package runner_test

import (
	"context"
	"io"
	"log/slog"
	"testing"
	"time"

	"github.com/stretchr/testify/require"

	"gitea.d-ma.be/mathias/tapir/internal/domain"
	"gitea.d-ma.be/mathias/tapir/internal/runner"
	"gitea.d-ma.be/mathias/tapir/internal/usecase"
)

const testUser = "11111111-1111-1111-1111-111111111111"

// --- fakes -----------------------------------------------------------------

type fakeSource struct {
	subs        []domain.Subscription
	videos      map[string][]domain.Video // keyed by channel id
	transcripts map[string]domain.Transcript
}

func (f *fakeSource) ListSubscriptions(_ context.Context, _ string) ([]domain.Subscription, error) {
	return f.subs, nil
}

func (f *fakeSource) NewVideos(_ context.Context, sub domain.Subscription) ([]domain.Video, error) {
	return f.videos[sub.ChannelID], nil
}

func (f *fakeSource) FetchTranscript(_ context.Context, v domain.Video) (domain.Transcript, error) {
	if t, ok := f.transcripts[v.ProviderVideoID]; ok {
		return t, nil
	}
	return domain.Transcript{VideoID: v.ID, UserID: v.UserID, Source: domain.SourceCaptions, Content: "default transcript text"}, nil
}

// fakeStore assigns deterministic ids ("id-"+provider video id) so a pre-seeded
// seen set lines up with UpsertVideo output, modelling cross-restart dedup.
// auto controls the summarization mode; requested is the manual-mode queue keyed
// by store id; cleared records the ids whose queue flag the runner reset.
type fakeStore struct {
	seen        map[string]bool
	upserted    []domain.Video
	auto        bool
	requested   map[string]bool
	cleared     []string
	rateLimited map[string]time.Time // id -> when 429'd (seeds the backoff window)
	statuses    map[string]string    // id -> last SetTranscriptStatus value
}

func (f *fakeStore) UpsertVideo(_ context.Context, v domain.Video) (string, error) {
	f.upserted = append(f.upserted, v)
	return "id-" + v.ProviderVideoID, nil
}

func (f *fakeStore) SeenVideoIDs(_ context.Context, _ string) (map[string]bool, error) {
	cp := make(map[string]bool, len(f.seen))
	for k, v := range f.seen {
		cp[k] = v
	}
	return cp, nil
}

func (f *fakeStore) GetAutoSummarize(_ context.Context, _ string) (bool, error) {
	return f.auto, nil
}

func (f *fakeStore) RequestedVideoIDs(_ context.Context, _ string) (map[string]bool, error) {
	cp := make(map[string]bool, len(f.requested))
	for k, v := range f.requested {
		cp[k] = v
	}
	return cp, nil
}

func (f *fakeStore) ClearSummarizeRequested(_ context.Context, _, videoID string) error {
	f.cleared = append(f.cleared, videoID)
	return nil
}

func (f *fakeStore) RateLimitedVideoIDs(_ context.Context, _ string) (map[string]time.Time, error) {
	cp := make(map[string]time.Time, len(f.rateLimited))
	for k, v := range f.rateLimited {
		cp[k] = v
	}
	return cp, nil
}

func (f *fakeStore) UpsertChannelError(_ context.Context, _, _, _ string) error { return nil }

func (f *fakeStore) SetTranscriptStatus(_ context.Context, _, videoID, status string) error {
	if f.statuses == nil {
		f.statuses = map[string]string{}
	}
	f.statuses[videoID] = status
	return nil
}

type fakeSummarizer struct{}

func (fakeSummarizer) Summarize(_ context.Context, v domain.Video, _ domain.Transcript) (domain.Summary, error) {
	return domain.Summary{UserID: v.UserID, VideoID: v.ID, Summary: "s", AIProvider: "local", AIModel: "koala/phi4-mini"}, nil
}

type recordingSink struct{ delivered []domain.Summary }

func (s *recordingSink) Name() string { return "store" }
func (s *recordingSink) Deliver(_ context.Context, sum domain.Summary) error {
	s.delivered = append(s.delivered, sum)
	return nil
}

func sub(channelID, title string) domain.Subscription {
	return domain.Subscription{UserID: testUser, ChannelID: channelID, ChannelTitle: title, Active: true}
}

func vid(provID, title string) domain.Video {
	return domain.Video{UserID: testUser, Provider: domain.ProviderYouTube, ProviderVideoID: provID, Title: title}
}

func vidAt(provID, title string, publishedAt time.Time) domain.Video {
	v := vid(provID, title)
	v.PublishedAt = publishedAt
	return v
}

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

// --- tests -----------------------------------------------------------------

func TestRunOnce_SummarizesNewVideos(t *testing.T) {
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1"), vid("v2", "Video 2")}},
	}
	st := &fakeStore{seen: map[string]bool{}, auto: true}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 2, stats.Candidates)
	require.Equal(t, 2, stats.Summarized)
	require.Equal(t, 0, stats.SkippedSeen)
	require.Len(t, sink.delivered, 2)

	// Each delivered summary must carry the durable store id as its video id.
	require.Equal(t, "id-v1", sink.delivered[0].VideoID)
	require.Equal(t, "id-v2", sink.delivered[1].VideoID)
}

func TestRunOnce_SkipsAlreadySummarized(t *testing.T) {
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1"), vid("v2", "Video 2")}},
	}
	// v1 was summarized in a prior run (durable seen set).
	st := &fakeStore{seen: map[string]bool{"id-v1": true}, auto: true}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 1, stats.SkippedSeen)
	require.Equal(t, 1, stats.Summarized)
	require.Len(t, sink.delivered, 1)
	require.Equal(t, "id-v2", sink.delivered[0].VideoID, "only the unseen video is summarized")
}

func TestRunOnce_SkipsVideosWithoutTranscript(t *testing.T) {
	src := &fakeSource{
		subs:        []domain.Subscription{sub("chan1", "Channel One")},
		videos:      map[string][]domain.Video{"chan1": {vid("v1", "Video 1")}},
		transcripts: map[string]domain.Transcript{"v1": {Source: domain.SourceNone}},
	}
	st := &fakeStore{seen: map[string]bool{}, auto: true}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 1, stats.SkippedNoText)
	require.Equal(t, 0, stats.Summarized)
	require.Empty(t, sink.delivered, "no summary delivered when there is no transcript")
}

func TestRunOnce_ManualMode_SkipsUnrequested(t *testing.T) {
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1"), vid("v2", "Video 2")}},
	}
	// Manual mode, nothing queued: discover (upsert) but summarize nothing.
	st := &fakeStore{seen: map[string]bool{}, auto: false, requested: map[string]bool{}}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 2, stats.Candidates)
	require.Equal(t, 2, stats.SkippedManual, "manual mode skips unqueued videos")
	require.Equal(t, 0, stats.Summarized)
	require.Empty(t, sink.delivered, "no summary in manual mode without a request")
	require.Len(t, st.upserted, 2, "discovery still persists every candidate")
}

func TestRunOnce_ManualMode_ProcessesRequested(t *testing.T) {
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1"), vid("v2", "Video 2")}},
	}
	// Manual mode, v1 queued (by store id). Only v1 is summarized; its flag clears.
	st := &fakeStore{seen: map[string]bool{}, auto: false, requested: map[string]bool{"id-v1": true}}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 1, stats.Summarized, "only the queued video is summarized")
	require.Equal(t, 1, stats.SkippedManual, "the unqueued video is skipped")
	require.Len(t, sink.delivered, 1)
	require.Equal(t, "id-v1", sink.delivered[0].VideoID)
	require.Equal(t, []string{"id-v1"}, st.cleared, "the queue flag is cleared after summarizing")
}

// noFetchSource fails the test if a transcript fetch happens — used to prove the
// runner skips a rate-limited video before touching the caption endpoint.
type noFetchSource struct{ *fakeSource }

func (noFetchSource) FetchTranscript(context.Context, domain.Video) (domain.Transcript, error) {
	panic("FetchTranscript must not be called for a rate-limited video within the backoff window")
}

func TestRunOnce_SkipsRateLimitedWithinBackoff(t *testing.T) {
	base := time.Date(2026, 6, 3, 12, 0, 0, 0, time.UTC)
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1")}},
	}
	// v1 was rate-limited 5m ago; backoff is 1h, so it is still inside the window.
	st := &fakeStore{
		seen:        map[string]bool{},
		auto:        true,
		rateLimited: map[string]time.Time{"id-v1": base.Add(-5 * time.Minute)},
	}
	eng := usecase.NewEngine(noFetchSource{src}, fakeSummarizer{}, &recordingSink{})
	r := runner.New(noFetchSource{src}, st, eng, testUser, quietLogger(),
		runner.WithBackoff(time.Hour), runner.WithClock(func() time.Time { return base }))

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 1, stats.SkippedRateLimited, "still throttled -> skipped")
	require.Equal(t, 0, stats.Summarized)
	require.Empty(t, st.statuses, "no status write: the engine was never invoked")
}

func TestRunOnce_RetriesRateLimitedAfterBackoff(t *testing.T) {
	base := time.Date(2026, 6, 3, 12, 0, 0, 0, time.UTC)
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1")}},
	}
	// v1 was rate-limited 2h ago; backoff is 1h, so the window has expired.
	st := &fakeStore{
		seen:        map[string]bool{},
		auto:        true,
		rateLimited: map[string]time.Time{"id-v1": base.Add(-2 * time.Hour)},
	}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger(),
		runner.WithBackoff(time.Hour), runner.WithClock(func() time.Time { return base }))

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 0, stats.SkippedRateLimited, "window expired -> not skipped")
	require.Equal(t, 1, stats.Summarized, "the video is retried and summarized")
	require.Len(t, sink.delivered, 1)
	require.Equal(t, "fetched", st.statuses["id-v1"], "status advances to fetched on success")
}

func TestRunOnce_UpsertsEveryCandidate(t *testing.T) {
	src := &fakeSource{
		subs:   []domain.Subscription{sub("chan1", "Channel One")},
		videos: map[string][]domain.Video{"chan1": {vid("v1", "Video 1"), vid("v2", "Video 2")}},
	}
	// Even an already-seen video gets upserted so its metadata stays fresh.
	st := &fakeStore{seen: map[string]bool{"id-v1": true}, auto: true}
	eng := usecase.NewEngine(src, fakeSummarizer{}, &recordingSink{})
	r := runner.New(src, st, eng, testUser, quietLogger())

	_, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Len(t, st.upserted, 2, "every candidate is upserted, including seen ones")
}

// TestRunOnce_NewestFirstOrdering asserts that within a pass, candidates are
// processed newest-first (published_at DESC, NULLS LAST) across all channels,
// and that the set of processed videos is identical to what per-channel inline
// processing would produce (only the order differs).
//
// Fixture: two channels, four videos with mixed published_at (one NULL).
//
//	Per-channel (before): chanA=[v-old, v-mid], chanB=[v-new, v-null]
//	                    → [v-old, v-mid, v-new, v-null]
//	Newest-first (after): [v-new, v-mid, v-old, v-null]
func TestRunOnce_NewestFirstOrdering(t *testing.T) {
	old := time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC)
	mid := time.Date(2024, 6, 1, 0, 0, 0, 0, time.UTC)
	newt := time.Date(2024, 12, 1, 0, 0, 0, 0, time.UTC)
	// zero time = NULL published_at (schema 001: nullable)

	src := &fakeSource{
		subs: []domain.Subscription{
			sub("chanA", "Channel A"),
			sub("chanB", "Channel B"),
		},
		videos: map[string][]domain.Video{
			"chanA": {
				vidAt("v-old", "Old Video", old),
				vidAt("v-mid", "Mid Video", mid),
			},
			"chanB": {
				vidAt("v-new", "New Video", newt),
				vidAt("v-null", "No Date Video", time.Time{}), // NULL
			},
		},
	}
	st := &fakeStore{seen: map[string]bool{}, auto: true}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)

	// Same set: all 4 candidates processed regardless of order.
	require.Equal(t, 4, stats.Candidates)
	require.Equal(t, 4, stats.Summarized, "same set of videos processed as per-channel order")
	require.Len(t, sink.delivered, 4)

	// Build video-id → delivery-position map.
	order := make(map[string]int, len(sink.delivered))
	for i, s := range sink.delivered {
		order[s.VideoID] = i
		t.Logf("position %d: %s", i, s.VideoID)
	}

	require.Less(t, order["id-v-new"], order["id-v-mid"], "newest (Dec) before mid (Jun)")
	require.Less(t, order["id-v-mid"], order["id-v-old"], "mid (Jun) before old (Jan)")
	require.Less(t, order["id-v-old"], order["id-v-null"], "dated before NULL (NULLS LAST)")
}

// TestRunOnce_NewestFirstNullsOnly asserts that when all candidates have NULL
// published_at, discovery order (stable) is preserved as the tiebreak.
func TestRunOnce_NewestFirstNullsOnly(t *testing.T) {
	src := &fakeSource{
		subs: []domain.Subscription{
			sub("chanA", "Channel A"),
			sub("chanB", "Channel B"),
		},
		videos: map[string][]domain.Video{
			"chanA": {vidAt("v1", "V1", time.Time{}), vidAt("v2", "V2", time.Time{})},
			"chanB": {vidAt("v3", "V3", time.Time{})},
		},
	}
	st := &fakeStore{seen: map[string]bool{}, auto: true}
	sink := &recordingSink{}
	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
	r := runner.New(src, st, eng, testUser, quietLogger())

	stats, err := r.RunOnce(context.Background())
	require.NoError(t, err)
	require.Equal(t, 3, stats.Summarized, "all null-date videos processed")

	// Discovery order: chanA[v1, v2], chanB[v3] → [v1, v2, v3].
	// All have NULL published_at so the sort is stable; discovery order must hold.
	require.Equal(t, "id-v1", sink.delivered[0].VideoID)
	require.Equal(t, "id-v2", sink.delivered[1].VideoID)
	require.Equal(t, "id-v3", sink.delivered[2].VideoID)
}