Arg parsing is off, fix it. Immediately.

build.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+OSES="windows linux darwin"
+
+for os in $OSES; do
+	make slackdump-${os}.zip
+done

cmd/slackdump/slackdump.go

@@ -10,6 +10,8 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"path/filepath"
+	"strings"
 
 	"github.com/joho/godotenv"
 	"github.com/rusq/slackdump"
@@ -18,6 +20,9 @@ import (
 const (
 	outputTypeJSON = "json"
 	outputTypeText = "text"
+
+	slackTokenEnv  = "SLACK_TOKEN"
+	slackCookieEnv = "COOKIE"
 )
 
 var _ = godotenv.Load()
@@ -60,21 +65,8 @@ func (lf listFlags) present() bool {
 	return lf.users || lf.channels
 }
 
-func init() {
-	flag.Usage = func() {
-		fmt.Fprintf(
-			flag.CommandLine.Output(),
-			"Slackdump dumps messages and files from slack using the provided api token.\n"+
-				"Will create a number of files having the channel_id as a name.\n"+
-				"Files are downloaded into a respective folder with channel_id\n\n"+
-				"Usage: %s [flags] [channel_id1 ... channel_idN]\n",
-			os.Args[0])
-		flag.PrintDefaults()
-	}
-}
-
 func main() {
-	params, err := checkParameters()
+	params, err := checkParameters(os.Args[1:])
 	if err != nil {
 		flag.Usage()
 		log.Fatal(err)
@@ -113,36 +105,48 @@ func createFile(filename string) (f io.WriteCloser, err error) {
 	return os.Create(filename)
 }
 
-func checkParameters() (params, error) {
+func checkParameters(args []string) (params, error) {
+	fs := flag.NewFlagSet("", flag.ExitOnError)
+	fs.Usage = func() {
+		fmt.Fprintf(
+			flag.CommandLine.Output(),
+			"Slackdump dumps messages and files from slack using the provided api token.\n"+
+				"Will create a number of files having the channel_id as a name.\n"+
+				"Files are downloaded into a respective folder with channel_id name\n\n"+
+				"Usage:  %s [flags] [channel_id1 ... channel_idN]\n\n",
+			filepath.Base(os.Args[0]))
+		fs.PrintDefaults()
+	}
+
 	var p params
-	// flags
-	{
-		flag.BoolVar(&p.list.channels, "c", false, "list channels (aka conversations) and their IDs for export.")
-		flag.BoolVar(&p.list.users, "u", false, "list users and their IDs. ")
-		flag.BoolVar(&p.dumpFiles, "f", false, "enable files download")
-		flag.StringVar(&p.output.filename, "o", "-", "output `filename` for users and channels.  Use '-' for standard\noutput.")
-		flag.StringVar(&p.output.format, "r", "", "report `format`.  One of 'json' or 'text'")
-		flag.StringVar(&p.creds.token, "t", os.Getenv("SLACK_TOKEN"), "Specify slack `API_token`, get it here:\nhttps://api.slack.com/custom-integrations/legacy-tokens\n"+
-			"It is also possible to define SLACK_TOKEN environment variable.")
-		flag.StringVar(&p.creds.cookie, "cookie", os.Getenv("COOKIE"), "d= cookie value")
-		flag.Parse()
+	fs.BoolVar(&p.list.channels, "c", false, "list channels (aka conversations) and their IDs for export.")
+	fs.BoolVar(&p.list.users, "u", false, "list users and their IDs. ")
+	fs.BoolVar(&p.dumpFiles, "f", false, "enable files download")
+	fs.StringVar(&p.output.filename, "o", "-", "output `filename` for users and channels.  Use '-' for standard\noutput.")
+	fs.StringVar(&p.output.format, "r", "", "report `format`.  One of 'json' or 'text'")
+	fs.StringVar(&p.creds.token, "t", os.Getenv(slackTokenEnv), "Specify slack `API_token`, (environment: "+slackTokenEnv+")")
+	fs.StringVar(&p.creds.cookie, "cookie", os.Getenv(slackCookieEnv), "d= cookie `value` (environment: "+slackCookieEnv+")")
+	fs.Parse(args)
 
-		os.Unsetenv("SLACK_TOKEN")
-		os.Unsetenv("COOKIE")
+	os.Unsetenv(slackTokenEnv)
+	os.Unsetenv(slackCookieEnv)
 
-		p.channelsToExport = flag.Args()
-	}
+	p.channelsToExport = fs.Args()
+
+	return p, p.validate()
+}
 
+func (p *params) validate() error {
 	if !p.creds.valid() {
-		return p, fmt.Errorf("slack token or cookie not specified")
+		return fmt.Errorf("slack token or cookie not specified")
 	}
 
 	if len(p.channelsToExport) == 0 && !p.list.present() {
-		return p, fmt.Errorf("no list flags specified and no channels to export")
+		return fmt.Errorf("no list flags specified and no channels to export")
 	}
 
-	if !p.output.validFormat() {
-		return p, fmt.Errorf("invalid output type: %q, must use one of %v", p.output.format, []string{outputTypeJSON, outputTypeText})
+	if !p.list.present() && !p.output.validFormat() {
+		return fmt.Errorf("invalid output type: %q, must use one of %v", p.output.format, []string{outputTypeJSON, outputTypeText})
 	}
 
 	// channels and users listings will be in the text format (if not specified otherwise)
@@ -153,8 +157,9 @@ func checkParameters() (params, error) {
 			p.output.format = outputTypeJSON
 		}
 	}
+	p.creds.cookie = strings.TrimPrefix(p.creds.cookie, "d=")
 
-	return p, nil
+	return nil
 }
 
 func listEntities(ctx context.Context, output output, creds slackCreds, list listFlags) error {

cmd/slackdump/slackdump_test.go

@@ -1,6 +1,10 @@
 package main
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
 
 func Test_output_validFormat(t *testing.T) {
 	type fields struct {
@@ -29,3 +33,60 @@ func Test_output_validFormat(t *testing.T) {
 		})
 	}
 }
+
+func Test_checkParameters(t *testing.T) {
+	type args struct {
+		args []string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    params
+		wantErr bool
+	}{
+		{
+			"channels",
+			args{[]string{"-c", "-t", "x", "-cookie", "d"}},
+			params{
+				list: listFlags{
+					users:    false,
+					channels: true,
+				},
+				creds: slackCreds{
+					token:  "x",
+					cookie: "d",
+				},
+				output:           output{filename: "-"},
+				channelsToExport: []string{},
+			},
+			false,
+		},
+		{
+			"users",
+			args{[]string{"-u", "-t", "x", "-cookie", "d"}},
+			params{
+				list: listFlags{
+					channels: false,
+					users:    true,
+				},
+				creds: slackCreds{
+					token:  "x",
+					cookie: "d",
+				},
+				output:           output{filename: "-"},
+				channelsToExport: []string{},
+			},
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := checkParameters(tt.args.args)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("checkParameters() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}

messages.go

@@ -9,16 +9,20 @@ import (
 	"github.com/slack-go/slack"
 )
 
-// Messages keeps slice of messages
+// minMsgTimeApart defines the time interval in minutes to separate group
+// of messages from a single user in the conversation.  This increases the
+// readability of the text output.
+const minMsgTimeApart = 2
+
+// Messages keeps the slice of messages.
 type Messages struct {
 	Messages  []slack.Message
 	ChannelID string
 	SD        *SlackDumper
 }
 
-// ToText outputs Messages m to io.Writer w in Text format
-func (m Messages) ToText(w io.Writer) (err error) {
-	const minMsgTimeApart = 2 //minutes
+// ToText outputs Messages m to io.Writer w in text format.
+func (m *Messages) ToText(w io.Writer) (err error) {
 	writer := bufio.NewWriter(w)
 	defer writer.Flush()
 

slackdump.go

@@ -2,6 +2,7 @@ package slackdump
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -139,6 +140,17 @@ func (sd *SlackDumper) DumpMessages(ctx context.Context, channelID string, dumpF
 	return &Messages{Messages: allMessages, ChannelID: channelID, SD: sd}, nil
 }
 
+// ErrNoThread is the error indicating that error is not a threaded message.
+var ErrNoThread = errors.New("message has no thread")
+
+// DumpThread retrieves all messages in the thread and returns them as a slice of messages.
+func (sd *SlackDumper) DumpThread(m *slack.Message) ([]slack.Message, error) {
+	if m.ThreadTimestamp == "" {
+		return nil, ErrNoThread
+	}
+	panic("implement me")
+}
+
 // UpdateUserMap updates user[id]->*User mapping from the current Users slice.
 func (sd *SlackDumper) UpdateUserMap() error {
 	if sd.Users.Len() == 0 {