package scheduler

import (
	"context"
	"errors"
	"io"
	"log/slog"
	"sync"
	"testing"
	"time"
)

func quietScheduler() *Scheduler {
	return New(nil, slog.New(slog.NewTextHandler(io.Discard, nil)), nil)
}

// The registry's guarantees are the ones worth pinning: a task cannot be registered
// twice, a run cannot overlap itself, and a panicking job cannot take the gateway down.

func TestDuplicateTaskIDsPanic(t *testing.T) {
	// Two tasks sharing an id would share a history, an enabled switch and a Run Now
	// button, and the console would have no way to say which it was describing.
	sched := quietScheduler()
	sched.Register(Task{ID: "one", Name: "One", Run: noop})
	defer func() {
		if recover() == nil {
			t.Fatal("registering a duplicate id should panic at start-up, not be tolerated")
		}
	}()
	sched.Register(Task{ID: "one", Name: "One again", Run: noop})
}

func TestATaskNeedsAnIDAndAFunction(t *testing.T) {
	sched := quietScheduler()
	defer func() {
		if recover() == nil {
			t.Fatal("a task with no function should be refused at registration")
		}
	}()
	sched.Register(Task{ID: "broken"})
}

func TestQuietTimePausesManualTasks(t *testing.T) {
	sched := quietScheduler()
	ran := false
	sched.Register(Task{ID: "quiet", Name: "Quiet", Run: func(context.Context) (string, error) {
		ran = true
		return "", nil
	}})
	sched.SetPaused(func() bool { return true })
	if err := sched.RunNow(context.Background(), "quiet"); err == nil {
		t.Fatal("manual task started during quiet time")
	}
	if ran {
		t.Fatal("quiet-time task function ran")
	}
}

func TestAPanickingTaskBecomesAFailedRun(t *testing.T) {
	// A background job is the one place a panic takes the whole process down for a reason
	// nobody is watching for. One housekeeping job with a nil map must not be able to stop
	// the gateway serving television.
	sched := quietScheduler()
	sched.Register(Task{ID: "panics", Name: "Panics", Run: func(context.Context) (string, error) {
		panic("nil map")
	}})
	if err := sched.RunNow(context.Background(), "panics"); err != nil {
		t.Fatalf("RunNow: %v", err)
	}
	status := waitForRun(t, sched, "panics")
	if status.LastRun.Status != "failed" {
		t.Fatalf("expected a failed run, got %q", status.LastRun.Status)
	}
	if status.LastRun.Error == "" {
		t.Fatal("the recovered panic should be recorded as the failure")
	}
}

func TestRunNowRefusesToStackASecondRun(t *testing.T) {
	// The button is pressable while a job is running, and an overnight job started twice
	// would double whatever it does.
	release := make(chan struct{})
	sched := quietScheduler()
	sched.Register(Task{ID: "slow", Name: "Slow", Run: func(context.Context) (string, error) {
		<-release
		return "", nil
	}})
	if err := sched.RunNow(context.Background(), "slow"); err != nil {
		t.Fatalf("first run: %v", err)
	}
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) && !running(sched, "slow") {
		time.Sleep(5 * time.Millisecond)
	}
	if err := sched.RunNow(context.Background(), "slow"); err == nil {
		t.Fatal("a second RunNow while the first is in flight should be refused")
	}
	close(release)
}

func TestRunNowRejectsAnUnknownTask(t *testing.T) {
	if err := quietScheduler().RunNow(context.Background(), "nothing"); err == nil {
		t.Fatal("an unknown task id should be an error, not a silent no-op")
	}
}

func TestAFailingTaskRecordsItsError(t *testing.T) {
	sched := quietScheduler()
	sched.Register(Task{ID: "fails", Name: "Fails", Run: func(context.Context) (string, error) {
		return "", errors.New("postgres did not answer")
	}})
	_ = sched.RunNow(context.Background(), "fails")
	status := waitForRun(t, sched, "fails")
	if status.LastRun.Error != "postgres did not answer" {
		t.Fatalf("unexpected error %q", status.LastRun.Error)
	}
}

func TestSetIntervalZeroRestoresTheDeclaredCadence(t *testing.T) {
	// Zero is "as the code declares", so a task whose schedule changes in a later release
	// takes effect for every operator who never overrode it.
	sched := quietScheduler()
	sched.Register(Task{ID: "daily", Name: "Daily", Interval: 24 * time.Hour, Run: noop})
	if err := sched.SetInterval(context.Background(), "daily", 2*time.Hour); err != nil {
		t.Fatalf("SetInterval: %v", err)
	}
	if got := statusOf(t, sched, "daily").Interval; got != int64((2 * time.Hour).Seconds()) {
		t.Fatalf("override not applied, got %d", got)
	}
	if err := sched.SetInterval(context.Background(), "daily", 0); err != nil {
		t.Fatalf("SetInterval: %v", err)
	}
	if got := statusOf(t, sched, "daily").Interval; got != int64((24 * time.Hour).Seconds()) {
		t.Fatalf("expected the declared interval back, got %d", got)
	}
}

func TestIntervalsAreFloored(t *testing.T) {
	// The scheduler only wakes every thirty seconds, so a one-second interval is a promise
	// it cannot keep — and a job set to run every second by a slipped decimal point is one
	// that would sit permanently due.
	sched := quietScheduler()
	sched.Register(Task{ID: "daily", Name: "Daily", Interval: 24 * time.Hour, Run: noop})
	_ = sched.SetInterval(context.Background(), "daily", time.Second)
	if got := statusOf(t, sched, "daily").Interval; got != 60 {
		t.Fatalf("expected a one-minute floor, got %d", got)
	}
}

func TestADisabledTaskAdvertisesNoNextRun(t *testing.T) {
	// The console prints "next run" from this field; a disabled task showing a time would
	// read as one that is going to run anyway.
	sched := quietScheduler()
	sched.Register(Task{ID: "daily", Name: "Daily", Interval: time.Hour, Run: noop})
	_ = sched.SetEnabled(context.Background(), "daily", false)
	if status := statusOf(t, sched, "daily"); status.NextRun != nil {
		t.Fatalf("a disabled task should advertise no next run, got %v", status.NextRun)
	}
}

func TestSnapshotKeepsRegistrationOrder(t *testing.T) {
	// The registry is written as a readable list, and the console lays it out in that
	// order; a map iteration would reshuffle the page on every poll.
	sched := quietScheduler()
	for _, id := range []string{"a", "b", "c", "d"} {
		sched.Register(Task{ID: id, Name: id, Run: noop})
	}
	for attempt := 0; attempt < 5; attempt++ {
		snapshot := sched.Snapshot()
		for i, id := range []string{"a", "b", "c", "d"} {
			if snapshot[i].ID != id {
				t.Fatalf("order changed: %v", snapshot)
			}
		}
	}
}

func TestGroupsAreDistinctAndSorted(t *testing.T) {
	sched := quietScheduler()
	sched.Register(Task{ID: "a", Group: "System", Run: noop})
	sched.Register(Task{ID: "b", Group: "Housekeeping", Run: noop})
	sched.Register(Task{ID: "c", Group: "System", Run: noop})
	sched.Register(Task{ID: "d", Run: noop}) // ungrouped
	groups := sched.Groups()
	if len(groups) != 2 || groups[0] != "Housekeeping" || groups[1] != "System" {
		t.Fatalf("unexpected groups %v", groups)
	}
}

func TestNilSchedulerIsSafe(t *testing.T) {
	// Every unit test in the api package builds a Server with no scheduler, and the admin
	// handler calls straight through to it.
	var sched *Scheduler
	if len(sched.Snapshot()) != 0 {
		t.Fatal("a nil scheduler should answer with an empty registry")
	}
	sched.Register(Task{ID: "a", Run: noop})
	sched.Start(context.Background())
}

func noop(context.Context) (string, error) { return "", nil }

func running(sched *Scheduler, id string) bool {
	for _, status := range sched.Snapshot() {
		if status.ID == id {
			return status.Running
		}
	}
	return false
}

func statusOf(t *testing.T, sched *Scheduler, id string) Status {
	t.Helper()
	for _, status := range sched.Snapshot() {
		if status.ID == id {
			return status
		}
	}
	t.Fatalf("no task %q", id)
	return Status{}
}

func waitForRun(t *testing.T, sched *Scheduler, id string) Status {
	t.Helper()
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		status := statusOf(t, sched, id)
		if status.LastRun != nil && !status.Running {
			return status
		}
		time.Sleep(5 * time.Millisecond)
	}
	t.Fatalf("task %q did not finish", id)
	return Status{}
}

var _ sync.Locker = (*sync.Mutex)(nil)

// The console needs both cadences to draw its control honestly: the one in force and the
// one the code declares. Reporting only the effective interval made "every ten minutes
// because that is the default" and "every ten minutes because somebody chose it" identical
// on the wire, so nothing could offer a way back to the default or mark a task as no longer
// running as shipped.
func TestSnapshotReportsTheDeclaredCadenceBesideTheEffectiveOne(t *testing.T) {
	sched := quietScheduler()
	sched.Register(Task{ID: "credits", Name: "Credits", Interval: 10 * time.Minute, Run: noop})

	before := sched.Snapshot()[0]
	if before.Interval != 600 || before.DefaultInterval != 600 {
		t.Fatalf("unoverridden task: interval %d, default %d, want 600 and 600",
			before.Interval, before.DefaultInterval)
	}

	if err := sched.SetInterval(context.Background(), "credits", time.Hour); err != nil {
		t.Fatalf("SetInterval: %v", err)
	}
	after := sched.Snapshot()[0]
	if after.Interval != 3600 {
		t.Fatalf("effective interval %d, want 3600", after.Interval)
	}
	// The declared cadence must survive the override, or the way back is lost.
	if after.DefaultInterval != 600 {
		t.Fatalf("declared cadence %d, want 600 — an override must not overwrite it",
			after.DefaultInterval)
	}
}

// A task that declares no cadence at all runs only when somebody presses the button, and
// the console has to be able to say so rather than printing "every 0 seconds".
func TestATaskWithNoDeclaredCadenceReportsZeroForBoth(t *testing.T) {
	sched := quietScheduler()
	sched.Register(Task{ID: "manual", Name: "Manual", Run: noop})

	status := sched.Snapshot()[0]
	if status.Interval != 0 || status.DefaultInterval != 0 {
		t.Fatalf("interval %d, default %d, want 0 and 0", status.Interval, status.DefaultInterval)
	}
}