package worker

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

	"code.nochebuena.dev/go/logz"
)

func newLogger() logz.Logger { return logz.New(logz.Options{}) }

func startWorker(t *testing.T, cfg Config) Component {
	t.Helper()
	c := New(newLogger(), cfg)
	if err := c.OnInit(); err != nil {
		t.Fatalf("OnInit: %v", err)
	}
	if err := c.OnStart(); err != nil {
		t.Fatalf("OnStart: %v", err)
	}
	return c
}

func TestNew(t *testing.T) {
	if New(newLogger(), Config{}) == nil {
		t.Fatal("New returned nil")
	}
}

func TestWorker_DispatchAndExecute(t *testing.T) {
	done := make(chan struct{})
	c := startWorker(t, Config{PoolSize: 1, BufferSize: 10, ShutdownTimeout: time.Second})

	c.Dispatch(func(ctx context.Context) error {
		close(done)
		return nil
	})

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("task not executed in time")
	}
	c.OnStop()
}

func TestWorker_BackpressureFull(t *testing.T) {
	// Block the single worker so the queue fills up.
	block := make(chan struct{})
	c := startWorker(t, Config{PoolSize: 1, BufferSize: 1, ShutdownTimeout: time.Second})

	c.Dispatch(func(ctx context.Context) error { <-block; return nil }) // fills worker
	c.Dispatch(func(ctx context.Context) error { return nil })          // fills buffer

	ok := c.Dispatch(func(ctx context.Context) error { return nil }) // should be dropped
	if ok {
		t.Error("expected Dispatch to return false when queue is full")
	}
	close(block)
	c.OnStop()
}

func TestWorker_OnStop_DrainsQueue(t *testing.T) {
	var count int64
	c := startWorker(t, Config{PoolSize: 2, BufferSize: 50, ShutdownTimeout: 5 * time.Second})

	for i := 0; i < 10; i++ {
		c.Dispatch(func(ctx context.Context) error {
			atomic.AddInt64(&count, 1)
			return nil
		})
	}
	c.OnStop()

	if atomic.LoadInt64(&count) != 10 {
		t.Errorf("expected 10 tasks completed, got %d", count)
	}
}

func TestWorker_OnStop_Timeout(t *testing.T) {
	c := startWorker(t, Config{PoolSize: 1, BufferSize: 1,
		ShutdownTimeout: 50 * time.Millisecond})

	// Dispatch a task that blocks longer than ShutdownTimeout.
	c.Dispatch(func(ctx context.Context) error {
		time.Sleep(500 * time.Millisecond)
		return nil
	})

	start := time.Now()
	c.OnStop()
	elapsed := time.Since(start)

	// OnStop should return after ~ShutdownTimeout, not after 500ms.
	if elapsed > 300*time.Millisecond {
		t.Errorf("OnStop blocked too long: %v", elapsed)
	}
}

func TestWorker_TaskTimeout(t *testing.T) {
	var ctxCancelled int64
	c := startWorker(t, Config{
		PoolSize: 1, BufferSize: 10,
		TaskTimeout:     50 * time.Millisecond,
		ShutdownTimeout: time.Second,
	})

	done := make(chan struct{})
	c.Dispatch(func(ctx context.Context) error {
		defer close(done)
		select {
		case <-ctx.Done():
			atomic.StoreInt64(&ctxCancelled, 1)
		case <-time.After(500 * time.Millisecond):
		}
		return nil
	})

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("task did not complete in time")
	}
	if atomic.LoadInt64(&ctxCancelled) != 1 {
		t.Error("expected task context to be cancelled by TaskTimeout")
	}
	c.OnStop()
}

func TestWorker_MultipleWorkers(t *testing.T) {
	const n = 5
	var wg sync.WaitGroup
	wg.Add(n)
	started := make(chan struct{}, n)

	c := startWorker(t, Config{PoolSize: n, BufferSize: n, ShutdownTimeout: time.Second})

	block := make(chan struct{})
	for i := 0; i < n; i++ {
		c.Dispatch(func(ctx context.Context) error {
			started <- struct{}{}
			<-block
			wg.Done()
			return nil
		})
	}

	// All n tasks should start concurrently.
	timer := time.NewTimer(time.Second)
	defer timer.Stop()
	for i := 0; i < n; i++ {
		select {
		case <-started:
		case <-timer.C:
			t.Fatalf("only %d/%d workers started concurrently", i, n)
		}
	}
	close(block)
	c.OnStop()
}

func TestWorker_TaskError(t *testing.T) {
	c := startWorker(t, Config{PoolSize: 1, BufferSize: 10, ShutdownTimeout: time.Second})

	done := make(chan struct{})
	c.Dispatch(func(ctx context.Context) error {
		defer close(done)
		return errors.New("task error")
	})

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("task did not run")
	}
	c.OnStop() // should not panic
}

func TestWorker_Lifecycle(t *testing.T) {
	c := New(newLogger(), Config{PoolSize: 2, BufferSize: 10, ShutdownTimeout: time.Second})
	if err := c.OnInit(); err != nil {
		t.Fatalf("OnInit: %v", err)
	}
	if err := c.OnStart(); err != nil {
		t.Fatalf("OnStart: %v", err)
	}
	done := make(chan struct{})
	c.Dispatch(func(ctx context.Context) error { close(done); return nil })
	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("task not executed")
	}
	if err := c.OnStop(); err != nil {
		t.Fatalf("OnStop: %v", err)
	}
}