package scheduler

import (
	"context"
	"errors"
	"sync/atomic"
	"testing"
	"time"
)

func TestRunOnce(t *testing.T) {
	var calls atomic.Int32
	s := New(0, func(ctx context.Context) error {
		calls.Add(1)
		return nil
	})
	if err := s.Run(context.Background()); err != nil {
		t.Fatalf("Run: %v", err)
	}
	if got := calls.Load(); got != 1 {
		t.Errorf("run called %d times, want 1", got)
	}
}

func TestRunPeriodic(t *testing.T) {
	var calls atomic.Int32
	s := New(10*time.Millisecond, func(ctx context.Context) error {
		calls.Add(1)
		return nil
	})
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() { done <- s.Run(ctx) }()

	time.Sleep(55 * time.Millisecond)
	cancel()
	if err := <-done; err != nil {
		t.Fatalf("Run: %v", err)
	}
	if got := calls.Load(); got < 3 {
		t.Errorf("run called %d times, want >= 3", got)
	}
}

func TestRunStopsOnError(t *testing.T) {
	var calls atomic.Int32
	wantErr := errors.New("boom")
	s := New(5*time.Millisecond, func(ctx context.Context) error {
		n := calls.Add(1)
		if n == 2 {
			return wantErr
		}
		return nil
	})
	if err := s.Run(context.Background()); !errors.Is(err, wantErr) {
		t.Fatalf("Run() error = %v, want %v", err, wantErr)
	}
	if got := calls.Load(); got != 2 {
		t.Errorf("run called %d times, want 2", got)
	}
}

func TestRunCancelledBeforeStart(t *testing.T) {
	var calls atomic.Int32
	s := New(time.Second, func(ctx context.Context) error {
		calls.Add(1)
		return nil
	})
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	if err := s.Run(ctx); err != nil {
		t.Fatalf("Run: %v", err)
	}
	if got := calls.Load(); got != 0 {
		t.Errorf("run called %d times, want 0", got)
	}
}

func TestRunCancellationIsNotAnError(t *testing.T) {
	var calls atomic.Int32
	s := New(5*time.Millisecond, func(ctx context.Context) error {
		calls.Add(1)
		time.Sleep(50 * time.Millisecond) // outlive cancellation
		return ctx.Err()
	})
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() { done <- s.Run(ctx) }()

	time.Sleep(12 * time.Millisecond)
	cancel()
	if err := <-done; err != nil {
		t.Fatalf("Run returned %v on cancellation, want nil", err)
	}
}