package calendar_test

// Tests for the memoised EF transfer plan (transfer_plan_cache.go). These
// live in the external test package (calendar_test), exercising the real
// tridentine sanctoral data through the public Compute entry point, the same
// style precedence_ef_repro_test.go already uses -- the risk this cache
// introduces is entirely about whether the CACHE KEY captures every real
// input, which can only be demonstrated by varying an input through Compute
// and checking the observed office actually changes, not by testing the
// cache's internals in isolation.

import (
	"sync"
	"testing"
	"time"

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

// TestEFTransferPlanCacheInvalidatesOnOverlay is THE bad-key test: it warms
// the memoised plan for (2008, EF, the shipped calendar) across a whole
// week -- mobile.Days's own access pattern -- then asks the SAME year
// through a layer stack with ONE user overlay added (suppressing the
// Annunciation) and asserts the observed office on 31 March and 1 April
// CHANGES accordingly.
//
// What is varied: the layer stack / merged sanctoral content (a user
// overlay), holding year and Selection fixed. This is deliberately not a
// synthetic scenario: with the Annunciation present, its RG 96(a) proper
// seat (the Monday after Low Sunday, RG 97/98) forces St Joseph -- also
// impeded that year -- to walk one day further, to 1 April
// (TestEFTwoTransfersDoNotCollide already pins this). Suppress the
// Annunciation and it no longer claims that Monday, so Joseph lands ON it,
// 31 March, and 1 April reverts to an ordinary feria. Verified empirically
// against the pre-cache code before this test was written (both outcomes
// reproduced exactly as asserted below).
//
// A cache keyed on year alone -- or on year+sel without the merged content
// -- would serve 2008's BASE-CALENDAR plan back for the overlaid query too,
// since both share every other key component; this test fails loudly if
// that happens (it would see 1 April still reporting Joseph, and 31 March
// still reporting the Annunciation, from the first, unrelated warm-up).
func TestEFTransferPlanCacheInvalidatesOnOverlay(t *testing.T) {
	sel := calendar.DefaultSelection()
	sel.Form = "old"
	base := caldata.Tridentine()
	baseLayers := []calendar.Layer{base}

	compute := func(layers []calendar.Layer, date string) string {
		d, err := time.Parse("2006-01-02", date)
		if err != nil {
			t.Fatalf("bad test date %q: %v", date, err)
		}
		return calendar.Compute(d.UTC(), sel, layers).Observed.Slug
	}

	// Warm the cache for (2008, sel, base-only-hash) across a whole week,
	// exactly like mobile.Days resolving seven consecutive dates against the
	// same Prepared layer stack.
	for _, date := range []string{
		"2008-03-26", "2008-03-27", "2008-03-28", "2008-03-29",
		"2008-03-30", "2008-03-31", "2008-04-01", "2008-04-02",
	} {
		compute(baseLayers, date)
	}
	if got := compute(baseLayers, "2008-03-31"); got != "annunciation-of-the-blessed-virgin-mary" {
		t.Fatalf("baseline 2008-03-31 = %q, want annunciation-of-the-blessed-virgin-mary", got)
	}
	if got := compute(baseLayers, "2008-04-01"); got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Fatalf("baseline 2008-04-01 = %q, want joseph-spouse-of-the-bl-virgin-mary", got)
	}

	// Same year, same Selection, ONE overlay layer added: suppress the
	// Annunciation. If the cache key omitted the sanctoral content, these
	// two calls would silently return the baseline plan warmed above.
	overlay := calendar.Layer{ID: "user", Cels: map[string]calendar.RawCelebration{
		"annunciation-of-the-blessed-virgin-mary": {
			Fields:   map[string]string{"suppress": "true"},
			Variants: map[string]map[string]string{},
		},
	}}
	overlaid := []calendar.Layer{base, overlay}

	if got := compute(overlaid, "2008-03-31"); got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("overlaid 2008-03-31 = %q, want joseph-spouse-of-the-bl-virgin-mary (Joseph now lands here, the Annunciation no longer claims it)", got)
	}
	if got := compute(overlaid, "2008-04-01"); got == "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("overlaid 2008-04-01 = %q, want NOT joseph (a stale cache hit from the base-calendar warm-up)", got)
	}

	// And the base calendar's own answer must be unaffected by having since
	// computed the overlaid one -- the two keys must not collide either way.
	if got := compute(baseLayers, "2008-03-31"); got != "annunciation-of-the-blessed-virgin-mary" {
		t.Errorf("base calendar 2008-03-31 after overlaid query = %q, want annunciation-of-the-blessed-virgin-mary (unaffected)", got)
	}
	if got := compute(baseLayers, "2008-04-01"); got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("base calendar 2008-04-01 after overlaid query = %q, want joseph-spouse-of-the-bl-virgin-mary (unaffected)", got)
	}
}

// TestEFTransferPlanCacheInvalidatesOnYear is a lighter companion: the same
// week-then-query pattern, varying the YEAR instead of the overlay (2008 vs
// 2035, both real Joseph/Annunciation collision years -- see
// TestEFTwoTransfersDoNotCollide -- but with different transfer targets).
// year is an explicit field of the cache key already, so this mainly guards
// against a key struct refactor accidentally dropping it; the overlay test
// above is the one guarding the field that is easy to omit by mistake.
func TestEFTransferPlanCacheInvalidatesOnYear(t *testing.T) {
	sel := calendar.DefaultSelection()
	sel.Form = "old"
	layers := []calendar.Layer{caldata.Tridentine()}

	compute := func(date string) string {
		d, err := time.Parse("2006-01-02", date)
		if err != nil {
			t.Fatalf("bad test date %q: %v", date, err)
		}
		return calendar.Compute(d.UTC(), sel, layers).Observed.Slug
	}

	if got := compute("2008-04-01"); got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Fatalf("2008-04-01 = %q, want joseph-spouse-of-the-bl-virgin-mary", got)
	}
	// 2035's Joseph lands on 2035-04-03, not 04-01 (a later Easter shifts the
	// whole window). If the cache ignored the year, this would wrongly
	// return 2008's plan.
	if got := compute("2035-04-01"); got == "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("2035-04-01 = %q, want NOT joseph (that is 2008's landing day, not 2035's)", got)
	}
	if got := compute("2035-04-03"); got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("2035-04-03 = %q, want joseph-spouse-of-the-bl-virgin-mary", got)
	}
}

// TestEFTransferPlanCacheConcurrentUse exercises the memoised plan from many
// goroutines at once -- gomobile may call Day/Days in from multiple threads,
// and none of the tests above (all sequential) can catch a data race on the
// shared cache map/list. Run with -race; it is the actual proof of the
// "thread-safe" claim, not merely built with a mutex and assumed correct.
func TestEFTransferPlanCacheConcurrentUse(t *testing.T) {
	sel := calendar.DefaultSelection()
	sel.Form = "old"
	base := caldata.Tridentine()
	overlay := calendar.Layer{ID: "user", Cels: map[string]calendar.RawCelebration{
		"annunciation-of-the-blessed-virgin-mary": {
			Fields:   map[string]string{"suppress": "true"},
			Variants: map[string]map[string]string{},
		},
	}}
	baseLayers := []calendar.Layer{base}
	overlaidLayers := []calendar.Layer{base, overlay}
	// A third, disjoint key exercising the occupancy-index collision path
	// (TestEFOccupancyIndexDetectsSameDateClass1Collision) concurrently too
	// -- the plan alone does not touch efOccupancyIndex.occupied unless a
	// candidate's own precedence doesn't already decide it, which the
	// Joseph/Annunciation scenario above never triggers (see that test's own
	// doc comment).
	collideLayers := []calendar.Layer{base, {ID: "user", Cels: map[string]calendar.RawCelebration{
		"zz-test-alpha": {Fields: map[string]string{"rank": "class-1", "date": "07-06", "name.en": "ZZ Test Alpha"}, Variants: map[string]map[string]string{}},
		"zz-test-beta":  {Fields: map[string]string{"rank": "class-1", "date": "07-06", "name.en": "ZZ Test Beta"}, Variants: map[string]map[string]string{}},
	}}}

	years := []int{2008, 2011, 2035, 2046}

	var wg sync.WaitGroup
	for g := 0; g < 15; g++ {
		g := g
		wg.Add(1)
		go func() {
			defer wg.Done()
			switch g % 3 {
			case 0:
				for i := 0; i < 6; i++ {
					y := years[(g+i)%len(years)]
					for _, md := range []string{"03-19", "03-31", "04-01"} {
						d, err := time.Parse("2006-01-02", time.Date(y, 1, 1, 0, 0, 0, 0, time.UTC).Format("2006")+"-"+md)
						if err != nil {
							t.Errorf("bad date: %v", err)
							return
						}
						_ = calendar.Compute(d.UTC(), sel, baseLayers).Observed.Slug
					}
				}
			case 1:
				for i := 0; i < 6; i++ {
					y := years[(g+i)%len(years)]
					for _, md := range []string{"03-19", "03-31", "04-01"} {
						d, err := time.Parse("2006-01-02", time.Date(y, 1, 1, 0, 0, 0, 0, time.UTC).Format("2006")+"-"+md)
						if err != nil {
							t.Errorf("bad date: %v", err)
							return
						}
						_ = calendar.Compute(d.UTC(), sel, overlaidLayers).Observed.Slug
					}
				}
			default:
				for i := 0; i < 6; i++ {
					for _, ymd := range []string{"2026-07-06", "2026-07-07", "2026-07-08"} {
						d, err := time.Parse("2006-01-02", ymd)
						if err != nil {
							t.Errorf("bad date: %v", err)
							return
						}
						_ = calendar.Compute(d.UTC(), sel, collideLayers).Observed.Slug
					}
				}
			}
		}()
	}
	wg.Wait()

	// After the concurrent hammering, correctness must still hold for all
	// three keys -- the concurrency test is not a substitute for the
	// correctness tests above, so re-assert their outcomes here too.
	d, _ := time.Parse("2006-01-02", "2008-04-01")
	if got := calendar.Compute(d.UTC(), sel, baseLayers).Observed.Slug; got != "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("after concurrent use, base 2008-04-01 = %q, want joseph-spouse-of-the-bl-virgin-mary", got)
	}
	if got := calendar.Compute(d.UTC(), sel, overlaidLayers).Observed.Slug; got == "joseph-spouse-of-the-bl-virgin-mary" {
		t.Errorf("after concurrent use, overlaid 2008-04-01 = %q, want NOT joseph", got)
	}
	d2, _ := time.Parse("2006-01-02", "2026-07-06")
	if got := calendar.Compute(d2.UTC(), sel, collideLayers).Observed.Slug; got != "ef-time-after-pentecost-6-monday" {
		t.Errorf("after concurrent use, colliding 2026-07-06 = %q, want ef-time-after-pentecost-6-monday", got)
	}
}

// TestEFOccupancyIndexDetectsSameDateClass1Collision covers a path the tests
// above do not: efOccupancyIndex.occupied's use from computeEF's
// transferIfImpededEF call site (the per-candidate fallback for a class-1
// entry efTransferPlan judged NOT impeded by temporal precedence alone), and
// efOccupancyIndex's own use inside efTransferPlan's initial impeded check
// (occupiedByClass1(when, cel.Slug) -- "does some OTHER fixed-date class-1
// SANCTORAL feast already sit on `when`", the doc comment's own example, RG
// 97/98). Neither TestEFTwoTransfersDoNotCollide nor the overlay/year tests
// above exercise it: St Joseph and the Annunciation are impeded by HOLY
// WEEK'S OWN temporal precedence, on DIFFERENT original dates -- never by
// colliding with each other's original date -- so no existing test had ever
// driven two class-1 SANCTORAL entries onto the exact same calendar date.
//
// A synthetic overlay is used because no two class-1 feasts share a fixed
// date in the shipped 1962 calendar (an ordinary Time-after-Pentecost
// Monday, 6 July 2026, was checked empirically before writing this test:
// alone, a single synthetic class-1 entry there is simply observed, since
// nothing outranks or occupies it; the real collision case exists only by
// construction).
//
// What is varied: whether a SECOND class-1 entry shares the first one's
// date -- both entries otherwise identical (rank class-1, real content
// unrelated to any liturgical rule under test). If efOccupancyIndex failed
// to detect the collision (or wrongly matched exceptSlug against ITSELF,
// the most dangerous failure shape -- see the mutation proof below), 6 July
// would keep reporting the lone entry regardless.
func TestEFOccupancyIndexDetectsSameDateClass1Collision(t *testing.T) {
	sel := calendar.DefaultSelection()
	sel.Form = "old"
	base := caldata.Tridentine()

	compute := func(layers []calendar.Layer, date string) string {
		d, err := time.Parse("2006-01-02", date)
		if err != nil {
			t.Fatalf("bad test date %q: %v", date, err)
		}
		return calendar.Compute(d.UTC(), sel, layers).Observed.Slug
	}

	alpha := calendar.RawCelebration{
		Fields:   map[string]string{"rank": "class-1", "date": "07-06", "name.en": "ZZ Test Alpha"},
		Variants: map[string]map[string]string{},
	}
	beta := calendar.RawCelebration{
		Fields:   map[string]string{"rank": "class-1", "date": "07-06", "name.en": "ZZ Test Beta"},
		Variants: map[string]map[string]string{},
	}

	soloLayers := []calendar.Layer{base, {ID: "user", Cels: map[string]calendar.RawCelebration{
		"zz-test-alpha": alpha,
	}}}
	collideLayers := []calendar.Layer{base, {ID: "user", Cels: map[string]calendar.RawCelebration{
		"zz-test-alpha": alpha,
		"zz-test-beta":  beta,
	}}}

	// Alone, alpha is simply observed on its own date: nothing occupies 6
	// July, so efTransferPlan judges it unimpeded and computeEF's fallback
	// (occ.occupied via transferIfImpededEF) must agree and leave it there.
	if got := compute(soloLayers, "2026-07-06"); got != "zz-test-alpha" {
		t.Fatalf("alpha alone, 2026-07-06 = %q, want zz-test-alpha", got)
	}

	// Add beta on the SAME date. Both now occupy each other's date, so BOTH
	// are impeded (RG 97/98) and transfer forward in table/impeded-first
	// order (alpha to 7 July, beta to 8 -- empirically confirmed before
	// writing this test); 6 July itself reverts to the ordinary temporal
	// office, since NEITHER candidate keeps its place.
	if got := compute(collideLayers, "2026-07-06"); got != "ef-time-after-pentecost-6-monday" {
		t.Errorf("alpha+beta colliding, 2026-07-06 = %q, want ef-time-after-pentecost-6-monday (a stale/broken occupancy index would still show zz-test-alpha)", got)
	}
	if got := compute(collideLayers, "2026-07-07"); got != "zz-test-alpha" {
		t.Errorf("alpha+beta colliding, 2026-07-07 = %q, want zz-test-alpha (transferred here)", got)
	}
	if got := compute(collideLayers, "2026-07-08"); got != "zz-test-beta" {
		t.Errorf("alpha+beta colliding, 2026-07-08 = %q, want zz-test-beta (transferred here)", got)
	}

	// And alpha alone (no beta) must be unaffected by having since computed
	// the colliding scenario -- the two overlays must not cross-contaminate
	// the shared cache.
	if got := compute(soloLayers, "2026-07-06"); got != "zz-test-alpha" {
		t.Errorf("alpha alone after collision query, 2026-07-06 = %q, want zz-test-alpha (unaffected)", got)
	}
}