scripts/mailing-list-member-retirement: Add an initial PoC

Can read fsi.mbox (228 MiB) but lacks features (e.g. limiting the
parsing to messages of the past year) and it would be nice to indicate
which messages couldn't be read.
But it basically works :)

1 files changed, 80 insertions, 0 deletions

diff --git a/scripts/mailing-list-member-retirement/main.go b/scripts/mailing-list-member-retirement/main.go
new file mode 100644
index 0000000..7ce7867
--- /dev/null
+++ b/scripts/mailing-list-member-retirement/main.go
@@ -0,0 +1,80 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+	"github.com/emersion/go-mbox"
+	"github.com/emersion/go-message/mail"
+	_ "github.com/emersion/go-message/charset"
+)
+
+// Prints the email addresses (one per line) of all senders by parsing an MBOX.
+
+func main() {
+	mboxNamePtr := flag.String("mbox", "test.mbox", "MBOX to read")
+	flag.Parse()
+	PrintAllMboxSenders(*mboxNamePtr)
+}
+
+func PrintAllMboxSenders(fileName string) {
+	f, err := os.Open(fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer func() {
+		if err = f.Close(); err != nil {
+			log.Fatal(err)
+		}
+	}()
+	fr := bufio.NewReader(f)
+	mr := mbox.NewReader(fr)
+	for {
+		r, err := mr.NextMessage()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			log.Fatal(err)
+		}
+		PrintMessageSender(r)
+	}
+}
+
+func PrintMessageSender(r io.Reader) {
+	mr, err := mail.CreateReader(r)
+	if err != nil {
+		if err.Error() == "charset \"cp-850\": ianaindex: invalid encoding name" {
+			fmt.Fprintf(os.Stderr, "Ignored a mail due to an invalid charset\n")
+			return // TODO: Print message ID
+		}
+		log.Fatal(err)
+	}
+
+	addr, err := mr.Header.AddressList("From")
+	if err != nil {
+		if strings.Contains(err.Error(), "invalid utf-8 in quoted-string") {
+			addr := strings.TrimPrefix(err.Error(), "mail: missing word in phrase: mail: invalid utf-8 in quoted-string: ")
+			fmt.Fprintf(os.Stderr, "Ignored due to invalid UTF-8 encoding: %v\n", addr)
+			return
+		} else if err.Error() == "mail: missing @ in addr-spec" {
+			fmt.Fprintf(os.Stderr, "Ignored a sender due to missing @\n")
+			return // TODO: Print invalid address
+		} else if err.Error() == "mail: no angle-addr" {
+			fmt.Fprintf(os.Stderr, "Ignored a mail due to no angle-address\n")
+			return // TODO: Print message ID
+		}
+		log.Fatal(err)
+	} else if len(addr) != 1 {
+		if len(addr) == 0 {
+			fmt.Fprintf(os.Stderr, "Ignored a mail due to a missing sender\n")
+			return // TODO: Print message ID
+		}
+		fmt.Fprintf(os.Stderr, "A mail has an unexpected number of senders: %v\n", len(addr))
+		return // TODO: Print message ID
+	}
+	fmt.Println(addr[0].Address)
+}