package asks

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/nats-io/nats-server/v2/server"
	"github.com/nats-io/nats.go"
	"github.com/nats-io/nats.go/jetstream"
)

// machine is the lab's one machine, as the controller's fixture names it.
const machine = "anchor"

// credential is what a lab process connects as (the controller fixture's credentials.json, mesh-tools'
// bus.Credential).
type credential struct {
	URL      string `json:"url"`
	Node     string `json:"node,omitempty"`
	Module   string `json:"module,omitempty"`
	User     string `json:"user"`
	Password string `json:"password"`
}

// lab is one run of the proof: the repositories it builds from, its directory, its bus, its phone.
type lab struct {
	t      *testing.T
	repos  clones
	dir    string
	url    string
	creds  map[string]credential
	server *server.Server
	// observer is the lab's own user on the bus, outside the mesh's composition: it plays the controller's
	// conditions verb and reads the router's state, and is never used to show that something is allowed.
	observer *nats.Conn
	tg       *fakeTelegram

	mu         sync.Mutex
	conditions []map[string]any
	// notFree are the machines the controller's root-free verb answers as not root-free.
	notFree   map[string]string
	rootAsked int
	desk      []string // what the desk was shown
	procs     []*exec.Cmd
	logs      map[string]*bytes.Buffer
}

// clones is where each core repository the proof builds is checked out: side by side in MESH_LAB_REPOS (beside
// mesh-lab by default), or one by one in MESH_LAB_CONTROLLER, MESH_LAB_TOOLS and MESH_LAB_CATALOGUE — a branch
// under review is often a worktree of its own.
type clones struct{ controller, tools, catalogue string }

func clonesFor(t *testing.T) clones {
	repos := os.Getenv("MESH_LAB_REPOS")
	if repos == "" {
		repos = filepath.Join("..", "..")
	}
	at := func(env, name string) string {
		dir := os.Getenv(env)
		if dir == "" {
			dir = filepath.Join(repos, name)
		}
		abs, err := filepath.Abs(dir)
		if err != nil {
			t.Fatal(err)
		}
		return abs
	}
	c := clones{controller: at("MESH_LAB_CONTROLLER", "mesh-controller"), tools: at("MESH_LAB_TOOLS", "mesh-tools"),
		catalogue: at("MESH_LAB_CATALOGUE", "mesh-catalog")}
	for _, want := range []string{filepath.Join(c.controller, "go.mod"), filepath.Join(c.tools, "node-tools", "go.mod"),
		filepath.Join(c.catalogue, "modules", "messenger", "go.mod"), filepath.Join(c.catalogue, "modules", "telegram", "go.mod")} {
		if _, err := os.Stat(want); err != nil {
			t.Skipf("NOT RUN: the proof builds the controller, the runtime, the router and the Telegram channel from "+
				"their clones, and there is no %s (set MESH_LAB_REPOS, or MESH_LAB_CONTROLLER, MESH_LAB_TOOLS and "+
				"MESH_LAB_CATALOGUE)", want)
		}
	}
	// The controller beside is, on the build seat, the one the mesh runs: until it carries the proof's fixture
	// (mesh-controller's TestTheAsksLabBus), the proof cannot compose its bus, and says so rather than fail
	// every pull request of the lab for a merge not yet made.
	fixtures, _ := filepath.Glob(filepath.Join(c.controller, "internal", "inventory", "*_test.go"))
	has := false
	for _, f := range fixtures {
		if body, err := os.ReadFile(f); err == nil && strings.Contains(string(body), "func TestTheAsksLabBus(") {
			has = true
		}
	}
	if !has {
		t.Skipf("NOT RUN: the controller at %s has no TestTheAsksLabBus, the fixture that composes the proof's bus "+
			"(mesh-controller #157): the proof runs once the controller it is given carries it", c.controller)
	}
	return c
}

// run runs a command in a directory and fails the test with what it said.
func (l *lab) run(dir string, env []string, name string, args ...string) string {
	l.t.Helper()
	cmd := exec.Command(name, args...)
	cmd.Dir = dir
	cmd.Env = append(os.Environ(), env...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		l.t.Fatalf("%s %s in %s: %v\n%s", name, strings.Join(args, " "), dir, err, out)
	}
	return string(out)
}

// compose asks the controller at its commit for the bus it would compose, then (bus set) to raise it.
func (l *lab) compose(bus string) {
	// The anchor composed as a machine the controller measured root-free: verified-sender reaches the router
	// only then (ADR 0259 §8). The not-free case is played live, through the root-free verb, in the proof.
	env := []string{"GOFLAGS=-mod=vendor", "GOPROXY=off", "MESH_LAB_ASKS_OUT=" + l.dir, "MESH_LAB_ASKS_ROOT_FREE=true",
		"MESH_LAB_ASKS_CATALOGUE=" + filepath.Join(l.repos.catalogue, "modules"),
		"MESH_LAB_ASKS_RUNTIME=" + filepath.Join(l.repos.tools, "node-tools", "module.json")}
	if bus != "" {
		env = append(env, "MESH_LAB_ASKS_BUS="+bus)
	}
	out := l.run(l.repos.controller, env, "go", "test", "-count=1", "-v", "-run",
		"^TestTheAsksLabBus$", "./internal/inventory/")
	if !strings.Contains(out, "--- PASS: TestTheAsksLabBus") {
		l.t.Fatalf("the controller did not compose the lab's bus (is its fixture on this commit?):\n%s", out)
	}
}

// startBus starts a server of the mesh's release with the controller's composed accounts, and the lab's
// observer beside them.
func (l *lab) startBus() {
	l.t.Helper()
	accounts, err := os.ReadFile(filepath.Join(l.dir, "accounts.conf"))
	if err != nil {
		l.t.Fatal(err)
	}
	const usersOpen = "    users = [\n"
	if !bytes.Contains(accounts, []byte(usersOpen)) {
		l.t.Fatalf("the composed accounts block has no users list:\n%s", accounts)
	}
	observerPassword := fmt.Sprintf("observer-%d", time.Now().UnixNano())
	accounts = bytes.Replace(accounts, []byte(usersOpen),
		[]byte(usersOpen+fmt.Sprintf("      { user: \"lab-observer\", password: %q }\n", observerPassword)), 1)
	port := freePort(l.t)
	conf := fmt.Sprintf("listen: \"127.0.0.1:%d\"\njetstream {\n  store_dir: %q\n}\n\n%s", port,
		filepath.Join(l.dir, "jetstream"), accounts)
	path := filepath.Join(l.dir, "bus.conf")
	if err := os.WriteFile(path, []byte(conf), 0o600); err != nil {
		l.t.Fatal(err)
	}
	opts, err := server.ProcessConfigFile(path)
	if err != nil {
		l.t.Fatalf("the composed configuration is not one the server reads: %v", err)
	}
	// The server's own log, in the lab's directory: a refusal it says is evidence, kept with the run.
	opts.NoSigs, opts.LogFile = true, filepath.Join(l.dir, "bus.log")
	opts.Trace = os.Getenv("MESH_LAB_ASKS_TRACE") != ""
	s, err := server.NewServer(opts)
	if err != nil {
		l.t.Fatal(err)
	}
	s.ConfigureLogger()
	go s.Start()
	if !s.ReadyForConnections(30 * time.Second) {
		l.t.Fatal("the lab's bus did not come up")
	}
	l.server, l.url = s, s.ClientURL()
	l.t.Cleanup(func() { s.Shutdown(); s.WaitForShutdown() })
	raw, err := os.ReadFile(filepath.Join(l.dir, "credentials.json"))
	if err != nil {
		l.t.Fatal(err)
	}
	if err := json.Unmarshal(raw, &l.creds); err != nil {
		l.t.Fatal(err)
	}
	l.observer, err = nats.Connect(l.url, nats.UserInfo("lab-observer", observerPassword))
	if err != nil {
		l.t.Fatal(err)
	}
	l.t.Cleanup(l.observer.Close)
}

func freePort(t *testing.T) int {
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer ln.Close()
	return ln.Addr().(*net.TCPAddr).Port
}

// as connects as one of the composed users. refused collects what the server refused it.
func (l *lab) as(user string) (*nats.Conn, *refusals) {
	l.t.Helper()
	c, ok := l.creds[user]
	if !ok {
		l.t.Fatalf("the controller composed no user %s", user)
	}
	r := &refusals{}
	nc, err := nats.Connect(l.url, nats.UserInfo(c.User, c.Password), nats.CustomInboxPrefix("_INBOX."+c.User),
		nats.ErrorHandler(func(_ *nats.Conn, _ *nats.Subscription, err error) { r.add(err) }))
	if err != nil {
		l.t.Fatalf("connecting as %s: %v", user, err)
	}
	l.t.Cleanup(nc.Close)
	return nc, r
}

// refusals are the permission violations the server said to one connection.
type refusals struct {
	mu   sync.Mutex
	said []string
}

func (r *refusals) add(err error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.said = append(r.said, err.Error())
}

func (r *refusals) of(subject string) bool {
	r.mu.Lock()
	defer r.mu.Unlock()
	for _, s := range r.said {
		if strings.Contains(strings.ToLower(s), "permissions violation") && strings.Contains(s, subject) {
			return true
		}
	}
	return false
}

// refusedToPublish publishes once as a user and says whether the server refused it.
func (l *lab) refusedToPublish(user, subject string, body []byte) bool {
	l.t.Helper()
	nc, r := l.as(user)
	if err := nc.Publish(subject, body); err != nil {
		return true
	}
	_ = nc.Flush()
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if r.of(subject) {
			return true
		}
		time.Sleep(50 * time.Millisecond)
	}
	return false
}

// build builds one Go program from a directory into the lab's bin.
func (l *lab) build(dir, pkg, name string, ldflags string) string {
	out := filepath.Join(l.dir, "bin", name)
	args := []string{"build", "-o", out}
	if ldflags != "" {
		args = append(args, "-ldflags", ldflags)
	}
	l.run(dir, []string{"GOPRIVATE=git.novox.be", "GOFLAGS=-mod=mod", "CGO_ENABLED=0"}, "go", append(args, pkg)...)
	return out
}

// runtime starts the mesh's runtime on a module's own credential, serving that module's bundle alone: how
// the mesh runs a module that `runs-as` an account of its own.
func (l *lab) runtime(module, runtimeBin, bundle string, env map[string]string) {
	l.t.Helper()
	user := machine + "." + module
	c := l.creds[user]
	c.URL, c.Node, c.Module = l.url, machine, module
	credPath := filepath.Join(l.dir, module, "broker")
	if err := os.MkdirAll(filepath.Dir(credPath), 0o700); err != nil {
		l.t.Fatal(err)
	}
	raw, _ := json.Marshal(c)
	if err := os.WriteFile(credPath, raw, 0o600); err != nil {
		l.t.Fatal(err)
	}
	toolEnv, _ := json.Marshal(map[string]map[string]string{module: env})
	cmd := exec.Command(runtimeBin, "serve")
	cmd.Env = append(os.Environ(), "MESH_BROKER_FILE="+credPath, "MESH_TOOL_MODULES="+module+"="+bundle,
		"MESH_TOOL_ENV="+string(toolEnv))
	logs := &bytes.Buffer{}
	cmd.Stdout, cmd.Stderr = &lockedWriter{w: logs, mu: &l.mu}, &lockedWriter{w: logs, mu: &l.mu}
	if err := cmd.Start(); err != nil {
		l.t.Fatal(err)
	}
	l.mu.Lock()
	l.procs = append(l.procs, cmd)
	if l.logs == nil {
		l.logs = map[string]*bytes.Buffer{}
	}
	l.logs[module] = logs
	l.mu.Unlock()
	l.t.Cleanup(func() {
		_ = cmd.Process.Signal(os.Interrupt)
		done := make(chan struct{})
		go func() { _ = cmd.Wait(); close(done) }()
		select {
		case <-done:
		case <-time.After(5 * time.Second):
			_ = cmd.Process.Kill()
		}
		if l.t.Failed() || os.Getenv("MESH_LAB_ASKS_SAY") != "" {
			l.mu.Lock()
			l.t.Logf("--- what the %s runtime said:\n%s", module, logs.String())
			l.mu.Unlock()
		}
	})
}

// said is what a runtime said so far.
func (l *lab) said(module string) string {
	l.mu.Lock()
	defer l.mu.Unlock()
	if b := l.logs[module]; b != nil {
		return b.String()
	}
	return ""
}

// waitSaid waits for a runtime to say something.
func (l *lab) waitSaid(module, what string, within time.Duration) {
	l.t.Helper()
	deadline := time.Now().Add(within)
	for time.Now().Before(deadline) {
		if strings.Contains(l.said(module), what) {
			return
		}
		time.Sleep(200 * time.Millisecond)
	}
	l.t.Fatalf("the %s runtime never said %q within %s:\n%s", module, what, within, l.said(module))
}

type lockedWriter struct {
	w  *bytes.Buffer
	mu *sync.Mutex
}

func (w *lockedWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.w.Write(p)
}

// playController answers the controller's `conditions` verb from the lab's list, and its `root-free` verb from
// the lab's word on each machine (free unless notFree names it), as the router asks them. That a machine is
// root-free is the controller's own judgement, proven in its repository (probe_agent_root_test.go); here the
// lab says it, so the proof can show what the router does with each answer.
func (l *lab) playController() {
	l.t.Helper()
	free, err := l.observer.Subscribe("mesh.seat.mesh-controller.tool.root-free", func(m *nats.Msg) {
		var args struct {
			Machines []string `json:"machines"`
		}
		_ = json.Unmarshal(m.Data, &args)
		var out []map[string]any
		l.mu.Lock()
		for _, name := range args.Machines {
			why, not := l.notFree[name]
			if !not {
				why = "the lab says no agent can become root here"
			}
			out = append(out, map[string]any{"machine": name, "free": !not, "why": why,
				"judged": time.Now().UTC().Format(time.RFC3339Nano)})
		}
		l.rootAsked++
		l.mu.Unlock()
		raw, _ := json.Marshal(map[string]any{"result": map[string]any{"machines": out}, "node": machine})
		_ = m.Respond(raw)
	})
	if err != nil {
		l.t.Fatal(err)
	}
	l.t.Cleanup(func() { _ = free.Unsubscribe() })
	sub, err := l.observer.Subscribe("mesh.seat.mesh-controller.tool.conditions", func(m *nats.Msg) {
		l.mu.Lock()
		list := append([]map[string]any{}, l.conditions...)
		l.mu.Unlock()
		raw, _ := json.Marshal(map[string]any{"result": map[string]any{"conditions": list}, "node": machine})
		_ = m.Respond(raw)
	})
	if err != nil {
		l.t.Fatal(err)
	}
	l.t.Cleanup(func() { _ = sub.Unsubscribe() })
}

// raise says a condition as the controller does: on its event, and in its conditions verb from then on.
func (l *lab) raise(c map[string]any) {
	l.t.Helper()
	l.mu.Lock()
	l.conditions = append(l.conditions, c)
	l.mu.Unlock()
	l.sayCondition("condition-raised", c)
}

// clear ends a condition as the controller does.
func (l *lab) clear(key string) {
	l.t.Helper()
	l.mu.Lock()
	var kept []map[string]any
	var gone map[string]any
	for _, c := range l.conditions {
		if c["key"] == key {
			gone = c
			continue
		}
		kept = append(kept, c)
	}
	l.conditions = kept
	l.mu.Unlock()
	if gone != nil {
		gone["cleared"] = time.Now().UTC().Format(time.RFC3339Nano)
		l.sayCondition("condition-cleared", gone)
	}
}

func (l *lab) sayCondition(event string, c map[string]any) {
	l.t.Helper()
	nc, _ := l.as("controller")
	js, err := nc.JetStream()
	if err != nil {
		l.t.Fatal(err)
	}
	raw, _ := json.Marshal(c)
	msg := nats.NewMsg("mesh.seat.mesh-controller.event." + event)
	msg.Data = raw
	msg.Header.Set("x-event-id", fmt.Sprintf("%s.%v.%d", event, c["key"], time.Now().UnixNano()))
	if _, err := js.PublishMsg(msg); err != nil {
		l.t.Fatalf("saying %s as the controller: %v", event, err)
	}
}

// playDesk is the desk channel (kind `desktop`) at the bus, on the machine's runtime's credential, which
// carries the desk channel: it says it is ready, and keeps what the router shows it — the link's code.
func (l *lab) playDesk(ctx context.Context) {
	l.t.Helper()
	// The desk channel runs as an account of its own (it carries a link's code), on its own credential.
	nc, _ := l.as(machine + ".desk-channel")
	stand := func() {
		raw, _ := json.Marshal(map[string]any{"ready": true, "at": time.Now().UTC()})
		js, _ := nc.JetStream()
		msg := nats.NewMsg("mesh.seat.intake.event.standing.desktop")
		msg.Data = raw
		msg.Header.Set("x-event-id", fmt.Sprintf("standing.desktop.%d", time.Now().UnixNano()))
		if _, err := js.PublishMsg(msg); err != nil {
			l.t.Logf("the desk could not say it is ready: %v", err)
		}
	}
	stand()
	go func() {
		tick := time.NewTicker(20 * time.Second)
		defer tick.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-tick.C:
				stand()
			}
		}
	}()
	js, err := jetstream.New(nc)
	if err != nil {
		l.t.Fatal(err)
	}
	bind, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	worker, err := js.Consumer(bind, "SEAT_CHANNEL", "SEAT_CHANNEL_DESKTOP_worker")
	if err != nil {
		l.t.Fatalf("the desk's worker: %v", err)
	}
	consuming, err := worker.Consume(func(m jetstream.Msg) {
		var shown struct {
			Title string `json:"title"`
			Body  string `json:"body"`
		}
		_ = json.Unmarshal(m.Data(), &shown)
		l.mu.Lock()
		l.desk = append(l.desk, shown.Title+": "+shown.Body)
		l.mu.Unlock()
		_ = m.Ack()
	})
	if err != nil {
		l.t.Fatal(err)
	}
	l.t.Cleanup(consuming.Stop)
}

var linkCode = regexp.MustCompile(`(\d{3}) (\d{3})\.`)

// codeOnTheDesk waits for the link's code the router shows on the desk.
func (l *lab) codeOnTheDesk(within time.Duration) string {
	l.t.Helper()
	deadline := time.Now().Add(within)
	for time.Now().Before(deadline) {
		l.mu.Lock()
		for _, s := range l.desk {
			if m := linkCode.FindStringSubmatch(s); m != nil {
				l.mu.Unlock()
				return m[1] + m[2]
			}
		}
		l.mu.Unlock()
		time.Sleep(100 * time.Millisecond)
	}
	l.mu.Lock()
	defer l.mu.Unlock()
	l.t.Fatalf("the desk was never shown a code; it was shown %q\nthe router said:\n%s", l.desk, l.logs["messenger"])
	return ""
}

// routerRecord reads one key of the router's state, as the lab's observer.
func (l *lab) routerRecord(bucket, key string) (jetstream.KeyValueEntry, jetstream.KeyValue) {
	l.t.Helper()
	js, err := jetstream.New(l.observer)
	if err != nil {
		l.t.Fatal(err)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	kv, err := js.KeyValue(ctx, bucket)
	if err != nil {
		l.t.Fatalf("the router's bucket %s: %v", bucket, err)
	}
	e, err := kv.Get(ctx, key)
	if err != nil {
		l.t.Fatalf("the router's %s %s: %v", bucket, key, err)
	}
	return e, kv
}