package dispatch

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

func TestRoundRobinApplicationsAndQueues(t *testing.T) {
	var r roster
	for i := 0; i < 40; i++ {
		r.add(Job{Context: context.Background(), Application: "noisy", Queue: "many-workers"})
	}
	for i := 0; i < 4; i++ {
		r.add(Job{Context: context.Background(), Application: "noisy", Queue: "other-queue"})
		r.add(Job{Context: context.Background(), Application: "quiet", Queue: "only-worker"})
	}
	want := []string{"noisy/many-workers", "quiet/only-worker", "noisy/other-queue", "quiet/only-worker", "noisy/many-workers", "quiet/only-worker", "noisy/other-queue", "quiet/only-worker"}
	for _, expected := range want {
		j, ok := r.next()
		if !ok || j.Application+"/"+j.Queue != expected {
			t.Fatalf("dispatch=%s/%s want=%s", j.Application, j.Queue, expected)
		}
		r.finish(j.Application)
	}
}
func TestPoolBoundsCancellationAndIsolation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	p := New(ctx, 2, 4)
	started := make(chan string, 4)
	var active, same atomic.Int32
	block := func(app string) Job {
		return Job{Context: ctx, Application: app, Queue: "queue", Run: func(ctx context.Context) {
			if active.Add(1) > 2 {
				t.Error("global dispatch concurrency exceeded")
			}
			defer active.Add(-1)
			if app == "noisy" {
				if same.Add(1) > 1 {
					t.Error("application ran concurrent claims")
				}
				defer same.Add(-1)
			}
			started <- app
			<-ctx.Done()
		}}
	}
	for _, app := range []string{"noisy", "noisy", "noisy", "quiet"} {
		if !p.Submit(block(app)) {
			t.Fatal("unexpected rejection")
		}
	}
	if p.Submit(block("overflow")) {
		t.Fatal("unbounded pending jobs")
	}
	seen := map[string]bool{}
	for range 2 {
		select {
		case app := <-started:
			seen[app] = true
		case <-time.After(time.Second):
			t.Fatal("one application blocked another")
		}
	}
	if !seen["quiet"] || !seen["noisy"] {
		t.Fatal("missing isolated application")
	}
	cancel()
	select {
	case <-p.Done():
	case <-time.After(time.Second):
		t.Fatal("shutdown did not cancel claims")
	}
	if len(p.slots) != 0 || active.Load() != 0 || p.Submit(block("late")) {
		t.Fatal("shutdown leaked slots or accepted more work")
	}
}
func TestPoolConcurrentSubmitAndShutdown(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	p := New(ctx, 4, 32)
	var wg sync.WaitGroup
	for i := 0; i < 20; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := 0; j < 100; j++ {
				p.Submit(Job{Context: ctx, Application: fmt.Sprint(i % 5), Queue: fmt.Sprint(i % 3), Run: func(ctx context.Context) {
					select {
					case <-ctx.Done():
					case <-time.After(time.Millisecond):
					}
				}})
			}
		}()
	}
	cancel()
	wg.Wait()
	select {
	case <-p.Done():
	case <-time.After(time.Second):
		t.Fatal("shutdown stuck")
	}
	if len(p.slots) != 0 {
		t.Fatal("pending jobs leaked")
	}
}

func TestCancelledJobsDoNotUseQueueTurnOrCapacity(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	var r roster
	released := 0
	r.add(Job{Context: ctx, Application: "stale", Queue: "gone", release: func() { released++ }})
	r.add(Job{Context: context.Background(), Application: "ready", Queue: "ready"})
	j, ok := r.next()
	if !ok || j.Application != "ready" || released != 1 {
		t.Fatal("cancelled job blocked live work")
	}
	r.finish("ready")
	if len(r.apps) != 0 {
		t.Fatal("empty applications retained")
	}
}