Change storage paths to follow OS conventions; migrate folder (#2955)

storage.go

@@ -20,6 +20,7 @@ import (
 	"runtime"
 
 	"github.com/mholt/certmagic"
+	"go.uber.org/zap"
 )
 
 // StorageConverter is a type that can convert itself
@@ -31,10 +32,28 @@ type StorageConverter interface {
 	CertMagicStorage() (certmagic.Storage, error)
 }
 
-// homeDir returns the best guess of the current user's home
+// HomeDir returns the best guess of the current user's home
 // directory from environment variables. If unknown, "." (the
-// current directory) is returned instead.
-func homeDir() string {
+// current directory) is returned instead, except GOOS=android,
+// which returns "/sdcard".
+func HomeDir() string {
+	home := homeDirUnsafe()
+	if home == "" && runtime.GOOS == "android" {
+		home = "/sdcard"
+	}
+	if home == "" {
+		home = "."
+	}
+	return home
+}
+
+// homeDirUnsafe is a low-level function that returns
+// the user's home directory from environment
+// variables. Careful: if it cannot be determined, an
+// empty string is returned. If not accounting for
+// that case, use HomeDir() instead; otherwise you
+// may end up using the root of the file system.
+func homeDirUnsafe() string {
 	home := os.Getenv("HOME")
 	if home == "" && runtime.GOOS == "windows" {
 		drive := os.Getenv("HOMEDRIVE")
@@ -44,21 +63,96 @@ func homeDir() string {
 			home = os.Getenv("USERPROFILE")
 		}
 	}
-	if home == "" {
-		home = "."
+	if home == "" && runtime.GOOS == "plan9" {
+		home = os.Getenv("home")
 	}
 	return home
 }
 
-// dataDir returns a directory path that is suitable for storage.
-// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables
-func dataDir() string {
-	baseDir := filepath.Join(homeDir(), ".local", "share")
-	if xdgData := os.Getenv("XDG_DATA_HOME"); xdgData != "" {
-		baseDir = xdgData
+// AppConfigDir returns the directory where to store user's config.
+//
+// If XDG_CONFIG_HOME is set, it returns: $XDG_CONFIG_HOME/caddy.
+// Otherwise, os.UserConfigDir() is used; if successful, it appends
+// "Caddy" (Windows & Mac) or "caddy" (every other OS) to the path.
+// If it returns an error, the fallback path "./caddy" is returned.
+//
+// The config directory is not guaranteed to be different from
+// AppDataDir().
+//
+// Unlike os.UserConfigDir(), this function prefers the
+// XDG_CONFIG_HOME env var on all platforms, not just Unix.
+//
+// Ref: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
+func AppConfigDir() string {
+	basedir := os.Getenv("XDG_CONFIG_HOME")
+	if basedir == "" {
+		var err error
+		basedir, err = os.UserConfigDir()
+		if err != nil {
+			Log().Warn("unable to determine directory for user configuration; falling back to current directory", zap.Error(err))
+			return "./caddy"
+		}
 	}
-	return filepath.Join(baseDir, "caddy")
+	subdir := "caddy"
+	switch runtime.GOOS {
+	case "windows", "darwin":
+		subdir = "Caddy"
+	}
+	return filepath.Join(basedir, subdir)
 }
 
-// TODO: Consider using Go 1.13's os.UserConfigDir() (https://golang.org/pkg/os/#UserConfigDir)
-// if we are going to store the last-loaded config anywhere
+// AppDataDir returns a directory path that is suitable for storing
+// application data on disk. It uses the environment for finding the
+// best place to store data, and appends a "caddy" or "Caddy" (depending
+// on OS and environment) subdirectory.
+//
+// For a base directory path:
+// If XDG_DATA_HOME is set, it returns: $XDG_DATA_HOME/caddy; otherwise,
+// on Windows it returns: %AppData%/Caddy,
+// on Mac: $HOME/Library/Application Support/Caddy,
+// on Plan9: $home/lib/caddy,
+// on Android: $HOME/caddy,
+// and on everything else: $HOME/.local/share/caddy.
+//
+// If a data directory cannot be determined, it returns "./caddy"
+// (this is not ideal, and the environment should be fixed).
+//
+// The data directory is not guaranteed to be different from AppConfigDir().
+//
+// Ref: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
+func AppDataDir() string {
+	if basedir := os.Getenv("XDG_DATA_HOME"); basedir != "" {
+		return filepath.Join(basedir, "caddy")
+	}
+	switch runtime.GOOS {
+	case "windows":
+		appData := os.Getenv("AppData")
+		if appData != "" {
+			return filepath.Join(appData, "Caddy")
+		}
+	case "darwin":
+		home := homeDirUnsafe()
+		if home != "" {
+			return filepath.Join(home, "Library", "Application Support", "Caddy")
+		}
+	case "plan9":
+		home := homeDirUnsafe()
+		if home != "" {
+			return filepath.Join(home, "lib", "caddy")
+		}
+	case "android":
+		home := homeDirUnsafe()
+		if home != "" {
+			return filepath.Join(home, "caddy")
+		}
+	default:
+		home := homeDirUnsafe()
+		if home != "" {
+			return filepath.Join(home, ".local", "share", "caddy")
+		}
+	}
+	return "./caddy"
+}
+
+// ConfigAutosavePath is the default path to which the last config will be persisted.
+var ConfigAutosavePath = filepath.Join(AppConfigDir(), "autosave.json")