package main

import (
	"fmt"
	"os"
	"path/filepath"
)

// dataDir returns the data directory and creates it with mode 0700 when it does
// not exist. It is ONECHAT_DIR when that is set. Otherwise it is
// $XDG_DATA_HOME/onechat when XDG_DATA_HOME is an absolute path, or else
// ~/.local/share/onechat.
func dataDir() (string, error) {
	dir := os.Getenv("ONECHAT_DIR")
	if dir == "" {
		var err error

		dir, err = defaultDataDir()
		if err != nil {
			return "", err
		}
	}

	err := os.MkdirAll(dir, 0o700)
	if err != nil {
		return "", fmt.Errorf("create data directory: %w", err)
	}

	return dir, nil
}

// defaultDataDir returns the data directory for an unset ONECHAT_DIR. The XDG
// specification says to ignore a relative XDG_DATA_HOME.
func defaultDataDir() (string, error) {
	xdg := os.Getenv("XDG_DATA_HOME")
	if filepath.IsAbs(xdg) {
		return filepath.Join(xdg, "onechat"), nil
	}

	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("find data directory: set ONECHAT_DIR: %w", err)
	}

	return filepath.Join(home, ".local", "share", "onechat"), nil
}