package activator

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"slices"
	"strings"
	"testing"
	"time"

	"github.com/carlosframework/platform/internal/cgroup"
	"github.com/carlosframework/platform/internal/edge"
	"github.com/carlosframework/platform/internal/instancectl"
	"github.com/carlosframework/platform/internal/registry"
	"github.com/carlosframework/platform/internal/release"
)

// stageVersion writes <OptDir>/versions/<ver>/app with body and points
// host's live link at it. Each version's body differs, so each has its own
// digest.
func stageVersion(t *testing.T, b *ExecBackend, host, ver, body string) string {
	t.Helper()
	bin := filepath.Join(b.OptDir, "versions", ver, "app")
	if err := os.MkdirAll(filepath.Dir(bin), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(bin, []byte("#!/bin/sh\n# "+ver+"\n"+body), 0o755); err != nil {
		t.Fatal(err)
	}
	repointLiveLink(t, b, host, bin)
	return bin
}

// repointLiveLink is root's repoint: live/<host> names target from now on.
func repointLiveLink(t *testing.T, b *ExecBackend, host, target string) {
	t.Helper()
	if err := os.MkdirAll(b.liveDir(), 0o755); err != nil {
		t.Fatal(err)
	}
	tmp := b.liveLink(host) + ".tmp"
	os.Remove(tmp)
	if err := os.Symlink(target, tmp); err != nil {
		t.Fatal(err)
	}
	if err := os.Rename(tmp, b.liveLink(host)); err != nil {
		t.Fatal(err)
	}
}

// servingBody is a staged build that records the path it was exec'd by
// ($0) in marker, then becomes the test binary's fake app (TestMain), so it
// binds --socket and answers the health wait.
func servingBody(t *testing.T, marker string) string {
	t.Helper()
	self, err := os.Executable()
	if err != nil {
		t.Fatal(err)
	}
	t.Setenv("ACTIVATOR_FAKE_APP", "1")
	return "printf '%s' \"$0\" > '" + marker + "'\nexec '" + self + "' \"$@\"\n"
}

// Settings spec §4.2: the identity is captured per route. A unit row on a
// SplitBackend has none, whatever its backend could do; an exec row gets
// the exec half. A bare ExecBackend answers for itself, and a backend
// without the capability answers nil.
func TestIdentityIsPerRoute(t *testing.T) {
	exec := testExecBackend(t)
	// The unit half is an ExecBackend too, so a nil for the unit row is the
	// row's answer, not an accident of its backend's type.
	split := &SplitBackend{Exec: exec, Unit: testExecBackend(t)}
	unitRow := registry.Route{Host: "u.example.com", Backing: registry.BackingUnit}
	execRow := registry.Route{Host: "e.example.com"}
	if ib := identityFor(split, unitRow); ib != nil {
		t.Fatalf("a unit row got an identity backend: %T", ib)
	}
	if ib := identityFor(split, execRow); ib != identityBackend(exec) {
		t.Fatalf("an exec row got %v, want the exec half", ib)
	}
	if ib := identityFor(exec, execRow); ib != identityBackend(exec) {
		t.Fatalf("a bare ExecBackend answered %v for itself", ib)
	}
	if ib := identityFor(&fakeBackend{}, execRow); ib != nil {
		t.Fatalf("a backend without the capability answered %T", ib)
	}
}

// A cold default instance has no live link until the Materialize hook
// stages one. LiveIdentity runs the hook first and captures what it
// materialized, read once.
func TestLiveIdentityMaterializesFirst(t *testing.T) {
	b := testExecBackend(t)
	host := "cold.example.com"
	var bin string
	calls := 0
	b.Materialize = func(_ context.Context, h string) error {
		calls++
		bin = stageVersion(t, b, h, "v1", "exit 0\n")
		return nil
	}
	id, err := b.LiveIdentity(context.Background(), registry.Route{Host: host})
	if err != nil {
		t.Fatalf("LiveIdentity: %v", err)
	}
	want, _ := release.FileSHA256(bin)
	if calls != 1 || id.Version != "v1" || id.StagedPath != bin || id.Digest != want {
		t.Fatalf("materialized %d times, identity %+v; want v1 at %s (%s)", calls, id, bin, want)
	}
	// A link that exists is not materialized again.
	if _, err := b.LiveIdentity(context.Background(), registry.Route{Host: host}); err != nil || calls != 1 {
		t.Fatalf("second capture: %v, materialized %d times", err, calls)
	}
	// A materialize failure is the capture's failure.
	b.Materialize = func(context.Context, string) error { return errors.New("controld: 502") }
	if _, err := b.LiveIdentity(context.Background(), registry.Route{Host: "other.example.com"}); err == nil || !strings.Contains(err.Error(), "502") {
		t.Fatalf("a failed materialize = %v", err)
	}
}

// Flat, generations off: StartGenExe execs the recorded file by path on the
// canonical socket, though root repointed the link after the capture. The
// handle names that build, its path and digest, and the host's cache is
// purged as on any wake. A copy whose bytes changed starts nothing.
func TestStartGenExeFlatExecsTheRecordedFile(t *testing.T) {
	requireUnixSockets(t)
	b := testExecBackend(t)
	b.RunDirOverride = shortRunDir(t)
	cache := edge.NewCache(edge.DefaultCacheMaxEntries, edge.DefaultCacheMaxBodyBytes)
	b.Cache = cache
	host := "flat.example.com"
	marker := filepath.Join(t.TempDir(), "argv0")
	a := stageVersion(t, b, host, "vA", servingBody(t, marker))
	rt := flatGenRoute(b, host)
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	id, err := b.LiveIdentity(ctx, rt)
	if err != nil {
		t.Fatal(err)
	}
	stageVersion(t, b, host, "vB", servingBody(t, marker)) // root's repoint lands after the record

	stale := edge.CacheKey{Host: host, Method: "GET", Path: "/"}
	cache.Put(stale, "", &edge.CachedResponse{StatusCode: 200, Header: http.Header{}, Body: []byte("old"), StoredAt: time.Now(), TTL: time.Minute})

	proc, g, err := b.StartGenExe(ctx, rt, 3, false, id)
	if err != nil {
		t.Fatalf("StartGenExe: %v", err)
	}
	defer proc.Stop(context.Background()) //nolint:errcheck
	if got := waitForFile(t, marker, 2*time.Second); got != a {
		t.Fatalf("execd %q, want the recorded %q", got, a)
	}
	// No TierOf here, so the build's tier is GenTier's fallback, the default.
	want := Gen{N: 3, Socket: rt.Socket, Control: rt.Socket + ".control", Build: "vA", StagedPath: a, Digest: id.Digest, Tier: cgroup.TierDefault}
	if g != want {
		t.Fatalf("handle = %+v, want %+v", g, want)
	}
	if _, ok := cache.GetFor(stale, httptest.NewRequest("GET", "http://"+host+"/", nil)); ok {
		t.Fatal("the host's cache survived the spawn")
	}
	stopCtx, stopCancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer stopCancel()
	if err := proc.Stop(stopCtx); err != nil {
		t.Fatal(err)
	}

	os.Remove(marker)
	bad := id
	bad.Digest = strings.Repeat("0", 64)
	p, _, err := b.StartGenExe(ctx, rt, 4, false, bad)
	if !errors.Is(err, release.ErrStagedCopyChanged) || p != nil {
		t.Fatalf("a changed copy = %v, %v; want ErrStagedCopyChanged and no process", p, err)
	}
	time.Sleep(200 * time.Millisecond)
	if _, err := os.Stat(marker); !os.IsNotExist(err) {
		t.Fatal("a refused identity ran something")
	}
}

// Flat, generations on: the recorded file binds generation n's own socket,
// as StartGen does.
func TestStartGenExeFlatPerGenBindsTheGenerationSocket(t *testing.T) {
	requireUnixSockets(t)
	b := testExecBackend(t)
	b.RunDirOverride = shortRunDir(t)
	host := "pergen.example.com"
	marker := filepath.Join(t.TempDir(), "argv0")
	a := stageVersion(t, b, host, "vA", servingBody(t, marker))
	rt := flatGenRoute(b, host)
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	id, err := b.LiveIdentity(ctx, rt)
	if err != nil {
		t.Fatal(err)
	}
	stageVersion(t, b, host, "vB", servingBody(t, marker))
	proc, g, err := b.StartGenExe(ctx, rt, 9, true, id)
	if err != nil {
		t.Fatalf("StartGenExe: %v", err)
	}
	defer proc.Stop(context.Background()) //nolint:errcheck
	own := genSocketPathIn(filepath.Join(b.RunDirOverride, "g"), host, 9)
	if g.Socket != own || g.Control != own+".control" || !isSocket(own) {
		t.Fatalf("handle = %+v, want generation 9's bound socket %s", g, own)
	}
	if got := waitForFile(t, marker, 2*time.Second); got != a {
		t.Fatalf("execd %q, want the recorded %q", got, a)
	}
	if _, err := os.Lstat(rt.Socket); !os.IsNotExist(err) {
		t.Fatalf("the canonical path was bound with generations on (lstat: %v)", err)
	}
}

// A foreign row keeps its canonical socket whatever perGen says, as
// StartStaged and StartGen keep it, and execs the recorded file there.
func TestStartGenExeForeignRunsOnTheCanonicalSocket(t *testing.T) {
	requireUnixSockets(t)
	b := testExecBackend(t)
	host := "foreign.example.com"
	marker := filepath.Join(t.TempDir(), "argv0")
	a := stageVersion(t, b, host, "vA", servingBody(t, marker))
	rt := registry.Route{Host: host, Kind: "instance", DBPath: filepath.Join(b.DataDir, host+".db"), Socket: tmpSock(t)}
	if l, _ := b.Layout(rt); l != LayoutForeign {
		t.Fatalf("fixture layout = %v, want LayoutForeign", l)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	id, err := b.LiveIdentity(ctx, rt)
	if err != nil {
		t.Fatal(err)
	}
	stageVersion(t, b, host, "vB", servingBody(t, marker))
	proc, g, err := b.StartGenExe(ctx, rt, 2, true, id)
	if err != nil {
		t.Fatalf("StartGenExe: %v", err)
	}
	defer proc.Stop(context.Background()) //nolint:errcheck
	if g.Socket != rt.Socket || g.Build != "vA" {
		t.Fatalf("handle = %+v, want vA on the canonical %s", g, rt.Socket)
	}
	if got := waitForFile(t, marker, 2*time.Second); got != a {
		t.Fatalf("execd %q, want the recorded %q", got, a)
	}
}

// Flat seed: SeedExe runs the recorded file, though the link moved after
// the capture, and Seed still runs the link. A changed copy seeds nothing.
func TestSeedExeFlatRunsTheRecordedFile(t *testing.T) {
	b := testExecBackend(t)
	host := "seedexe.example.com"
	marker := filepath.Join(t.TempDir(), "argv0")
	record := "printf '%s' \"$0\" > '" + marker + "'\n"
	a := stageVersion(t, b, host, "vA", record)
	rt := registry.Route{Host: host, Kind: "instance", Seed: `["seed"]`}
	id, err := b.LiveIdentity(context.Background(), rt)
	if err != nil {
		t.Fatal(err)
	}
	bPath := stageVersion(t, b, host, "vB", record)
	if err := b.SeedExe(context.Background(), rt, id); err != nil {
		t.Fatalf("SeedExe: %v", err)
	}
	if got := waitForFile(t, marker, time.Second); got != a {
		t.Fatalf("seeded with %q, want the recorded %q", got, a)
	}

	os.Remove(marker)
	bad := id
	bad.Digest = strings.Repeat("0", 64)
	if err := b.SeedExe(context.Background(), rt, bad); !errors.Is(err, release.ErrStagedCopyChanged) {
		t.Fatalf("a changed copy = %v, want ErrStagedCopyChanged", err)
	}
	if _, err := os.Stat(marker); !os.IsNotExist(err) {
		t.Fatal("a refused identity seeded")
	}

	if err := b.Seed(context.Background(), rt); err != nil {
		t.Fatalf("Seed: %v", err)
	}
	if got := waitForFile(t, marker, time.Second); got != b.liveLink(host) {
		t.Fatalf("Seed ran %q, want the live link (today's, which resolves to %s)", got, bPath)
	}
}

// identityControl is a root control channel that can name an executable
// for the original templates (StagedExeControl) and for a generation
// (GenControl). Each verb is recorded with the file it named.
type identityControl struct{ *fakeControl }

func exeLine(verb, host, what string, x instancectl.StagedExe) string {
	return fmt.Sprintf("%s %s %s %s %s %s", verb, host, what, x.Path, x.Version, x.Digest)
}

func (c identityControl) StartExe(_ context.Context, host string, role instancectl.Role, max int64, x instancectl.StagedExe) (string, error) {
	c.rec(exeLine("startexe", host, string(role), x))
	c.rec(fmt.Sprintf("tier startexe %d", max))
	if c.onStart != nil {
		c.onStart()
	}
	return c.inv, c.startErr
}
func (c identityControl) SeedExe(_ context.Context, host string, max int64, x instancectl.StagedExe) (instancectl.SeedResponse, error) {
	c.rec(exeLine("seedexe", host, "seed", x))
	c.rec(fmt.Sprintf("tier seedexe %d", max))
	return c.seed, nil
}
func (c identityControl) StartGen(_ context.Context, host string, n uint64, _ int64) (string, error) {
	c.rec(fmt.Sprintf("startgen %s %d", host, n))
	return "", errors.New("test: the live-link generation start was used")
}
func (c identityControl) StartGenExe(_ context.Context, host string, n uint64, max int64, x instancectl.StagedExe) (string, error) {
	c.rec(exeLine("startgenexe", host, fmt.Sprint(n), x))
	c.rec(fmt.Sprintf("tier startgenexe %d", max))
	if c.onStart != nil {
		c.onStart()
	}
	return c.inv, c.startErr
}
func (c identityControl) StartSidecarExe(_ context.Context, host string, _ int64, x instancectl.StagedExe) (string, error) {
	c.rec(exeLine("startsidecarexe", host, "sidecar", x))
	return c.inv, nil
}
func (c identityControl) StopGen(_ context.Context, host string, n uint64, kill bool) error {
	c.rec(fmt.Sprintf("stopgen %s %d kill=%v", host, n, kill))
	return nil
}
func (c identityControl) ResetGen(context.Context, string, uint64) error { return nil }
func (c identityControl) Parent(context.Context, string, int64) error    { return nil }

// noPlainVerbs fails when ctl saw a start or seed that names no executable:
// the live link's layout.
func noPlainVerbs(t *testing.T, ctl *fakeControl) {
	t.Helper()
	for _, line := range strings.Split(ctl.joined(), "\n") {
		if strings.HasPrefix(line, "start ") || strings.HasPrefix(line, "seed ") || strings.HasPrefix(line, "startgen ") {
			t.Errorf("a live-link verb was used: %q in\n%s", line, ctl.joined())
		}
	}
}

// Nested: StartGenExe asks root for the recorded file, by path, version and
// digest, after root's repoint of the live link to B. With generations off
// that is the original run unit (generation 0); with them on, generation n.
// Never a plain Start or StartGen.
func TestNestedStartExeNamesTheRecordedFile(t *testing.T) {
	t.Parallel()
	for _, tc := range []struct {
		name string
		gens bool
		n    uint64
		want func(host string, x instancectl.StagedExe) string
	}{
		{"generation 0", false, 1, func(h string, x instancectl.StagedExe) string { return exeLine("startexe", h, "run", x) }},
		{"generation n", true, 6, func(h string, x instancectl.StagedExe) string { return exeLine("startgenexe", h, "6", x) }},
	} {
		t.Run(tc.name, func(t *testing.T) {
			ctl := &fakeControl{inv: "inv1"}
			unit := &fakeUnit{}
			b, rt := nestedBackend(t, ctl, unit)
			b.Control = identityControl{ctl}
			b.GenContainment = tc.gens
			a := stageVersion(t, b, rt.Host, "vA", "exit 0\n")
			id, err := b.LiveIdentity(context.Background(), rt)
			if err != nil {
				t.Fatal(err)
			}
			stageVersion(t, b, rt.Host, "vB", "exit 0\n")
			sock := rt.Socket
			if tc.gens {
				sock = nestedGenSocketIn(b.pathsFor(rt).runDir, tc.n)
			}
			var stopServing func()
			ctl.onStart = func() { stopServing = serveOK(t, sock) }
			defer func() {
				if stopServing != nil {
					stopServing()
				}
			}()
			unit.set("active", "inv1", true, true)
			p, g, err := b.StartGenExe(context.Background(), rt, tc.n, tc.gens, id)
			if err != nil {
				t.Fatalf("StartGenExe: %v", err)
			}
			x := instancectl.StagedExe{Path: a, Version: "vA", Digest: id.Digest}
			if !strings.Contains(ctl.joined(), tc.want(rt.Host, x)) {
				t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), tc.want(rt.Host, x))
			}
			noPlainVerbs(t, ctl)
			if g.Build != "vA" || g.StagedPath != a || g.Digest != id.Digest || g.Socket != sock {
				t.Fatalf("handle = %+v", g)
			}
			unit.set("inactive", "inv1", false, false)
			waitFor(t, "the unit to exit", p.Exited)
		})
	}
}

// Nested seed: SeedExe asks root to run the seed unit on the recorded file,
// not a plain Seed on the link root moved to B. A changed copy asks root
// for nothing.
func TestNestedSeedExeNamesTheRecordedFile(t *testing.T) {
	ctl := &fakeControl{seed: instancectl.SeedResponse{InvocationID: "s1", Result: "success", Status: "0", Code: "exited"}}
	b, rt := nestedBackend(t, ctl, &fakeUnit{})
	b.Control = identityControl{ctl}
	rt.Seed = `["seed"]`
	a := stageVersion(t, b, rt.Host, "vA", "exit 0\n")
	id, err := b.LiveIdentity(context.Background(), rt)
	if err != nil {
		t.Fatal(err)
	}
	stageVersion(t, b, rt.Host, "vB", "exit 0\n")
	if err := b.SeedExe(context.Background(), rt, id); err != nil {
		t.Fatalf("SeedExe: %v", err)
	}
	x := instancectl.StagedExe{Path: a, Version: "vA", Digest: id.Digest}
	if want := exeLine("seedexe", rt.Host, "seed", x); !strings.Contains(ctl.joined(), want) {
		t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), want)
	}
	noPlainVerbs(t, ctl)

	ctl.mu.Lock()
	ctl.calls = nil
	ctl.mu.Unlock()
	bad := id
	bad.Digest = strings.Repeat("0", 64)
	if err := b.SeedExe(context.Background(), rt, bad); !errors.Is(err, release.ErrStagedCopyChanged) {
		t.Fatalf("a changed copy = %v, want ErrStagedCopyChanged", err)
	}
	if ctl.joined() != "" {
		t.Fatalf("a refused identity reached root:\n%s", ctl.joined())
	}
}

// repointingGate is g's gate followed, on every answer, by root's repoint of
// host's live link at to: the window between a declined start's gate and
// the moment what it starts is bound or exec'd.
func repointingGate(t *testing.T, b *ExecBackend, host, to string, g *liveGate) func(registry.Route, string) error {
	t.Helper()
	return func(rt registry.Route, build string) error {
		err := g.gate(rt, build)
		repointLiveLink(t, b, host, to)
		return err
	}
}

// declinedPinFixture is a nested backend whose root channel names
// executables, with v1 and v2 staged and the live link at v1. It returns
// v1's identity and v2's path.
func declinedPinFixture(t *testing.T, ctl *fakeControl, unit *fakeUnit) (*ExecBackend, registry.Route, instancectl.StagedExe, string) {
	t.Helper()
	b, rt := nestedBackend(t, ctl, unit)
	b.Control = identityControl{ctl}
	v1 := stageVersion(t, b, rt.Host, "v1", "exit 0\n")
	v2 := stageVersion(t, b, rt.Host, "v2", "exit 0\n")
	repointLiveLink(t, b, rt.Host, v1)
	sum, err := release.FileSHA256(v1)
	if err != nil {
		t.Fatal(err)
	}
	return b, rt, instancectl.StagedExe{Path: v1, Version: "v1", Digest: sum}, v2
}

// Task 5 (readiness 2, recon A §1): a declined box's nested live-link start
// pins the link once. The gate is asked about the build the link names, and
// root is asked to bind exactly that file (StartExe at generation 0,
// StartGenExe at generation n), so root's repoint of the link at v2 after
// the gate answered still runs v1. Never a plain Start or StartGen, which
// would bind whatever the link names when root lays the unit out.
func TestADeclinedNestedLiveLinkStartRunsThePinnedFile(t *testing.T) {
	t.Parallel()
	for _, tc := range []struct {
		name string
		gens bool
		want func(host string, x instancectl.StagedExe) string
	}{
		{"generation 0", false, func(h string, x instancectl.StagedExe) string { return exeLine("startexe", h, "run", x) }},
		{"generation n", true, func(h string, x instancectl.StagedExe) string { return exeLine("startgenexe", h, "6", x) }},
	} {
		t.Run(tc.name, func(t *testing.T) {
			ctl := &fakeControl{inv: "inv1"}
			unit := &fakeUnit{}
			b, rt, x, v2 := declinedPinFixture(t, ctl, unit)
			b.GenContainment = tc.gens
			g := &liveGate{refuse: map[string]bool{"v2": true}}
			b.LiveExecGate = repointingGate(t, b, rt.Host, v2, g)
			sock := rt.Socket
			if tc.gens {
				sock = nestedGenSocketIn(b.pathsFor(rt).runDir, 6)
			}
			var stopServing func()
			ctl.onStart = func() { stopServing = serveOK(t, sock) }
			defer func() {
				if stopServing != nil {
					stopServing()
				}
			}()
			unit.set("active", "inv1", true, true)
			var (
				p   Proc
				ver string
				err error
			)
			if tc.gens {
				var gen Gen
				p, gen, err = b.StartGen(context.Background(), rt, 6, true)
				ver = gen.Build
			} else {
				p, ver, err = b.Start(context.Background(), rt)
			}
			if err != nil {
				t.Fatalf("start: %v", err)
			}
			if !strings.Contains(ctl.joined(), tc.want(rt.Host, x)) {
				t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), tc.want(rt.Host, x))
			}
			noPlainVerbs(t, ctl)
			if got := g.builds(); !slices.Equal(got, []string{"v1"}) {
				t.Fatalf("gate asked %v, want [v1]", got)
			}
			if ver != "v1" {
				t.Fatalf("version %q, want the pinned v1", ver)
			}
			unit.set("inactive", "inv1", false, false)
			waitFor(t, "the unit to exit", p.Exited)
		})
	}
}

// The same for the legacy sidecar's nested live-link start: root is asked
// to bind the pinned v1 (StartSidecarExe), never a plain sidecar start.
func TestADeclinedNestedSidecarStartRunsThePinnedFile(t *testing.T) {
	t.Parallel()
	ctl := &fakeControl{inv: "inv1"}
	unit := &fakeUnit{}
	b, rt, x, v2 := declinedPinFixture(t, ctl, unit)
	g := &liveGate{refuse: map[string]bool{"v2": true}}
	b.LiveExecGate = repointingGate(t, b, rt.Host, v2, g)
	unit.set("active", "inv1", true, true)
	p, err := b.StartSidecar(context.Background(), rt)
	if err != nil {
		t.Fatalf("StartSidecar: %v", err)
	}
	if want := exeLine("startsidecarexe", rt.Host, "sidecar", x); !strings.Contains(ctl.joined(), want) {
		t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), want)
	}
	noPlainVerbs(t, ctl)
	if got := g.builds(); !slices.Equal(got, []string{"v1"}) {
		t.Fatalf("gate asked %v, want [v1]", got)
	}
	unit.set("inactive", "inv1", false, false)
	waitFor(t, "the sidecar unit to exit", p.Exited)
}

// A declined box's live link outside the version store names no build the
// gate could judge or root could validate: every nested live-link start
// (run, sidecar, seed) is refused in recordBuild's words, the gate is asked
// nothing, and root is asked for nothing.
func TestADeclinedLinkOutsideTheStoreAsksRootForNothing(t *testing.T) {
	ctl := &fakeControl{inv: "inv1", seed: instancectl.SeedResponse{InvocationID: "s1", Result: "success", Status: "0", Code: "exited"}}
	b, rt := nestedBackend(t, ctl, &fakeUnit{})
	b.Control = identityControl{ctl}
	rt.Seed = `["seed"]`
	hand := filepath.Join(t.TempDir(), "app")
	if err := os.WriteFile(hand, []byte("#!/bin/sh\nexit 0\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	repointLiveLink(t, b, rt.Host, hand)
	g := &liveGate{}
	b.LiveExecGate = g.gate
	if _, _, err := b.Start(context.Background(), rt); !errors.Is(err, errBuildStateUnwritten) {
		t.Fatalf("Start = %v, want errBuildStateUnwritten", err)
	}
	if _, err := b.StartSidecar(context.Background(), rt); !errors.Is(err, errBuildStateUnwritten) {
		t.Fatalf("StartSidecar = %v, want errBuildStateUnwritten", err)
	}
	if err := b.Seed(context.Background(), rt); !errors.Is(err, errBuildStateUnwritten) {
		t.Fatalf("Seed = %v, want errBuildStateUnwritten", err)
	}
	if got := ctl.joined(); got != "" {
		t.Fatalf("root was asked:\n%s", got)
	}
	if got := g.builds(); len(got) != 0 {
		t.Fatalf("gate asked %v about a link that names no build", got)
	}
}

// Task 5 (recon A §2): a declined box's flat seed on the live link pins the
// link once and execs the gated file by path, so root's repoint at v2 after
// the gate answered still seeds with v1. A held build seeds nothing: no
// process runs and no database is created.
func TestADeclinedFlatSeedRunsThePinnedFile(t *testing.T) {
	t.Parallel()
	b := testExecBackend(t)
	host := "seedpin.example.com"
	marker := filepath.Join(t.TempDir(), "argv0")
	// $0 into marker, then the database the seed was handed (--db, $3).
	body := "printf '%s' \"$0\" > '" + marker + "'\n: > \"$3\"\n"
	v1 := stageVersion(t, b, host, "v1", body)
	v2 := stageVersion(t, b, host, "v2", body)
	repointLiveLink(t, b, host, v1)
	rt := registry.Route{Host: host, Kind: "instance", Seed: `["seed"]`}
	db := b.pathsFor(rt).dbPath
	g := &liveGate{refuse: map[string]bool{"v2": true}}
	b.LiveExecGate = repointingGate(t, b, host, v2, g)
	if err := b.Seed(context.Background(), rt); err != nil {
		t.Fatalf("Seed: %v", err)
	}
	if got := waitForFile(t, marker, time.Second); got != v1 {
		t.Fatalf("seeded with %q, want the pinned %q", got, v1)
	}
	if got := g.builds(); !slices.Equal(got, []string{"v1"}) {
		t.Fatalf("gate asked %v, want [v1]", got)
	}
	if _, err := os.Stat(db); err != nil {
		t.Fatalf("the seed's database: %v", err)
	}

	// The link names held v2 now. A fresh instance seeds nothing.
	os.Remove(marker)
	if err := removeSeedDB(db); err != nil {
		t.Fatal(err)
	}
	held := &liveGate{refuse: map[string]bool{"v2": true}}
	b.LiveExecGate = held.gate
	if err := b.Seed(context.Background(), rt); !errors.Is(err, errLiveHeld) {
		t.Fatalf("Seed onto held v2 = %v, want the gate's refusal", err)
	}
	time.Sleep(100 * time.Millisecond)
	if _, err := os.Stat(marker); !os.IsNotExist(err) {
		t.Fatal("held v2 ran as the seed")
	}
	if _, err := os.Stat(db); !os.IsNotExist(err) {
		t.Fatalf("a refused seed left a database: %v", err)
	}
	if got := held.builds(); !slices.Equal(got, []string{"v2"}) {
		t.Fatalf("gate asked %v, want [v2]", got)
	}
}

// The nested seed: root is asked to run the seed unit on the pinned v1
// (SeedExe), never a plain Seed of the link. A held build asks root for
// nothing.
func TestADeclinedNestedSeedRunsThePinnedFile(t *testing.T) {
	ctl := &fakeControl{seed: instancectl.SeedResponse{InvocationID: "s1", Result: "success", Status: "0", Code: "exited"}}
	b, rt, x, v2 := declinedPinFixture(t, ctl, &fakeUnit{})
	rt.Seed = `["seed"]`
	g := &liveGate{refuse: map[string]bool{"v2": true}}
	b.LiveExecGate = repointingGate(t, b, rt.Host, v2, g)
	if err := b.Seed(context.Background(), rt); err != nil {
		t.Fatalf("Seed: %v", err)
	}
	if want := exeLine("seedexe", rt.Host, "seed", x); !strings.Contains(ctl.joined(), want) {
		t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), want)
	}
	noPlainVerbs(t, ctl)
	if got := g.builds(); !slices.Equal(got, []string{"v1"}) {
		t.Fatalf("gate asked %v, want [v1]", got)
	}

	ctl.mu.Lock()
	ctl.calls = nil
	ctl.mu.Unlock()
	held := &liveGate{refuse: map[string]bool{"v2": true}}
	b.LiveExecGate = held.gate
	if err := b.Seed(context.Background(), rt); !errors.Is(err, errLiveHeld) {
		t.Fatalf("Seed onto held v2 = %v, want the gate's refusal", err)
	}
	if got := ctl.joined(); got != "" {
		t.Fatalf("a held seed reached root:\n%s", got)
	}
	if got := held.builds(); !slices.Equal(got, []string{"v2"}) {
		t.Fatalf("gate asked %v, want [v2]", got)
	}
}

// BuildIdentity names build's staged copy of rt's app at the path root's
// validation expects (VersionPath under the row's account) and hashes it
// now. An invalid version or app, or a missing copy, names nothing. The
// SplitBackend forwards it for exec rows and refuses unit rows.
func TestBuildIdentityNamesTheStagedCopy(t *testing.T) {
	b := testExecBackend(t)
	rt := registry.Route{Host: "own.example.com", App: "blog"}
	path := release.VersionPath(b.OptDir, release.RouteAccount(rt), "v1", "blog")
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte("#!/bin/sh\n# v1\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	sum, err := release.FileSHA256(path)
	if err != nil {
		t.Fatal(err)
	}
	want := release.StagedIdentity{Version: "v1", StagedPath: path, Digest: sum}
	if id, err := b.BuildIdentity(rt, "v1"); err != nil || id != want {
		t.Fatalf("BuildIdentity = %+v, %v; want %+v", id, err, want)
	}
	for _, bad := range []string{"", "..", "../v1", "v1/blog", "v9"} {
		if id, err := b.BuildIdentity(rt, bad); err == nil {
			t.Errorf("BuildIdentity(%q) = %+v, want a refusal", bad, id)
		}
	}
	for _, app := range []string{"", "..", "a/b"} {
		bad := rt
		bad.App = app
		if id, err := b.BuildIdentity(bad, "v1"); err == nil {
			t.Errorf("BuildIdentity for app %q = %+v, want a refusal", app, id)
		}
	}
	split := &SplitBackend{Exec: b, Unit: testExecBackend(t)}
	if id, err := split.BuildIdentity(rt, "v1"); err != nil || id != want {
		t.Fatalf("SplitBackend.BuildIdentity = %+v, %v; want %+v", id, err, want)
	}
	unitRow := rt
	unitRow.Backing = registry.BackingUnit
	if id, err := split.BuildIdentity(unitRow, "v1"); err == nil {
		t.Fatalf("a unit row's BuildIdentity = %+v, want a refusal", id)
	}
}

// A control channel that cannot name an executable for the original
// template refuses a generation-0 start that names one. It never drops the
// file and binds the live link instead.
func TestStartRoleRefusesAnExeTheControlCannotName(t *testing.T) {
	b := testExecBackend(t)
	ctl := &fakeControl{inv: "inv"}
	b.Control = ctl
	x := instancectl.StagedExe{Path: "/opt/carlos/versions/v2/blog", Version: "v2", Digest: strings.Repeat("a", 64)}
	if _, err := b.startRole(context.Background(), registry.Route{Host: "n.example.com"}, instancectl.RoleRun, 0, &x, cgroup.Limit{}); err == nil {
		t.Fatal("a generation-0 start with an executable the control cannot name was accepted")
	}
	if ctl.joined() != "" {
		t.Fatalf("root was asked:\n%s", ctl.joined())
	}
}

// tierFollowsTheLink is production's tier shape for a test backend: b.Tier
// reads the manifest of whatever the live link names when it is asked, and
// TierOf reads one named version's. vA declares children (1 GiB); every
// other build is the default (512 MiB).
func tierFollowsTheLink(b *ExecBackend, vA string) {
	b.TierOf = func(_ registry.Route, v string) cgroup.Limit {
		if v == vA {
			return cgroup.TierChildren
		}
		return cgroup.TierDefault
	}
	b.Tier = func(rt registry.Route) cgroup.Limit {
		v, _ := b.LiveVersion(rt.Host)
		return b.TierOf(rt, v)
	}
}

const childrenMax = "1073741824" // cgroup.TierChildren.MemoryMax

// Ruling R-TIER: the recorded build runs under its own tier, not the tier
// of whatever root repointed the live link to after the record. A declares
// children (1 GiB), B the default (512 MiB), and the link names B by the
// time each spawn and seed runs. Flat, the limit lands on the host cgroup
// (flag off) or generation n's child (flag on); nested, it is the memory_max
// root is sent. The handle carries A's tier.
func TestStartGenExeAndSeedExeUseTheRecordedBuildsTier(t *testing.T) {
	flat := func(t *testing.T, gens bool) (*ExecBackend, registry.Route, release.StagedIdentity, string) {
		const host = "tier.example.com"
		b, parent := delegatedBackend(t, host)
		b.RunDirOverride = shortRunDir(t)
		b.GenContainment = gens
		if gens {
			cgroup.FakePlacementForTest(t) // a temp dir is no cgroupfs, and a generation is never moved by PID
		}
		tierFollowsTheLink(b, "vA")
		marker := filepath.Join(t.TempDir(), "argv0")
		stageVersion(t, b, host, "vA", servingBody(t, marker))
		rt := flatGenRoute(b, host)
		id, err := b.LiveIdentity(context.Background(), rt)
		if err != nil {
			t.Fatal(err)
		}
		stageVersion(t, b, host, "vB", servingBody(t, marker))
		if got := b.tier(rt); got != cgroup.TierDefault {
			t.Fatalf("fixture: the live tier is %v, want B's default", got)
		}
		return b, rt, id, parent
	}
	readMax := func(t *testing.T, path string) string {
		t.Helper()
		got, err := os.ReadFile(path)
		if err != nil {
			t.Fatal(err)
		}
		return string(got)
	}
	t.Run("flat, generations off", func(t *testing.T) {
		requireUnixSockets(t)
		b, rt, id, parent := flat(t, false)
		proc, g, err := b.StartGenExe(context.Background(), rt, 3, false, id)
		if err != nil {
			t.Fatalf("StartGenExe: %v", err)
		}
		defer proc.Stop(context.Background()) //nolint:errcheck
		if got := readMax(t, filepath.Join(parent, "memory.max")); got != childrenMax || g.Tier != cgroup.TierChildren {
			t.Fatalf("host cgroup memory.max = %s, handle tier %v; want A's 1 GiB", got, g.Tier)
		}
	})
	t.Run("flat, generations on", func(t *testing.T) {
		requireUnixSockets(t)
		b, rt, id, parent := flat(t, true)
		proc, g, err := b.StartGenExe(context.Background(), rt, 9, true, id)
		if err != nil {
			t.Fatalf("StartGenExe: %v", err)
		}
		defer proc.Stop(context.Background()) //nolint:errcheck
		if got := readMax(t, filepath.Join(parent, "g9", "memory.max")); got != childrenMax || g.Tier != cgroup.TierChildren {
			t.Fatalf("g9 memory.max = %s, handle tier %v; want A's 1 GiB", got, g.Tier)
		}
	})
	t.Run("flat seed", func(t *testing.T) {
		b, rt, id, parent := flat(t, false)
		rt.Seed = `["seed"]`
		// A's script execs the fake app, which exits 2 with no --socket:
		// the seed's verdict is not this test's, its cgroup limit is.
		_ = b.SeedExe(context.Background(), rt, id)
		if got := readMax(t, filepath.Join(parent, "memory.max")); got != childrenMax {
			t.Fatalf("host cgroup memory.max after the seed = %s, want A's 1 GiB", got)
		}
	})
	for _, tc := range []struct {
		name string
		gens bool
		want string
	}{
		{"nested, generation 0", false, "tier startexe " + childrenMax},
		{"nested, generation n", true, "tier startgenexe " + childrenMax},
	} {
		t.Run(tc.name, func(t *testing.T) {
			ctl := &fakeControl{inv: "inv1"}
			unit := &fakeUnit{}
			b, rt := nestedBackend(t, ctl, unit)
			b.Control = identityControl{ctl}
			b.GenContainment = tc.gens
			tierFollowsTheLink(b, "vA")
			stageVersion(t, b, rt.Host, "vA", "exit 0\n")
			id, err := b.LiveIdentity(context.Background(), rt)
			if err != nil {
				t.Fatal(err)
			}
			stageVersion(t, b, rt.Host, "vB", "exit 0\n")
			sock := rt.Socket
			if tc.gens {
				sock = nestedGenSocketIn(b.pathsFor(rt).runDir, 6)
			}
			var stopServing func()
			ctl.onStart = func() { stopServing = serveOK(t, sock) }
			defer func() {
				if stopServing != nil {
					stopServing()
				}
			}()
			unit.set("active", "inv1", true, true)
			p, g, err := b.StartGenExe(context.Background(), rt, 6, tc.gens, id)
			if err != nil {
				t.Fatalf("StartGenExe: %v", err)
			}
			if !strings.Contains(ctl.joined(), tc.want) || g.Tier != cgroup.TierChildren {
				t.Fatalf("root was asked:\n%s\nwant %q; handle tier %v", ctl.joined(), tc.want, g.Tier)
			}
			unit.set("inactive", "inv1", false, false)
			waitFor(t, "the unit to exit", p.Exited)
		})
	}
	t.Run("nested seed", func(t *testing.T) {
		ctl := &fakeControl{seed: instancectl.SeedResponse{InvocationID: "s1", Result: "success", Status: "0", Code: "exited"}}
		b, rt := nestedBackend(t, ctl, &fakeUnit{})
		b.Control = identityControl{ctl}
		tierFollowsTheLink(b, "vA")
		rt.Seed = `["seed"]`
		stageVersion(t, b, rt.Host, "vA", "exit 0\n")
		id, err := b.LiveIdentity(context.Background(), rt)
		if err != nil {
			t.Fatal(err)
		}
		stageVersion(t, b, rt.Host, "vB", "exit 0\n")
		if err := b.SeedExe(context.Background(), rt, id); err != nil {
			t.Fatalf("SeedExe: %v", err)
		}
		if want := "tier seedexe " + childrenMax; !strings.Contains(ctl.joined(), want) {
			t.Fatalf("root was asked:\n%s\nwant %q", ctl.joined(), want)
		}
	})
}

// A control channel that cannot name the recorded file refuses a nested
// generation-0 start before root is asked anything. That is proven not to
// have run: never start-uncertain, so it cannot become a failure record.
func TestAMissingStagedExeCapabilityIsNeverMayHaveRun(t *testing.T) {
	ctl := &fakeControl{inv: "inv1"}
	b, rt := nestedBackend(t, ctl, &fakeUnit{})
	stageVersion(t, b, rt.Host, "vA", "exit 0\n")
	id, err := b.LiveIdentity(context.Background(), rt)
	if err != nil {
		t.Fatal(err)
	}
	proc, _, err := b.StartGenExe(context.Background(), rt, 1, false, id)
	if !errors.Is(err, errNoStagedExeControl) {
		t.Fatalf("StartGenExe = %v, want errNoStagedExeControl", err)
	}
	if startMayHaveRun(proc, err) {
		t.Fatalf("a start root was never asked for reads as may-have-run: %v", err)
	}
	if ctl.joined() != "" {
		t.Fatalf("root was asked:\n%s", ctl.joined())
	}
}