path: root/lib/rites/rite_ef/rubrics_ef.ml

(* RG 475-476 (docs/research/LT.txt, grep "dicitur symbolum"; scan1.txt line
   ~3872-3888), quoted here in full so every branch below can cite its own
   letter without re-quoting the whole rubric:

     "475. Post Evangelium aut homiliam, dicitur symbolum:
        a) in qualibet dominica, etsi eius Officium alicui festo locum
     cedat, vel Missa votiva II classis celebretur;
        b) in festis I classis et in Missis votivis I classis;
        c) in festis II classis Domini et B. Mariae Virg.;
        d) per octavas Nativitatis Domini, Paschatis et Pentecostes, etiam
     in festis occurrentibus et in Missis votivis;
        e) in festis nataliciis Apostolorum et Evangelistarum, necnon in
     festis Cathedrae S. Petri et S. Barnabae Ap.

     476. Non dicitur symbolum:
        a) in Missis sive chrismatis sive in Cena Domini, feria V
     Hebdomadae sanctae, et in Missa Vigiliae paschalis;
        b) in festis II classis, iis exceptis quae supra, n. 475 c et e,
     recensentur;
        c) in Missis votivis II classis;
        d) in Missis festivis et votivis III et IV classis;
        e) ratione alicuius commemorationis in Missa occurrentis;
        f) in Missis defunctorum."

   SCOPE NOTE, checked once here rather than at every clause below: this
   engine resolves ONE observed office and ONE Mass per civil day (see
   Rite.t.readings' own doc comment) -- it has no separate "which votive
   Mass is said" dimension. So the "vel/et...votivis" halves of 475(a)/(b),
   476(c) entirely, and 476(d)'s "et votivis" half are genuinely
   inapplicable to this implementation -- a documented scope limit, not a
   defect. 476(e) needs no branch at all: [creed] below reads only
   [observed], never a day's admitted commemorations, so a commemoration
   can never change its answer by construction.

   476(f) ("in Missis defunctorum") is DIFFERENT: this file used to carry
   it in the same "not modelled" list above, on the reasoning that
   [creed]'s inputs (temporal/observed/date) have no notion of "this Mass
   is a Requiem". That reasoning was wrong, found by the LMS Ordo layer
   (test_lms_ordo.ml, allow-list entry L1, now closed -- see
   expected-divergences-lms.sexp) on 2025-11-03, All Souls' Day: colitur
   said the Creed where the Ordo, correctly, does not. [observed] DOES
   carry a usable signal -- RG 117 assigns black to Masses of the dead,
   and {!Colour.Black} is used by exactly TWO celebrations in this whole
   engine, verified by grepping every [colour Black]/[Colour.Black] site
   in lib/ and data/: [commemoration-of-all-souls] in
   data/ef/sanctoral.sexp, and Good Friday in temporal_ef.ml (which is a
   Holy Week FERIA, RG 23(b), already excluded by the [n >= -6 && n <=
   -1] branch below regardless of colour, and has no Mass at all in the
   1955-restored Holy Week). So on every day this engine can actually
   construct, [colour = Black] if and only if the Mass is a Requiem --
   a citable implication ON THIS DATA, not a heuristic guess. [creed]
   below uses it as 476(f)'s own guard. This is a PROXY, not a general
   "is this a Requiem Mass" field, and it is only as good as that
   two-member population: {!test_rubrics_ef}'s own
   [test_colour_black_population_is_exactly_two] fails loudly the day a
   third [Colour.Black] celebration is added anywhere, so the proxy
   cannot silently rot into covering (or missing) a non-Requiem black
   Mass. If that ever happens, this guard needs re-deriving, not merely
   re-approving. *)

open Colitur_kernel

(* RG 475(e): "in festis nataliciis Apostolorum et Evangelistarum, necnon in
   festis Cathedrae S. Petri et S. Barnabae Ap." NATALICIUM means the feast
   of the saint's own death (dies natalis) -- not every feast that merely
   names him. That is precisely why the clause has to name the Chair of St
   Peter and St Barnabas EXPLICITLY: neither is a natalicium (Peter's own is
   29 June, shared with Paul; Barnabas's is his own day, 11 June, but the
   clause names him anyway, redundantly with the natalicium reading, rather
   than leave it to inference), so neither would be covered without the
   explicit "necnon".

   DERIVED, not copied from any list supplied with this task: grepped
   data/ef/sanctoral.sexp directly for every entry whose English or Polish
   name mentions "Apostle"/"Evangelist"/"Aposto{l/ł}a", then each
   candidate's own date, rank and status checked against the calendarium
   and against whether it is that saint's own dies natalis. Every entry
   below was cross-checked against the shipped data, not assumed:

     andrew (30 Nov, Class2) -- his natalicium.
     barnabas (11 June, Class3) -- named explicitly; also his own natalicium.
     bartholomew (24 Aug, Class2) -- his natalicium.
     chair-of-st-peter (22 Feb, Class2) -- named explicitly ("Cathedrae S.
       Petri"); NOT a natalicium (Peter's own is 29 June, shared with Paul)
       -- exactly why the clause has to name it.
     james-the-greater (25 July, Class2) -- his natalicium.
     john-the-evangelist (27 Dec, Class2) -- his natalicium (the one Apostle
       traditionally held to have died a natural death; "natalicium" still
       names his own feast day, not only a martyr's).
     luke-the-evangelist (18 Oct, Class2) -- his natalicium.
     mark (25 April, Class2) -- the Evangelist ("Marka Ewangelisty" in the
       data's own Polish name); NOT "mark-i" (7 Oct), a different saint (a
       Pope), excluded.
     matthew (21 Sep, Class2) -- Apostle and Evangelist, his natalicium.
     matthias (24 Feb, Class2) -- his natalicium.
     sts-peter-paul (29 June, Class1) -- the natalicium of both.
     sts-philip-james (11 May, Class2) -- the natalicium of both (James the
       Less; there is no separate "james-the-less" entry in the data).
     sts-simon-jude (28 Oct, Class2) -- the natalicium of both.
     thomas (21 Dec, Class2) -- his natalicium.

   Checked and DELIBERATELY EXCLUDED (the Trap this clause is built around):
     conversion-of-st-paul (25 Jan, Class3) -- not a natalicium: it
       commemorates an EVENT of his life, not his death.
     in-commemoratione-sancti-pauli-apostoli (30 June, Class3, status
       Feast, so it CAN be observed, unlike the two entries below) -- a
       secondary commemoration of Paul, not his dies natalis (his own is 29
       June, with Peter); its own name says so ("In Commemoratione", not a
       feast of his martyrdom).
     "peter" (25 Jan) and "paul" (22 Feb) -- both status
       [Commemoration_only] (RG 110's own Peter/Paul companions, on the
       Conversion and Chair days respectively: {!Precedence_ef.disposition}'s
       own citation), so neither can ever be [observed]; moot either way,
       but neither is a natalicium regardless.
     mark-i (7 Oct) -- a different saint (Pope St Mark), not the
       Evangelist. *)
let creed_apostle_slugs =
  [ "andrew"; "barnabas"; "bartholomew"; "chair-of-st-peter"; "james-the-greater";
    "john-the-evangelist"; "luke-the-evangelist"; "mark"; "matthew"; "matthias";
    "sts-peter-paul"; "sts-philip-james"; "sts-simon-jude"; "thomas" ]

let creed ~(temporal : (Vocab_ef.season, Vocab_ef.rank) Temporal.t)
    ~(observed : Vocab_ef.rank Celebration.t) ~(date : Date.t) : bool =
  let easter = Computus.gregorian_easter (Date.year date) in
  let n = Date.to_rata date - Date.to_rata easter in
  let m = Date.month date and dd = Date.day date in
  let slug = Slug.to_string observed.Celebration.slug in
  if
    (* RG 475(d): "per octavas Nativitatis Domini, Paschatis et
       Pentecostes, etiam in festis occurrentibus et in Missis votivis" --
       an unconditional window override, checked first: EVEN a saint's
       feast that wins the day within one of the three octaves (St Stephen,
       26 December, is the live witness -- RG 67's own "Com. octavae
       Nativitatis" note, quoted in full in temporal_ef.ml's [named]) still
       says the Creed. Pure date/Easter-offset arithmetic, not season or
       rank: Ascension (Easter+39) and the Pentecost Vigil (Easter+48) are
       both [Class1] and both fall inside the Paschaltide SEASON but
       outside either 8-day OCTAVE, so a rank- or season-based test here
       would wrongly include them -- checked and rejected for exactly this
       reason.

       Nativity: 25-31 December (its own day plus 7) + 1 January (RG 91
       entry 5's own "Octave Day of the Nativity", the identical table
       entry as 24 December's vigil -- temporal_ef.ml's [named]). Easter:
       Easter Sunday (offset 0) through Low Sunday (offset 7) -- RG 11's
       own "dominicae Paschatis et Pentecostes sunt pariter festa I classis
       CUM OCTAVA". Pentecost: Pentecost (offset 49) through Trinity Sunday
       (offset 56), the RG 91-entry-14-adjacent "octave day" Trinity Sunday
       itself names in temporal_ef.ml. *)
    (m = 12 && dd >= 25 && dd <= 31)
    || (m = 1 && dd = 1)
    || (n >= 0 && n <= 7)
    || (n >= 49 && n <= 56)
  then true
  else if
    (* RG 475(a): "in qualibet dominica, ETSI EIUS OFFICIUM ALICUI FESTO
       LOCUM CEDAT" -- the Creed is said on any Sunday even when a feast
       displaces the Sunday's own office (RG 16(a): a Feast of the Lord I
       or II class occurring on a II-class Sunday takes its place "cum
       omnibus iuribus et privilegiis"). Read off [temporal]'s own weekday
       -- the day's calendar fact, independent of whatever [observed] turns
       out to be -- never off [observed]'s slug or rank, which is exactly
       what would go silently wrong the day such an impeding feast wins:
       see {!Colitur_kernel.Precedence.rules.admit}'s own [~temporal]
       parameter (precedence.mli) for the identical argument, made there
       for RG 111(b) rather than RG 475(a). *)
    temporal.Temporal.weekday = Date.Sun
  then true
  else if
    (* RG 23 (Caput IV, "De Feriis"): "Feriae I classis sunt: a) feria IV
       cinerum; b) omnes feriae Hebdomadae sanctae." Ash Wednesday and every
       feria of Holy Week (Monday through Saturday -- RG 91 entry 2's
       Sacred Triduum, Thursday-Saturday, is a THIRD sub-case of this same
       "feria", not a "festum": RG 35, immediately below in Caput VI,
       defines "festum" as a distinct liturgical-day category from "feria",
       RG 21-27) are FERIAE, never FESTA, however high their RG 91 rank --
       so 475(b)/(c)'s "in festis" never reaches them, regardless of rank.

       This single structural check subsumes 476(a)'s own explicit naming
       of the Chrism Mass, the Mass of the Lord's Supper (both Holy
       Thursday) and the Easter Vigil Mass (Holy Saturday's date): both are
       already excluded here as Holy Week feriae, so 476(a) needs no
       separate branch. (Good Friday needs no rubric at all -- RG 28's own
       closing sentence on the Paschal Vigil aside, Good Friday's own
       liturgical action has no Mass in the 1955-restored Holy Week to
       begin with, so the question is moot there independent of this
       check -- but this structural test correctly excludes it too, since
       it is also named in RG 23(b).)

       RG 24-25 (immediately following, same Caput IV) name TWO MORE
       ferial classes this branch does not reach: feriae II classis (RG
       24 -- the Advent ferias 17-23 December, and the Quatuor Temporum
       sets of Advent, Lent and September) and feriae III classis (RG 25
       -- the numbered Lenten/Passiontide ferias from the Thursday after
       Ash Wednesday to the Saturday before Passion Sunday II, and the
       un-Embered Advent ferias to 16 December). NEITHER is excluded by a
       check anywhere in this module -- this branch and RG 33's vigil
       branch immediately below are the whole of what [creed] tests
       before falling through to 475(b)/(c)/(e)'s own rank/subject/slug
       guards. They do not need an explicit exclusion of their own for
       475(b): temporal_ef.ml's own [ferial_rank] never returns [Class1]
       for them (only Ash Wednesday and Holy Week do, RG 23's own population,
       already excluded above), so that branch is unreachable for them
       regardless of anything checked here. But RG 24's own II-class set
       DOES reach 475(c)'s [Class2] guard below, and 475(e)'s
       apostle-slug guard carries no rank floor at all, so both classes
       genuinely reach a live branch of this function. Getting [false]
       there is NOT established by this exclusion, or by any check in
       this file: it rests on an unstated property of {!Temporal_ef} --
       every ferial-origin office it builds carries [subject = Temporal]
       and an "ef-"-prefixed slug, never [Lord]/[Bvm] or a name on
       {!creed_apostle_slugs}. Verified directly in temporal_ef.ml: the
       Ember/Rogation/generic-ferial branches all go through [build]'s
       own default [subject = Temporal], with exactly two documented
       exceptions, neither able to reach a live branch below -- the
       Sacred Triduum ([subject = Lord], but [Class1], already excluded
       above) and the votive Office of the BVM on Saturday, RG 91 entry
       27 ([subject = Bvm], but [Class4], never satisfying 475(c)'s own
       [Class2] guard).

       (CORRECTED, review fix: this comment, and 475(b)'s own immediately
       below, previously read as though "the two exclusions immediately
       above" disposed of ferias in general -- they dispose of feria I
       classis only. RG 24/25's own higher classes were excluded by NO
       check, an unstated-invariant gap now named here rather than
       silently relied on: test/test_rubrics_ef.ml's own ferial-invariant
       sweep now asserts the Temporal_ef property above directly against
       real output, so a future change that broke it would fail that
       test rather than silently changing the Creed.) *)
    n = -46 || (n >= -6 && n <= -1)
  then false
  else if
    (* RG 28-34 (Caput V, "De Vigiliis"): a vigil is its OWN liturgical-day
       category, distinct from "festum" (RG 35, Caput VI) the same way a
       feria is (immediately above) -- so 475(b)/(c)'s "in festis" does not
       reach a vigil either, regardless of its own RG 91 rank. This is also
       why 476(a) has to name the Easter Vigil explicitly: RG 28's own
       closing sentence says the Paschal Vigil, uniquely, "non sit dies
       liturgicus" [is not a liturgical day] at all, so it is not even a
       "vigilia" in RG 29-32's numbered sense -- nothing else in this
       taxonomy would have excluded it without that explicit clause, unlike
       every OTHER vigil, which is excluded merely by being one.
       {!Precedence_ef.is_vigil} already tests both slug conventions this
       codebase's data uses (the temporal cycle's "-vigil" suffix and the
       sanctoral bootstrap's "vigil-of-" prefix) for the identical RG 33
       question; reused here rather than re-derived, on the same footing as
       {!Precedence_ef.marian_slugs} just below. *)
    Precedence_ef.is_vigil slug
  then false
  else if
    (* RG 476(f): "in Missis defunctorum" -- the Creed is never said at a
       Requiem Mass, checked here, ahead of 475(b)'s rank branch, the same
       "category excludes regardless of rank" position as the feria and
       vigil checks immediately above (All Souls' Day is [Class1], so
       without this guard 475(b) would grant it [true] unopposed, which is
       exactly the defect this guard fixes -- see this file's own header
       for the two-member [Colour.Black] population this proxy rests on,
       and {!Colour.Black}'s own citation, RG 117, for why colour is the
       Requiem signal. Placed before, not after, 475(b)/(c)/(e) so a black
       Class1 or Class2 day can never reach them; nothing above this point
       (the Nativity/Easter/Pentecost octave override, the Sunday rule, the
       feria and vigil exclusions) is ever reachable by a Requiem Mass on
       the shipped data either -- a Requiem is never kept on a Sunday or
       inside a privileged octave -- so this guard's own position relative
       to THOSE branches is moot on real data, checked, not merely assumed:
       {!creed_apostle_slugs} and [marian_slugs] contain no Black-coloured
       entry, and 2 November can never fall inside any of the three
       octaves 475(d) names. *)
    observed.Celebration.colour = Colour.Black
  then false
  else if
    (* RG 475(b): "in festis I classis". Genuine feasts only, by
       construction of the two exclusions immediately above (feria I
       classis -- Ash Wednesday and Holy Week, the only feriae that are
       ever [Class1]; RG 24/25's II- and III-class feriae are a different
       population and never reach this rank at all, see the RG 23
       comment's own note above -- and vigils) -- every remaining
       [Class1] candidate reaching this branch is a real festum: the
       Nativity, Epiphany, Ascension, Corpus Christi, the Sacred Heart,
       Christ the King, a I-class sanctoral feast (the Assumption, the
       Immaculate Conception...), or a I-class Sunday (already [true]
       above via 475(a), so this branch is never the FIRST to grant those
       a [true], only ever redundant with it). *)
    observed.Celebration.rank = Vocab_ef.Class1
  then true
  else if
    (* RG 475(c): "in festis II classis Domini et B. Mariae Virg." --
       [subject = Lord] is reliably set on genuine II-class sanctoral
       feasts of the Lord (Exaltation of the Holy Cross, the Purification,
       the Transfiguration, the Commemoration of the Baptism of the Lord,
       the Dedication of the Lateran Archbasilica -- checked directly
       against data/ef/sanctoral.sexp: six [subject = Lord] entries ship,
       none a vigil or feria) and on the two temporal-cycle Class2 Lord
       feasts (Holy Family, Holy Name of Jesus). [subject = Bvm], by
       contrast, is NOT reliable for the BVM half: checked directly against
       the data, almost every Marian sanctoral entry (the Assumption, the
       Annunciation, the Immaculate Heart, the Nativity of the BVM...)
       ships [subject = Saint] instead -- {!Precedence_ef.marian_slugs} is
       the list built (and, here, reused rather than re-derived) precisely
       because the [subject] field cannot be trusted alone for this
       question; see its own citation in precedence_ef.mli.

       This [Class2] guard is also the one live branch RG 24's own
       II-class feriae (Advent 17-23, the Advent/Lent/September Ember
       sets) genuinely reach -- the RG 23 comment above (this file, the
       [n = -46 ...] branch) has the full account of why they still come
       out [false] here: an unstated Temporal_ef property, checked by a
       test, not a guard in this file. *)
    observed.Celebration.rank = Vocab_ef.Class2
    && (observed.Celebration.subject = Subject.Lord
       || observed.Celebration.subject = Subject.Bvm
       || List.mem slug Precedence_ef.marian_slugs)
  then true
  else
    (* RG 475(e): see {!creed_apostle_slugs}'s own citation. Checked last
       and without a rank guard, on purpose -- Barnabas is only [Class3]
       and the Chair of St Peter's own [subject] is [Saint], so neither
       would ever be reached by the two branches above; every [Class1]
       entry on the list (Sts Peter & Paul) is already [true] via 475(b),
       so this branch is redundant, never wrong, for those. *)
    List.mem slug creed_apostle_slugs