Name the municipality when the CEP does not existv0.2.0

Answering only "não encontrei" wastes the trip. A CEP that fails is
almost never a random number: it is someone who knows the city and
guessed the rest, most often at the "-000" that 957 municipalities never
received. The API now names that municipality on the 404, so the reply
names it too.

It stays an answer to a failure. No 📮, no address block, and no CEP
suggested from inside the range — the range is sparse (Areal's 118 CEPs
span nearly five thousand numbers), so the reply gives the count and says
so instead of letting the two ends read as a list of valid CEPs.

cep.is/go v0.1.0 discards the 404 body, so internal/lookup reads it with
one extra GET, on that path alone and never inside a retry. Everything
that can go wrong there — a slow answer, broken JSON, a faixa naming no
municipality — falls back to the reply the bot has always given. The
wrapper goes away the day the library exposes the field.

1 files changed, 20 insertions, 1 deletions

diff --git a/internal/bot/bot.go b/internal/bot/bot.go
index b29dc36..4abf02c 100644
--- a/internal/bot/bot.go
+++ b/internal/bot/bot.go
@@ -13,11 +13,16 @@ import (
 
 	cepis "cep.is/go"
 
+	"cep.is/telegrambot/internal/lookup"
 	"cep.is/telegrambot/internal/telegram"
 )
 
 // Lookups is the subset of the cep.is client this bot needs. Depending on the
 // interface rather than the concrete client keeps the seam narrow and visible.
+//
+// A failure may be a [*lookup.NotFoundError], which still matches
+// cepis.ErrCEPNotFound and additionally names the municipality the CEP would
+// belong to; nothing here has to know that, because [ErrorMessage] reads it.
 type Lookups interface {
 	Lookup(ctx context.Context, cep string) (*cepis.Address, error)
 }
@@ -211,7 +216,7 @@ func (b *Bot) handleInline(ctx context.Context, query *telegram.InlineQuery) err
 	if err != nil {
 		b.logger.Info("inline lookup failed", slog.String("error", err.Error()))
 		return b.answerInline(ctx, query, []telegram.InlineQueryResult{
-			b.inlineNotice(query, inlineErrorTitle(err), "Toque para enviar o motivo", ErrorMessage(err)),
+			b.inlineNotice(query, inlineErrorTitle(err), inlineErrorDescription(err), ErrorMessage(err)),
 		}, inlineCacheOther)
 	}
 
@@ -260,6 +265,20 @@ func inlineErrorTitle(err error) string {
 	return "Não consegui consultar agora"
 }
 
+// inlineErrorDescription is the second line of the notice. Naming the
+// municipality here is what lets someone see, in the results list, that the
+// city they had in mind is right and the number is not — before sending
+// anything to the chat.
+//
+// Titles and descriptions are plain text for Telegram, so nothing here is
+// escaped: HTML applies to the message body alone.
+func inlineErrorDescription(err error) string {
+	if faixa := lookup.FaixaOf(err); faixa != nil {
+		return "Cairia em " + faixa.Place() + " — toque para ver"
+	}
+	return "Toque para enviar o motivo"
+}
+
 // rateKey is the token bucket's key: the author when there is one, and the chat
 // otherwise. A channel post has no author, and channel ids are negative, so the
 // two spaces cannot collide.