package postgres

import (
	"context"
	"sync"
	"testing"
	"time"

	"github.com/barkstack/pawsql/internal/config"
	"github.com/barkstack/pawsql/internal/router"
)

func TestResolverDefersManagedDatabaseStartup(t *testing.T) {
	routes, err := router.NewStaticResolver([]config.DatabaseConfig{
		{Name: "external", Upstream: "192.0.2.1:5432"},
		{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD"}},
	})
	if err != nil {
		t.Fatal(err)
	}
	ensurer := &fakeEnsurer{addresses: map[string]string{"managed": "127.0.0.1:55432"}}
	resolver := NewResolver(routes, []config.DatabaseConfig{
		{Name: "external", Upstream: "192.0.2.1:5432"},
		{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD"}},
	}, ensurer)

	backend, err := resolver.ResolveDatabase(context.Background(), "external")
	if err != nil {
		t.Fatal(err)
	}
	if backend.Address != "192.0.2.1:5432" || ensurer.calls != 0 {
		t.Errorf("external backend = %#v, calls = %d", backend, ensurer.calls)
	}

	backend, err = resolver.ResolveDatabase(context.Background(), "managed")
	if err != nil {
		t.Fatal(err)
	}
	if backend.Address != "127.0.0.1:55432" || ensurer.calls != 1 {
		t.Errorf("managed backend = %#v, calls = %d", backend, ensurer.calls)
	}
}

func TestResolverSerializesManagedStartup(t *testing.T) {
	routes, err := router.NewStaticResolver([]config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD"}}})
	if err != nil {
		t.Fatal(err)
	}
	ensurer := &fakeEnsurer{addresses: map[string]string{"managed": "127.0.0.1:55432"}, gate: make(chan struct{}), started: make(chan struct{})}
	resolver := NewResolver(routes, []config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD"}}}, ensurer)

	var wg sync.WaitGroup
	for range 2 {
		wg.Add(1)
		go func() {
			defer wg.Done()
			_, _ = resolver.ResolveDatabase(context.Background(), "managed")
		}()
	}
	<-ensurer.started
	close(ensurer.gate)
	wg.Wait()
	if ensurer.calls != 2 {
		t.Errorf("EnsureDatabase calls = %d, want 2 route resolutions", ensurer.calls)
	}
	if ensurer.maxActive != 1 {
		t.Errorf("concurrent EnsureDatabase calls = %d, want 1", ensurer.maxActive)
	}
}

func TestResolverStopsDatabaseAfterIdleTimeout(t *testing.T) {
	routes, err := router.NewStaticResolver([]config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD", IdleTimeout: 20 * time.Millisecond}}})
	if err != nil {
		t.Fatal(err)
	}
	controller := &fakeEnsurer{addresses: map[string]string{"managed": "127.0.0.1:55432"}, stopped: make(chan string, 1)}
	resolver := NewResolver(routes, []config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD", IdleTimeout: 20 * time.Millisecond}}}, controller)

	if _, err := resolver.ResolveDatabase(context.Background(), "managed"); err != nil {
		t.Fatal(err)
	}
	resolver.ReleaseConnection("managed")
	select {
	case database := <-controller.stopped:
		if database != "managed" {
			t.Errorf("stopped database = %q", database)
		}
	case <-time.After(time.Second):
		t.Fatal("managed database was not stopped after idle timeout")
	}
}

func TestResolverCancelsIdleStopForNewConnection(t *testing.T) {
	routes, err := router.NewStaticResolver([]config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD", IdleTimeout: 40 * time.Millisecond}}})
	if err != nil {
		t.Fatal(err)
	}
	controller := &fakeEnsurer{addresses: map[string]string{"managed": "127.0.0.1:55432"}, stopped: make(chan string, 1)}
	resolver := NewResolver(routes, []config.DatabaseConfig{{Name: "managed", Postgres: &config.PostgresConfig{Image: "postgres:18", Volume: "managed-data", PasswordEnv: "MANAGED_PASSWORD", IdleTimeout: 40 * time.Millisecond}}}, controller)

	if _, err := resolver.ResolveDatabase(context.Background(), "managed"); err != nil {
		t.Fatal(err)
	}
	resolver.ReleaseConnection("managed")
	if _, err := resolver.ResolveDatabase(context.Background(), "managed"); err != nil {
		t.Fatal(err)
	}
	select {
	case database := <-controller.stopped:
		t.Fatalf("stopped active database %q", database)
	case <-time.After(80 * time.Millisecond):
	}
	resolver.ReleaseConnection("managed")
	select {
	case <-controller.stopped:
	case <-time.After(time.Second):
		t.Fatal("managed database was not stopped after final lease release")
	}
}

func TestResolverMetersTrafficAndStopsTrafficIdleSession(t *testing.T) {
	postgres := &config.PostgresConfig{
		Image:              "postgres:18",
		Volume:             "managed-data",
		PasswordEnv:        "MANAGED_PASSWORD",
		TrafficIdleTimeout: 100 * time.Millisecond,
	}
	routes, err := router.NewStaticResolver([]config.DatabaseConfig{{Name: "managed", Postgres: postgres}})
	if err != nil {
		t.Fatal(err)
	}
	controller := &fakeEnsurer{addresses: map[string]string{"managed": "127.0.0.1:55432"}, stopped: make(chan string, 1)}
	resolver := NewResolver(routes, []config.DatabaseConfig{{Name: "managed", Postgres: postgres}}, controller)

	if _, err := resolver.ResolveDatabase(context.Background(), "managed"); err != nil {
		t.Fatal(err)
	}
	time.Sleep(70 * time.Millisecond)
	resolver.RecordTraffic("managed", true, 7)
	resolver.RecordTraffic("managed", false, 11)
	stats, ok := resolver.TrafficStats("managed")
	if !ok || stats.ActiveConnections != 1 || stats.ClientBytes != 7 || stats.BackendBytes != 11 || stats.LastActivity.IsZero() {
		t.Errorf("TrafficStats() = %#v, %t", stats, ok)
	}
	select {
	case database := <-controller.stopped:
		t.Fatalf("stopped database %q despite recent traffic", database)
	case <-time.After(50 * time.Millisecond):
	}
	select {
	case database := <-controller.stopped:
		if database != "managed" {
			t.Errorf("stopped database = %q", database)
		}
	case <-time.After(time.Second):
		t.Fatal("managed database was not stopped after traffic idle timeout")
	}
}

type fakeEnsurer struct {
	mu          sync.Mutex
	addresses   map[string]string
	calls       int
	active      int
	maxActive   int
	gate        chan struct{}
	started     chan struct{}
	startedOnce sync.Once
	stopped     chan string
}

func (f *fakeEnsurer) EnsureDatabase(_ context.Context, database string, _ config.PostgresConfig) (string, error) {
	f.mu.Lock()
	f.calls++
	f.active++
	if f.active > f.maxActive {
		f.maxActive = f.active
	}
	if f.started != nil {
		f.startedOnce.Do(func() { close(f.started) })
	}
	f.mu.Unlock()
	if f.gate != nil {
		<-f.gate
	}
	f.mu.Lock()
	f.active--
	address := f.addresses[database]
	f.mu.Unlock()
	return address, nil
}

func (f *fakeEnsurer) StopDatabase(_ context.Context, database string) error {
	if f.stopped != nil {
		f.stopped <- database
	}
	return nil
}