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, 18 insertions, 2 deletions

diff --git a/internal/app/fakes_test.go b/internal/app/fakes_test.go
index 011d4af..9281a53 100644
--- a/internal/app/fakes_test.go
+++ b/internal/app/fakes_test.go
@@ -182,12 +182,16 @@ func (f *fakeTelegram) pendingCount() int {
 
 // fakeCEPIS is a real HTTP server speaking the cep.is native contract, with
 // enough of it to exercise every branch the bot has: an address with a street
-// coordinate, one that is a whole municipality, a 404, a 400 and a 500.
+// coordinate, one that is a whole municipality, a 404 that names the
+// municipality the CEP would fall in, a 404 that does not, a 400 and a 500.
 type fakeCEPIS struct {
 	server *httptest.Server
 
-	mu       sync.Mutex
+	mu sync.Mutex
+	// bodies are the 200s, missing are the 404s that carry a faixa, and
+	// statuses forces a status for a CEP regardless of the other two.
 	bodies   map[string]string
+	missing  map[string]string
 	statuses map[string]int
 	requests int
 }
@@ -208,6 +212,14 @@ func newFakeCEPIS(t *testing.T) *fakeCEPIS {
 				`"unidade":"","bairro":"Centro","localidade":"Linhares","uf":"ES","estado":"Espírito Santo",` +
 				`"regiao":"Sudeste","ibge":"3203205","gia":"","ddd":"27","siafi":"5665"}`,
 		},
+		// 25845000 is the CEP the "-000" guess produces for Areal/RJ, which
+		// is coded street by street and never received that number: the
+		// municipality exists, the CEP does not.
+		missing: map[string]string{
+			"25845000": `{"erro":"cep_nao_encontrado","mensagem":"CEP não existe na base do DNE",` +
+				`"faixa":{"localidade":"Areal","uf":"RJ","estado":"Rio de Janeiro","regiao":"Sudeste",` +
+				`"ibge":"3300225","cep_ini":"25845001","cep_fim":"25849899","ceps":118}}`,
+		},
 		statuses: map[string]int{
 			"50000000": http.StatusInternalServerError,
 		},
@@ -225,6 +237,7 @@ func (f *fakeCEPIS) handle(w http.ResponseWriter, r *http.Request) {
 	cep := strings.TrimPrefix(r.URL.Path, "/")
 	status, forced := f.statuses[cep]
 	body, known := f.bodies[cep]
+	absent, attributed := f.missing[cep]
 	f.mu.Unlock()
 
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
@@ -235,6 +248,9 @@ func (f *fakeCEPIS) handle(w http.ResponseWriter, r *http.Request) {
 	case known:
 		w.WriteHeader(http.StatusOK)
 		w.Write([]byte(body))
+	case attributed:
+		w.WriteHeader(http.StatusNotFound)
+		w.Write([]byte(absent))
 	case len(cep) != 8:
 		w.WriteHeader(http.StatusBadRequest)
 		w.Write([]byte(`{"erro":"cep_invalido","mensagem":"CEP deve ter 8 dígitos"}`))