package web_test

import (
	"context"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"testing"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/stretchr/testify/require"

	"gitea.d-ma.be/mathias/tapir/internal/adapters/chat"
	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
	"gitea.d-ma.be/mathias/tapir/internal/domain"
	"gitea.d-ma.be/mathias/tapir/internal/web"
)

// videoZ is a video id used by the isolation test for a DIFFERENT user's video.
const videoZ = "33333333-3333-3333-3333-333333333333"

// --- chat test doubles -----------------------------------------------------

// fakeChatter is a web.Chatter that records the request it received and returns a
// canned reply. It performs NO network and NO fetch — it stands in for the real
// chat.Service so the handler behaviour is what's under test.
type fakeChatter struct {
	models    []string
	reply     chat.Reply
	err       error
	gotReq    chat.Request
	callCount int
}

func (f *fakeChatter) Models() []string { return f.models }

func (f *fakeChatter) DefaultModel(summaryModel string) string {
	for _, m := range f.models {
		if m == summaryModel {
			return summaryModel
		}
	}
	if len(f.models) > 0 {
		return f.models[0]
	}
	return ""
}

func (f *fakeChatter) Answer(_ context.Context, req chat.Request) (chat.Reply, error) {
	f.callCount++
	f.gotReq = req
	if f.err != nil {
		return chat.Reply{}, f.err
	}
	return f.reply, nil
}

// tripwireProcessor and tripwireFetcher are the YouTube-reaching collaborators
// (summarize → caption fetch, and the paste metadata fetch). Wired into the App
// for the safety test, they fail it the instant chat routes into either — the
// behavioural proof that chat never triggers a fetch (ADR-027).
type tripwireProcessor struct{ t *testing.T }

func (p tripwireProcessor) ProcessVideo(context.Context, string, string) error {
	p.t.Fatal("chat triggered summarization (→ caption fetch) — must never happen (ADR-027)")
	return nil
}

type tripwireFetcher struct{ t *testing.T }

func (f tripwireFetcher) FetchVideo(context.Context, string, string) (domain.Video, error) {
	f.t.Fatal("chat triggered a YouTube video fetch — must never happen (ADR-027)")
	return domain.Video{}, nil
}

// --- helpers ---------------------------------------------------------------

// newChatApp builds the App under test as the registered stub user, with a Chat
// backend wired. Mirrors newApp but adds chat (and any extra wiring via mutate).
func newChatApp(t *testing.T, chatter web.Chatter, mutate func(*web.App)) *web.App {
	t.Helper()
	s := newStore(t)
	app := &web.App{
		Store:    s,
		Identity: s,
		Auth:     web.StubAuth{U: web.User{Subject: stubSubject}},
		Chat:     chatter,
	}
	if mutate != nil {
		mutate(app)
	}
	return app
}

// seededProviderVideoID mirrors seedVideo's derivation so the chat path's
// (provider, providerVideoID) transcript key matches the seeded video row.
func seededProviderVideoID(videoID string) string { return "pv-" + videoID[:8] }

// seedTranscript stores a shared (provider, providerVideoID) transcript — the
// ADR-021 stored content the chat reads. Captions source = usable text.
func seedTranscript(t *testing.T, s *store.Store, videoID, content string) {
	t.Helper()
	err := s.SaveTranscript(context.Background(), "youtube", seededProviderVideoID(videoID),
		domain.Transcript{Source: domain.SourceCaptions, Language: "en", Content: content})
	require.NoError(t, err)
}

func getChat(t *testing.T, app *web.App, videoID string) *httptest.ResponseRecorder {
	t.Helper()
	return do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoID+"/chat", nil))
}

func postChat(t *testing.T, app *web.App, videoID string, form url.Values, htmx bool) *httptest.ResponseRecorder {
	t.Helper()
	req := httptest.NewRequest(http.MethodPost, "/v/"+videoID+"/chat", strings.NewReader(form.Encode()))
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	if htmx {
		req.Header.Set("HX-Request", "true")
	}
	return do(t, app, req)
}

// --- scenarios -------------------------------------------------------------

// The "dig deeper" affordance appears on a summary detail view only when chat is
// enabled, and links to that video's chat — the single entry point (ADR-027 §1).
func TestChatEntryAffordanceOnSummaryView(t *testing.T) {
	ctx := context.Background()
	withChat := newChatApp(t, &fakeChatter{models: []string{"phi4-mini"}}, nil)
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, withChat, videoX, "body x"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})

	html := body(t, do(t, withChat, httptest.NewRequest(http.MethodGet, "/v/"+videoX, nil)))
	require.Contains(t, html, "Dig deeper", "the deeper-dive affordance is shown when chat is enabled")
	require.Contains(t, html, "/v/"+videoX+"/chat", "it links to this video's chat")

	// With no chat backend wired the affordance is absent (routes unmounted).
	noChat := newApp(t)
	require.NoError(t, deliver(ctx, noChat, videoX, "body x"))
	html = body(t, do(t, noChat, httptest.NewRequest(http.MethodGet, "/v/"+videoX, nil)))
	require.NotContains(t, html, "Dig deeper", "no affordance when chat is disabled")
}

// THE KEY SAFETY ASSERTION (ADR-027): a chat answer is produced entirely from the
// stored transcript — the model receives the stored text, and neither the
// summarize→fetch path nor the YouTube fetch path is ever touched. The tripwire
// collaborators t.Fatal the test if chat reaches them.
func TestChatAnswersFromStoredTranscriptWithoutAnyFetch(t *testing.T) {
	ctx := context.Background()
	const transcript = "STORED-TRANSCRIPT-MARKER: the host explains attention budgets."
	chatter := &fakeChatter{
		models: []string{"phi4-mini"},
		reply:  chat.Reply{Answer: "It is about attention budgets."},
	}
	app := newChatApp(t, chatter, func(a *web.App) {
		a.Processor = tripwireProcessor{t} // fails the test if chat summarizes/fetches
		a.Fetcher = tripwireFetcher{t}     // fails the test if chat fetches video metadata
	})
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
	seedTranscript(t, app.Store.(*store.Store), videoX, transcript)

	form := url.Values{"question": {"what is it about?"}, "model": {"phi4-mini"}}
	rec := postChat(t, app, videoX, form, true)

	require.Equal(t, http.StatusOK, rec.Code)
	require.Contains(t, body(t, rec), "It is about attention budgets.", "the answer is rendered")
	require.Equal(t, 1, chatter.callCount, "the model was asked exactly once")
	require.Equal(t, transcript, chatter.gotReq.Transcript,
		"the model answered from the STORED transcript, not a fetched one")
	// The tripwires never firing IS the no-fetch / no-YouTube proof.
}

// A video with no stored transcript yields an honest "not available" — and never
// a fetch, never a model call (ADR-027 §2: do not add an on-demand-fetch path).
func TestChatUnavailableWhenNoStoredTranscript(t *testing.T) {
	ctx := context.Background()
	chatter := &fakeChatter{models: []string{"phi4-mini"}}
	app := newChatApp(t, chatter, func(a *web.App) {
		a.Processor = tripwireProcessor{t}
		a.Fetcher = tripwireFetcher{t}
	})
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
	// NB: no seedTranscript — the transcript is absent.

	rec := getChat(t, app, videoX)
	require.Equal(t, http.StatusOK, rec.Code)
	require.Contains(t, body(t, rec), "isn't available", "honest not-available copy")

	// Asking anyway still triggers nothing: no model call, no fetch.
	rec = postChat(t, app, videoX, url.Values{"question": {"hi"}, "model": {"phi4-mini"}}, true)
	require.Equal(t, http.StatusOK, rec.Code)
	require.Equal(t, 0, chatter.callCount, "no model call without a stored transcript")
}

// Chat is reachable ONLY from the user's own summary view: opening chat for a
// video that belongs to another user 404s (the summary read is RLS-scoped), so a
// guessed/arbitrary video id is not a chat surface (ADR-027 §5 isolation).
func TestChatOnlyReachableForOwnVideo(t *testing.T) {
	chatter := &fakeChatter{models: []string{"phi4-mini"}}
	app := newChatApp(t, chatter, func(a *web.App) {
		a.Processor = tripwireProcessor{t}
		a.Fetcher = tripwireFetcher{t}
	})
	p := rawPool(t)
	resetDB(t, p)

	// A summarized video with a stored transcript owned by ANOTHER user.
	const other = "22222222-2222-2222-2222-222222222222"
	seedForeignSummaryWithTranscript(t, p, other, videoZ, "Foreign Title")

	rec := getChat(t, app, videoZ)
	require.Equal(t, http.StatusNotFound, rec.Code, "cannot open chat for another user's video")
	require.Equal(t, 0, chatter.callCount, "no model call for a non-owned video")

	rec = postChat(t, app, videoZ, url.Values{"question": {"hi"}, "model": {"phi4-mini"}}, true)
	require.Equal(t, http.StatusNotFound, rec.Code, "cannot post chat to another user's video")
}

// The switcher offers exactly the backend's models, defaults to the summary's own
// model, and a switch re-runs against the SAME transcript with the chosen model
// (ADR-027 §3 — model-comparison instrumentation). A model dropped from the offer
// set (e.g. cloud disabled) is not rendered.
func TestChatModelSwitcherDefaultAndSwitch(t *testing.T) {
	ctx := context.Background()
	// The seeded summary's model is "phi4-mini" (see handlers_test summary()).
	chatter := &fakeChatter{
		models: []string{"phi4-mini", "gemma4-26b"}, // note: no cloud model offered
		reply:  chat.Reply{Answer: "answer"},
	}
	app := newChatApp(t, chatter, nil)
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
	seedTranscript(t, app.Store.(*store.Store), videoX, "the transcript text")

	html := body(t, getChat(t, app, videoX))
	require.Contains(t, html, "gemma4-26b", "every offered model is in the switcher")
	require.NotContains(t, html, "mistral", "a non-offered (cloud-disabled) model is absent")
	require.Contains(t, html, `value="phi4-mini" selected`, "defaults to the summary's own model")

	// Switching to gemma re-runs against the same stored transcript.
	form := url.Values{"question": {"q"}, "model": {"gemma4-26b"}}
	rec := postChat(t, app, videoX, form, true)
	require.Equal(t, http.StatusOK, rec.Code)
	require.Equal(t, "gemma4-26b", chatter.gotReq.Model, "the chosen model answers")
	require.Equal(t, "the transcript text", chatter.gotReq.Transcript, "against the same transcript")
}

// A truncated transcript surfaces the honest bounded-context note (ADR-027 §2).
func TestChatTruncationNoteShown(t *testing.T) {
	ctx := context.Background()
	chatter := &fakeChatter{
		models: []string{"phi4-mini"},
		reply:  chat.Reply{Answer: "answer", Truncated: true},
	}
	app := newChatApp(t, chatter, nil)
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
	seedTranscript(t, app.Store.(*store.Store), videoX, "long transcript")

	rec := postChat(t, app, videoX, url.Values{"question": {"q"}, "model": {"phi4-mini"}}, true)
	require.Contains(t, body(t, rec), "bounded portion", "the truncation note is shown")
}

// A multi-turn conversation is carried in the request (hidden fields), not the DB:
// prior turns ride back into the next answer, and nothing is persisted (ADR-027 §4).
func TestChatMultiTurnHistoryIsEphemeral(t *testing.T) {
	ctx := context.Background()
	chatter := &fakeChatter{models: []string{"phi4-mini"}, reply: chat.Reply{Answer: "second answer"}}
	app := newChatApp(t, chatter, nil)
	p := rawPool(t)
	resetDB(t, p)
	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
	seedTranscript(t, app.Store.(*store.Store), videoX, "the transcript")

	// Second turn posts the prior exchange as hidden history fields.
	form := url.Values{
		"question": {"follow-up question"},
		"model":    {"phi4-mini"},
		"hq":       {"first question"},
		"ha":       {"first answer"},
	}
	rec := postChat(t, app, videoX, form, true)
	require.Equal(t, http.StatusOK, rec.Code)

	require.Len(t, chatter.gotReq.History, 1, "the prior turn was carried into the request")
	require.Equal(t, "first question", chatter.gotReq.History[0].Question)
	require.Equal(t, "first answer", chatter.gotReq.History[0].Answer)

	html := body(t, rec)
	require.Contains(t, html, "second answer", "the new answer renders")
	require.Contains(t, html, "first question", "the conversation persists in page state")

	// Nothing was written to the DB — there is no chat table; the summaries/actions
	// are unchanged by a chat turn.
	row, err := app.Store.GetSummaryByVideo(ctx, userID, videoX)
	require.NoError(t, err)
	require.Equal(t, "summary body", row.Summary, "chat never mutates stored data")
}

// --- foreign-user seeding (isolation) --------------------------------------

// seedForeignSummaryWithTranscript creates a fully-summarized, transcript-backed
// video owned by a DIFFERENT user via the raw pool (which bypasses RLS), so the
// isolation test can confirm the requesting user cannot open chat for it.
func seedForeignSummaryWithTranscript(t *testing.T, p *pgxpool.Pool, otherUserID, videoID, title string) {
	t.Helper()
	ctx := context.Background()
	_, err := p.Exec(ctx, `INSERT INTO users (id) VALUES ($1) ON CONFLICT (id) DO NOTHING`, otherUserID)
	require.NoError(t, err)
	_, err = p.Exec(ctx,
		`INSERT INTO videos (id, user_id, provider, provider_video_id, title, url)
		 VALUES ($1, $2, 'youtube', $3, $4, 'https://z')`,
		videoID, otherUserID, seededProviderVideoID(videoID), title)
	require.NoError(t, err)
	_, err = p.Exec(ctx,
		`INSERT INTO summaries (user_id, video_id, summary, ai_provider, ai_model)
		 VALUES ($1, $2, 'foreign summary', 'local', 'phi4-mini')`,
		otherUserID, videoID)
	require.NoError(t, err)
	_, err = p.Exec(ctx,
		`INSERT INTO transcripts (provider, provider_video_id, source, language, content)
		 VALUES ('youtube', $1, 'captions', 'en', 'foreign transcript')`,
		seededProviderVideoID(videoID))
	require.NoError(t, err)
}