package daecommon

import (
	"os"
	"path/filepath"
	"sync"

	"github.com/adrg/xdg"
)

// EnvVars are variables which are derived based on the environment which the
// process is running in.
type EnvVars struct {
	RuntimeDirPath string
	StateDirPath   string
}

// GetEnvVars will return the EnvVars of the current processes, as determined by
// the process's environment.
var GetEnvVars = sync.OnceValue(func() (v EnvVars) {
	// RUNTIME_DIRECTORY/STATE_DIRECTORY are used by the systemd service in
	// conjunction with the RuntimeDirectory/StateDirectory directives.

	v.RuntimeDirPath = envOr(
		"RUNTIME_DIRECTORY",
		func() string { return filepath.Join(xdg.RuntimeDir, "isle") },
	)

	v.StateDirPath = envOr(
		"STATE_DIRECTORY",
		func() string { return filepath.Join(xdg.StateHome, "isle") },
	)

	return
})

////////////////////////////////////////////////////////////////////////////////
// Jigs

func envOr(name string, fallback func() string) string {
	if v := os.Getenv(name); v != "" {
		return v
	}
	return fallback()
}