package httpapi

import (
	"context"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"strconv"
	"sync"
	"testing"
	"time"

	"textmachine/platform/internal/auth"
	"textmachine/platform/internal/pgstore"
)

// stream_session_test.go: the stream's own authentication, which is NOT the guard's.
//
// The guard admits a caller once, at the door. This route then runs for hours on that one decision,
// and until PD-379 nothing ever asked again — so `logout`, `logout-all`, `tmplatformctl revoke` and
// the session's absolute ceiling all stopped at the door and left the channel behind it open. What
// is pinned here is the thing a unit on "the check was called" would not pin: that a stream ALREADY
// RUNNING and ALREADY DELIVERING frames stops, that it says why, and that it says it at the right
// position.

// revocableSessions is a store whose two questions have two answers, because that is the shape of
// the defect: the row the GUARD read was live, and the row a second later is not.
type revocableSessions struct {
	mu    sync.Mutex
	asked int
	// liveFor is how many re-checks answer "live" before the session is gone. 1 means the stream
	// runs one full iteration and is cut on the next.
	liveFor int
	// fail, when set, is answered instead of a verdict: the store could not be ASKED, which is not
	// the same as an answer and must not be reported to the client as one.
	fail error
}

func (s *revocableSessions) Lookup(context.Context, []byte, time.Time) (auth.Session, error) {
	// Always live: the guard is deliberately not the mechanism under test. A stream that only ever
	// ended because the DOOR closed would be the defect itself, dressed as a fix.
	return auth.Session{
		UserID:            "u1",
		IdleExpiresAt:     time.Now().Add(time.Hour),
		AbsoluteExpiresAt: time.Now().Add(time.Hour),
	}, nil
}

func (s *revocableSessions) Touch(context.Context, []byte, time.Time, time.Duration) error {
	return nil
}

func (s *revocableSessions) StillLive(context.Context, []byte, time.Time) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.asked++
	if s.fail != nil {
		return s.fail
	}
	if s.asked > s.liveFor {
		return auth.ErrNoSession
	}
	return nil
}

func (s *revocableSessions) count() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.asked
}

// streamUnder opens the event stream against a caller whose session behaves as `sessions` says.
// `lastEventID` is the client's watermark, because a FRESH connection starts at the head and would
// be handed no history at all — a fixture that proved nothing about a stream that is running.
func streamUnder(t *testing.T, lib *fakeLibrary, sessions auth.SessionStore, lastEventID string) *httptest.ResponseRecorder {
	t.Helper()
	h := v0ServerWith(t, Deps{
		Library: lib,
		Auth: &auth.Authenticator{
			Sessions: sessions, IdleTTL: time.Hour,
			Deny: ProblemHandler(CodeUnauthenticated),
		},
	})
	// ⚠ A DEADLINE ON THE REQUEST, and it is what makes this a usable pin rather than a trap. Without
	// the session check the stream of a book that is not at rest never ends — which is PD-379 exactly
	// — so a mutation removing the check does not fail these tests, it HANGS them, and the package
	// dies on Go's ten-minute timeout with no test named. Measured: that is what the planted mutation
	// actually did. A hang is the weakest possible signal in CI, where it reads as infrastructure
	// trouble; with this deadline the same mutation fails in two seconds, on the assertion that says
	// what it broke.
	ctx, cancel := context.WithTimeout(t.Context(), 2*time.Second)
	defer cancel()
	r := httptest.NewRequest("GET", "/v0/books/bk_1/events", nil).WithContext(ctx)
	r.Header.Set("Authorization", "Bearer token")
	if lastEventID != "" {
		r.Header.Set("Last-Event-ID", lastEventID)
	}
	w := httptest.NewRecorder()
	h.ServeHTTP(w, r)
	return w
}

// A RUNNING stream — one that has already delivered frames — is ended by a revocation, and it is
// ended where the client actually got to.
//
// The last assertion is the one that matters most and the one a plausible fix gets wrong: the
// terminal frame carries the watermark this CONNECTION reached, not the head of the book's history.
// Stamping the head would move a client's `Last-Event-ID` forward across every frame this connection
// never delivered, so signing in again would silently skip them — the same trap `hello` fell into
// (PD-406).
//
// Mutations caught: dropping the re-check from the pump; putting it AFTER the frames; sending `end`
// or `resync_required` instead of a name of its own; stamping the terminal frame with
// `state.Position`.
func TestARevokedSessionEndsAStreamThatIsAlreadyRunning(t *testing.T) {
	// A FULL batch, which is what puts the second iteration under test where a test can reach it.
	// A short batch leaves the pump in its `select`, waiting out a real one-second tick that this
	// package's other stream tests are all written to avoid — and the catch-up path a full batch
	// takes is the one that repeats the session check WITHOUT the tick's pacing, so it is the
	// unfriendlier of the two to be checking anyway.
	//
	// It also separates the two numbers the terminal frame has to choose between: the client is
	// brought to framesPerRead, while the book's head is beyond it.
	var backlog []pgstore.Frame
	for i := 1; i <= framesPerRead; i++ {
		backlog = append(backlog, pgstore.Frame{
			Position: int64(i), Event: pgstore.FrameProgress,
			Data: json.RawMessage(`{"progress":{"done":1}}`),
		})
	}
	lib := &fakeLibrary{
		stream: pgstore.StreamState{Position: 400, Revision: 9, StructureVersion: 1},
		frames: backlog,
	}
	sessions := &revocableSessions{liveFor: 1}
	got := frames(t, streamUnder(t, lib, sessions, "0").Body.String())

	var delivered int
	for _, f := range got {
		if f.Event == "progress" || f.Event == "note" {
			delivered++
		}
	}
	if delivered == 0 {
		t.Fatalf("the stream delivered no frames at all (%v): this fixture proves nothing about a "+
			"RUNNING stream — it would pass against a stream cut at the door", got)
	}
	// ⚠ THE LITERAL, once, on purpose. Every other assertion here goes through the constant, so
	// renaming its VALUE — to `end`, or to `resync_required`, or to anything at all — would leave the
	// whole file green while the wire said something else entirely. What a client dispatches on is
	// the string, and the string is what the canon is being asked to ratify (0.8.0).
	if eventSessionEnded != "session_ended" {
		t.Errorf("the terminal frame goes on the wire as %q; the name proposed for the canon is "+
			"%q, and a client dispatches on the string and not on our constant", eventSessionEnded, "session_ended")
	}
	last := got[len(got)-1]
	if last.Event != eventSessionEnded {
		t.Fatalf("the stream ended with %q, want %q: a revoked caller must be told which of the "+
			"three endings this is", last.Event, eventSessionEnded)
	}
	if want := strconv.Itoa(framesPerRead); last.ID != want {
		t.Errorf("%s carries id %q, want %q — the position this connection brought the client to, "+
			"not the head of the book's history (400)", eventSessionEnded, last.ID, want)
	}
	for _, f := range got {
		if f.Event == "end" {
			t.Error("the stream sent `end`: the BOOK did not finish, the session did, and a client " +
				"reads `end` as 'stop reconnecting'")
		}
	}
	if n := sessions.count(); n < 2 {
		t.Errorf("the session was re-checked %d time(s): a stream that asks once is the defect", n)
	}
}

// The re-check runs BEFORE the frames of its own tick, so a caller whose access was taken away gets
// what was already on the wire and nothing further.
//
// Mutation caught: moving the check below `ReadFrames`, which would hand one more batch of the
// book's contents to a caller who has been signed out.
func TestARevokedCallerIsGivenNoFurtherFrames(t *testing.T) {
	lib := &fakeLibrary{
		stream: pgstore.StreamState{Position: 2, Revision: 1, StructureVersion: 1},
		frames: []pgstore.Frame{
			{Position: 1, Event: pgstore.FrameProgress, Data: json.RawMessage(`{"progress":{"done":1}}`)},
			{Position: 2, Event: pgstore.FrameProgress, Data: json.RawMessage(`{"progress":{"done":2}}`)},
		},
	}
	// Dead on the very first re-check: the guard let this caller in and the revocation landed
	// between the door and the first tick.
	got := frames(t, streamUnder(t, lib, &revocableSessions{liveFor: 0}, "0").Body.String())
	for _, f := range got {
		switch f.Event {
		case "hello", eventSessionEnded: // the handshake, and the reason it stopped
		default:
			t.Errorf("a revoked caller received a %q frame: nothing of the book may follow the "+
				"revocation", f.Event)
		}
	}
}

// A store that cannot be ASKED has not answered. The stream ends — an unaskable session is an
// unrevokable stream — but the client is NOT told it was signed out, because it was not.
//
// Mutation caught: treating a store failure as a revocation (which would sign every watcher out on a
// database blip); treating it as "live" (which restores the defect for as long as the failure lasts).
func TestAnUnaskableSessionEndsTheStreamWithoutClaimingARevocation(t *testing.T) {
	lib := &fakeLibrary{
		stream: pgstore.StreamState{Position: 1, Revision: 1, StructureVersion: 1},
		frames: []pgstore.Frame{
			{Position: 1, Event: pgstore.FrameProgress, Data: json.RawMessage(`{"progress":{"done":1}}`)},
		},
	}
	got := frames(t, streamUnder(t, lib, &revocableSessions{fail: context.DeadlineExceeded}, "0").Body.String())
	for _, f := range got {
		if f.Event == eventSessionEnded {
			t.Errorf("the client was told its session ended, but the store only failed to answer: "+
				"the two are different facts and only one of them is about the caller (%v)", got)
		}
		if f.Event == "end" {
			t.Error("the client was told the BOOK ended on a store failure")
		}
	}
}

// A stream mounted without its guard is refused, loudly, before a single byte of the body.
//
// The identity and the means to re-check it are ONE value, so "authenticated but unrevokable" is not
// a state a handler can be handed — and this pins that the missing half is refused rather than
// served. A 200 with an empty body would look like a healthy connection to everything watching, and
// what it would actually be is PD-379 restored.
//
// Mutation caught: reading the caller with anything that tolerates a zero principal.
func TestAStreamWithoutItsGuardIsRefusedRatherThanServed(t *testing.T) {
	h := &v0{
		lib: &fakeLibrary{stream: pgstore.StreamState{Position: 1, Revision: 1, StructureVersion: 1}},
		log: slog.New(slog.NewJSONHandler(&nopWriter{}, nil)),
	}
	r := httptest.NewRequest("GET", "/v0/books/bk_1/events", nil)
	r.SetPathValue("bookId", "bk_1")
	w := httptest.NewRecorder()
	h.streamEvents(w, r)
	if w.Code != http.StatusInternalServerError {
		t.Errorf("an unguarded event stream answered %d, want %d: serving it would serve a stream "+
			"that revocation cannot reach", w.Code, http.StatusInternalServerError)
	}
	if w.Header().Get("Content-Type") == "text/event-stream" {
		t.Error("an unguarded event stream began streaming before refusing")
	}
}

// The zero principal — the one a route outside guard() would produce — answers "not live" rather
// than "live". The direction is the whole point: the only way this can be wrong must be the way
// that refuses.
func TestAPrincipalWithNoSessionBehindItIsNotLive(t *testing.T) {
	if err := (auth.Principal{UserID: "u1"}).StillLive(t.Context()); !errors.Is(err, auth.ErrNoSession) {
		t.Errorf("a principal with no store behind it answered %v, want %v", err, auth.ErrNoSession)
	}
}

type nopWriter struct{}

func (nopWriter) Write(p []byte) (int, error) { return len(p), nil }