kernel: the LiturgicalDay result schema

Temporal is embedded rather than flattened, so season/week/weekday have one
home and cannot disagree with themselves. transferred_in/out make transfers
visible in the result -- an ordo must print 'transferred from the 25th', and
the nothing-lost invariant reads these fields. citations exists and is empty
until Plan 4; adding it later would widen a type every consumer matches on.

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/kernel/liturgical_day.ml b/lib/kernel/liturgical_day.ml
new file mode 100644
index 0000000..65e3ba5
--- /dev/null
+++ b/lib/kernel/liturgical_day.ml
@@ -0,0 +1,19 @@
+open Sexplib0.Sexp_conv
+
+(* The single stable result schema (parent spec §2). *)
+type ('s, 'r) t = {
+  date : Date.t;
+  rite : string;
+  temporal : ('s, 'r) Temporal.t;
+      (** embedded, not flattened: it is already a coherent unit with its own
+          invariants, and re-listing season/week/weekday here would create two
+          places for them to disagree *)
+  observed : 'r Celebration.t;
+  commemorations : ('r Celebration.t * Precedence.privilege) list;
+  transferred_in : 'r Celebration.t option;
+      (** arrived here from an impeded day *)
+  transferred_out : Date.t option;
+      (** this day's celebration went there *)
+  citations : Citation.t list;  (** always empty until Plan 4 *)
+}
+[@@deriving sexp]