Fix/linter (#66)

* added lint targets * fix linter errors * enhance error handling * !!BREAKING!! rename Id to ID in tpls
2025-12-16 12:01:00 +01:00 · 2024-01-25 19:03:34 +01:00
parent 9cd1fc0596
commit 14f8c3fd43
19 changed files with 264 additions and 203 deletions
--- a/12
+++ b/12
@@ -56,6 +56,14 @@ test: clean
 	mkdir -p t/out
 	go test ./... $(ARGS)

+testlint: test lint
+
+lint:
+	golangci-lint run
+
+lint-full:
+	golangci-lint run --enable-all --exclude-use-default --disable exhaustivestruct,exhaustruct,depguard,interfacer,deadcode,golint,structcheck,scopelint,varcheck,ifshort,maligned,nosnakecase,godot,funlen,gofumpt,cyclop,noctx,gochecknoglobals,paralleltest
+
 testfuzzy: clean
 	go test -fuzz ./... $(ARGS)

@@ -88,5 +96,5 @@ show-versions: buildlocal
 	@echo "### go version used for building:"
 	@grep -m 1 go go.mod

-lint:
-	golangci-lint run -p bugs -p unused
+# lint:
+# 	golangci-lint run -p bugs -p unused
--- a/ad.go
+++ b/ad.go
@@ -30,7 +30,7 @@ type Index struct {
 type Ad struct {
 	Title        string `goquery:"h1"`
 	Slug         string
-	Id           string
+	ID           string
 	Condition    string `goquery:".addetailslist--detail--value,text"`
 	Category     string
 	CategoryTree []string `goquery:".breadcrump-link,text"`
@@ -46,7 +46,7 @@ func (ad *Ad) LogValue() slog.Value {
 	return slog.GroupValue(
 		slog.String("title", ad.Title),
 		slog.String("price", ad.Price),
-		slog.String("id", ad.Id),
+		slog.String("id", ad.ID),
 		slog.Int("imagecount", len(ad.Images)),
 		slog.Int("bodysize", len(ad.Text)),
 		slog.String("categorytree", strings.Join(ad.CategoryTree, "+")),
@@ -76,7 +76,7 @@ func (ad *Ad) CalculateExpire() {
 	if len(ad.Created) > 0 {
 		ts, err := time.Parse("02.01.2006", ad.Created)
 		if err == nil {
-			ad.Expire = ts.AddDate(0, 2, 1).Format("02.01.2006")
+			ad.Expire = ts.AddDate(0, ExpireMonths, ExpireDays).Format("02.01.2006")
 		}
 	}
 }
--- a/config.go
+++ b/config.go
@@ -17,7 +17,6 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package main

 import (
-	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -35,16 +34,16 @@ import (
 )

 const (
-	VERSION    string = "0.3.1"
+	VERSION    string = "0.3.2"
 	Baseuri    string = "https://www.kleinanzeigen.de"
 	Listuri    string = "/s-bestandsliste.html"
 	Defaultdir string = "."

-	DefaultTemplate string = "Title: {{.Title}}\nPrice: {{.Price}}\nId: {{.Id}}\n" +
+	DefaultTemplate string = "Title: {{.Title}}\nPrice: {{.Price}}\nId: {{.ID}}\n" +
 		"Category: {{.Category}}\nCondition: {{.Condition}}\n" +
 		"Created: {{.Created}}\nExpire: {{.Expire}}\n\n{{.Text}}\n"

-	DefaultTemplateWin string = "Title: {{.Title}}\r\nPrice: {{.Price}}\r\nId: {{.Id}}\r\n" +
+	DefaultTemplateWin string = "Title: {{.Title}}\r\nPrice: {{.Price}}\r\nId: {{.ID}}\r\n" +
 		"Category: {{.Category}}\r\nCondition: {{.Condition}}\r\n" +
 		"Created: {{.Created}}\r\nExpires: {{.Expire}}\r\n\r\n{{.Text}}\r\n"

@@ -56,6 +55,14 @@ const (
 	// for image download throttling
 	MinThrottle int = 2
 	MaxThrottle int = 20
+
+	// we extract the slug from the uri
+	SlugURIPartNum int = 6
+
+	ExpireMonths int = 2
+	ExpireDays   int = 1
+
+	WIN string = "windows"
 )

 const Usage string = `This is kleingebaeck, the kleinanzeigen.de backup tool.
@@ -107,17 +114,17 @@ func (c *Config) IncrImgs(num int) {
 }

 // load commandline flags and config file
-func InitConfig(w io.Writer) (*Config, error) {
-	var k = koanf.New(".")
+func InitConfig(output io.Writer) (*Config, error) {
+	var kloader = koanf.New(".")

 	// determine template based on os
 	template := DefaultTemplate
-	if runtime.GOOS == "windows" {
+	if runtime.GOOS == WIN {
 		template = DefaultTemplateWin
 	}

 	// Load default values using the confmap provider.
-	if err := k.Load(confmap.Provider(map[string]interface{}{
+	if err := kloader.Load(confmap.Provider(map[string]interface{}{
 		"template":       template,
 		"outdir":         ".",
 		"loglevel":       "notice",
@@ -125,37 +132,39 @@ func InitConfig(w io.Writer) (*Config, error) {
 		"adnametemplate": DefaultAdNameTemplate,
 		"useragent":      DefaultUserAgent,
 	}, "."), nil); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to load default values into koanf: %w", err)
 	}

 	// setup custom usage
-	f := flag.NewFlagSet("config", flag.ContinueOnError)
-	f.Usage = func() {
-		fmt.Fprintln(w, Usage)
+	flagset := flag.NewFlagSet("config", flag.ContinueOnError)
+	flagset.Usage = func() {
+		fmt.Fprintln(output, Usage)
 		os.Exit(0)
 	}

 	// parse commandline flags
-	f.StringP("config", "c", "", "config file")
-	f.StringP("outdir", "o", "", "directory where to store ads")
-	f.IntP("user", "u", 0, "user id")
-	f.IntP("limit", "l", 0, "limit ads to be downloaded (default 0, unlimited)")
-	f.BoolP("verbose", "v", false, "be verbose")
-	f.BoolP("debug", "d", false, "enable debug log")
-	f.BoolP("version", "V", false, "show program version")
-	f.BoolP("help", "h", false, "show usage")
-	f.BoolP("manual", "m", false, "show manual")
-	f.BoolP("force", "f", false, "force")
+	flagset.StringP("config", "c", "", "config file")
+	flagset.StringP("outdir", "o", "", "directory where to store ads")
+	flagset.IntP("user", "u", 0, "user id")
+	flagset.IntP("limit", "l", 0, "limit ads to be downloaded (default 0, unlimited)")
+	flagset.BoolP("verbose", "v", false, "be verbose")
+	flagset.BoolP("debug", "d", false, "enable debug log")
+	flagset.BoolP("version", "V", false, "show program version")
+	flagset.BoolP("help", "h", false, "show usage")
+	flagset.BoolP("manual", "m", false, "show manual")
+	flagset.BoolP("force", "f", false, "force")

-	if err := f.Parse(os.Args[1:]); err != nil {
-		return nil, err
+	if err := flagset.Parse(os.Args[1:]); err != nil {
+		return nil, fmt.Errorf("failed to parse program arguments: %w", err)
 	}

 	// generate a  list of config files to try  to load, including the
 	// one provided via -c, if any
 	var configfiles []string
-	configfile, _ := f.GetString("config")
+
+	configfile, _ := flagset.GetString("config")
 	home, _ := os.UserHomeDir()
+
 	if configfile != "" {
 		configfiles = []string{configfile}
 	} else {
@@ -171,31 +180,30 @@ func InitConfig(w io.Writer) (*Config, error) {
 	for _, cfgfile := range configfiles {
 		if path, err := os.Stat(cfgfile); !os.IsNotExist(err) {
 			if !path.IsDir() {
-				if err := k.Load(file.Provider(cfgfile), toml.Parser()); err != nil {
-					return nil, errors.New("error loading config file: " + err.Error())
+				if err := kloader.Load(file.Provider(cfgfile), toml.Parser()); err != nil {
+					return nil, fmt.Errorf("error loading config file: %w", err)
 				}
 			}
-		}
-		// else: we ignore the file if it doesn't exists
+		} // else: we ignore the file if it doesn't exists
 	}

 	// env overrides config file
-	if err := k.Load(env.Provider("KLEINGEBAECK_", ".", func(s string) string {
-		return strings.Replace(strings.ToLower(
-			strings.TrimPrefix(s, "KLEINGEBAECK_")), "_", ".", -1)
+	if err := kloader.Load(env.Provider("KLEINGEBAECK_", ".", func(s string) string {
+		return strings.ReplaceAll(strings.ToLower(
+			strings.TrimPrefix(s, "KLEINGEBAECK_")), "_", ".")
 	}), nil); err != nil {
-		return nil, errors.New("error loading environment: " + err.Error())
+		return nil, fmt.Errorf("error loading environment: %w", err)
 	}

 	// command line overrides env
-	if err := k.Load(posflag.Provider(f, ".", k), nil); err != nil {
-		return nil, errors.New("error loading flags: " + err.Error())
+	if err := kloader.Load(posflag.Provider(flagset, ".", kloader), nil); err != nil {
+		return nil, fmt.Errorf("error loading flags: %w", err)
 	}

 	// fetch values
 	conf := &Config{}
-	if err := k.Unmarshal("", &conf); err != nil {
-		return nil, errors.New("error unmarshalling: " + err.Error())
+	if err := kloader.Unmarshal("", &conf); err != nil {
+		return nil, fmt.Errorf("error unmarshalling: %w", err)
 	}

 	// adjust loglevel
@@ -207,7 +215,7 @@ func InitConfig(w io.Writer) (*Config, error) {
 	}

 	// are there any args left on commandline? if so threat them as adlinks
-	conf.Adlinks = f.Args()
+	conf.Adlinks = flagset.Args()

 	return conf, nil
 }
--- a/fetch.go
+++ b/fetch.go
@@ -19,6 +19,7 @@ package main

 import (
 	"errors"
+	"fmt"
 	"io"
 	"log/slog"
 	"net/http"
@@ -33,10 +34,10 @@ type Fetcher struct {
 	Cookies []*http.Cookie
 }

-func NewFetcher(c *Config) (*Fetcher, error) {
+func NewFetcher(conf *Config) (*Fetcher, error) {
 	jar, err := cookiejar.New(nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to create a cookie jar obj: %w", err)
 	}

 	return &Fetcher{
@@ -44,35 +45,37 @@ func NewFetcher(c *Config) (*Fetcher, error) {
 				Transport: &loggingTransport{}, // implemented in http.go
 				Jar:       jar,
 			},
-			Config:  c,
+			Config:  conf,
 			Cookies: []*http.Cookie{},
 		},
 		nil
 }

 func (f *Fetcher) Get(uri string) (io.ReadCloser, error) {
-	req, err := http.NewRequest("GET", uri, nil)
+	req, err := http.NewRequest(http.MethodGet, uri, nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to create a new HTTP request obj: %w", err)
 	}

 	req.Header.Set("User-Agent", f.Config.UserAgent)

 	if len(f.Cookies) > 0 {
 		uriobj, _ := url.Parse(Baseuri)
+
 		slog.Debug("have cookies, sending them",
 			"sample-cookie-name", f.Cookies[0].Name,
 			"sample-cookie-expire", f.Cookies[0].Expires,
 		)
+
 		f.Client.Jar.SetCookies(uriobj, f.Cookies)
 	}

 	res, err := f.Client.Do(req)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to initiate HTTP request to %s: %w", uri, err)
 	}

-	if res.StatusCode != 200 {
+	if res.StatusCode != http.StatusOK {
 		return nil, errors.New("could not get page via HTTP")
 	}

@@ -85,12 +88,15 @@ func (f *Fetcher) Get(uri string) (io.ReadCloser, error) {
 // fetch an image
 func (f *Fetcher) Getimage(uri string) (io.ReadCloser, error) {
 	slog.Debug("fetching ad image", "uri", uri)
+
 	body, err := f.Get(uri)
 	if err != nil {
 		if f.Config.IgnoreErrors {
 			slog.Info("Failed to download image, error ignored", "error", err.Error())
+
 			return nil, nil
 		}
+
 		return nil, err
 	}

--- a/go.mod
+++ b/go.mod
@@ -31,6 +31,7 @@ require (
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 // indirect
 	github.com/pelletier/go-toml v1.9.5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	golang.org/x/net v0.0.0-20220722155237-a158d28d115b // indirect
 	golang.org/x/sys v0.14.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
--- a/go.sum
+++ b/go.sum
@@ -50,6 +50,8 @@ github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 h1:zYyBkD/k9seD2A7fsi6
 github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646/go.mod h1:jpp1/29i3P1S/RLdc7JQKbRpFeM1dOBd8T9ki5s+AY8=
 github.com/pelletier/go-toml v1.9.5 h1:4yBQzkHv+7BHq2PQUZF3Mx0IYxG7LsP222s7Agd3ve8=
 github.com/pelletier/go-toml v1.9.5/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
--- a/http.go
+++ b/http.go
@@ -19,6 +19,7 @@ package main

 import (
 	"bytes"
+	"fmt"
 	"io"
 	"log/slog"
 	"math"
@@ -32,17 +33,20 @@ import (
 // easier associated in debug output
 var letters = []rune("ABCDEF0123456789")

-func getid() string {
-	b := make([]rune, 8)
-	for i := range b {
-		b[i] = letters[rand.Intn(len(letters))]
-	}
-	return string(b)
-}
+const IDLEN int = 8

 // retry after HTTP 50x errors or err!=nil
 const RetryCount = 3

+func getid() string {
+	b := make([]rune, IDLEN)
+	for i := range b {
+		b[i] = letters[rand.Intn(len(letters))]
+	}
+
+	return string(b)
+}
+
 // used to inject debug log and implement retries
 type loggingTransport struct{}

@@ -75,6 +79,7 @@ func drainBody(resp *http.Response) {
 				// unable to copy data? uff!
 				panic(err)
 			}
+
 			resp.Body.Close()
 		}
 	}
@@ -82,8 +87,8 @@ func drainBody(resp *http.Response) {

 // the actual logging transport with retries
 func (t *loggingTransport) RoundTrip(req *http.Request) (*http.Response, error) {
-	// just requred for debugging
-	id := getid()
+	// just required for debugging
+	requestid := getid()

 	// clone the request body, put into request on retry
 	var bodyBytes []byte
@@ -92,16 +97,16 @@ func (t *loggingTransport) RoundTrip(req *http.Request) (*http.Response, error)
 		req.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))
 	}

-	slog.Debug("REQUEST", "id", id, "uri", req.URL, "host", req.Host)
+	slog.Debug("REQUEST", "id", requestid, "uri", req.URL, "host", req.Host)

 	// first try
 	resp, err := http.DefaultTransport.RoundTrip(req)
 	if err == nil {
-		slog.Debug("RESPONSE", "id", id, "status", resp.StatusCode,
+		slog.Debug("RESPONSE", "id", requestid, "status", resp.StatusCode,
 			"contentlength", resp.ContentLength)
 	}

-	// enter retry check and loop, if first req were successfull, leave loop immediately
+	// enter retry check and loop, if first req were successful, leave loop immediately
 	retries := 0
 	for shouldRetry(err, resp) && retries < RetryCount {
 		time.Sleep(backoff(retries))
@@ -118,12 +123,16 @@ func (t *loggingTransport) RoundTrip(req *http.Request) (*http.Response, error)
 		resp, err = http.DefaultTransport.RoundTrip(req)

 		if err == nil {
-			slog.Debug("RESPONSE", "id", id, "status", resp.StatusCode,
+			slog.Debug("RESPONSE", "id", requestid, "status", resp.StatusCode,
 				"contentlength", resp.ContentLength, "retry", retries)
 		}

 		retries++
 	}

-	return resp, err
+	if err != nil {
+		return resp, fmt.Errorf("failed to get HTTP response for %s: %w", req.URL, err)
+	}
+
+	return resp, nil
 }
--- a/image.go
+++ b/image.go
@@ -19,6 +19,7 @@ package main

 import (
 	"bytes"
+	"fmt"
 	"image/jpeg"
 	"log/slog"
 	"os"
@@ -33,14 +34,14 @@ type Image struct {
 	Filename string
 	Hash     *goimagehash.ImageHash
 	Data     *bytes.Buffer
-	Uri      string
+	URI      string
 }

 // used for logging to avoid printing Data
 func (img *Image) LogValue() slog.Value {
 	return slog.GroupValue(
 		slog.String("filename", img.Filename),
-		slog.String("uri", img.Uri),
+		slog.String("uri", img.URI),
 		slog.String("hash", img.Hash.ToString()),
 	)
 }
@@ -51,7 +52,7 @@ type Cache []*goimagehash.ImageHash
 func NewImage(buf *bytes.Buffer, filename string, uri string) *Image {
 	img := &Image{
 		Filename: filename,
-		Uri:      uri,
+		URI:      uri,
 		Data:     buf,
 	}

@@ -62,12 +63,12 @@ func NewImage(buf *bytes.Buffer, filename string, uri string) *Image {
 func (img *Image) CalcHash() error {
 	jpgdata, err := jpeg.Decode(img.Data)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to decode JPEG image: %w", err)
 	}

 	hash1, err := goimagehash.DifferenceHash(jpgdata)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to calculate diff hash of image: %w", err)
 	}

 	img.Hash = hash1
@@ -80,16 +81,18 @@ func (img *Image) Similar(hash *goimagehash.ImageHash) bool {
 	distance, err := img.Hash.Distance(hash)
 	if err != nil {
 		slog.Debug("failed to compute diff hash distance", "error", err)
+
 		return false
 	}

 	if distance < MaxDistance {
 		slog.Debug("distance computation", "image-A", img.Hash.ToString(),
 			"image-B", hash.ToString(), "distance", distance)
+
 		return true
-	} else {
-		return false
 	}
+
+	return false
 }

 // check current image against all known hashes.
@@ -108,7 +111,7 @@ func (img *Image) SimilarExists(cache Cache) bool {
 func ReadImages(addir string, dont bool) (Cache, error) {
 	files, err := os.ReadDir(addir)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to read ad directory contents: %w", err)
 	}

 	cache := Cache{}
@@ -122,6 +125,7 @@ func ReadImages(addir string, dont bool) (Cache, error) {
 		ext := filepath.Ext(file.Name())
 		if !file.IsDir() && (ext == ".jpg" || ext == ".jpeg" || ext == ".JPG" || ext == ".JPEG") {
 			filename := filepath.Join(addir, file.Name())
+
 			data, err := ReadImage(filename)
 			if err != nil {
 				return nil, err
@@ -137,6 +141,5 @@ func ReadImages(addir string, dont bool) (Cache, error) {
 		}
 	}

-	//return nil, errors.New("ende")
 	return cache, nil
 }
--- a/kleingebaeck.1
+++ b/kleingebaeck.1
@@ -133,7 +133,7 @@
 .\" ========================================================================
 .\"
 .IX Title "KLEINGEBAECK 1"
-.TH KLEINGEBAECK 1 "2024-01-24" "1" "User Commands"
+.TH KLEINGEBAECK 1 "2024-01-25" "1" "User Commands"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
@@ -182,7 +182,7 @@ Format is pretty simple:
 \&    template = """
 \&    Title: {{.Title}}
 \&    Price: {{.Price}}
-\&    Id: {{.Id}}
+\&    Id: {{.ID}}
 \&    Category: {{.Category}}
 \&    Condition: {{.Condition}}
 \&    Created: {{.Created}}
@@ -191,7 +191,7 @@ Format is pretty simple:
 \&    """
 .Ve
 .PP
-Be carefull  if you want  to change the  template.  The variable  is a
+Be careful  if you want  to change the  template.  The variable  is a
 multiline string surrounded  by three double quotes. You  can left out
 certain   fields  and   use  any   formatting  you   like.  Refer   to
 <https://pkg.go.dev/text/template>  for   details  how  to   write  a
--- a/kleingebaeck.go
+++ b/kleingebaeck.go
@@ -43,7 +43,7 @@ CONFIGURATION
        template = """
        Title: {{.Title}}
        Price: {{.Price}}
-        Id: {{.Id}}
+        Id: {{.ID}}
        Category: {{.Category}}
        Condition: {{.Condition}}
        Created: {{.Created}}
@@ -51,7 +51,7 @@ CONFIGURATION
        {{.Text}}
        """

-    Be carefull if you want to change the template. The variable is a
+    Be careful if you want to change the template. The variable is a
    multiline string surrounded by three double quotes. You can left out
    certain fields and use any formatting you like. Refer to
    <https://pkg.go.dev/text/template> for details how to write a template.
--- a/kleingebaeck.pod
+++ b/kleingebaeck.pod
@@ -43,7 +43,7 @@ Format is pretty simple:
    template = """
    Title: {{.Title}}
    Price: {{.Price}}
-    Id: {{.Id}}
+    Id: {{.ID}}
    Category: {{.Category}}
    Condition: {{.Condition}}
    Created: {{.Created}}
@@ -51,7 +51,7 @@ Format is pretty simple:
    {{.Text}}
    """

-Be carefull  if you want  to change the  template.  The variable  is a
+Be careful  if you want  to change the  template.  The variable  is a
 multiline string surrounded  by three double quotes. You  can left out
 certain   fields  and   use  any   formatting  you   like.  Refer   to
 L<https://pkg.go.dev/text/template>  for   details  how  to   write  a
--- a/main.go
+++ b/main.go
@@ -22,10 +22,8 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
-	"math/rand"
 	"os"
 	"runtime/debug"
-	"time"

 	"github.com/lmittmann/tint"
 	"github.com/tlinden/yadu"
@@ -37,38 +35,43 @@ func main() {
 	os.Exit(Main(os.Stdout))
 }

-func Main(w io.Writer) int {
+func Main(output io.Writer) int {
 	logLevel := &slog.LevelVar{}
 	opts := &tint.Options{
 		Level:     logLevel,
 		AddSource: false,
-		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+		ReplaceAttr: func(groups []string, attr slog.Attr) slog.Attr {
 			// Remove time from the output
-			if a.Key == slog.TimeKey {
+			if attr.Key == slog.TimeKey {
 				return slog.Attr{}
 			}
-			return a
+
+			return attr
 		},
 		NoColor: IsNoTty(),
 	}

 	logLevel.Set(LevelNotice)
-	handler := tint.NewHandler(w, opts)
+
+	handler := tint.NewHandler(output, opts)
 	logger := slog.New(handler)
+
 	slog.SetDefault(logger)

-	conf, err := InitConfig(w)
+	conf, err := InitConfig(output)
 	if err != nil {
 		return Die(err)
 	}

 	if conf.Showversion {
-		fmt.Fprintf(w, "This is kleingebaeck version %s\n", VERSION)
+		fmt.Fprintf(output, "This is kleingebaeck version %s\n", VERSION)
+
 		return 0
 	}

 	if conf.Showhelp {
-		fmt.Fprintln(w, Usage)
+		fmt.Fprintln(output, Usage)
+
 		return 0
 	}

@@ -77,6 +80,7 @@ func Main(w io.Writer) int {
 		if err != nil {
 			return Die(err)
 		}
+
 		return 0
 	}

@@ -94,7 +98,8 @@ func Main(w io.Writer) int {
 		}

 		logLevel.Set(slog.LevelDebug)
-		handler := yadu.NewHandler(w, opts)
+
+		handler := yadu.NewHandler(output, opts)
 		debuglogger := slog.New(handler).With(
 			slog.Group("program_info",
 				slog.Int("pid", os.Getpid()),
@@ -118,10 +123,8 @@ func Main(w io.Writer) int {
 		return Die(err)
 	}

-	// randomization needed here and there
-	rand.Seed(time.Now().UnixNano())
-
-	if len(conf.Adlinks) >= 1 {
+	switch {
+	case len(conf.Adlinks) >= 1:
 		// directly backup ad listing[s]
 		for _, uri := range conf.Adlinks {
 			err := ScrapeAd(fetch, uri)
@@ -129,25 +132,27 @@ func Main(w io.Writer) int {
 				return Die(err)
 			}
 		}
-	} else if conf.User > 0 {
+	case conf.User > 0:
 		// backup all ads of the given user (via config or cmdline)
 		err := ScrapeUser(fetch)
 		if err != nil {
 			return Die(err)
 		}
-	} else {
+	default:
 		return Die(errors.New("invalid or no user id or no ad link specified"))
 	}

 	if conf.StatsCountAds > 0 {
 		adstr := "ads"
+
 		if conf.StatsCountAds == 1 {
 			adstr = "ad"
 		}
-		fmt.Fprintf(w, "Successfully downloaded %d %s with %d images to %s.\n",
+
+		fmt.Fprintf(output, "Successfully downloaded %d %s with %d images to %s.\n",
 			conf.StatsCountAds, adstr, conf.StatsCountImages, conf.Outdir)
 	} else {
-		fmt.Fprintf(w, "No ads found.")
+		fmt.Fprintf(output, "No ads found.")
 	}

 	return 0
@@ -155,5 +160,6 @@ func Main(w io.Writer) int {

 func Die(err error) int {
 	slog.Error("Failure", "error", err.Error())
+
 	return 1
 }
--- a/main_test.go
+++ b/main_test.go
@@ -43,7 +43,7 @@ const LISTTPL string = `<!DOCTYPE html>
 {{ range . }}
     <h2 class="text-module-begin">
        <a class="ellipsis"
-           href="/s-anzeige/{{ .Slug }}/{{ .Id }}">{{ .Title }}</a>
+           href="/s-anzeige/{{ .Slug }}/{{ .ID }}">{{ .Title }}</a>
     </h2>
 {{ end }}
  </body>
@@ -247,7 +247,7 @@ var invalidtests = []Tests{
 type AdConfig struct {
 	Title     string
 	Slug      string
-	Id        string
+	ID        string
 	Price     string
 	Category  string
 	Condition string
@@ -259,7 +259,7 @@ type AdConfig struct {
 var adsrc = []AdConfig{
 	{
 		Title: "First Ad",
-		Id:    "1", Price: "5€",
+		ID:    "1", Price: "5€",
 		Category:  "Klimbim",
 		Text:      "Thing to sale",
 		Slug:      "first-ad",
@@ -269,7 +269,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title: "Secnd Ad",
-		Id:    "2", Price: "5€",
+		ID:    "2", Price: "5€",
 		Category:  "Kram",
 		Text:      "Thing to sale",
 		Slug:      "second-ad",
@@ -279,7 +279,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Third Ad",
-		Id:        "3",
+		ID:        "3",
 		Price:     "5€",
 		Category:  "Kuddelmuddel",
 		Text:      "Thing to sale",
@@ -290,7 +290,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Forth Ad",
-		Id:        "4",
+		ID:        "4",
 		Price:     "5€",
 		Category:  "Krempel",
 		Text:      "Thing to sale",
@@ -301,7 +301,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Fifth Ad",
-		Id:        "5",
+		ID:        "5",
 		Price:     "5€",
 		Category:  "Kladderadatsch",
 		Text:      "Thing to sale",
@@ -312,7 +312,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Sixth Ad",
-		Id:        "6",
+		ID:        "6",
 		Price:     "5€",
 		Category:  "Klunker",
 		Text:      "Thing to sale",
@@ -334,17 +334,17 @@ type Adsource struct {
 }

 // Render a HTML template for an adlisting or an ad
-func GetTemplate(l []AdConfig, a AdConfig, htmltemplate string) string {
+func GetTemplate(adconfigs []AdConfig, adconfig AdConfig, htmltemplate string) string {
 	tmpl, err := tpl.New("template").Parse(htmltemplate)
 	if err != nil {
 		panic(err)
 	}

 	var out bytes.Buffer
-	if len(a.Id) == 0 {
-		err = tmpl.Execute(&out, l)
+	if len(adconfig.ID) == 0 {
+		err = tmpl.Execute(&out, adconfigs)
 	} else {
-		err = tmpl.Execute(&out, a)
+		err = tmpl.Execute(&out, adconfig)
 	}

 	if err != nil {
@@ -391,10 +391,9 @@ func InitValidSources() []Adsource {
 	// prepare urls for the ads
 	for _, ad := range adsrc {
 		ads = append(ads, Adsource{
-			uri:     fmt.Sprintf("%s/s-anzeige/%s/%s", Baseuri, ad.Slug, ad.Id),
+			uri:     fmt.Sprintf("%s/s-anzeige/%s/%s", Baseuri, ad.Slug, ad.ID),
 			content: GetTemplate(nil, ad, ADTPL),
 		})
-		//panic(GetTemplate(nil, ad, ADTPL))
 	}

 	return ads
@@ -447,46 +446,48 @@ func GetImage(path string) []byte {

 // setup httpmock
 func SetIntercept(ads []Adsource) {
-	ch := http.Header{}
-	ch.Add("Set-Cookie", "session=permanent")
+	headers := http.Header{}
+	headers.Add("Set-Cookie", "session=permanent")

-	for _, ad := range ads {
-		if ad.status == 0 {
-			ad.status = 200
+	for _, advertisement := range ads {
+		if advertisement.status == 0 {
+			advertisement.status = 200
 		}

-		httpmock.RegisterResponder("GET", ad.uri,
-			httpmock.NewStringResponder(ad.status, ad.content).HeaderAdd(ch))
+		httpmock.RegisterResponder("GET", advertisement.uri,
+			httpmock.NewStringResponder(advertisement.status, advertisement.content).HeaderAdd(headers))
 	}

 	// we just use 2 images, put this here
 	for _, image := range []string{"t/1.jpg", "t/2.jpg"} {
 		httpmock.RegisterResponder("GET", image,
-			httpmock.NewBytesResponder(200, GetImage(image)).HeaderAdd(ch))
+			httpmock.NewBytesResponder(200, GetImage(image)).HeaderAdd(headers))
 	}
-
 }

-func VerifyAd(ad AdConfig) error {
-	body := ad.Title + ad.Price + ad.Id + "Kleinanzeigen => " +
-		ad.Category + ad.Condition + ad.Created
+func VerifyAd(advertisement AdConfig) error {
+	body := advertisement.Title + advertisement.Price + advertisement.ID + "Kleinanzeigen => " +
+		advertisement.Category + advertisement.Condition + advertisement.Created

 	// prepare ad dir name using DefaultAdNameTemplate
 	c := Config{Adnametemplate: "{{ .Slug }}"}
-	adstruct := Ad{Slug: ad.Slug, Id: ad.Id}
+	adstruct := Ad{Slug: advertisement.Slug, ID: advertisement.ID}
+
 	addir, err := AdDirName(&c, &adstruct)
 	if err != nil {
 		return err
 	}

 	file := fmt.Sprintf("t/out/%s/Adlisting.txt", addir)
+
 	content, err := os.ReadFile(file)
 	if err != nil {
-		return err
+		return fmt.Errorf("unable to read adlisting file: %w", err)
 	}

 	if body != strings.TrimSpace(string(content)) {
 		msg := fmt.Sprintf("ad content doesn't match.\nExpect: %s\n   Got: %s\n", body, content)
+
 		return errors.New(msg)
 	}

@@ -504,20 +505,21 @@ func TestMain(t *testing.T) {
 	SetIntercept(InitValidSources())

 	// run commandline tests
-	for _, tt := range tests {
+	for _, test := range tests {
 		var buf bytes.Buffer
-		os.Args = strings.Split(tt.args, " ")
+
+		os.Args = strings.Split(test.args, " ")

 		ret := Main(&buf)

-		if ret != tt.exitcode {
+		if ret != test.exitcode {
 			t.Errorf("%s with cmd <%s> did not exit with %d but %d",
-				tt.name, tt.args, tt.exitcode, ret)
+				test.name, test.args, test.exitcode, ret)
 		}

-		if !strings.Contains(buf.String(), tt.expect) {
+		if !strings.Contains(buf.String(), test.expect) {
 			t.Errorf("%s with cmd <%s> output did not match.\nExpect: %s\n   Got: %s\n",
-				tt.name, tt.args, tt.expect, buf.String())
+				test.name, test.args, test.expect, buf.String())
 		}
 	}

@@ -540,20 +542,21 @@ func TestMainInvalids(t *testing.T) {
 	SetIntercept(InitInvalidSources())

 	// run commandline tests
-	for _, tt := range invalidtests {
+	for _, test := range invalidtests {
 		var buf bytes.Buffer
-		os.Args = strings.Split(tt.args, " ")
+
+		os.Args = strings.Split(test.args, " ")

 		ret := Main(&buf)

-		if ret != tt.exitcode {
+		if ret != test.exitcode {
 			t.Errorf("%s with cmd <%s> did not exit with %d but %d",
-				tt.name, tt.args, tt.exitcode, ret)
+				test.name, test.args, test.exitcode, ret)
 		}

-		if !strings.Contains(buf.String(), tt.expect) {
+		if !strings.Contains(buf.String(), test.expect) {
 			t.Errorf("%s with cmd <%s> output did not match.\nExpect: %s\n   Got: %s\n",
-				tt.name, tt.args, tt.expect, buf.String())
+				test.name, test.args, test.expect, buf.String())
 		}
 	}
 }
--- a/scrape.go
+++ b/scrape.go
@@ -19,10 +19,10 @@ package main

 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"log/slog"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"

@@ -43,7 +43,9 @@ func ScrapeUser(fetch *Fetcher) error {

 	for {
 		var index Index
+
 		slog.Debug("fetching page", "uri", uri)
+
 		body, err := fetch.Get(uri)
 		if err != nil {
 			return err
@@ -52,7 +54,7 @@ func ScrapeUser(fetch *Fetcher) error {

 		err = goq.NewDecoder(body).Decode(&index)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to goquery decode HTML index body: %w", err)
 		}

 		if len(index.Links) == 0 {
@@ -67,16 +69,16 @@ func ScrapeUser(fetch *Fetcher) error {
 		}

 		page++
-		uri = baseuri + "&pageNum=" + fmt.Sprintf("%d", page)
+		uri = baseuri + "&pageNum=" + strconv.Itoa(page)
 	}

-	for i, adlink := range adlinks {
+	for index, adlink := range adlinks {
 		err := ScrapeAd(fetch, Baseuri+adlink)
 		if err != nil {
 			return err
 		}

-		if fetch.Config.Limit > 0 && i == fetch.Config.Limit-1 {
+		if fetch.Config.Limit > 0 && index == fetch.Config.Limit-1 {
 			break
 		}
 	}
@@ -86,18 +88,20 @@ func ScrapeUser(fetch *Fetcher) error {

 // scrape an ad. uri is the full uri of the ad, dir is the basedir
 func ScrapeAd(fetch *Fetcher, uri string) error {
-	ad := &Ad{}
+	advertisement := &Ad{}

 	// extract slug and id from uri
 	uriparts := strings.Split(uri, "/")
-	if len(uriparts) < 6 {
-		return errors.New("invalid uri: " + uri)
+	if len(uriparts) < SlugURIPartNum {
+		return fmt.Errorf("invalid uri: %s", uri)
 	}
-	ad.Slug = uriparts[4]
-	ad.Id = uriparts[5]
+
+	advertisement.Slug = uriparts[4]
+	advertisement.ID = uriparts[5]

 	// get the ad
 	slog.Debug("fetching ad page", "uri", uri)
+
 	body, err := fetch.Get(uri)
 	if err != nil {
 		return err
@@ -105,36 +109,37 @@ func ScrapeAd(fetch *Fetcher, uri string) error {
 	defer body.Close()

 	// extract ad contents with goquery/goq
-	err = goq.NewDecoder(body).Decode(&ad)
+	err = goq.NewDecoder(body).Decode(&advertisement)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to goquery decode HTML ad body: %w", err)
 	}

-	if len(ad.CategoryTree) > 0 {
-		ad.Category = strings.Join(ad.CategoryTree, " => ")
+	if len(advertisement.CategoryTree) > 0 {
+		advertisement.Category = strings.Join(advertisement.CategoryTree, " => ")
 	}

-	if ad.Incomplete() {
-		slog.Debug("got ad", "ad", ad)
-		return errors.New("could not extract ad data from page, got empty struct")
+	if advertisement.Incomplete() {
+		slog.Debug("got ad", "ad", advertisement)
+
+		return fmt.Errorf("could not extract ad data from page, got empty struct")
 	}

-	ad.CalculateExpire()
+	advertisement.CalculateExpire()

 	// write listing
-	addir, err := WriteAd(fetch.Config, ad)
+	addir, err := WriteAd(fetch.Config, advertisement)
 	if err != nil {
 		return err
 	}

-	slog.Debug("extracted ad listing", "ad", ad)
+	slog.Debug("extracted ad listing", "ad", advertisement)

 	fetch.Config.IncrAds()

-	return ScrapeImages(fetch, ad, addir)
+	return ScrapeImages(fetch, advertisement, addir)
 }

-func ScrapeImages(fetch *Fetcher, ad *Ad, addir string) error {
+func ScrapeImages(fetch *Fetcher, advertisement *Ad, addir string) error {
 	// fetch images
 	img := 1
 	adpath := filepath.Join(fetch.Config.Outdir, addir)
@@ -145,16 +150,17 @@ func ScrapeImages(fetch *Fetcher, ad *Ad, addir string) error {
 		return err
 	}

-	g := new(errgroup.Group)
+	egroup := new(errgroup.Group)

-	for _, imguri := range ad.Images {
+	for _, imguri := range advertisement.Images {
 		imguri := imguri
 		file := filepath.Join(adpath, fmt.Sprintf("%d.jpg", img))
-		g.Go(func() error {
+
+		egroup.Go(func() error {
 			// wait a little

-			t := GetThrottleTime()
-			time.Sleep(t)
+			throttle := GetThrottleTime()
+			time.Sleep(throttle)

 			body, err := fetch.Getimage(imguri)
 			if err != nil {
@@ -164,7 +170,7 @@ func ScrapeImages(fetch *Fetcher, ad *Ad, addir string) error {
 			buf := new(bytes.Buffer)
 			_, err = buf.ReadFrom(body)
 			if err != nil {
-				return err
+				return fmt.Errorf("failed to read from image buffer: %w", err)
 			}

 			buf2 := buf.Bytes() // needed for image writing
@@ -177,7 +183,8 @@ func ScrapeImages(fetch *Fetcher, ad *Ad, addir string) error {

 			if !fetch.Config.ForceDownload {
 				if image.SimilarExists(cache) {
-					slog.Debug("similar image exists, not written", "uri", image.Uri)
+					slog.Debug("similar image exists, not written", "uri", image.URI)
+
 					return nil
 				}
 			}
@@ -187,17 +194,18 @@ func ScrapeImages(fetch *Fetcher, ad *Ad, addir string) error {
 				return err
 			}

-			slog.Debug("wrote image", "image", image, "size", len(buf2), "throttle", t)
+			slog.Debug("wrote image", "image", image, "size", len(buf2), "throttle", throttle)
+
 			return nil
 		})
 		img++
 	}

-	if err := g.Wait(); err != nil {
-		return err
+	if err := egroup.Wait(); err != nil {
+		return fmt.Errorf("failed to finalize error waitgroup: %w", err)
 	}

-	fetch.Config.IncrImgs(len(ad.Images))
+	fetch.Config.IncrImgs(len(advertisement.Images))

 	return nil
 }
--- a/store.go
+++ b/store.go
@@ -28,30 +28,32 @@ import (
 	tpl "text/template"
 )

-func AdDirName(c *Config, ad *Ad) (string, error) {
-	tmpl, err := tpl.New("adname").Parse(c.Adnametemplate)
+func AdDirName(conf *Config, advertisement *Ad) (string, error) {
+	tmpl, err := tpl.New("adname").Parse(conf.Adnametemplate)
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to parse adname template: %w", err)
 	}

 	buf := bytes.Buffer{}
-	err = tmpl.Execute(&buf, ad)
+
+	err = tmpl.Execute(&buf, advertisement)
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to execute adname template: %w", err)
 	}

 	return buf.String(), nil
 }

-func WriteAd(c *Config, ad *Ad) (string, error) {
+func WriteAd(conf *Config, advertisement *Ad) (string, error) {
 	// prepare ad dir name
-	addir, err := AdDirName(c, ad)
+	addir, err := AdDirName(conf, advertisement)
 	if err != nil {
 		return "", err
 	}

 	// prepare output dir
-	dir := filepath.Join(c.Outdir, addir)
+	dir := filepath.Join(conf.Outdir, addir)
+
 	err = Mkdir(dir)
 	if err != nil {
 		return "", err
@@ -59,26 +61,27 @@ func WriteAd(c *Config, ad *Ad) (string, error) {

 	// write ad file
 	listingfile := filepath.Join(dir, "Adlisting.txt")
-	f, err := os.Create(listingfile)
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()

-	if runtime.GOOS == "windows" {
-		ad.Text = strings.ReplaceAll(ad.Text, "<br/>", "\r\n")
+	listingfd, err := os.Create(listingfile)
+	if err != nil {
+		return "", fmt.Errorf("failed to create Adlisting.txt: %w", err)
+	}
+	defer listingfd.Close()
+
+	if runtime.GOOS == WIN {
+		advertisement.Text = strings.ReplaceAll(advertisement.Text, "<br/>", "\r\n")
 	} else {
-		ad.Text = strings.ReplaceAll(ad.Text, "<br/>", "\n")
+		advertisement.Text = strings.ReplaceAll(advertisement.Text, "<br/>", "\n")
 	}

-	tmpl, err := tpl.New("adlisting").Parse(c.Template)
+	tmpl, err := tpl.New("adlisting").Parse(conf.Template)
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to parse adlisting template: %w", err)
 	}

-	err = tmpl.Execute(f, ad)
+	err = tmpl.Execute(listingfd, advertisement)
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to execute adlisting template: %w", err)
 	}

 	slog.Info("wrote ad listing", "listingfile", listingfile)
@@ -89,14 +92,14 @@ func WriteAd(c *Config, ad *Ad) (string, error) {
 func WriteImage(filename string, buf []byte) error {
 	file, err := os.Create(filename)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to open image file: %w", err)
 	}
 	defer file.Close()

 	_, err = file.Write(buf)

 	if err != nil {
-		return err
+		return fmt.Errorf("failed to write to image file: %w", err)
 	}

 	return nil
@@ -111,12 +114,12 @@ func ReadImage(filename string) (*bytes.Buffer, error) {

 	data, err := os.ReadFile(filename)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to read image file: %w", err)
 	}

 	_, err = buf.Write(data)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to write image into buffer: %w", err)
 	}

 	return &buf, nil
@@ -127,5 +130,6 @@ func fileExists(filename string) bool {
 	if os.IsNotExist(err) {
 		return false
 	}
+
 	return !info.IsDir()
 }
--- a/store_test.go
+++ b/store_test.go
@@ -26,6 +26,8 @@ import (
 // doesn't  show up  in the  coverage report  for unknown  reasons, so
 // here's a single test for it
 func TestWriteImage(t *testing.T) {
+	t.Parallel()
+
 	buf := []byte{1, 2, 3, 4, 5, 6, 7, 8}
 	file := "t/out/t.jpg"

@@ -33,5 +35,4 @@ func TestWriteImage(t *testing.T) {
 	if err != nil {
 		t.Errorf("Could not write mock image to %s: %s", file, err.Error())
 	}
-
 }
--- a/t/config-empty.conf
+++ b/t/config-empty.conf
@@ -1,6 +1,6 @@
 # empty config for Main() unit tests to force unit tests NOT to use an
 # eventually existing ~/.kleingebaeck!
 template="""
-{{.Title}}{{.Price}}{{.Id}}{{.Category}}{{.Condition}}{{.Created}}
+{{.Title}}{{.Price}}{{.ID}}{{.Category}}{{.Condition}}{{.Created}}
 """

--- a/t/fullconfig.conf
+++ b/t/fullconfig.conf
@@ -2,5 +2,5 @@ user = 1
 loglevel = "verbose"
 outdir = "t/out"
 template="""
-{{.Title}}{{.Price}}{{.Id}}{{.Category}}{{.Condition}}{{.Created}}
+{{.Title}}{{.Price}}{{.ID}}{{.Category}}{{.Condition}}{{.Created}}
 """
--- a/util.go
+++ b/util.go
@@ -20,6 +20,7 @@ package main
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"math/rand"
 	"os"
 	"os/exec"
@@ -33,7 +34,7 @@ func Mkdir(dir string) error {
 	if _, err := os.Stat(dir); errors.Is(err, os.ErrNotExist) {
 		err := os.Mkdir(dir, os.ModePerm)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to create directory %s: %w", dir, err)
 		}
 	}

@@ -44,7 +45,8 @@ func man() error {
 	man := exec.Command("less", "-")

 	var b bytes.Buffer
-	b.Write([]byte(manpage))
+
+	b.WriteString(manpage)

 	man.Stdout = os.Stdout
 	man.Stdin = &b
@@ -53,7 +55,7 @@ func man() error {
 	err := man.Run()

 	if err != nil {
-		return err
+		return fmt.Errorf("failed to execute 'less': %w", err)
 	}

 	return nil
@@ -61,7 +63,7 @@ func man() error {

 // returns TRUE if stdout is NOT a tty or windows
 func IsNoTty() bool {
-	if runtime.GOOS == "windows" || !isatty.IsTerminal(os.Stdout.Fd()) {
+	if runtime.GOOS == WIN || !isatty.IsTerminal(os.Stdout.Fd()) {
 		return true
 	}