package calendar

import (
	"context"
	"io"
	"log/slog"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/store"
)

func testStore(t *testing.T) (*store.Store, int64) {
	t.Helper()
	st, err := store.Open(filepath.Join(t.TempDir(), "school.db"))
	if err != nil {
		t.Fatalf("open: %v", err)
	}
	t.Cleanup(func() { _ = st.Close() })
	if err := st.Migrate(context.Background()); err != nil {
		t.Fatalf("migrate: %v", err)
	}
	if err := st.SeedChildren(context.Background(), "Harry"); err != nil {
		t.Fatalf("seed: %v", err)
	}
	child, err := st.ChildByName(context.Background(), "Harry")
	if err != nil || child == nil {
		t.Fatalf("child: %v %v", child, err)
	}
	return st, child.ID
}

// seedEvent stores one calendar event for a child.
func seedEvent(t *testing.T, st *store.Store, childID int64, title string, due time.Time, importance string, ref string) store.Item {
	t.Helper()
	item := store.Item{
		Source:      "compass",
		Type:        "event",
		Title:       title,
		Body:        title + "\nTeacher(s): KSH",
		DueAt:       &due,
		URL:         "https://example.invalid/Organise/Calendar/",
		SourcePage:  "calendar",
		Importance:  importance,
		ExternalRef: ref,
	}
	if _, _, err := st.UpsertItems(context.Background(), childID, []store.Item{item}); err != nil {
		t.Fatalf("upsert: %v", err)
	}
	items, err := st.ItemsForChild(context.Background(), childID)
	if err != nil {
		t.Fatalf("items: %v", err)
	}
	for _, it := range items {
		if it.ExternalRef == ref {
			return it
		}
	}
	t.Fatalf("seeded item %q not found", ref)
	return store.Item{}
}

func silentLogger() *slog.Logger { return slog.New(slog.NewTextHandler(io.Discard, nil)) }

func TestSyncIsIdempotent(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	seedEvent(t, st, childID, "End of Year Senior Music Concert - HALL - KSH", due, "high", "concert")
	ha := newFakeHA(t, "calendar.school")
	c := testClient(t, ha.URL, "calendar.school")

	first, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("first Sync: %v", err)
	}
	if first.Candidates != 1 || first.Created != 1 || first.Failed != 0 {
		t.Fatalf("first result = %+v", first)
	}
	if ha.created() != 1 {
		t.Fatalf("first Sync made %d create calls", ha.created())
	}

	// The item now carries the Home Assistant event id, so it is no longer a
	// candidate: a re-run writes nothing.
	second, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("second Sync: %v", err)
	}
	if second.Candidates != 0 || second.Created != 0 {
		t.Fatalf("second result = %+v", second)
	}
	if ha.created() != 1 {
		t.Fatalf("re-run duplicated the event (%d create calls)", ha.created())
	}
}

func TestSyncAdoptsAnEventByItsMarker(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	item := seedEvent(t, st, childID, "Year 11 Assembly - HALL - CMA", due, "high", "assembly")
	ha := newFakeHA(t, "calendar.school")
	// The event exists in Home Assistant, but the item has no id (a crashed
	// run, or a Home Assistant that reports no uid). The marker adopts it.
	ha.events = []map[string]any{{
		"uid":         "uid-existing",
		"summary":     "Harry — Year 11 Assembly - HALL - CMA",
		"description": "source: " + Marker(item.ID),
		"start":       due.Format(time.RFC3339),
	}}
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Created != 0 || res.Skipped != 1 {
		t.Fatalf("result = %+v", res)
	}
	if ha.created() != 0 {
		t.Fatalf("Sync wrote a duplicate (%d create calls)", ha.created())
	}
	ci, err := st.CalendarItemByID(ctx, item.ID)
	if err != nil {
		t.Fatalf("item: %v", err)
	}
	if ci.HAEventUID != "uid-existing" {
		t.Errorf("adopted uid = %q", ci.HAEventUID)
	}
}

func TestSyncRecordsALoudFailure(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	item := seedEvent(t, st, childID, "Tour to China photo - THEATRE", due, "high", "photo")
	ha := newFakeHA(t, "calendar.school")
	ha.failCreate = true
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Failed != 1 || len(res.Errors) != 1 {
		t.Fatalf("result = %+v", res)
	}
	summary, err := st.CalendarPushSummary(ctx)
	if err != nil {
		t.Fatalf("summary: %v", err)
	}
	if summary.Failed != 1 || summary.Last == nil || summary.Last.OK {
		t.Fatalf("push summary = %+v", summary)
	}
	if !strings.Contains(summary.Last.Error, "calendar is busy") {
		t.Errorf("recorded error loses the reason: %q", summary.Last.Error)
	}
	// A failed write leaves the item as a candidate, so a later run retries it.
	ci, err := st.CalendarItemByID(ctx, item.ID)
	if err != nil {
		t.Fatalf("item: %v", err)
	}
	if ci.HAEventUID != "" {
		t.Errorf("failed item should not carry an event id, got %q", ci.HAEventUID)
	}
}

func TestSyncDryRunWritesNothing(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	seedEvent(t, st, childID, "Senior Concert Band rehearsal - ENS", due, "high", "band")
	ha := newFakeHA(t, "calendar.school")
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: time.Now(), DryRun: true}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Created != 1 || !res.DryRun {
		t.Fatalf("result = %+v", res)
	}
	if ha.created() != 0 {
		t.Fatalf("dry run wrote %d events", ha.created())
	}
}

func TestSyncWindowIsTodayAndFuture(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	now := time.Now()
	day := StartOfDay(now)

	seedEvent(t, st, childID, "5 - 11HLEGB5 - D8 - LHT", now.Add(3*time.Hour), "normal", "lesson")
	seedEvent(t, st, childID, "Yesterday excursion - CITY", day.Add(-time.Hour), "high", "yesterday")
	seedEvent(t, st, childID, "Year 11 Assembly - HALL", day.Add(time.Minute), "high", "today")

	ha := newFakeHA(t, "calendar.school")
	c := testClient(t, ha.URL, "calendar.school")

	candidates, err := st.CalendarCandidates(ctx, nil, nil, day, 0)
	if err != nil {
		t.Fatalf("candidates: %v", err)
	}
	// A routine lesson is never high, and yesterday is behind the window. The
	// event earlier today stays a candidate: a scan that runs late in the day
	// must still record today's school events.
	if len(candidates) != 1 || candidates[0].Title != "Year 11 Assembly - HALL" {
		t.Fatalf("candidates = %+v", candidates)
	}
	res, err := Sync(ctx, st, c, Options{Now: now}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Candidates != 1 || res.Created != 1 || ha.created() != 1 {
		t.Fatalf("result = %+v (create calls %d)", res, ha.created())
	}
}

func TestSyncReportsAReadFailureInsteadOfWritingBlind(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	seedEvent(t, st, childID, "Year 11 Assembly - HALL", due, "high", "assembly")
	ha := newFakeHA(t, "calendar.school")
	ha.Close() // the calendar is unreachable
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Failed != 1 || res.Created != 0 {
		t.Fatalf("result = %+v", res)
	}
	if !strings.Contains(res.Errors[0], "reading existing events failed") {
		t.Errorf("error = %q", res.Errors[0])
	}
}

// TestSyncWritesASchoolWideEventOnce proves the shared Compass week calendar is
// not duplicated: one event stored against both children is written once, and
// both children's items record the same Home Assistant event id.
func TestSyncWritesASchoolWideEventOnce(t *testing.T) {
	ctx := context.Background()
	st, harryID := testStore(t)
	if err := st.SeedChildren(ctx, "Finn"); err != nil {
		t.Fatalf("seed finn: %v", err)
	}
	finn, err := st.ChildByName(ctx, "Finn")
	if err != nil || finn == nil {
		t.Fatalf("finn: %v %v", finn, err)
	}

	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	harryItem := seedEvent(t, st, harryID, "Year 11 Assembly - HALL - CMA", due, "high", "assembly")
	finnItem := seedEvent(t, st, finn.ID, "Year 11 Assembly - HALL - CMA", due, "high", "assembly")

	ha := newFakeHA(t, "calendar.school")
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("Sync: %v", err)
	}
	if res.Candidates != 1 || res.Created != 1 {
		t.Fatalf("result = %+v", res)
	}
	if ha.created() != 1 {
		t.Fatalf("school-wide event was written %d times", ha.created())
	}
	// A school-wide event carries just its title, not a child's name.
	if got := str(ha.lastCreate["summary"]); got != "Year 11 Assembly - HALL - CMA" {
		t.Errorf("summary = %q", got)
	}
	uid := res.Events[0].UID
	if uid == "" {
		t.Fatal("event written without a Home Assistant id")
	}
	for _, id := range []int64{harryItem.ID, finnItem.ID} {
		ci, err := st.CalendarItemByID(ctx, id)
		if err != nil || ci == nil {
			t.Fatalf("item %d: %v %v", id, ci, err)
		}
		if ci.HAEventUID != uid {
			t.Errorf("item %d uid = %q, want %q", id, ci.HAEventUID, uid)
		}
	}
}

// TestSyncWithoutEventIDsStillNeverDuplicates proves the fallback path: when
// Home Assistant reports no event id, the item keeps the description marker as
// its reference, so a re-run writes nothing.
func TestSyncWithoutEventIDsStillNeverDuplicates(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	due := time.Now().Add(4 * time.Hour).UTC().Truncate(time.Minute)
	item := seedEvent(t, st, childID, "Year 11 Assembly - HALL", due, "high", "assembly")

	ha := newFakeHA(t, "calendar.school")
	ha.returnUID = false
	c := testClient(t, ha.URL, "calendar.school")

	first, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("first Sync: %v", err)
	}
	if first.Created != 1 || ha.created() != 1 {
		t.Fatalf("first result = %+v (create calls %d)", first, ha.created())
	}
	ci, err := st.CalendarItemByID(ctx, item.ID)
	if err != nil || ci == nil {
		t.Fatalf("item: %v %v", ci, err)
	}
	if ci.HAEventUID != Marker(item.ID) {
		t.Errorf("reference = %q, want the description marker %q", ci.HAEventUID, Marker(item.ID))
	}

	second, err := Sync(ctx, st, c, Options{Now: time.Now()}, silentLogger())
	if err != nil {
		t.Fatalf("second Sync: %v", err)
	}
	if second.Candidates != 0 || second.Created != 0 {
		t.Fatalf("second result = %+v", second)
	}
	if ha.created() != 1 {
		t.Fatalf("re-run duplicated the event (%d create calls)", ha.created())
	}
}

// seedCalendarItem stores one item and returns it.
func seedCalendarItem(t *testing.T, st *store.Store, childID int64, item store.Item) store.Item {
	t.Helper()
	if _, _, err := st.UpsertItems(context.Background(), childID, []store.Item{item}); err != nil {
		t.Fatalf("upsert: %v", err)
	}
	items, err := st.ItemsForChild(context.Background(), childID)
	if err != nil {
		t.Fatalf("items: %v", err)
	}
	for _, it := range items {
		if it.ExternalRef == item.ExternalRef {
			return it
		}
	}
	t.Fatalf("seeded item %q not found", item.ExternalRef)
	return store.Item{}
}

// TestSyncWritesPeriodsWorkAndOverdueOnce proves FR-8: a child's own periods,
// the work due in the future and the overdue work all reach the calendar, and a
// re-run adds nothing. Submitted work is never written.
func TestSyncWritesPeriodsWorkAndOverdueOnce(t *testing.T) {
	ctx := context.Background()
	st, childID := testStore(t)
	loc := time.Local
	now := StartOfDay(time.Now().In(loc)).Add(6 * time.Hour)
	period := now.Add(2 * time.Hour).Truncate(time.Minute)
	overdue := now.AddDate(0, 0, -3).Truncate(time.Minute)
	future := now.AddDate(0, 0, 3).Truncate(time.Minute)

	seedCalendarItem(t, st, childID, store.Item{
		Source: "compass", Type: "event", Subject: "7SCF",
		Title: "1 - 7SCF - H14LAB - KNI", DueAt: &period,
		SourcePage: "child-profile", Importance: "normal", ExternalRef: "period-1",
	})
	seedCalendarItem(t, st, childID, store.Item{
		Source: "compass", Type: "task", Subject: "Science", Title: "Lab report",
		Body: "Status: Overdue", DueAt: &overdue, Importance: "high", ExternalRef: "overdue-1",
	})
	seedCalendarItem(t, st, childID, store.Item{
		Source: "compass", Type: "task", Subject: "Maths", Title: "Exercise 4",
		Body: "Status: Pending", DueAt: &future, Importance: "normal", ExternalRef: "due-1",
	})
	seedCalendarItem(t, st, childID, store.Item{
		Source: "compass", Type: "task", Subject: "English", Title: "Done essay",
		Body: "Status: On Time", DueAt: &overdue, Importance: "normal", ExternalRef: "submitted-1",
	})

	ha := newFakeHA(t, "calendar.school")
	c := testClient(t, ha.URL, "calendar.school")

	res, err := Sync(ctx, st, c, Options{Now: now}, silentLogger())
	if err != nil {
		t.Fatalf("first Sync: %v", err)
	}
	if res.Created != 3 || res.Failed != 0 {
		t.Fatalf("first result = %+v", res)
	}
	if ha.created() != 3 {
		t.Fatalf("first Sync made %d create calls, want 3", ha.created())
	}
	kinds := map[Kind]int{}
	for _, ev := range res.Events {
		kinds[ev.Kind]++
	}
	if kinds[KindPeriod] != 1 || kinds[KindOverdue] != 1 || kinds[KindDue] != 1 {
		t.Errorf("kinds = %+v, want one period, one overdue and one due", kinds)
	}

	second, err := Sync(ctx, st, c, Options{Now: now}, silentLogger())
	if err != nil {
		t.Fatalf("second Sync: %v", err)
	}
	if second.Created != 0 || second.Candidates != 0 {
		t.Fatalf("second result = %+v, want nothing new", second)
	}
	if ha.created() != 3 {
		t.Fatalf("re-run duplicated events (%d create calls)", ha.created())
	}
}