1 package mailmux
2 
3 import (
4 	"bufio"
5 	"errors"
6 	"fmt"
7 	"io"
8 	"math/rand"
9 	"os"
10 	"strings"
11 )
12 
13 func randomLine(f *os.File) (string, error) {
14 	fi, err := f.Stat()
15 	if err != nil {
16 		return "", err
17 	}
18 	offset := rand.Int63n(fi.Size())
19 	offset, err = f.Seek(offset, io.SeekStart)
20 	if err != nil {
21 		return "", err
22 	}
23 
24 	br := bufio.NewReader(f)
25 	for {
26 		b, err := br.ReadByte()
27 		if b == '\n' {
28 			break
29 		}
30 		if err != nil {
31 			return "", err
32 		}
33 	}
34 	line, err := br.ReadString('\n')
35 	if errors.Is(err, io.EOF) {
36 		// the file ends without a newline - no problem
37 	} else if err != nil {
38 		return "", err
39 	}
40 
41 	line = strings.TrimSpace(line)
42 	if line == "" {
43 		// empty line. we're either at the end or hit a blank line. try again
44 		return randomLine(f)
45 	}
46 	return line, nil
47 }
48 
49 func randomUsername(dictpath string) (string, error) {
50 	f, err := os.Open(dictpath)
51 	if err != nil {
52 		return "", fmt.Errorf("open dictionary: %w", err)
53 	}
54 	defer f.Close()
55 
56 	first, err := randomLine(f)
57 	if err != nil {
58 		return "", fmt.Errorf("first random word: %w", err)
59 	}
60 	first = strings.ToLower(first)
61 	second, err := randomLine(f)
62 	if err != nil {
63 		return "", fmt.Errorf("second random word: %w", err)
64 	}
65 	second = strings.ToLower(second)
66 
67 	return fmt.Sprintf("%s_%s%02d", first, second, rand.Intn(99)), nil
68 }