funknetz/config_path.go

package main

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

func defaultConfigPath() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(home, ".funknetz.json"), nil
}

// resolveConfigPath picks the config file from -c / --config in args (no program name).
// The default is ~/.funknetz.json. A relative path is resolved against the process CWD.
func resolveConfigPath(args []string) (string, error) {
	fs := flag.NewFlagSet("funknetz", flag.ContinueOnError)
	fs.SetOutput(io.Discard)
	var config string
	fs.StringVar(&config, "config", "", "path to the station config file")
	fs.StringVar(&config, "c", "", "path to the station config file")
	rest := args
	for {
		if err := fs.Parse(rest); err != nil {
			return "", err
		}
		rest = fs.Args()
		if len(rest) == 0 {
			break
		}
		// A non-flag word ends a parse. Skip it and keep later flags.
		rest = rest[1:]
	}
	if config == "" {
		path, err := defaultConfigPath()
		if err != nil {
			return "", fmt.Errorf("config path: %w", err)
		}
		return path, nil
	}
	abs, err := filepath.Abs(config)
	if err != nil {
		return "", fmt.Errorf("config path: %w", err)
	}
	return abs, nil
}