package calendar

import (
	"strings"
	"testing"
	"time"
)

func TestTemporalEFSeasons(t *testing.T) {
	cases := []struct {
		date   string
		season Season
	}{
		{"2025-01-01", Christmas},          // Circumcision
		{"2025-01-20", TimeAfterEpiphany},  // after II Sunday after Epiphany
		{"2025-02-16", Septuagesima},       // Septuagesima Sunday (easter-63)
		{"2025-03-05", Lent},               // Ash Wednesday
		{"2025-04-06", Passiontide},        // Passion Sunday (easter-14)
		{"2025-04-13", Passiontide},        // Palm Sunday
		{"2025-04-20", Easter_},            // Easter
		{"2025-06-08", Easter_},            // Pentecost (still Paschaltide)
		{"2025-06-15", TimeAfterPentecost}, // Trinity
		{"2025-06-22", TimeAfterPentecost}, // II Sunday after Pentecost
		{"2025-10-26", TimeAfterPentecost}, // Christ the King
		{"2025-11-30", Advent},             // I Sunday of Advent
		{"2025-12-25", Christmas},          // Nativity
	}
	for _, c := range cases {
		got := temporalEF(d(c.date))
		if got.Season != c.season {
			t.Errorf("temporalEF(%s).Season = %s, want %s", c.date, got.Season, c.season)
		}
	}
}

func TestTemporalEFChristTheKing(t *testing.T) {
	// EF: last Sunday of October (2025-10-26), not the last before Advent.
	if got := temporalEF(d("2025-10-26")); got.Cel.Slug != "ef-christ-the-king" {
		t.Errorf("2025-10-26 slug = %q want ef-christ-the-king", got.Cel.Slug)
	}
	if got := efChristTheKing(2025).Format("2006-01-02"); got != "2025-10-26" {
		t.Errorf("efChristTheKing(2025) = %s want 2025-10-26", got)
	}
}

// TestTemporalEFSundayRanks: RG 11-12 / RG 91 entry 6 -- Sundays of Advent,
// Lent and Passiontide, and Low Sunday, are I class; all others (including
// Septuagesima's own three Sundays and the ordinary Sundays after Epiphany/
// Pentecost) stay II class. Before the fix, only Advent I was I class; every
// other Advent/Lent Sunday was left at the generic-Sunday II-class default.
func TestTemporalEFSundayRanks(t *testing.T) {
	cases := []struct {
		date string
		want Rank
	}{
		{"2025-11-30", RankClass1}, // Advent I
		{"2025-12-07", RankClass1}, // Advent II
		{"2025-12-14", RankClass1}, // Advent III (Gaudete)
		{"2025-12-21", RankClass1}, // Advent IV
		{"2025-03-09", RankClass1}, // Lent I
		{"2025-03-16", RankClass1}, // Lent II
		{"2025-03-23", RankClass1}, // Lent III
		{"2025-03-30", RankClass1}, // Lent IV (Laetare)
		{"2025-04-06", RankClass1}, // Passion Sunday
		{"2025-04-13", RankClass1}, // Palm Sunday
		{"2025-04-27", RankClass1}, // Low Sunday
		{"2025-02-16", RankClass2}, // Septuagesima Sunday -- NOT I class
		{"2025-02-23", RankClass2}, // Sexagesima Sunday -- NOT I class
		{"2025-03-02", RankClass2}, // Quinquagesima Sunday -- NOT I class
		{"2025-06-22", RankClass2}, // II Sunday after Pentecost -- ordinary II class
	}
	for _, c := range cases {
		got := temporalEF(d(c.date))
		if got.Cel.Rank != c.want {
			t.Errorf("temporalEF(%s).Cel.Rank = %s, want %s (%s)", c.date, got.Cel.Rank, c.want, got.Cel.Slug)
		}
	}
}

// TestTemporalEFRoseSundays: RG 131 -- rose is permitted on Gaudete (Advent
// III) and Laetare (Lent IV), for that Sunday's own Office and Mass only.
// Before the fix, efColour had no Rose case at all.
func TestTemporalEFRoseSundays(t *testing.T) {
	if got := temporalEF(d("2025-12-14")).Cel.Colour; got != Rose {
		t.Errorf("Gaudete (2025-12-14) colour = %s, want rose", got)
	}
	if got := temporalEF(d("2025-03-30")).Cel.Colour; got != Rose {
		t.Errorf("Laetare (2025-03-30) colour = %s, want rose", got)
	}
	// The Advent/Lent Sundays either side stay violet -- rose is an indult for
	// that one Sunday, not a season colour.
	if got := temporalEF(d("2025-12-07")).Cel.Colour; got != Violet {
		t.Errorf("Advent II (2025-12-07) colour = %s, want violet", got)
	}
	if got := temporalEF(d("2025-03-23")).Cel.Colour; got != Violet {
		t.Errorf("Lent III (2025-03-23) colour = %s, want violet", got)
	}
}

// TestTemporalEFHolyThursdayColour: RG 128(b)/RG 122 -- Holy Thursday's Mass
// of Chrism and Mass in Cena Domini are white, a whole-day exception to
// Passiontide's violet. Good Friday and Holy Saturday, either side, stay
// violet (their own black/no-colour exceptions are a separate, unmodelled
// gap -- see RG 132, precedence_ef.go's own doc comments).
// TestTemporalEFTriduumColours pins all three days of the Sacred Triduum,
// which take three different colours for three different reasons.
//
// Renamed from TestTemporalEFHolyThursdayColour, which asserted Good Friday
// was violet "(unchanged)" -- encoding a gap this file's own comment used to
// call "separate, unmodelled". It is modelled now, so the test that pinned
// the gap had to move with it. A test asserting the absence of a feature
// passes for exactly as long as the feature is absent, which is not the same
// as being correct.
func TestTemporalEFTriduumColours(t *testing.T) {
	easter := d("2025-04-20")
	holyThu := easter.AddDate(0, 0, -3)
	goodFri := easter.AddDate(0, 0, -2)
	holySat := easter.AddDate(0, 0, -1)
	// RG 128(b)'s named exception list, and RG 122 affirmatively.
	if got := temporalEF(holyThu).Cel.Colour; got != White {
		t.Errorf("Holy Thursday colour = %s, want white", got)
	}
	// RG 128(b) excepts the day from Passiontide's violet; RG 132 assigns
	// black. missalemeum's own colour set for the day is "bv", black first.
	if got := temporalEF(goodFri).Cel.Colour; got != Black {
		t.Errorf("Good Friday colour = %s, want black (RG 128(b) + RG 132)", got)
	}
	// Holy Saturday IS still violet: RG 128(b)'s exception for it covers only
	// the deacon at the Easter Preconium and the celebrant at the renewal of
	// baptismal promises, not the day, and this model carries one colour per
	// day. Asserted in the other direction on purpose, so a careless "the
	// whole Triduum is black" change fails here.
	if got := temporalEF(holySat).Cel.Colour; got != Violet {
		t.Errorf("Holy Saturday colour = %s, want violet (unchanged)", got)
	}
}

// TestTemporalEFEmberDayRanks: RG 91 entry 18 -- the Ember days of Lent (and,
// unchanged, September and Advent) are II-class privileged ferias, not the
// ordinary III-class Lenten ferias around them. Before the fix, efEmberSlug
// had no Lent case at all, so Lent's Ember Wed/Fri/Sat fell through to the
// ordinary III-class Lenten-feria rank.
func TestTemporalEFEmberDayRanks(t *testing.T) {
	// Lent I Sunday 2025 = 2025-03-09; Ember Wed/Fri/Sat = +3/+5/+6.
	lentI := d("2025-03-09")
	for _, off := range []int{3, 5, 6} {
		day := lentI.AddDate(0, 0, off)
		got := temporalEF(day)
		if got.Cel.Rank != RankClass2 {
			t.Errorf("Lent Ember day %s rank = %s, want class-2 (%s)", day.Format("2006-01-02"), got.Cel.Rank, got.Cel.Slug)
		}
	}
}

// TestTemporalEFChristmastideBoundary pins RG 72's boundary and, just as
// importantly, the SEPARATION it required.
//
// RG 72: "Tempus natalicium decurrit a I Vesperis Nativitatis Domini usque ad
// diem 13 ianuarii INCLUSIVE." Christmas Time runs to 13 January, so 6-13
// January is the Epiphany section OF Christmas Time, not the beginning of Time
// after Epiphany. RG 119(a) backs it from the colour side, white "usque ad
// expletum tempus Epiphaniae".
//
// lectio ended Christmas Time on 5 January, so those eight days came out
// green. The fix could not be the boundary constant alone: efSeason both named
// the slugs and reported the season, so moving it renamed every slug in the
// window and orphaned the ef-time-after-epiphany-sunday-1 lectionary key. The
// season and the slug are now separate axes -- efSeason and efSlugSeason --
// and this test pins BOTH, because a future "simplification" that merges them
// again would pass any test that checked only one.
func TestTemporalEFChristmastideBoundary(t *testing.T) {
	for _, c := range []struct {
		date, season, slug string
	}{
		// Epiphany itself is inside Christmas Time, not the start of what
		// follows it. Its slug is unchanged.
		{"2026-01-06", "christmas", "ef-epiphany"},
		// The window: season christmas, slugs and week numbers still Epiphany's.
		{"2026-01-07", "christmas", "ef-time-after-epiphany-1-wednesday"},
		{"2026-01-11", "christmas", "ef-time-after-epiphany-sunday-1"},
		{"2026-01-12", "christmas", "ef-time-after-epiphany-1-monday"},
		// 13 January is INCLUSIVE -- the last day of Christmas Time. It carries
		// the Commemoration of the Baptism, so only the season is asserted.
		{"2026-01-13", "christmas", ""},
		// 14 January is the first day that is genuinely Time after Epiphany.
		{"2026-01-14", "time-after-epiphany", ""},
		// The other end, unchanged: 5 January is Christmas Time by the old
		// boundary too, so a regression that moved the boundary the wrong way
		// would not show here -- which is why 14 January above is asserted.
		{"2026-01-05", "christmas", ""},
	} {
		got := temporalEF(d(c.date))
		if string(got.Season) != c.season {
			t.Errorf("%s: season = %q, want %q (RG 72: Christmas Time runs to 13 January inclusive)",
				c.date, got.Season, c.season)
		}
		if c.slug != "" && got.Cel.Slug != c.slug {
			t.Errorf("%s: slug = %q, want %q -- the SLUG season must stay Epiphany's here; "+
				"if this fails with an ef-christmas-* slug, efSeason and efSlugSeason have been "+
				"merged again and the lectionary keys are orphaned", c.date, got.Cel.Slug, c.slug)
		}
	}
	// The colour follows from the season, and is the reason any of this
	// matters: eight days a year were green that should be white.
	for _, day := range []string{"2026-01-07", "2026-01-09", "2026-01-12"} {
		if got := temporalEF(d(day)).Cel.Colour; got != White {
			t.Errorf("%s: colour = %s, want white (RG 119(a), following from the season)", day, got)
		}
	}
}

// TestTemporalEFEpiphanyWeekAnchor pins where the weeks after Epiphany are
// counted from. They are numbered from the FIRST SUNDAY after Epiphany, not
// from Epiphany itself -- the Sunday carries the Mass the week is named for
// ("Dominica I post Epiphaniam"), while Epiphany is a feast inside Christmas
// Time (RG 72), not the head of a numbered week.
//
// Counting from 6 January put every week one too high, all year until
// Septuagesima cut the season short.
func TestTemporalEFEpiphanyWeekAnchor(t *testing.T) {
	// 2026: Epiphany is a Tuesday, so the first Sunday after it is 11 January.
	for _, c := range []struct {
		date string
		week int
	}{
		{"2026-01-14", 1}, // Wednesday of the week running from 11 January
		{"2026-01-17", 1}, // still that week
		{"2026-01-20", 2},
		{"2026-01-27", 3},
	} {
		if got := temporalEF(d(c.date)).Week; got != c.week {
			t.Errorf("%s: week = %d, want %d (weeks after Epiphany count from the "+
				"first Sunday after it, not from 6 January)", c.date, got, c.week)
		}
	}
	// 2028: Epiphany falls ON a Thursday and 9 January is the Sunday; but the
	// year that matters for the off-by-one is one where Epiphany is itself a
	// Sunday, since then "the first Sunday AFTER Epiphany" is the following
	// week and a naive same-day anchor would be seven days out.
	y := 0
	for c := 2005; c <= 2050; c++ {
		if time.Date(c, time.January, 6, 0, 0, 0, 0, time.UTC).Weekday() == time.Sunday {
			y = c
			break
		}
	}
	if y == 0 {
		t.Fatal("no year in 2005..2050 has Epiphany on a Sunday -- adjust this test")
	}
	anchor := firstSundayAfterEpiphany(y)
	if anchor.Day() == 6 {
		t.Errorf("%d: Epiphany is a Sunday and the anchor landed on it (%s); the "+
			"first Sunday AFTER Epiphany is the next one", y, anchor.Format("2006-01-02"))
	}
	if got := temporalEF(anchor).Week; got != 1 {
		t.Errorf("%d: the first Sunday after Epiphany (%s) should be week 1, got %d",
			y, anchor.Format("2006-01-02"), got)
	}
}

// TestTemporalEFBVMSaturday pins RG 78, the votive Office of Our Lady on
// Saturday: "In sabbatis, in quibus occurrit Officium de feria IV classis, fit
// de sancta Maria in sabbato." A Saturday whose office would otherwise be a
// IV-class feria keeps Our Lady's office instead, and it is white.
//
// Two things are asserted in opposite directions on purpose. The office
// applies only where the feria really is IV class, so a Saturday in Lent or
// Advent -- III class ferias, violet -- must NOT turn white; and the slug must
// NOT change, because the day's readings are still the feria's and a bespoke
// slug would recur many times a year.
func TestTemporalEFBVMSaturday(t *testing.T) {
	// Ordinary per-annum Saturdays: IV class, so Our Lady's office, white.
	for _, day := range []string{"2026-06-20", "2026-06-27", "2026-07-04", "2026-10-31"} {
		got := temporalEF(d(day))
		if got.Cel.Colour != White {
			t.Errorf("%s: colour = %s, want white (RG 78, Our Lady on Saturday)", day, got.Cel.Colour)
		}
		if got.Cel.Rank != RankClass4 {
			t.Errorf("%s: rank = %v, want class-4 -- the office does not change the rank", day, got.Cel.Rank)
		}
		if !strings.HasPrefix(got.Cel.Slug, "ef-time-after-pentecost-") {
			t.Errorf("%s: slug = %q, want the ferial slug unchanged -- the readings are "+
				"still the feria's and a bespoke slug would recur many times a year", day, got.Cel.Slug)
		}
	}
	// Saturdays whose feria is NOT IV class keep their own colour. Lent and
	// Advent ferias are III class and violet; a fix that whitened every
	// Saturday would fail here.
	for _, c := range []struct {
		day    string
		colour Colour
	}{
		{"2026-03-07", Violet}, // Saturday in Lent
		{"2026-12-05", Violet}, // Saturday in Advent
		{"2026-04-04", Violet}, // Holy Saturday -- I class, privileged
	} {
		if got := temporalEF(d(c.day)).Cel.Colour; got != c.colour {
			t.Errorf("%s: colour = %s, want %s -- RG 78 applies only where the feria is IV class",
				c.day, got, c.colour)
		}
	}
}

// TestTemporalEFRogationDays pins RG 87's Minor Litanies: "Litaniae minores seu
// Rogationes, per se, assignantur feriis II, III et IV ante festum Ascensionis
// Domini." Easter+36 and +37 are that Monday and Tuesday; RG 128(d) makes them
// violet, "for the procession and Mass of the Greater and Lesser Litanies" --
// a penitential note inside white Paschaltide.
//
// The Wednesday is asserted in the opposite direction on purpose. Easter+38 is
// by construction the Vigil of the Ascension, II class, which wins the day; the
// rubric asks for a COMMEMORATION there, which this function cannot express
// since it returns one office per day. A change that extended the Rogation
// branch to +38 to "complete" the rubric would silently displace the Vigil, and
// this test is what stops it.
func TestTemporalEFRogationDays(t *testing.T) {
	// 2027: Easter is 28 March, so the Rogation days are 3-5 May and the
	// Monday is unimpeded that year.
	easter := d("2027-03-28")
	for off, want := range map[int]string{36: "ef-rogation-monday", 37: "ef-rogation-tuesday"} {
		day := easter.AddDate(0, 0, off)
		got := temporalEF(day)
		if got.Cel.Slug != want {
			t.Errorf("Easter+%d (%s): slug = %q, want %q", off, day.Format("2006-01-02"), got.Cel.Slug, want)
		}
		if got.Cel.Colour != Violet {
			t.Errorf("Easter+%d (%s): colour = %s, want violet (RG 128(d))",
				off, day.Format("2006-01-02"), got.Cel.Colour)
		}
	}
	// Easter+38 is the Ascension's Vigil and must stay so.
	if got := temporalEF(easter.AddDate(0, 0, 38)); got.Cel.Slug != "ef-ascension-vigil" {
		t.Errorf("Easter+38: slug = %q, want ef-ascension-vigil -- the Rogation Wednesday's "+
			"commemoration cannot be built here without displacing the Vigil", got.Cel.Slug)
	}
}