package calendar_test

import (
	"encoding/json"
	"os"
	"sort"
	"strings"
	"testing"
	"time"

	"github.com/lukaszkasprzak/lectio/internal/caldata"
	"github.com/lukaszkasprzak/lectio/internal/calendar"
)

// efOracleDay is one day of missalemeum's per-date proper API, as captured in
// sources/snapshot.tar.gz (missalemeum/en/YYYY-MM-DD.json, 2026-01-01 ..
// 2027-12-31, 730 days) and flattened by scripts/build-oracle-ef.sh.
//
// Three things about this data that will otherwise cost hours (see that
// script's own header for the full account):
//
//  1. ID looks like "sancti:MM-DD:rank:colour", but its embedded rank is the
//     rank of the PROPERS USED that day, not the day's own rank -- e.g.
//     2026-01-02 is a class-4 feria carrying id "sancti:01-01:1:w" because it
//     reuses the Circumcision's propers. Kept here for provenance/debugging
//     ONLY. Rank and Colour comparisons below use Rank/Colours, never ID.
//  2. Colours is an array -- 14 of 730 days carry two values (Gaudete/Laetare
//     "pv", Palm Sunday "rv", Good Friday "bv", Holy Saturday "vw") -- so the
//     comparison is membership, not equality.
//  3. A two-colour value on a weekday can be an artifact of proper reuse (a
//     feria inside Gaudete/Laetare week reusing the Sunday's own propers)
//     rather than a claim about that weekday's own colour. No special-casing
//     is needed for this: lectio's single ferial colour (violet) is already a
//     member of the reused set (e.g. ["p","v"]), so a plain membership check
//     absorbs it.
type efOracleDay struct {
	ID      string   `json:"id"`
	Tempora string   `json:"tempora"`
	Title   string   `json:"title"`
	Rank    int      `json:"rank"`
	Colours []string `json:"colours"`
}

// efColourLetters maps missalemeum's single-letter colour codes to lectio's
// Colour vocabulary (scripts/gen-sanctoral-ef.go's colourWord table, same
// mapping, kept in sync deliberately rather than imported across a
// package/build-tag boundary).
var efColourLetters = map[string]calendar.Colour{
	"w": calendar.White, "r": calendar.Red, "g": calendar.Green,
	"v": calendar.Violet, "b": calendar.Black, "p": calendar.Rose,
}

// efRankNumbers maps missalemeum's 1-4 rank number to lectio's EF Rank
// vocabulary. missalemeum has no separate "commemoration" rank number --
// RankCommemoration is a lectio-side concept for a losing sanctoral
// candidate, never the oracle's claim about the OBSERVED day.
var efRankNumbers = map[int]calendar.Rank{
	1: calendar.RankClass1, 2: calendar.RankClass2,
	3: calendar.RankClass3, 4: calendar.RankClass4,
}

// efSeasonFromString maps a missalemeum tempora/title phrase (for a day in the
// given month) to lectio's EF season. Order matters. Two position-dependent
// subtleties: the Whit-octave weekdays ("Monday after Pentecost") are still
// Paschaltide, so only "Sunday after Pentecost" is Time after Pentecost; and the
// resumed Sundays after Epiphany (celebrated in autumn) sit within Time after
// Pentecost, so an "after Epiphany" phrase in the second half of the year maps
// there, not to Time after Epiphany.
func efSeasonFromString(s string, month int) calendar.Season {
	s = strings.ToLower(s)
	// missalemeum's own EN-locale text still carries the occasional Latin
	// ligature (e.g. "Feria V after Sexagesimæ") -- confirmed in the
	// committed snapshot: "Sexagesimæ" appears 10 times, "Sexagesima" (no
	// ligature) only 4, and the ligatured form matched no case below,
	// silently mapping those 10 days to season "" (skipped from coverage
	// entirely, not merely a season miss). Normalising here fixes every
	// current and future ligature in one place, not just this one word.
	s = strings.ReplaceAll(s, "æ", "ae")
	has := func(subs ...string) bool {
		for _, sub := range subs {
			if strings.Contains(s, sub) {
				return true
			}
		}
		return false
	}
	switch {
	case has("vigil of christmas"): // last day of Advent
		return calendar.Advent
	case has("advent"):
		return calendar.Advent
	case has("sunday after pentecost"), has("trinity", "christ the king", "corpus christi"):
		return calendar.TimeAfterPentecost
	case has("after epiphany", "epiphany"):
		if month >= 6 { // resumed Epiphany Sundays, celebrated within Time after Pentecost
			return calendar.TimeAfterPentecost
		}
		return calendar.TimeAfterEpiphany
	case has("passion", "palm", "holy week", "maundy", "good friday", "holy saturday"):
		return calendar.Passiontide
	case has("septuagesima", "sexagesima", "quinquagesima"):
		return calendar.Septuagesima
	case has("ash wednesday", "lent"):
		return calendar.Lent
	case has("pentecost", "ascension", "rogation", "after easter", "easter", "low sunday", "paschal", "whit"):
		return calendar.Easter_ // incl. the Whit octave (Mon-Sat after Pentecost)
	case has("christmas", "nativity", "circumcision", "holy name", "octave day of christ"):
		return calendar.Christmas
	default:
		return "" // unknown phrase -> skip this day
	}
}

// efAllow is one cited allow-list entry: a genuine, defensible divergence
// between lectio's EF engine and the missalemeum oracle on Rank and/or
// Colour, kept out of the pass/fail count deliberately rather than silently
// skipped. Every entry names the date(s) it covers, which field(s) it
// excuses, and why -- with an RG citation where the divergence is a rubric
// question, or a plain "not built" note where it is a documented scope gap
// (see internal/calendar/precedence_ef.go and temporal_ef.go's own doc
// comments, and colitur's rules-register.md, for the fuller accounts).
type efAllow struct {
	date   string // "" = pattern-matched by match(), see below
	match  func(date string, day time.Time, oracle efOracleDay) bool
	field  string // "rank", "colour", or "rank+colour"
	reason string
}

var efAllowList = []efAllow{
	{
		// RG 124, "De coloribus paramentorum", section C "De colore rubro",
		// both photographic scans word for word: 124(b) gives red to
		// "Sanctorum Apostolorum et Evangelistarum, in eorum die natalicio,
		// excepto festo S. Ioannis (27 decembris)", and 124(e) to "Sanctorum
		// Martyrum, quorum colitur aut martyrium". Red is for Apostles,
		// Evangelists and Martyrs; a Confessor, Doctor or non-martyr Virgin is
		// white.
		//
		// missalemeum has these INVERTED IN BOTH DIRECTIONS -- ten confessors
		// and virgins in red, and two actual martyrs (Apollinaris and
		// Josaphat, both Bishop and Martyr) in white. Both directions failing
		// is why this is read as a systematic upstream error rather than a
		// judgement call: a rule applied backwards, not a series of
		// individual mistakes.
		//
		// colitur adjudicated the same fourteen slugs against the scans (its
		// C18 carries the per-slug reasoning, its M21 the oracle side, verdict
		// colitur). Twelve are corrected here; conversion-of-st-paul and
		// chair-of-st-peter already agreed.
		match: func(date string, day time.Time, o efOracleDay) bool {
			switch date[5:] {
			case "06-12", "06-18", "06-19", "07-12", "07-18", "07-20",
				"07-23", "07-29", "08-02", "08-28", "08-30", "11-14":
				return true
			}
			return false
		},
		field:  "colour",
		reason: "RG 124: red is for Apostles, Evangelists and Martyrs; missalemeum has ten confessors/virgins red and two martyrs white, inverted in both directions (colitur C18/M21)",
	},
	{
		// The 1962 Missal's own universal CALENDARIUM ranks both of these as
		// bare III-class feasts, with no commemoration rubric: "S. Ubaldi Ep.
		// et Conf., III classis" (16 May) and "S. Didaci Conf., III classis"
		// (13 November). Each also has its own Mass entry in the Proprium,
		// taking its readings from a Common with only its Oratio proper --
		// which a bare commemoration never has. missalemeum ranks both as
		// commemorations, so on these dates it leaves the day unimpeded and
		// shows a feria or the Saturday BVM Office; lectio now shows the feast.
		//
		// This entry MUST precede the BVM-Saturday entry below. When 16 May or
		// 13 November falls on a Saturday, that entry's predicate (Saturday +
		// an oracle title naming the B.V.M.) also matches, and would absorb
		// this divergence under a reason that is no longer true of it -- it
		// says "both engines agree only that the day is unimpeded", and the
		// whole point here is that the day IS impeded, by a feast missalemeum
		// does not rank as one.
		//
		// Found by auditing all 290 of colitur's fixed-date sanctoral entries
		// against that calendarium; these two were the only status defects.
		// colitur allow-list C38/M30, rules-register.md 6.25.
		match: func(date string, day time.Time, o efOracleDay) bool {
			md := date[5:]
			return (md == "05-16" || md == "11-13") &&
				!strings.Contains(strings.ToLower(o.Title), "ubald") &&
				!strings.Contains(strings.ToLower(o.Title), "didac")
		},
		field:  "rank+colour",
		reason: "Missal calendarium ranks St Ubaldus (16 May) and St Didacus (13 Nov) III classis, not commemorations; missalemeum keeps them as commemorations and so leaves the day unimpeded (colitur C38/M30)",
	},
	{
		// RG 128, "De colore violaceo": violet is used for vigils of II and III
		// class outside Paschaltide. The Vigil of the Assumption (14 August, II
		// class) and the Vigil of St Lawrence (9 August, III class) both
		// qualify. missalemeum shows white and red respectively -- values
		// lectio carried too, and colitur inherited from lectio, all three
		// descending from Divinum Officium's data files. The rule's sole
		// exception is named in the same place and is not either of these: the
		// Ascension's vigil, the one II-class vigil INSIDE Paschaltide, which
		// is white and is untouched.
		//
		// colitur allow-list C37/M29, rules-register.md 6.24.
		// NOT on a Sunday. RG 33 omits a II/III-class vigil whenever its date
		// falls on one, so lectio shows the Sunday and the divergence there is
		// missalemeum's own RG 33 gap -- already allow-listed further down,
		// with its own citation. Without this guard, 2026-08-09 (a Sunday whose
		// oracle title still reads "Vigil of St. Lawrence") matches on the
		// title alone and is stolen from that entry, reported under a colour
		// rule that has nothing to do with it. Same failure this list's first
		// entry exists to prevent, in the opposite direction.
		match: func(date string, day time.Time, o efOracleDay) bool {
			md := date[5:]
			return (md == "08-09" || md == "08-14") &&
				day.Weekday() != time.Sunday &&
				strings.Contains(strings.ToLower(o.Title), "vigil")
		},
		field:  "colour",
		reason: "RG 128: violet for vigils of II and III class outside Paschaltide; missalemeum shows white/red (colitur C37/M29)",
	},
	{
		// RG 91 entry 27, "Officium sanctae Mariae in sabbato": the votive
		// BVM Office on an otherwise-unoccupied IV-class Saturday. Not built
		// in lectio (temporal_ef.go constructs only a bare ferial slug on
		// these Saturdays; the vocabulary comment in colitur's own register
		// documents the same gap on its side). missalemeum's rank/colour for
		// these Saturdays reflects the BVM Office (usually white); lectio's
		// reflects the plain per-annum feria (green, class-4). A real,
		// scoped, pre-existing gap -- not one of the seven defects, and not
		// attempted here (a Plan-scale feature, per the sibling project's own
		// parking of the identical item).
		match: func(date string, day time.Time, o efOracleDay) bool {
			return day.Weekday() == time.Saturday &&
				strings.Contains(strings.ToLower(o.Title), "b. v. m")
		},
		field:  "rank+colour",
		reason: "RG 91 entry 27 (BVM Office on Saturday) is not built in lectio; both engines agree only that the day is unimpeded",
	},
	{
		// RG 72-73 place 6-13 January within Christmastide itself ("a I
		// Vesperis Nativitatis Domini usque ad diem 13 ianuarii inclusive");
		// RG 119(a) backs the same boundary from the white-colour side
		// ("...usque ad expletum tempus Epiphaniae"). lectio's efSeason
		// (temporal_ef.go) instead starts "time after Epiphany" on 6 January,
		// so a plain feria in this window gets green/TimeAfterEpiphany
		// instead of white/Christmastide. This is a real, PRE-EXISTING season-
		// boundary divergence -- colitur's own rules-register.md documents
		// the identical gap on its side (§3c item 1) as deliberate and
		// resolved in the OTHER engine's favour, not one of the seven named
		// defects, and not touched here: efSeason is a season-boundary
		// function with much wider reach than any of the seven, and changing
		// it is out of this task's scope.
		match: func(date string, day time.Time, o efOracleDay) bool {
			return day.Month() == time.January && day.Day() >= 6 && day.Day() <= 13
		},
		field:  "colour",
		reason: "RG 72-73/RG 119(a): 6-13 Jan is Christmastide, not lectio's time-after-Epiphany reading (efSeason, not one of the seven defects; see colitur rules-register.md §3c item 1)",
	},
	{
		// RG 33: "Vigilia II aut III classis penitus omittitur, si occurrat in
		// dominica quavis..." -- a II/III-class vigil is ENTIRELY OMITTED on
		// any Sunday. 9 August 2026 is a Sunday; the Vigil of St Lawrence (III
		// class) must vanish and the Sunday itself be observed -- which is
		// exactly what lectio does (see cmd/lectio-ef-dump: 2026-08-09
		// observed is the II-class Sunday, the vigil demoted to a losing
		// candidate). missalemeum's OWN data shows the vigil still winning
		// that Sunday, an RG 33 gap on missalemeum's side, not lectio's --
		// already identified and adjudicated in the primary source's favour
		// by the sibling project (rules-register.md §6, "the romanus-vs-
		// vigil-of-st-lawrence 9 August Sunday tie-break", M1).
		date:   "2026-08-09",
		field:  "rank+colour",
		reason: "RG 33: a II/III-class vigil is omitted on any Sunday; missalemeum itself shows an RG 33 gap here (colitur rules-register.md §6, M1) -- lectio's Sunday-observed answer is the Missal-correct one",
	},
	{
		// OPEN, not adjudicated by any primary text found so far. RG 91's
		// plain table gives St Joseph (19 March, I class) the day outright
		// over an ordinary III-class Friday of Passion Week -- no RG 96
		// collision requiring a transfer -- yet missalemeum shows Joseph
		// entirely displaced in 2027 specifically (the Friday's own office
		// observed, the Seven Sorrows commemorated instead). The sibling
		// project's much deeper primary-source pass over the SAME question
		// left it explicitly open (colitur rules-register.md §6, M13: "three
		// possibilities, none confirmed") rather than guess at an unfound
		// rubric. Not attempted here either, for the same reason -- adjudicating
		// it would mean finding a citation that a more thorough primary-source
		// audit did not.
		date:   "2027-03-19",
		field:  "rank+colour",
		reason: "unresolved even by primary-source review (colitur rules-register.md §6, M13); not adjudicated here either way",
	},
}

func efAllowed(date string, day time.Time, oracle efOracleDay, field string) (bool, string) {
	for _, a := range efAllowList {
		if a.date != "" && a.date != date {
			continue
		}
		if a.match != nil && !a.match(date, day, oracle) {
			continue
		}
		if a.field == field || a.field == "rank+colour" {
			return true, a.reason
		}
	}
	return false, ""
}

// TestOracleEF diffs the EF engine against missalemeum (Divinum Officium data)
// over 730 days (2026-01-01 .. 2027-12-31). Season, Rank and Colour are all
// asserted strictly (membership for Colour, since missalemeum's colour is an
// array); a prior version of this test asserted Season only, which is exactly
// why several precedence/colour defects (see precedence_ef.go, temporal_ef.go)
// shipped without ever failing a test.
func TestOracleEF(t *testing.T) {
	raw, err := os.ReadFile("testdata/oracle-ef.json")
	if err != nil {
		t.Skip("EF oracle snapshot missing; run scripts/build-oracle-ef.sh")
	}
	var oracle map[string]efOracleDay
	if err := json.Unmarshal(raw, &oracle); err != nil {
		t.Fatal(err)
	}
	sel := calendar.DefaultSelection()
	sel.Form = "old"
	layers := []calendar.Layer{caldata.Tridentine()}

	dates := make([]string, 0, len(oracle))
	for d := range oracle {
		dates = append(dates, d)
	}
	sort.Strings(dates)

	var seasonMiss, rankMiss, colourMiss, rankAllowed, colourAllowed, skipped, total int
	shownSeason, shownRank, shownColour := 0, 0, 0
	for _, date := range dates {
		od := oracle[date]
		src := od.Tempora
		if src == "" {
			src = od.Title
		}
		day, _ := time.Parse("2006-01-02", date)
		want := efSeasonFromString(src, int(day.Month()))
		total++
		got := calendar.Compute(day.UTC(), sel, layers)

		// An unrecognised season phrase skips the SEASON comparison only --
		// it must not also skip Rank/Colour for that day. A `continue` here
		// once did exactly that, silently zeroing oracle coverage for every
		// day whose phrase efSeasonFromString doesn't recognise (Holy
		// Thursday -- "maundy"/"holy week" don't match "Holy Thursday"
		// itself; the six September Ember days -- no "ember" case exists at
		// all, only Advent/Lent Ember days pass by an incidental substring
		// match on "advent"/"lent"). Reverting the Holy Thursday colour fix
		// (temporal_ef.go) left this test green under the old `continue`;
		// it does not under this one.
		if want == "" {
			skipped++
		} else if got.Season != want {
			seasonMiss++
			if shownSeason < 40 {
				t.Errorf("%s: EF season got %q want %q (from %q)", date, got.Season, want, src)
				shownSeason++
			}
		}

		wantRank, rankKnown := efRankNumbers[od.Rank]
		if rankKnown && got.Observed.Rank != wantRank {
			if ok, reason := efAllowed(date, day, od, "rank"); ok {
				rankAllowed++
				t.Logf("[allow-listed] %s: EF rank got %q want %q — %s", date, got.Observed.Rank, wantRank, reason)
			} else {
				rankMiss++
				if shownRank < 40 {
					t.Errorf("%s: EF rank got %q want %q (oracle rank %d, title %q)",
						date, got.Observed.Rank, wantRank, od.Rank, od.Title)
					shownRank++
				}
			}
		}

		colourOK := false
		for _, c := range od.Colours {
			if efColourLetters[c] == got.Colour {
				colourOK = true
				break
			}
		}
		// Membership alone cannot catch a Rose regression: violet is a
		// member of every rose/violet pair by construction (Gaudete/
		// Laetare), so "got violet, want one of [rose violet]" passes even
		// if RG 131's Rose support (temporal_ef.go) were reverted entirely.
		// On the day the rose/violet pair actually names -- oracle rank 1,
		// the Sunday itself, not a weekday reusing its propers (which
		// carries a lower rank and is deliberately membership-only, this
		// file's own doc comment item 3) -- a colour set containing rose
		// demands rose specifically, not merely "some member".
		if colourOK && od.Rank == 1 && got.Colour != calendar.Rose {
			for _, c := range od.Colours {
				if c == "p" {
					colourOK = false
					break
				}
			}
		}
		if !colourOK && len(od.Colours) > 0 {
			if ok, reason := efAllowed(date, day, od, "colour"); ok {
				colourAllowed++
				t.Logf("[allow-listed] %s: EF colour got %q want one of %v — %s", date, got.Colour, od.Colours, reason)
			} else {
				colourMiss++
				if shownColour < 40 {
					t.Errorf("%s: EF colour got %q want one of %v (title %q)",
						date, got.Colour, od.Colours, od.Title)
					shownColour++
				}
			}
		}
	}
	t.Logf("EF oracle: %d checked, %d skipped(unmapped), %d season mismatches, "+
		"%d rank mismatches (%d allow-listed), %d colour mismatches (%d allow-listed)",
		total, skipped, seasonMiss, rankMiss, rankAllowed, colourMiss, colourAllowed)
	if seasonMiss > 0 {
		t.Fatalf("%d/%d EF season mismatches vs missalemeum — temporalEF is wrong", seasonMiss, total)
	}
	if rankMiss > 0 {
		t.Fatalf("%d/%d EF rank mismatches vs missalemeum (not allow-listed)", rankMiss, total)
	}
	if colourMiss > 0 {
		t.Fatalf("%d/%d EF colour mismatches vs missalemeum (not allow-listed)", colourMiss, total)
	}
}

// TestEFLectionaryKeysAreReachableSlugs asserts that every section name in the
// EF temporal lectionary is a slug the calendar can actually compute. A key
// nothing ever matches is dead data: the reading sits in the file, the lookup
// misses it, and the day silently falls back to the preceding Sunday's Mass —
// which looks like a plausible answer, so nothing downstream notices.
//
// This is not hypothetical. Three sections were filed as ef-lent-1-{wednesday,
// friday,saturday} while temporal_ef.go's efEmberSlug computes
// ef-lent-ember-{wed,fri,sat}, so the Lenten Ember days served Lent I Sunday's
// Mass for as long as the data existed. The keys were stale: they predate Lent
// being added to efEmberSlug, and scripts/genlect.go — which keys off
// day.Observed.Slug — would already write the correct names if re-run.
//
// It survived every existing test because the wrong answer is a real Mass, and
// it survived cross-checking against colitur (the sibling OCaml engine)
// because colitur had bootstrapped the same wrong keys from this very file.
// Two engines agreeing is not evidence when one was seeded from the other.
func TestEFLectionaryKeysAreReachableSlugs(t *testing.T) {
	raw, err := os.ReadFile("../caldata/tridentine-lectionary.ini")
	if err != nil {
		t.Fatalf("read lectionary: %v", err)
	}

	keys := map[string]bool{}
	for _, line := range strings.Split(string(raw), "\n") {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "[") && strings.HasSuffix(line, "]") {
			keys[line[1:len(line)-1]] = true
		}
	}
	if len(keys) == 0 {
		t.Fatal("no sections parsed from the lectionary")
	}

	sel := calendar.DefaultSelection()
	sel.Form = "old"
	layers := []calendar.Layer{caldata.Tridentine()}

	// Twelve years. Every key in the shipped file is reached within five (the
	// movable ones recur annually; the Ember and vigil days are the only
	// awkward cases and they occur every year too), so this is a bit over
	// double the margin actually needed. Widening it costs test time linearly
	// and buys nothing measurable — 46 years took 91s, this takes a quarter of
	// that — but narrowing below five would start reporting live keys as dead.
	seen := map[string]bool{}
	for d := time.Date(2005, 1, 1, 0, 0, 0, 0, time.UTC); d.Year() <= 2016; d = d.AddDate(0, 0, 1) {
		seen[calendar.Compute(d, sel, layers).Observed.Slug] = true
	}

	var dead []string
	for k := range keys {
		if !seen[k] {
			dead = append(dead, k)
		}
	}
	sort.Strings(dead)
	if len(dead) > 0 {
		t.Errorf("lectionary keys no computed slug ever matches (dead data, the day "+
			"silently falls back to the preceding Sunday): %v", dead)
	}
}