Factor command line parsing into an internal package for reuse.

cmd/csaf_downloader/config.go

@@ -9,15 +9,9 @@
 package main
 
 import (
-	"fmt"
-	"log"
 	"net/http"
-	"os"
 
-	"github.com/BurntSushi/toml"
-	"github.com/csaf-poc/csaf_distribution/v2/util"
-	"github.com/jessevdk/go-flags"
-	"github.com/mitchellh/go-homedir"
+	"github.com/csaf-poc/csaf_distribution/v2/internal/options"
 )
 
 const (
@@ -43,106 +37,36 @@ type config struct {
 	Config string `short:"c" long:"config" description:"Path to config TOML file" value-name:"TOML-FILE" toml:"-"`
 }
 
-// configPaths are the potential file locations of the the config file.
+// configPaths are the potential file locations of the config file.
 var configPaths = []string{
 	"~/.config/csaf/downloader.toml",
 	"~/.csaf_downloader.toml",
 	"csaf_downloader.toml",
 }
 
-// newConfig returns a new configuration.
-func newConfig() *config {
-	return &config{
-		Worker:                 defaultWorker,
-		RemoteValidatorPresets: []string{defaultPreset},
-	}
-}
-
 // parseArgsConfig parses the command line and if need a config file.
 func parseArgsConfig() ([]string, *config, error) {
-
-	// Parse the command line first.
-	cmdLineCfg := newConfig()
-	parser := flags.NewParser(cmdLineCfg, flags.Default)
-	parser.Usage = "[OPTIONS] domain..."
-	args, err := parser.Parse()
-	if err != nil {
-		return nil, nil, err
+	p := options.Parser[config]{
+		DefaultConfigLocations: configPaths,
+		ConfigLocation: func(cfg *config) string {
+			return cfg.Config
+		},
+		Usage: "[OPTIONS] domain...",
+		SetDefaults: func(cfg *config) {
+			cfg.Worker = defaultWorker
+			cfg.RemoteValidatorPresets = []string{defaultPreset}
+		},
+		// Re-establish default values if not set.
+		EnsureDefaults: func(cfg *config) {
+			if cfg.Worker == 0 {
+				cfg.Worker = defaultWorker
+			}
+			if cfg.RemoteValidatorPresets == nil {
+				cfg.RemoteValidatorPresets = []string{defaultPreset}
+			}
+		},
 	}
-
-	// Directly quit if the version flag was set.
-	if cmdLineCfg.Version {
-		fmt.Println(util.SemVersion)
-		os.Exit(0)
-	}
-
-	var path string
-	// Do we have a config file explicitly given by command line?
-	if cmdLineCfg.Config != "" {
-		path = cmdLineCfg.Config
-	} else {
-		path = findConfigFile()
-	}
-	// No config file -> We are good.
-	if path == "" {
-		return args, cmdLineCfg, nil
-	}
-
-	if path, err = homedir.Expand(path); err != nil {
-		return nil, nil, err
-	}
-
-	// Load the config file
-	fileCfg := &config{}
-	if err := fileCfg.load(path); err != nil {
-		return nil, nil, err
-	}
-
-	// Parse command line a second time to overwrite the
-	// loaded config at places where explicitly command line
-	// options where given.
-	args, err = flags.NewParser(fileCfg, flags.Default).Parse()
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// Re-establish default values.
-	if fileCfg.Worker == 0 {
-		fileCfg.Worker = defaultWorker
-	}
-	if fileCfg.RemoteValidatorPresets == nil {
-		fileCfg.RemoteValidatorPresets = []string{defaultPreset}
-	}
-
-	return args, fileCfg, nil
-}
-
-// load loads a configuration from file.
-func (cfg *config) load(path string) error {
-	md, err := toml.DecodeFile(path, &cfg)
-	if err != nil {
-		return err
-	}
-	if undecoded := md.Undecoded(); len(undecoded) != 0 {
-		return fmt.Errorf("could not parse %q from %q", undecoded, path)
-	}
-	return nil
-}
-
-// findConfigFile looks for a file in the pre-defined paths in "configPath".
-// The returned value will be the name of file if found, otherwise an empty string.
-func findConfigFile() string {
-	for _, f := range configPaths {
-		name, err := homedir.Expand(f)
-		if err != nil {
-			log.Printf("warn: %v\n", err)
-			continue
-		}
-		if _, err := os.Stat(name); err == nil {
-			return name
-		}
-	}
-	return ""
+	return p.Parse()
 }
 
 // prepare prepares internal state of a loaded configuration.
@@ -150,14 +74,3 @@ func (cfg *config) prepare() error {
 	// TODO: Implement me!
 	return nil
 }
-
-// errCheck checks if err is not nil and terminates
-// the program if so.
-func errCheck(err error) {
-	if err != nil {
-		if flags.WroteHelp(err) {
-			os.Exit(0)
-		}
-		log.Fatalf("error: %v\n", err)
-	}
-}