Global code ovehaul - remove CAS and other, add 15 minute greet check

- Remove CAS, as it no longer works for us
- Remove other checks
- Implement 15 minute greet timeout check
- Fix chat logos
- Ditch thirdparty logger, use stdlib log facility wrapper for logging

internal/moon/greet.go

@@ -0,0 +1,98 @@
+package moon
+
+import (
+	"bunny-bot/internal/mylog"
+	"math/rand/v2"
+	"strings"
+
+	"github.com/NicoNex/echotron/v3"
+)
+
+// greetings are the templates used to greet a newly joined member. The single
+// verb is replaced with the newcomer's computed display name. The fourth one is
+// intentionally kept verbatim despite looking like a typo.
+var greetings = []string{
+	"Дарована, %s. Представьтес, пожалуйста, и расскажите, что вас сюда привело.",
+	"Добро пожаловать в наше скромное коммунити, %s. Представьтес, пожалуйста, и расскажите, что вас сюда привело.",
+	"Доброе утро, день или вечер, %s. Представьтес, пожалуйста, и расскажите, что вас сюда привело.",
+	"Наше вам с кисточкой тут, на канальчике, %s. Представьтес, пожалуйста, и расскажите, что вас сюда привело.",
+}
+
+// displayName builds the name substituted into a greeting for the given user.
+// Preference order: "FirstName LastName", then LastName alone, then FirstName
+// alone, then the username.
+func displayName(u *echotron.User) string {
+	if u == nil {
+		return ""
+	}
+
+	name := strings.TrimSpace(strings.Join([]string{u.FirstName, u.LastName}, " "))
+
+	if name != "" {
+		return name
+	}
+
+	return u.Username
+}
+
+// sendGreeting sends a randomly chosen greeting for the given newcomer into the chat.
+//
+// It returns the id of the greeting it sent and whether it was actually
+// delivered. Both matter: a newcomer who never received the question must not be
+// judged on their silence, and a newcomer who is banned later must have the
+// question taken back down.
+//
+// The mention makes the greeting a clickable link to the newcomer, and the
+// message is sent in HTML mode because that is the only mode in which an
+// arbitrary display name can be embedded safely — see greetMention.
+func sendGreeting(chatid int64, u *echotron.User) (int, bool) {
+	// Everything below dereferences u, including the error paths that name the
+	// user, so an entity with no id is refused here rather than crashing later.
+	if !usableUser(u) {
+		return 0, false
+	}
+
+	// math/rand is sufficient here: we pick one of four static templates, not a
+	// secret or a security-relevant value.
+	greeting := greetings[rand.IntN(len(greetings))] //nolint: gosec // G404
+
+	text := strings.Replace(greeting, "%s", greetingAddressee(u), 1)
+
+	res, err := Tg.SendMessage(text, chatid, &echotron.MessageOptions{
+		ParseMode: echotron.HTML,
+	})
+	if err != nil {
+		mylog.Errorf("GREETING NOT DELIVERED to user %d in chat %d: %s", u.ID, chatid, err)
+
+		return 0, false
+	}
+
+	mylog.Debugf("Greeted user %d in chat %d", u.ID, chatid)
+
+	// A response carrying no message still means the greeting was delivered; we
+	// simply have no id to retract later.
+	return sentMessageID(res), true
+}
+
+// greetingAddressee is the name the template's %s is replaced with: a mention of
+// the newcomer when they can be mentioned, and their plain display name when they
+// cannot, so an unmentionable user is still greeted rather than skipped.
+func greetingAddressee(u *echotron.User) string {
+	if mention := greetMention(u); mention != "" {
+		return mention
+	}
+
+	return displayName(u)
+}
+
+// sentMessageID pulls the id out of a send response, tolerating a response that
+// carries no message at all.
+func sentMessageID(res echotron.APIResponseMessage) int {
+	if res.Result == nil {
+		return 0
+	}
+
+	return res.Result.ID
+}
+
+/* vim: set ft=go noet ai ts=4 sw=4 sts=4: */