check seek error

* added lint targets
* fix linter errors
* enhance error handling
* !!BREAKING!! rename Id to ID in tpls

.github/ISSUE_TEMPLATE/note_to_self.md

@@ -5,3 +5,4 @@ title: "[bug-report]"
 labels: bug
 assignees: TLINDEN
 
+---

CODE_OF_CONDUCT.md

@@ -0,0 +1,114 @@
+# No Code of Conduct
+
+*TL;DR:* This project  does **NOT** have a so called  Code of Conduct,
+nor will it ever have one.
+
+## The Rant
+
+The reasons are somewhat complicated and  I'll try my best to document
+them here.
+
+Ethical codes  or rules come  along like laws.  But how is  ethical or
+moral behavior defined? And who  defines which behavior is ethical and
+which is not? Certainly not me.
+
+Unless  you  live  in  a  dictatorship (and  more  than  half  of  the
+population on  planet earth  do as  of this  writing), laws  come into
+existence by democratic procedures. Laws  cover almost every aspect of
+live in  a society. Laws allow  and forbid behavior and  laws sanction
+infringements.
+
+A software project like  this one on the other hand  is not a society.
+There   are   not   enough   people  involved   to   form   democratic
+structures. And there will always be  a minority of users who have the
+right to commit or reject code. How could any maintainer of a software
+project dare to decree rules upon  others? Actually, am I, the current
+maintainer of this very project authorized to do so?
+
+I think the anser to this question clearly is NO.
+
+The  issue  is  being  complicated  by  the  fact,  that  open  source
+development these days  happens on a planetary scale.  And this planet
+houses hundreds if not  thousands of different cultures, philosophies,
+ideologies and worldviews.  The answer  to many ethical questions will
+in most cases be vague and nebulous.
+
+Ones joke will always be another ones insult.
+
+Then there  is the  problem of  language. I myself  am not  an english
+native, but I publish everyting using  the english language. I am able
+to communicate with  most people in the open  source community because
+of that.   But I am  certainly not  able to understand  everything and
+everyone. There  might be nuances to  a sentence I don't  sense, there
+might be  sarcastic connotations I  don't understand or  references to
+historical figures, events  or traditions I don't know  and never have
+heard of.
+
+Judging over other  peoples online behavior looks like  a titanic task
+to me. It is just not my job  to judge others, I am not legitimized or
+authorized to do so and I am not interested in this kind of business.
+
+Another huge  problem with ethical rules  is that you need  to outline
+and enforce sanctions  on those who violate the rules.  But since I am
+not an  elected authority  how would I  be able to  do this?   I don't
+know.  And  what happens if  someone complains about myself?   Shall I
+remove myself from my own project? Come on!
+
+Last but  not least there's  the law. So,  let's say someone  in india
+writes something  insulting to some  other developer in an  issue.  Of
+course  german law  does not  apply  to indian  people. Moreover,  the
+insult might actually not be an  insult in india.  In the end, nothing
+would   happen.   Under   normal   circumstances,  maintainers   would
+eventually delete the posting, ban  the user or remove push privileges
+etc.
+
+But then, is there a way for  the offending user to defend himself? Of
+course not, since neither indian or german law alone applies. I cannot
+go to  a german court  and sue the  guy and he  cannot do the  same in
+india. Or -  we possibly could but the judges  in both countries would
+just laugh and close the case.
+
+That  being said,  I  don't have  the  power nor  the  tools, nor  the
+authority to enforce serious sanctions  of any meaningful kind against
+others. Therefore I cannot outline any rules whatsoever.
+
+And let's not  even start talking about  these undemocratic "comitees"
+many projects are  forming to circumvent this  problem.  Some projects
+even  include  external entities  like  a  lawyer or  some  bureaucrat
+somewhere  just to  have the  ability  to complain  against a  comitee
+member. What a mess!
+
+
+
+## So, what are the ethical rules within this project then?
+
+Well, there are none.
+
+This project is  about code, not society. It doesn't  matter where you
+come from,  how you look,  how you think,  what you believe,  who your
+friends are, whay you  said or did sometime in the  past. I don't even
+care if you are a human being. You are an alien so bored that you need
+to submit code on github? Fine with me. You're a convicted criminal? I
+don't give a shit!
+
+**The only thing I am interested here is Code and only Code.**
+
+So if anyhing happens  here I don't like or I  am obliged by (german!)
+law to act on, I will decide on  a case to case basis what to do.  And
+unfortunately,  since this  is the  nature  of a  github project,  you
+cannot complain, object or protest. I am very sorry!
+
+If you will, let's at least  outline these:
+
+- Please - just please -  behave towards others as you'd expect others
+  to behave towards yourself.
+
+- Don't judge others for any reason.
+
+- Only judge the code.
+
+But these are not rules, only a  friendly appeal to you as a developer
+and user.
+
+
+Thanks a lot!

CONTRIBUTING.md

@@ -0,0 +1,93 @@
+## Project Goals
+
+The goal  of this  project is  to build  a small  tool which  helps in
+maintaining backups of the german  ad site kleinanzeigen.de. It should
+be  small,  fast and  easy  to  understand.
+
+There will be no GUI, no web interface, no public API of some sort, no
+builtin interpreter.
+
+The  programming  language  used  for  this  project  will  always  be
+[GOLANG](https://go.dev/)  with  the  exception of  the  documentation
+([Perl POD](https://perldoc.perl.org/perlpod)) and the Makefile.
+
+# Contributing
+
+You can contribute to this project in various ways:
+
+## Open an issue
+
+If you encounter  a problem or don't understand how  the program works
+or if you think the documentation is unclear, please don't hesitate to
+open an issue.
+
+Please add as much information about the case as possible, such as:
+
+- Your environment (operating system etc)
+- kleingebaeck version (`kleingebaeck --version`)
+- Commandline used. Please replace sensitive information with mock data!
+- Repeat the command with debugging enabled (`-d` flag)
+- Actual program output, Please replace sensitive information with mock data!
+- Expected program output.
+- Error message - if any.
+
+Be aware  that I am  working on this (and  some others) project  in my
+spare  time which  is scarce.   Therefore  please don't  expect me  to
+respond to  your query within  hours or even  days. Be patient,  but I
+WILL respond.
+
+## Pull Requests
+
+Code and documentation help is  always much appreciated! Please follow
+thes guidelines to successfully contribute:
+
+-  Every  pull   request  shall  be  based   on  latest  `development`
+  branch. `main` is only used for releases.
+  
+- Execute the  unit tests before committing: `make  test`. There shall
+  be no errors.
+  
+- Strive  to be  backwards compatible  so that  users who  are already
+  using the program  don't have to change their habits  - unless it is
+  really neccessary.
+
+- Try to add a unit test for your fix, addition or modification.
+
+- Don't ever change existing unit tests!
+
+- Add a meaningful and comprehensive rationale about your contribution:
+  - Why do you think it might be useful for others?
+  - What did you actually change or add?
+  - Is there an open issue which  this PR fixes and if so, please link
+    to that issue.
+
+- [Re-]format your code with `gofmt -s`.
+
+- Avoid unneccesary dependencies, especially for very small functions.
+
+- **If** a  new dependency is being added, it  must be compatible with
+  our [license agreement](LICENSE).
+  
+- You  need to accept  that the  code or documentation  you contribute
+  will be redistributed under the  terms of said license agreement. If
+  your  contribution  is  considerably  large  or  if  you  contribute
+  regularly, then  feel free  to add  your name (and  if you want your
+  email    address)     to    the    *AUTHORS*    section    of    the
+  [manpage](kleingebaeck.pod).
+
+- Adhere to the above mentioned project goals.
+
+- If   you are  unsure if  your addition or  change will  be accepted,
+  better ask before starting coding. Open an issue about your proposal
+  and let's  discuss it! That way  we avoid doing unnessesary  work on
+  both sides.
+    
+Each pull  request will be  carefully reviewed and  if it is  a useful
+addition  it  will  be  accepted. However,  please  be  prepared  that
+sometimes a  PR will be  rejected.  The reasons  may vary and  will be
+documented.   Perhaps the  above guidelines  are not  matched, or  the
+addition seems  to be not so  useful from my perspective,  maybe there
+are  too  much  changes  or  there  might  be  changes  I  don't  even
+understand.
+
+But whatever happens: your contribution is always welcome!

Makefile

@@ -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

ad.go

@@ -1,5 +1,5 @@
 /*
-Copyright © 2023 Thomas von Dein
+Copyright © 2023-2024 Thomas von Dein
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -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")
 		}
 	}
 }

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"
@@ -35,19 +34,35 @@ import (
 )
 
 const (
-	VERSION         string = "0.3.0"
-	Baseuri         string = "https://www.kleinanzeigen.de"
-	Listuri         string = "/s-bestandsliste.html"
-	Defaultdir      string = "."
-	DefaultTemplate string = "Title: {{.Title}}\nPrice: {{.Price}}\nId: {{.Id}}\n" +
+	VERSION    string = "0.3.3"
+	Baseuri    string = "https://www.kleinanzeigen.de"
+	Listuri    string = "/s-bestandsliste.html"
+	Defaultdir string = "."
+
+	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"
-	Useragent string = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) " +
+
+	DefaultUserAgent string = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) " +
 		"AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
+
 	DefaultAdNameTemplate string = "{{.Slug}}"
+
+	// 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.
@@ -84,6 +99,7 @@ type Config struct {
 	Limit            int    `koanf:"limit"`
 	IgnoreErrors     bool   `koanf:"ignoreerrors"`
 	ForceDownload    bool   `koanf:"force"`
+	UserAgent        string `koanf:"useragent"` // conf only
 	Adlinks          []string
 	StatsCountAds    int
 	StatsCountImages int
@@ -98,54 +114,58 @@ 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",
 		"userid":         0,
 		"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")
+	flagset.BoolP("ignoreerrors", "", false, "ignore image download HTTP errors")
 
-	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 {
@@ -161,31 +181,30 @@ 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
@@ -197,7 +216,7 @@ 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
 }

fetch.go

@@ -19,55 +19,84 @@ package main
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"log/slog"
 	"net/http"
+	"net/http/cookiejar"
+	"net/url"
 )
 
 // convenient wrapper to fetch some web content
 type Fetcher struct {
-	Config    *Config
-	Client    *http.Client
-	Useragent string // FIXME: make configurable
+	Config  *Config
+	Client  *http.Client
+	Cookies []*http.Cookie
 }
 
-func NewFetcher(c *Config) *Fetcher {
-	return &Fetcher{
-		Client:    &http.Client{Transport: &loggingTransport{}}, // implemented in http.go
-		Useragent: Useragent,                                    // default in config.go
-		Config:    c,
+func NewFetcher(conf *Config) (*Fetcher, error) {
+	jar, err := cookiejar.New(nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create a cookie jar obj: %w", err)
 	}
+
+	return &Fetcher{
+			Client: &http.Client{
+				Transport: &loggingTransport{}, // implemented in http.go
+				Jar:       jar,
+			},
+			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.Useragent)
+	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")
 	}
 
+	slog.Debug("got cookies?", "cookies", res.Cookies())
+	f.Cookies = res.Cookies()
+
 	return res.Body, nil
 }
 
 // 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
 	}
 

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

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=

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
 }

image.go

@@ -19,6 +19,7 @@ package main
 
 import (
 	"bytes"
+	"fmt"
 	"image/jpeg"
 	"log/slog"
 	"os"
@@ -32,15 +33,15 @@ const MaxDistance = 3
 type Image struct {
 	Filename string
 	Hash     *goimagehash.ImageHash
-	Data     *bytes.Buffer
-	Uri      string
+	Data     *bytes.Reader
+	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()),
 	)
 }
@@ -48,10 +49,10 @@ func (img *Image) LogValue() slog.Value {
 // holds all images of an ad
 type Cache []*goimagehash.ImageHash
 
-func NewImage(buf *bytes.Buffer, filename string, uri string) *Image {
+func NewImage(buf *bytes.Reader, 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{}
@@ -122,12 +125,15 @@ 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
 			}
 
-			img := NewImage(data, filename, "")
+			reader := bytes.NewReader(data.Bytes())
+
+			img := NewImage(reader, filename, "")
 			if err = img.CalcHash(); err != nil {
 				return nil, err
 			}
@@ -137,6 +143,5 @@ func ReadImages(addir string, dont bool) (Cache, error) {
 		}
 	}
 
-	//return nil, errors.New("ende")
 	return cache, nil
 }

kleingebaeck.1

@@ -133,7 +133,7 @@
 .\" ========================================================================
 .\"
 .IX Title "KLEINGEBAECK 1"
-.TH KLEINGEBAECK 1 "2024-01-22" "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
@@ -174,14 +174,15 @@ well.   We    use   \s-1TOML\s0   as   our    configuration   language.   See
 .PP
 Format is pretty simple:
 .PP
-.Vb 10
+.Vb 11
 \&    user = 1010101
 \&    loglevel = verbose
 \&    outdir = "test"
+\&    useragent = "Mozilla/5.0"
 \&    template = """
 \&    Title: {{.Title}}
 \&    Price: {{.Price}}
-\&    Id: {{.Id}}
+\&    Id: {{.ID}}
 \&    Category: {{.Category}}
 \&    Condition: {{.Condition}}
 \&    Created: {{.Created}}
@@ -190,7 +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

kleingebaeck.go

@@ -39,10 +39,11 @@ CONFIGURATION
         user = 1010101
         loglevel = verbose
         outdir = "test"
+        useragent = "Mozilla/5.0"
         template = """
         Title: {{.Title}}
         Price: {{.Price}}
-        Id: {{.Id}}
+        Id: {{.ID}}
         Category: {{.Category}}
         Condition: {{.Condition}}
         Created: {{.Created}}
@@ -50,7 +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.

kleingebaeck.pod

@@ -39,10 +39,11 @@ Format is pretty simple:
     user = 1010101
     loglevel = verbose
     outdir = "test"
+    useragent = "Mozilla/5.0"
     template = """
     Title: {{.Title}}
     Price: {{.Price}}
-    Id: {{.Id}}
+    Id: {{.ID}}
     Category: {{.Category}}
     Condition: {{.Condition}}
     Created: {{.Created}}
@@ -50,7 +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

main.go

@@ -35,38 +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
 	}
 
@@ -75,6 +80,7 @@ func Main(w io.Writer) int {
 		if err != nil {
 			return Die(err)
 		}
+
 		return 0
 	}
 
@@ -92,7 +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()),
@@ -111,9 +118,13 @@ func Main(w io.Writer) int {
 	}
 
 	// used for all HTTP requests
-	fetch := NewFetcher(conf)
+	fetch, err := NewFetcher(conf)
+	if err != nil {
+		return Die(err)
+	}
 
-	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)
@@ -121,25 +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
@@ -147,5 +160,6 @@ func Main(w io.Writer) int {
 
 func Die(err error) int {
 	slog.Error("Failure", "error", err.Error())
+
 	return 1
 }

main_test.go

@@ -21,6 +21,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"net/http"
 	"os"
 	"strings"
 	"testing"
@@ -42,7 +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>
@@ -246,7 +247,7 @@ var invalidtests = []Tests{
 type AdConfig struct {
 	Title     string
 	Slug      string
-	Id        string
+	ID        string
 	Price     string
 	Category  string
 	Condition string
@@ -258,7 +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",
@@ -268,7 +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",
@@ -278,7 +279,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Third Ad",
-		Id:        "3",
+		ID:        "3",
 		Price:     "5€",
 		Category:  "Kuddelmuddel",
 		Text:      "Thing to sale",
@@ -289,7 +290,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Forth Ad",
-		Id:        "4",
+		ID:        "4",
 		Price:     "5€",
 		Category:  "Krempel",
 		Text:      "Thing to sale",
@@ -300,7 +301,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Fifth Ad",
-		Id:        "5",
+		ID:        "5",
 		Price:     "5€",
 		Category:  "Kladderadatsch",
 		Text:      "Thing to sale",
@@ -311,7 +312,7 @@ var adsrc = []AdConfig{
 	},
 	{
 		Title:     "Sixth Ad",
-		Id:        "6",
+		ID:        "6",
 		Price:     "5€",
 		Category:  "Klunker",
 		Text:      "Thing to sale",
@@ -333,17 +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 {
@@ -390,10 +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
@@ -446,43 +446,48 @@ func GetImage(path string) []byte {
 
 // setup httpmock
 func SetIntercept(ads []Adsource) {
-	for _, ad := range ads {
-		if ad.status == 0 {
-			ad.status = 200
+	headers := http.Header{}
+	headers.Add("Set-Cookie", "session=permanent")
+
+	for _, advertisement := range ads {
+		if advertisement.status == 0 {
+			advertisement.status = 200
 		}
 
-		httpmock.RegisterResponder("GET", ad.uri,
-			httpmock.NewStringResponder(ad.status, ad.content))
+		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)))
+			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)
 	}
 
@@ -500,20 +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())
 		}
 	}
 
@@ -536,20 +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())
 		}
 	}
 }

scrape.go

@@ -19,11 +19,12 @@ package main
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"log/slog"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"time"
 
 	"astuart.co/goq"
 	"golang.org/x/sync/errgroup"
@@ -42,7 +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
@@ -51,7 +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 {
@@ -66,16 +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
 		}
 	}
@@ -85,18 +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
@@ -104,36 +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)
@@ -144,26 +150,33 @@ 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
+
+			throttle := GetThrottleTime()
+			time.Sleep(throttle)
+
 			body, err := fetch.Getimage(imguri)
 			if err != nil {
 				return err
 			}
 
 			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
+			reader := bytes.NewReader(buf.Bytes())
 
-			image := NewImage(buf, "", imguri)
+			image := NewImage(reader, file, imguri)
 			err = image.CalcHash()
 			if err != nil {
 				return err
@@ -171,27 +184,34 @@ 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
 				}
 			}
 
-			err = WriteImage(file, buf2)
+			_, err = reader.Seek(0, 0)
+			if err != nil {
+				return fmt.Errorf("failed to seek(0) on image reader: %w", err)
+			}
+
+			err = WriteImage(file, reader)
 			if err != nil {
 				return err
 			}
 
-			slog.Debug("wrote image", "image", image, "size", len(buf2))
+			slog.Debug("wrote image", "image", image, "size", buf.Len(), "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
 }

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)
@@ -86,17 +89,17 @@ func WriteAd(c *Config, ad *Ad) (string, error) {
 	return addir, nil
 }
 
-func WriteImage(filename string, buf []byte) error {
+func WriteImage(filename string, reader *bytes.Reader) 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)
+	_, err = reader.WriteTo(file)
 
 	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()
 }

store_test.go

@@ -0,0 +1,39 @@
+/*
+Copyright © 2023-2024 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package main
+
+import (
+	"bytes"
+	"testing"
+)
+
+// this is  a weird thing.  WriteImage() is being called  in scrape.go
+// which is  being tested by  TestMain() in main_test.go.  However, it
+// 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()
+
+	reader := bytes.NewReader([]byte{1, 2, 3, 4, 5, 6, 7, 8})
+	file := "t/out/t.jpg"
+
+	err := WriteImage(file, reader)
+	if err != nil {
+		t.Errorf("Could not write mock image to %s: %s", file, err.Error())
+	}
+}

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}}
 """
 

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}}
 """

util.go

@@ -1,5 +1,5 @@
 /*
-Copyright © 2023 Thomas von Dein
+Copyright © 2023-2024 Thomas von Dein
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -20,9 +20,12 @@ package main
 import (
 	"bytes"
 	"errors"
+	"fmt"
+	"math/rand"
 	"os"
 	"os/exec"
 	"runtime"
+	"time"
 
 	"github.com/mattn/go-isatty"
 )
@@ -31,7 +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)
 		}
 	}
 
@@ -42,7 +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
@@ -51,7 +55,7 @@ func man() error {
 	err := man.Run()
 
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to execute 'less': %w", err)
 	}
 
 	return nil
@@ -59,10 +63,14 @@ 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
 	}
 
 	// it is a tty
 	return false
 }
+
+func GetThrottleTime() time.Duration {
+	return time.Duration(rand.Intn(MaxThrottle-MinThrottle+1)+MinThrottle) * time.Millisecond
+}