
	once sync.Once
	err  error
}

// NewDir creates a new Dir with the given path and default permissions (os.ModePerm).
func NewDir(path string) Dir {
	return Dir{path: path, perm: os.ModePerm}
}

// NewDirWithPerm creates a new Dir with the given path and permissions.
func NewDirWithPerm(path string, perm os.FileMode) Dir {
	return Dir{path: path, perm: perm}
}

// String returns the raw path without creating the directory. Satisfies fmt.Stringer.
func (d *Dir) String() string {
	return d.path
}

// Path creates the directory on first call (via sync.Once) and returns the path.
func (d *Dir) Path() (string, error) {
	d.once.Do(func() {
		if d.path == "" {
			return
		}
		d.err = os.MkdirAll(d.path, d.perm)
		if d.err != nil {
			d.err = fmt.Errorf("creating directory %q: %w", d.path, d.err)
		}
	})
	return d.path, d.err
}

// MustPath calls Path() and calls logFatal on error.
func (d *Dir) MustPath() string {
	path, err := d.Path()
	if err != nil {
		logFatal("creating directory:", err)
	}
	return path
}

// GoString implements fmt.GoStringer so that %#v (used by pretty.Sprintf)
// prints the path string instead of the internal struct fields.
func (d Dir) GoString() string { //nolint:govet
	return fmt.Sprintf("%q", d.path)
}

// MarshalText returns the raw path bytes. No side effects.
func (d *Dir) MarshalText() ([]byte, error) {
	return []byte(d.path), nil
}

// UnmarshalText sets the path from bytes. No side effects.
func (d *Dir) UnmarshalText(text []byte) error {
	d.path = string(text)
	if d.perm == 0 {
		d.perm = os.ModePerm
	}
	return nil
}