Fix 10: the catalogue reads a seat's views and stream-ridden accepts, and a consumed view of a seat

Builds: design 47 G §616, §699, A-102, A-131

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

go/catalogue/seat_from_definition.go

@@ -27,6 +27,14 @@ func SeatFromDefinition(d seatdef.Definition) Seat {
 	}
 	for _, st := range d.States {
 		s.States = append(s.States, st.Name)
+		if st.View {
+			s.Views = append(s.Views, st.Name)
+		}
+	}
+	for _, a := range d.Accepts {
+		if a.Stream != "" {
+			s.AcceptedOn = append(s.AcceptedOn, a.Stream+"."+a.Name)
+		}
 	}
 	for _, r := range d.Receives {
 		rv := Receivable{Kind: r.Kind, Comment: r.Comment, Dirs: r.Dirs, Offered: r.Offered}

go/catalogue/seats.go

@@ -49,6 +49,12 @@ type Seat struct {
 	// States are the names of the state the seat's holder keeps, which a module reads by `seat:<seat>.<state>` (design 47 G
 	// A-116, A-128). Compiled from the definition's states.
 	States []string
+	// Views are the names of those states the seat offers as views, which a module follows by `consumes`
+	// `seat:<seat>.views.<state>` (design 47 G §616, §699, A-131). Compiled from the definition's states marked `view`.
+	Views []string
+	// AcceptedOn are the accepted kinds that ride a stream, each as `<stream>.<kind>`, which a part names in `invokes` as
+	// `seat:<seat>.<stream>.<kind>` (design 47 G A-102, §415). Compiled from the definition's accepts.
+	AcceptedOn []string
 	// Receives is what other modules may contribute to the seat's holder, by kind (novox/hq ADR
 	// 0212): each kind is text in the tool's own grammar, placed by the holder with
 	// ${contribution:<seat>:<kind>}. Compiled, never stored: like the protocol, it is the mesh's

go/catalogue/state.go

@@ -97,6 +97,21 @@ func SeatRead(read string) (seat, local string, ok bool, err error) {
 	return rest[:at], rest[at+1:], true, nil
 }
 
+// SeatViewConsume splits a consumed view of a seat, `seat:<seat>.views.<state>`, into the seat and the state; ok is false for a
+// consumed entry that is not of this kind (an event, `<emitter>.<event>`), and err says why a `seat:` entry is malformed. The
+// holder is not in it: the grants part resolves it from the catalog half (design 47 G §616, A-131).
+func SeatViewConsume(consume string) (seat, state string, ok bool, err error) {
+	rest, isSeat := strings.CutPrefix(consume, SeatReadPrefix)
+	if !isSeat {
+		return "", "", false, nil
+	}
+	seat, view, named := strings.Cut(rest, ".views.")
+	if !named || !stateName.MatchString(seat) || !stateName.MatchString(view) {
+		return "", "", true, fmt.Errorf("%q does not name a seat and its view: a consumed view of a seat is seat:<seat>.views.<state>", consume)
+	}
+	return seat, view, true, nil
+}
+
 // ReadState splits a read into the owning module and the local name, or says why it is not one.
 func ReadState(read string) (module, local string, err error) {
 	at := strings.LastIndex(read, ".")

go/catalogue/state_test.go

@@ -88,8 +88,25 @@ func TestSeatRead(t *testing.T) {
 			t.Errorf("SeatRead(%q) = %q, %q, %v, %v", row.read, seat, local, ok, err)
 		}
 	}
-	s := SeatFromDefinition(seatdef.Definition{Seat: "mesh-provisioner", Scope: "mesh", States: []seatdef.State{{Name: "plans"}, {Name: "provisions"}}})
-	if len(s.States) != 2 || s.States[0] != "plans" || s.States[1] != "provisions" {
-		t.Errorf("the seat's states = %v", s.States)
+	for _, row := range []struct {
+		consume, seat, state string
+		ok, bad              bool
+	}{
+		{"seat:mesh-provisioner.views.plans", "mesh-provisioner", "plans", true, false},
+		{"mesh-provisioner.views.plans", "", "", false, false},
+		{"seat:mesh-provisioner.plans", "", "", true, true},
+		{"seat:.views.plans", "", "", true, true},
+	} {
+		seat, state, ok, err := SeatViewConsume(row.consume)
+		if seat != row.seat || state != row.state || ok != row.ok || (err != nil) != row.bad {
+			t.Errorf("SeatViewConsume(%q) = %q, %q, %v, %v", row.consume, seat, state, ok, err)
+		}
+	}
+	s := SeatFromDefinition(seatdef.Definition{Seat: "mesh-provisioner", Scope: "mesh",
+		States:  []seatdef.State{{Name: "plans", View: true}, {Name: "provisions"}},
+		Accepts: []seatdef.Message{{Name: "step", Stream: "check"}, {Name: "step"}}})
+	if len(s.States) != 2 || s.States[0] != "plans" || s.States[1] != "provisions" || len(s.Views) != 1 || s.Views[0] != "plans" ||
+		len(s.AcceptedOn) != 1 || s.AcceptedOn[0] != "check.step" {
+		t.Errorf("the seat's states = %v, views = %v, accepted on = %v", s.States, s.Views, s.AcceptedOn)
 	}
 }