package apply

import (
	"context"
	"errors"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/novox/mesh-host/internal/declaration"
	"github.com/novox/mesh-host/internal/store"
)

// A scheduled step is the recurring twin of run-once, with the gating rule deliberately reversed
// (novox/hq ADR 0053). These tests defend that, each named for the claim it holds up: installing it
// does not run it and the node is current at once; the host fires it when the cron is due and not
// before; a failed run is recorded and does not fail anything; and runs never stack. Time is
// injected — nothing here waits on the wall clock.

// fixedClock is a clock a test sets by hand.
type fixedClock struct {
	mu  sync.Mutex
	now time.Time
}

func (c *fixedClock) Now() time.Time {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.now
}

func (c *fixedClock) set(t time.Time) {
	c.mu.Lock()
	c.now = t
	c.mu.Unlock()
}

// recordingRun remembers every command it was asked to run, guarded for the goroutines fire() uses.
type recordingRun struct {
	mu   sync.Mutex
	runs int      // how many `docker run` (a fire) happened
	all  [][]string
}

func (r *recordingRun) run(ctx context.Context, name string, args ...string) (string, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.all = append(r.all, append([]string{name}, args...))
	switch args[0] {
	case "info":
		return "27.0\n", nil // a container runtime answers
	case "run":
		r.runs++
		return "", nil
	}
	return "", nil
}

func (r *recordingRun) fireCount() int {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.runs
}

// specOf returns the mesh-host.spec label value from a docker run argument list.
func specOf(args []string) string {
	for _, a := range args {
		if strings.HasPrefix(a, specLabel+"=") {
			return strings.TrimPrefix(a, specLabel+"=")
		}
	}
	return ""
}

func scheduledContainer(t *testing.T, schedule string) *declaration.Container {
	t.Helper()
	d := parseTrusted(t, `{"declaration":1,"resources":[
	  {"id":"sync","type":"container","name":"sync","image":"`+pinned+`","schedule":"`+schedule+`"}
	]}`)
	return d.Resources[0].(*declaration.Container)
}

// --- Requirement 4: installing a schedule does not run it, and the node is current at once. ---

func TestInstallingAScheduleDoesNotRunItAndReportsCurrent(t *testing.T) {
	// The deliberate inversion of run-once: the schedule is state that is present, so the apply is
	// current as soon as it is recorded — nothing is run, and no runtime is even probed.
	var calls []string
	run := func(ctx context.Context, name string, args ...string) (string, error) {
		calls = append(calls, name+" "+strings.Join(args, " "))
		return "", errors.New("installing a schedule must not run any command")
	}
	d := parseTrusted(t, `{"declaration":1,"resources":[
	  {"id":"sync","type":"container","name":"sync","image":"`+pinned+`","schedule":"0 3 * * *"}
	]}`)

	report, state, err := Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
	if err != nil {
		t.Fatalf("installing a schedule failed the apply: %v", err)
	}
	if len(calls) != 0 {
		t.Errorf("installing a schedule ran commands, so it did more than record state: %v", calls)
	}
	if report.Outcomes[0].Action != "created" {
		t.Errorf("an installed schedule was not reported created: %+v", report.Outcomes[0])
	}
	// Recorded as applied — the node is current, exactly as it is for a running service.
	applied, ok := state.Find("sync")
	if !ok {
		t.Fatal("an installed schedule was not recorded as applied")
	}
	if applied.Wrote == "" {
		t.Error("an installed schedule recorded no marker, so a re-apply cannot tell it is unchanged")
	}

	// And a re-apply of the same declaration is unchanged and still runs nothing.
	report2, _, err := Apply(context.Background(), archHost(t), d, state, store.OriginCarried, run, nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if report2.Changed() {
		t.Errorf("re-installing the same schedule reported a change: %+v", report2.Outcomes)
	}
}

func TestAScheduledStepDoesNotGateWhatFollows(t *testing.T) {
	// A run-once step gates: a failure halts what follows. A scheduled step is downstream of
	// convergence, so it never gates — a container declared after it is applied normally.
	d := parseTrusted(t, `{"declaration":1,"resources":[
	  {"id":"sync","type":"container","name":"sync","image":"`+pinned+`","schedule":"0 3 * * *"},
	  {"id":"web","type":"container","name":"web","image":"`+pinned+`"}
	]}`)

	var startedWeb bool
	specs := map[string]string{} // name -> spec label, so read-back sees a running container
	run := func(ctx context.Context, name string, args ...string) (string, error) {
		switch args[0] {
		case "info":
			return "27.0\n", nil
		case "inspect":
			// The container name is the last argument to `docker inspect --format ... <name>`.
			target := args[len(args)-1]
			if spec, up := specs[target]; up {
				return "true\t" + spec + "\n", nil
			}
			return "false\t\n", errors.New("no such container")
		case "run":
			n := nameOf(args)
			if n == "web" {
				startedWeb = true
			}
			specs[n] = specOf(args)
			return "deadbeef\n", nil
		}
		return "", nil
	}

	if _, _, err := Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil); err != nil {
		t.Fatalf("a declaration with a scheduled step failed to apply: %v", err)
	}
	if !startedWeb {
		t.Error("a container declared after a scheduled step was not started — the schedule gated, and it must not")
	}
}

// --- Requirement 5: the host fires the container when the cron is due, and not before. ---

func TestAScheduledStepRunsWhenDueAndNotBefore(t *testing.T) {
	clock := &fixedClock{now: time.Date(2026, 9, 7, 12, 0, 30, 0, time.UTC)}
	rec := &recordingRun{}
	s := NewScheduler(clock, rec.run, nil)

	d := &declaration.Declaration{Version: 1, Resources: []declaration.Resource{
		scheduledContainer(t, "* * * * *"), // every minute; next due 12:01:00
	}}
	s.Sync(d)

	// Not yet due: 12:00:45 is before 12:01:00, so nothing runs.
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 0, 45, 0, time.UTC))
	s.Wait()
	if n := rec.fireCount(); n != 0 {
		t.Fatalf("a scheduled step ran before it was due (%d run(s))", n)
	}

	// Due: 12:01:05 is at or after 12:01:00, so it runs once, to completion.
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 1, 5, 0, time.UTC))
	s.Wait()
	if n := rec.fireCount(); n != 1 {
		t.Fatalf("a scheduled step due did not run exactly once (%d run(s))", n)
	}

	// And it ran to completion, not detached and not with a restart policy — a step, not a service.
	rec.mu.Lock()
	var runArgs []string
	for _, c := range rec.all {
		if len(c) > 1 && c[1] == "run" {
			runArgs = c
		}
	}
	rec.mu.Unlock()
	joined := strings.Join(runArgs, " ")
	if strings.Contains(joined, "--detach") {
		t.Errorf("a scheduled step was detached, so its exit could not be observed: %s", joined)
	}
	if strings.Contains(joined, "--restart") {
		t.Errorf("a scheduled step was given a restart policy, which makes it a service: %s", joined)
	}
	if !strings.Contains(joined, pinned) {
		t.Errorf("a scheduled step ran the wrong image: %s", joined)
	}
}

// --- Requirement 6: a non-zero run is recorded and does not fail the apply or the node. ---

func TestAFailedRunIsRecordedAndDoesNotFailAnything(t *testing.T) {
	clock := &fixedClock{now: time.Date(2026, 9, 7, 12, 0, 30, 0, time.UTC)}

	var logged []string
	var logMu sync.Mutex
	log := func(line string) {
		logMu.Lock()
		logged = append(logged, line)
		logMu.Unlock()
	}

	run := func(ctx context.Context, name string, args ...string) (string, error) {
		switch args[0] {
		case "info":
			return "27.0\n", nil
		case "run":
			return "", errors.New("exit status 1") // the run fails, every time
		}
		return "", nil
	}
	s := NewScheduler(clock, run, log)
	s.Sync(&declaration.Declaration{Version: 1, Resources: []declaration.Resource{
		scheduledContainer(t, "* * * * *"),
	}})

	// Fire a run that exits non-zero. Advance returns nothing — there is no error to fail an apply,
	// because the run happens outside any apply and outside the store.
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 1, 5, 0, time.UTC))
	s.Wait()

	logMu.Lock()
	defer logMu.Unlock()
	var recorded bool
	for _, line := range logged {
		if strings.Contains(line, "non-zero") {
			recorded = true
		}
	}
	if !recorded {
		t.Errorf("a failed run was not recorded against the module: %v", logged)
	}
	// The scheduler is still healthy: the job's run flag was cleared, so the next occurrence can run.
	s.mu.Lock()
	stillRunning := s.jobs["sync"].running
	s.mu.Unlock()
	if stillRunning {
		t.Error("a failed run left the job marked running, which would block every future run")
	}
}

// --- Requirement 7: runs do not stack. ---

func TestASlowRunSkipsTheNextDueRunRatherThanStacking(t *testing.T) {
	clock := &fixedClock{now: time.Date(2026, 9, 7, 12, 0, 30, 0, time.UTC)}

	started := make(chan struct{})   // fire() signals it entered the runner
	release := make(chan struct{})   // the test lets the run finish
	var enters int
	var mu sync.Mutex
	run := func(ctx context.Context, name string, args ...string) (string, error) {
		if args[0] == "info" {
			return "27.0\n", nil
		}
		if args[0] == "run" {
			mu.Lock()
			enters++
			first := enters == 1
			mu.Unlock()
			if first {
				close(started)
				<-release // the first run outlasts the next due time
			}
			return "", nil
		}
		return "", nil
	}

	var logged []string
	var logMu sync.Mutex
	log := func(line string) {
		logMu.Lock()
		logged = append(logged, line)
		logMu.Unlock()
	}

	s := NewScheduler(clock, run, log)
	s.Sync(&declaration.Declaration{Version: 1, Resources: []declaration.Resource{
		scheduledContainer(t, "* * * * *"), // every minute
	}})

	// First occurrence: 12:01 is due — starts a run that blocks in the runner.
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 1, 5, 0, time.UTC))
	<-started // the run is now in flight and will not return until released

	// Second occurrence: 12:02 is due while the first run is still going. It must be skipped, not
	// started as a second concurrent copy.
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 2, 5, 0, time.UTC))

	// Let the first run finish and settle.
	close(release)
	s.Wait()

	mu.Lock()
	total := enters
	mu.Unlock()
	if total != 1 {
		t.Fatalf("a second run was started while the first was still going (%d run(s)) — runs stacked", total)
	}

	logMu.Lock()
	defer logMu.Unlock()
	var skipped bool
	for _, line := range logged {
		if strings.Contains(line, "skipped") {
			skipped = true
		}
	}
	if !skipped {
		t.Errorf("the overrun run was not logged as skipped: %v", logged)
	}
}

// --- Sync re-establishes schedules from the declaration (novox/hq ADR 0018, 0053). ---

func TestSyncForgetsAScheduleTheDeclarationNoLongerNames(t *testing.T) {
	clock := &fixedClock{now: time.Date(2026, 9, 7, 12, 0, 30, 0, time.UTC)}
	rec := &recordingRun{}
	s := NewScheduler(clock, rec.run, nil)

	s.Sync(&declaration.Declaration{Version: 1, Resources: []declaration.Resource{
		scheduledContainer(t, "* * * * *"),
	}})
	s.mu.Lock()
	have := len(s.jobs)
	s.mu.Unlock()
	if have != 1 {
		t.Fatalf("a declared schedule was not established: %d job(s)", have)
	}

	// A later declaration no longer names it — the schedule is dropped, and a due tick runs nothing.
	s.Sync(&declaration.Declaration{Version: 1, Resources: []declaration.Resource{
		parseTrusted(t, `{"declaration":1,"resources":[
		  {"id":"web","type":"container","name":"web","image":"`+pinned+`"}
		]}`).Resources[0],
	}})
	s.Advance(context.Background(), time.Date(2026, 9, 7, 12, 5, 5, 0, time.UTC))
	s.Wait()
	if n := rec.fireCount(); n != 0 {
		t.Errorf("a schedule the declaration no longer names still fired (%d run(s))", n)
	}
}