package pgstore

import (
	"context"
	"errors"
	"testing"
	"time"

	"textmachine/platform/internal/auth"
)

// sessions_test.go: the re-check a long-lived response makes on the session behind it.
//
// The four cases below are one table because what matters is the SHAPE of the answer set — which
// facts end a stream and which deliberately do not. Splitting them would let the idle case be
// deleted on its own, and the idle case is the whole correction (register row PD-379).

func TestStillLiveAnswersRevocationAndTheCeilingButNotTheIdleWindow(t *testing.T) {
	s, ctx := testDB(t)
	seedUser(t, s, ctx, "u1")
	now := time.Now().UTC()

	for _, c := range []struct {
		name string
		// make writes the row and returns its digest; ask is the moment the re-check is made.
		make func(t *testing.T) []byte
		ask  time.Time
		want error
		why  string
	}{
		{
			name: "a live session",
			make: func(t *testing.T) []byte { return seedSession(t, s, ctx, "u1", now, time.Hour, 24*time.Hour) },
			ask:  now.Add(time.Minute),
			want: nil,
			why:  "an ordinary session must keep its stream",
		},
		{
			name: "a revoked session",
			make: func(t *testing.T) []byte {
				d := seedSession(t, s, ctx, "u1", now, time.Hour, 24*time.Hour)
				if err := s.RevokeSession(ctx, d, now); err != nil {
					t.Fatal(err)
				}
				return d
			},
			ask:  now.Add(time.Minute),
			want: auth.ErrNoSession,
			why:  "`logout`, `logout-all` and `tmplatformctl revoke` all write exactly this, and this is the whole of PD-379",
		},
		{
			name: "a session past its ABSOLUTE ceiling",
			make: func(t *testing.T) []byte { return seedSession(t, s, ctx, "u1", now, time.Hour, time.Hour) },
			ask:  now.Add(2 * time.Hour),
			want: auth.ErrNoSession,
			why:  "the ceiling is the one clock a stream cannot slide, so it is the one that must end it",
		},
		{
			// ⚠ THE CORRECTION, and the reason this method exists instead of Lookup. The idle window
			// slides on a REQUEST, and a stream is ONE request for its whole life — so a stream can
			// never touch its own idle deadline. Answering ErrNoSession here would end the stream of a
			// user who is sitting and watching it, which is a regression dressed as a fix.
			name: "a session past its IDLE window but inside its ceiling",
			make: func(t *testing.T) []byte { return seedSession(t, s, ctx, "u1", now, time.Minute, 24*time.Hour) },
			ask:  now.Add(time.Hour),
			want: nil,
			why:  "the idle clause is deliberately absent: a stream cannot slide its own window",
		},
		{
			name: "a token no row matches",
			make: func(*testing.T) []byte { return auth.Digest(auth.NewToken()) },
			ask:  now,
			want: auth.ErrNoSession,
			why:  "the sweep deletes revoked rows too, so an absent row has to mean dead",
		},
	} {
		t.Run(c.name, func(t *testing.T) {
			digest := c.make(t)
			err := s.StillLive(ctx, digest, c.ask)
			if !errors.Is(err, c.want) {
				t.Errorf("StillLive = %v, want %v — %s", err, c.want, c.why)
			}
		})
	}
}

// Lookup and StillLive must DISAGREE about an idle-expired session, and that disagreement is the
// mechanism rather than an accident of two queries.
//
// Pinned as one assertion because the two halves are only meaningful together: a copy of Lookup's
// clauses under a new name would pass every case above except this one.
//
// Mutation caught: adding `and idle_expires_at > $2` to StillLive.
func TestTheStreamsQuestionIsNotTheDoorsQuestion(t *testing.T) {
	s, ctx := testDB(t)
	seedUser(t, s, ctx, "u1")
	now := time.Now().UTC()
	digest := seedSession(t, s, ctx, "u1", now, time.Minute, 24*time.Hour)
	later := now.Add(time.Hour)

	if _, err := s.Lookup(ctx, digest, later); !errors.Is(err, auth.ErrNoSession) {
		t.Errorf("Lookup admitted an idle-expired session (%v): the DOOR must still refuse it", err)
	}
	if err := s.StillLive(ctx, digest, later); err != nil {
		t.Errorf("StillLive ended a stream over the idle window (%v): a stream is one request and "+
			"can never slide its own deadline, so this would cut off a user who is watching", err)
	}
}

// seedSession writes one session row and returns its digest.
func seedSession(t *testing.T, s *Store, ctx context.Context, userID string, now time.Time, idle, maxAge time.Duration) []byte {
	t.Helper()
	d := auth.Digest(auth.NewToken())
	if err := s.CreateSession(ctx, d, userID, now, idle, maxAge); err != nil {
		t.Fatal(err)
	}
	return d
}

// The two deadlines of a session are DIFFERENT facts, and Lookup must not hand them back swapped.
//
// This test exists because the pack that generated this query measured that nothing asserted either
// field: a transposition of the two `time.Time` targets planted in the projection stayed green
// across all eighteen packages. Generating the Scan removed the drift between the SELECT list and
// the Scan — those two cannot disagree any more — but the projection from the generated row into
// auth.Session is still written by hand, and that half is what this pins.
//
// Cost if it is wrong, which is why it is worth a test of its own: auth.Authenticator slides the
// idle window only while `IdleExpiresAt.Before(AbsoluteExpiresAt)`. Swapped, that comparison is
// false for the whole life of every session, Touch becomes dead code, and every user is signed out
// at the idle TTL counted from LOGIN however active they are.
func TestTheTwoSessionDeadlinesAreNotInterchangeable(t *testing.T) {
	s, ctx := testDB(t)
	seedUser(t, s, ctx, "u_dl")
	now := time.Now().UTC().Truncate(time.Second)
	const idleTTL, maxAge = time.Hour, 24 * time.Hour
	// The two TTLs are far apart on purpose: a fixture where they coincide — which is what `Touch`
	// produces, because it clamps idle to absolute — cannot tell a transposition from a correct read.
	if err := s.CreateSession(ctx, []byte("digest-deadlines"), "u_dl", now, idleTTL, maxAge); err != nil {
		t.Fatal(err)
	}
	got, err := s.Lookup(ctx, []byte("digest-deadlines"), now)
	if err != nil {
		t.Fatal(err)
	}
	if got.UserID != "u_dl" {
		t.Errorf("UserID = %q, want u_dl", got.UserID)
	}
	if !got.IdleExpiresAt.Equal(now.Add(idleTTL)) {
		t.Errorf("IdleExpiresAt = %s, want %s (the absolute deadline %s means the two were swapped)",
			got.IdleExpiresAt, now.Add(idleTTL), now.Add(maxAge))
	}
	if !got.AbsoluteExpiresAt.Equal(now.Add(maxAge)) {
		t.Errorf("AbsoluteExpiresAt = %s, want %s (the idle deadline %s means the two were swapped)",
			got.AbsoluteExpiresAt, now.Add(maxAge), now.Add(idleTTL))
	}
	// The ordering is the property auth.Authenticator actually branches on, so it is asserted as
	// itself rather than left implicit in the two equalities above.
	if !got.IdleExpiresAt.Before(got.AbsoluteExpiresAt) {
		t.Error("the idle deadline must fall before the absolute one, or the idle window can never slide")
	}
}