package latest

import (
	"context"
	"crypto/sha256"
	"fmt"
	"log"
	"strings"
	"testing"
	"time"

	"bookmarkmanager/backend/internal/store"
)

// Sightings (issue #103) are specified at the Poller seam, with the store as
// the way in: a Sighting is seeded the way handlers.Put performs one, a round
// is run against the injected fetcher and a frozen clock, and the assertions
// are the two observable facts — whether the Series was fetched, and what the
// stored Latest Chapter is afterwards. Nothing here asserts counter arithmetic
// through an internal call or reads how a deferral is represented in a row.

const (
	sightingSlug = "chronicles-of-the-demon-faction-f886a8af"
	sightingKey  = "asura:" + sightingSlug
	sightingURL  = "https://asurascans.com/comics/" + sightingSlug
)

// sightingFixtureLatest is the newest chapter asuraSeriesFixture publishes.
const sightingFixtureLatest = 181.0

// sight performs one Sighting exactly as the JSON API does (handlers.Put):
// RecordSighting against the row as stored, then the Upsert that stores the
// reported value. The order is load-bearing — the raise comparison has nothing
// to compare against once the Upsert has landed — and the bookmark's own fields
// are carried over untouched, which is what a userscript PUT does when it
// echoes back the row it cached.
func sight(t *testing.T, s *store.Store, readerID int64, key string, num float64, at time.Time) {
	t.Helper()
	site, seriesID, ok := strings.Cut(key, ":")
	if !ok {
		t.Fatalf("key %q: no ':' separator", key)
	}
	b, found, err := s.Get(readerID, key)
	if err != nil || !found {
		t.Fatalf("sight %q: get: %v found=%v", key, err, found)
	}
	if err := s.RecordSighting(readerID, site, seriesID, &num, at.UnixMilli()); err != nil {
		t.Fatalf("sight %q: %v", key, err)
	}
	b.LatestChapter = fmt.Sprintf("Chapter %v", num)
	b.LatestChapterNum = &num
	b.UpdatedAt = at.UnixMilli()
	if _, err := s.Upsert(readerID, b); err != nil {
		t.Fatalf("sight %q: upsert: %v", key, err)
	}
}

// secondReader is another Reader on the same database. The owner seed is the
// only reader-creation path in this package, so a second Open as a different
// owner is how a test gets one (as TestRunOnceFetchesSharedSeriesOnce does).
func secondReader(t *testing.T, dbURL string) *store.Store {
	t.Helper()
	other, err := store.Open(dbURL,
		store.Owner{DiscordID: "second-reader", TokenHash: sha256.Sum256([]byte("second-token-hash"))},
		t.TempDir(), testCoverBaseURL)
	if err != nil {
		t.Fatalf("Open second reader: %v", err)
	}
	t.Cleanup(func() { other.Close() })
	return other
}

func readLatestNum(t *testing.T, s *store.Store, readerID int64, key string) float64 {
	t.Helper()
	b, ok, err := s.Get(readerID, key)
	if err != nil || !ok {
		t.Fatalf("Get %q: %v ok=%v", key, err, ok)
	}
	if b.LatestChapterNum == nil {
		t.Fatalf("%q has no latest chapter", key)
	}
	return *b.LatestChapterNum
}

// A Series only one Reader bookmarks is the case where being wrong can hurt
// nobody but the Reader who reported it, so their Sighting stands in for the
// Poll and the round leaves the Series alone.
func TestSightingOnSolitarySeriesDefersPoll(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedForCheck(t, s, sightingKey, sightingURL, now.Add(-2*time.Hour).UnixMilli())
	sight(t, s, s.OwnerID(), sightingKey, sightingFixtureLatest, now.Add(-10*time.Minute))

	f := &fakeFetcher{body: asuraSeriesFixture, status: 200}
	newTestPoller(t, s, f, now).runOnce(context.Background())

	if got := f.callCount(); got != 0 {
		t.Fatalf("fetched %d times after a Sighting on a solitary Series, want 0", got)
	}
}

// On a shared Series the Sighting still writes the Latest Chapter for everyone,
// but the Poll happens on schedule anyway — which is what corrects a wrong
// value within the hour instead of letting it persist.
func TestSightingOnSharedSeriesDoesNotDeferPoll(t *testing.T) {
	s, dbURL := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedForCheck(t, s, sightingKey, sightingURL, now.Add(-2*time.Hour).UnixMilli())
	other := secondReader(t, dbURL)
	if _, err := s.Upsert(other.OwnerID(), store.Bookmark{
		Key: sightingKey, Site: "asura", SeriesID: sightingSlug, UpdatedAt: 2000,
	}); err != nil {
		t.Fatalf("seed second reader: %v", err)
	}
	sight(t, s, s.OwnerID(), sightingKey, 200, now.Add(-10*time.Minute))

	// The Sighting updated the shared row immediately, before any Poll.
	if got := readLatestNum(t, s, s.OwnerID(), sightingKey); got != 200 {
		t.Fatalf("latest after the Sighting = %v, want 200", got)
	}

	f := &fakeFetcher{body: asuraSeriesFixture, status: 200}
	newTestPoller(t, s, f, now).runOnce(context.Background())

	if got := f.callCount(); got != 1 {
		t.Fatalf("fetched %d times after a Sighting on a shared Series, want 1", got)
	}
	if got := readLatestNum(t, s, s.OwnerID(), sightingKey); got != sightingFixtureLatest {
		t.Fatalf("latest after the Poll = %v, want the Site's own %v", got, sightingFixtureLatest)
	}
}

// Reporting a chapter is not reading one: a Sighting may move the Latest
// Chapter and nothing else. Both the solitary and the shared case, because the
// deferral branch must not be where this guarantee lives.
func TestSightingLeavesProgressAndOrderingUntouched(t *testing.T) {
	for _, shared := range []bool{false, true} {
		name := "solitary"
		if shared {
			name = "shared"
		}
		t.Run(name, func(t *testing.T) {
			s, dbURL := newTestStore(t)
			read := 5.0
			if _, err := s.Upsert(s.OwnerID(), store.Bookmark{
				Key: sightingKey, Site: "asura", SeriesID: sightingSlug, SeriesURL: sightingURL,
				LastChapter: "Chapter 5", LastChapterNum: read,
				LastChapterURL: sightingURL + "/chapter/5", UpdatedAt: 1000,
			}); err != nil {
				t.Fatalf("seed: %v", err)
			}
			if shared {
				other := secondReader(t, dbURL)
				if _, err := s.Upsert(other.OwnerID(), store.Bookmark{
					Key: sightingKey, Site: "asura", SeriesID: sightingSlug, UpdatedAt: 2000,
				}); err != nil {
					t.Fatalf("seed second reader: %v", err)
				}
			}

			sight(t, s, s.OwnerID(), sightingKey, 200, time.UnixMilli(9_000_000))

			b, ok, err := s.Get(s.OwnerID(), sightingKey)
			if err != nil || !ok {
				t.Fatalf("Get: %v ok=%v", err, ok)
			}
			if b.LatestChapterNum == nil || *b.LatestChapterNum != 200 {
				t.Fatalf("LatestChapterNum = %v, want 200", b.LatestChapterNum)
			}
			if b.LastChapterNum != read {
				t.Fatalf("LastChapterNum = %v, want %v: a Sighting is not Progress", b.LastChapterNum, read)
			}
			if b.UpdatedAt != 1000 {
				t.Fatalf("updated_at moved to %d: a Sighting must not reorder the list", b.UpdatedAt)
			}
		})
	}
}

// The ceiling is what makes trusting a client report safe: however recently a
// Series was sighted, one that has not been Polled in six hours is Polled.
func TestSightingCeilingForcesPoll(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedForCheck(t, s, sightingKey, sightingURL, now.Add(-7*time.Hour).UnixMilli())
	sight(t, s, s.OwnerID(), sightingKey, sightingFixtureLatest, now.Add(-time.Minute))

	f := &fakeFetcher{body: asuraSeriesFixture, status: 200}
	newTestPoller(t, s, f, now).runOnce(context.Background())

	if got := f.callCount(); got != 1 {
		t.Fatalf("fetched %d times past the %s ceiling, want 1", got, sightingCeilingRests*defaultRest)
	}
}

// Deferral is decided from live facts every round, so a Series that gains a
// second Bookmark stops deferring at once — and one that loses it defers again.
func TestDeferralFollowsTheBookmarkCount(t *testing.T) {
	s, dbURL := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedForCheck(t, s, sightingKey, sightingURL, now.Add(-2*time.Hour).UnixMilli())
	sight(t, s, s.OwnerID(), sightingKey, sightingFixtureLatest, now.Add(-10*time.Minute))

	f := &fakeFetcher{body: asuraSeriesFixture, status: 200}
	p := newTestPoller(t, s, f, now)
	p.runOnce(context.Background())
	if got := f.callCount(); got != 0 {
		t.Fatalf("solitary Series fetched %d times, want 0", got)
	}

	other := secondReader(t, dbURL)
	if _, err := s.Upsert(other.OwnerID(), store.Bookmark{
		Key: sightingKey, Site: "asura", SeriesID: sightingSlug, UpdatedAt: 2000,
	}); err != nil {
		t.Fatalf("seed second reader: %v", err)
	}
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("shared Series fetched %d times, want 1", got)
	}

	// The Poll above consumed the rest, so move past it before asking again.
	if err := other.Delete(other.OwnerID(), sightingKey); err != nil {
		t.Fatalf("delete second bookmark: %v", err)
	}
	later := now.Add(2 * time.Hour)
	p.Now = func() time.Time { return later }
	sight(t, s, s.OwnerID(), sightingKey, sightingFixtureLatest, later.Add(-time.Minute))
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("Series fetched %d times after returning to one Bookmark, want 1", got)
	}
}

// A Series nobody reports any more returns to the normal schedule on its own:
// the Sighting's standing lasts one rest, not forever.
func TestDeferralExpiresWithoutFurtherSightings(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedForCheck(t, s, sightingKey, sightingURL, now.Add(-2*time.Hour).UnixMilli())
	sight(t, s, s.OwnerID(), sightingKey, sightingFixtureLatest, now.Add(-10*time.Minute))

	f := &fakeFetcher{body: asuraSeriesFixture, status: 200}
	p := newTestPoller(t, s, f, now)
	p.runOnce(context.Background())
	if got := f.callCount(); got != 0 {
		t.Fatalf("fetched %d times while the Sighting stood, want 0", got)
	}

	p.Now = func() time.Time { return now.Add(90 * time.Minute) }
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("fetched %d times once the Sighting aged out, want 1", got)
	}
}

// demonicFixture publishes one chapter in demonicscans' live page shape, so a
// test can make a Site publish an arbitrary number rather than the one the
// captured fixture froze.
func demonicFixture(num float64) string {
	return fmt.Sprintf(
		`<a  href="/chaptered.php?manga=11799&chapter=%v" class="chplinks" title="Catastrophic Necromancer %v">Chapter %v</a>`,
		num, num, num)
}

const (
	demonicKey = "demonic:Catastrophic-Necromancer"
	demonicURL = "https://demonicscans.org/manga/Catastrophic-Necromancer"
)

// contradictOnce reports a chapter that does not exist and then runs the round
// that catches it, returning when that round ran so a caller can chain the
// next one. The wait is one rest and a minute: a Sighting stands in for exactly
// one rest, so that is the first moment this solitary Series is Polled again.
func contradictOnce(t *testing.T, s *store.Store, p *Poller, sightAt time.Time, real float64) time.Time {
	t.Helper()
	sight(t, s, s.OwnerID(), demonicKey, real+500, sightAt)
	at := sightAt.Add(defaultRest + time.Minute)
	p.Now = func() time.Time { return at }
	p.runOnce(context.Background())
	if got := readLatestNum(t, s, s.OwnerID(), demonicKey); got != real {
		t.Fatalf("latest after the Poll = %v, want the Site's own %v", got, real)
	}
	return at
}

func seedDemonic(t *testing.T, s *store.Store, checkedAt int64) {
	t.Helper()
	seedForCheck(t, s, demonicKey, demonicURL, checkedAt)
}

// A Poll finding a lower number than stored means the Sighting that raised it
// was false. The Reader is named — not the Series flagged — and both numbers are
// logged, because that is what tells a broken adapter from a deliberate lie.
func TestPollContradictingASightingNamesTheReaderAndBothNumbers(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())

	var logs strings.Builder
	prev := log.Writer()
	log.SetOutput(&logs)
	t.Cleanup(func() { log.SetOutput(prev) })

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, now)
	contradictOnce(t, s, p, now, 296)

	got := logs.String()
	for _, want := range []string{
		fmt.Sprintf("reader %d", s.OwnerID()), "796", "296", demonicKey,
	} {
		if !strings.Contains(got, want) {
			t.Fatalf("contradiction log = %q, want it to name %q", got, want)
		}
	}
}

// Three contradictions cost the Reader the right to defer. Nothing here writes
// a counter: the marks are earned through Polls, which is the only way
// production produces them.
func TestThreeContradictionsStopDeferral(t *testing.T) {
	s, _ := newTestStore(t)
	start := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, start.Add(-2*time.Hour).UnixMilli())

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, start)
	at := start
	for range store.SightingDisagreementLimit {
		at = contradictOnce(t, s, p, at.Add(time.Minute), 296)
	}
	fetchesSoFar := f.callCount()

	// The marked Reader sights the same solitary Series again. It still writes
	// the Latest Chapter — the penalty removes a privilege, it does not silence
	// anyone — but the Poll is no longer postponed: the round below runs while a
	// trusted Reader's Sighting would still be standing, and fetches anyway.
	sight(t, s, s.OwnerID(), demonicKey, 900, at.Add(31*time.Minute))
	if got := readLatestNum(t, s, s.OwnerID(), demonicKey); got != 900 {
		t.Fatalf("latest after a marked Reader's Sighting = %v, want 900", got)
	}
	p.Now = func() time.Time { return at.Add(defaultRest + time.Minute) }
	p.runOnce(context.Background())
	if got := f.callCount(); got != fetchesSoFar+1 {
		t.Fatalf("marked Reader's Sighting still deferred the Poll (fetches %d, want %d)",
			got, fetchesSoFar+1)
	}
}

// The owner's remedy for a mark a broken Site adapter produced restores the
// privilege without a wait and without SQL.
func TestClearingMarksRestoresDeferral(t *testing.T) {
	s, _ := newTestStore(t)
	start := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, start.Add(-2*time.Hour).UnixMilli())

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, start)
	at := start
	for range store.SightingDisagreementLimit {
		at = contradictOnce(t, s, p, at.Add(time.Minute), 296)
	}
	if err := s.ClearReaderMarks(s.OwnerID()); err != nil {
		t.Fatalf("ClearReaderMarks: %v", err)
	}

	fetchesSoFar := f.callCount()
	sight(t, s, s.OwnerID(), demonicKey, 900, at.Add(31*time.Minute))
	p.Now = func() time.Time { return at.Add(defaultRest + time.Minute) }
	p.runOnce(context.Background())
	if got := f.callCount(); got != fetchesSoFar {
		t.Fatalf("fetched %d times after the marks were cleared, want %d: deferral must resume",
			got, fetchesSoFar)
	}
}

// Recovery is automatic but expensive: twenty Polls that each confirm a
// Sighting of this Reader's clear the marks. Each round needs a new chapter,
// because only a report that raises the stored number is attributed and so only
// that one can be confirmed.
func TestTwentyAgreementsClearTheMarks(t *testing.T) {
	s, _ := newTestStore(t)
	start := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, start.Add(-2*time.Hour).UnixMilli())

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, start)
	at := start
	for range store.SightingDisagreementLimit {
		at = contradictOnce(t, s, p, at.Add(time.Minute), 296)
	}

	chapter := 296.0
	for range store.SightingAgreementsToClear {
		chapter++
		sight(t, s, s.OwnerID(), demonicKey, chapter, at.Add(time.Minute))
		f.body = demonicFixture(chapter) // the Site publishes what was reported
		at = at.Add(defaultRest + time.Minute)
		p.Now = func() time.Time { return at }
		p.runOnce(context.Background())
	}

	fetchesSoFar := f.callCount()
	chapter++
	sight(t, s, s.OwnerID(), demonicKey, chapter, at.Add(31*time.Minute))
	p.Now = func() time.Time { return at.Add(defaultRest + time.Minute) }
	p.runOnce(context.Background())
	if got := f.callCount(); got != fetchesSoFar {
		t.Fatalf("fetched %d times after %d confirmations, want %d: the marks must be forgiven",
			got, store.SightingAgreementsToClear, fetchesSoFar)
	}
}

// A Poll finding a higher number is the Site publishing since the Sighting and
// means nothing about the Reader — no mark, and no credit either.
func TestPollFindingHigherNumberIsNotAContradiction(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())
	// Reported truthfully, then the Site published one more.
	sight(t, s, s.OwnerID(), demonicKey, 295, now.Add(-10*time.Minute))

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, now)
	// One rest on, the Sighting has lapsed and the Poll happens.
	p.Now = func() time.Time { return now.Add(7 * time.Hour) }
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("fetched %d times past the ceiling, want 1", got)
	}

	// Unmarked, so a fresh Sighting still defers.
	at := now.Add(9 * time.Hour)
	sight(t, s, s.OwnerID(), demonicKey, 296, at.Add(-time.Minute))
	p.Now = func() time.Time { return at }
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("a Reader whose report the Site overtook lost the right to defer (fetches %d, want 1)", got)
	}
}

// A Poll that overtakes a Sighting takes ownership of the row: the value stored
// afterwards is the Poll's own, so a later retraction is not the Reader's fault
// and must not be charged to them.
func TestAttributionDoesNotSurviveAPollThatOvertookIt(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())
	sight(t, s, s.OwnerID(), demonicKey, 295, now.Add(-10*time.Minute))

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, now)
	at := now.Add(defaultRest + time.Minute)
	p.Now = func() time.Time { return at }
	p.runOnce(context.Background())
	if got := readLatestNum(t, s, s.OwnerID(), demonicKey); got != 296 {
		t.Fatalf("latest after the Poll = %v, want the Site's own 296", got)
	}

	var logs strings.Builder
	prev := log.Writer()
	log.SetOutput(&logs)
	t.Cleanup(func() { log.SetOutput(prev) })

	f.body = demonicFixture(290) // the Site retracts what only the Poll wrote
	p.Now = func() time.Time { return at.Add(defaultRest + time.Minute) }
	p.runOnce(context.Background())
	if strings.Contains(logs.String(), "sighting contradicted") {
		t.Fatalf("a retraction of the Poll's own value was charged to a Reader: %s", logs.String())
	}
}

// A PUT with no Latest Chapter in it — a favourite toggle, progress written
// from a chapter page — is nobody looking at the Series page, so it buys no
// deferral. Otherwise a client could suppress a Series' Polls while reporting
// nothing, and with nothing reported there would be nothing to judge.
func TestPutWithoutALatestChapterDoesNotDefer(t *testing.T) {
	s, _ := newTestStore(t)
	now := time.UnixMilli(20 * time.Hour.Milliseconds())
	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())
	// The handler's own call, with the field the client omitted.
	if err := s.RecordSighting(s.OwnerID(), "demonic", "Catastrophic-Necromancer",
		nil, now.Add(-time.Minute).UnixMilli()); err != nil {
		t.Fatalf("RecordSighting: %v", err)
	}

	f := &fakeFetcher{body: demonicFixture(296), status: 200}
	p := newTestPoller(t, s, f, now)
	p.runOnce(context.Background())
	if got := f.callCount(); got != 1 {
		t.Fatalf("fetched %d times after a PUT carrying no chapter, want 1", got)
	}
}