package httprc_test

import (
	"context"
	"encoding/json"
	"io"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"os"
	"strconv"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/lestrrat-go/httprc/v3"
	"github.com/lestrrat-go/httprc/v3/tracesink"
	"github.com/stretchr/testify/require"
)

func TestResource(t *testing.T) {
	const dummy = "https://127.0.0.1:99999999"
	r, err := httprc.NewResource[[]byte](dummy, httprc.BytesTransformer())
	require.NoError(t, err, `NewResource should succeed`)
	require.Equal(t, httprc.DefaultMinInterval, r.MinInterval(), `r.MinInterval should return DefaultMinInterval`)
	require.Equal(t, httprc.DefaultMaxInterval, r.MaxInterval(), `r.MaxInterval should return DefaultMaxInterval`)

	r, err = httprc.NewResource[[]byte](dummy, httprc.BytesTransformer(), httprc.WithMinInterval(12*time.Second))
	require.NoError(t, err, `NewResource should succeed`)
	require.Equal(t, 12*time.Second, r.MinInterval(), `r.MinInterval should return expected value`)
	require.Equal(t, httprc.DefaultMaxInterval, r.MaxInterval(), `r.MaxInterval should return DefaultMaxInterval`)

	r, err = httprc.NewResource[[]byte](dummy, httprc.BytesTransformer(), httprc.WithMaxInterval(12*time.Second))
	require.NoError(t, err, `NewResource should succeed`)
	require.Equal(t, httprc.DefaultMinInterval, r.MinInterval(), `r.MinInterval should return DefaultMinInterval`)
	require.Equal(t, 12*time.Second, r.MaxInterval(), `r.MaxInterval should return expected value`)
}

func TestClient(t *testing.T) {
	type Hello struct {
		Hello string `json:"hello"`
	}

	start := time.Now()
	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "max-age=2")
		var version string
		if time.Since(start) > 2*time.Second {
			version = "2"
		}
		switch r.URL.Path {
		case "/json/helloptr", "/json/hello", "/json/hellomap":
			w.Header().Set("Content-Type", "application/json")
			switch version {
			case "2":
				w.Write([]byte(`{"hello":"world2"}`))
			default:
				w.Write([]byte(`{"hello":"world"}`))
			}
		case "/int":
			w.Header().Set("Content-Type", "text/plain")
			w.Write([]byte(`42`))
		case "/string":
			w.Header().Set("Content-Type", "text/plain")
			w.Write([]byte(`Lorem ipsum dolor sit amet`))
		case "/custom":
		}
	})

	srv := httptest.NewServer(h)
	defer srv.Close()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	options := []httprc.NewClientOption{
		//		httprc.WithTraceSink(tracesink.NewSlog(slog.New(slog.NewJSONHandler(os.Stdout, nil)))),
	}
	cl := httprc.NewClient(options...)
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err, `cl.Run should succeed`)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	testcases := []struct {
		URL       string
		Create    func() (httprc.Resource, error)
		Expected  any
		Expected2 any
	}{
		{
			URL: srv.URL + "/json/helloptr",
			Create: func() (httprc.Resource, error) {
				r, err := httprc.NewResource[*Hello](srv.URL+"/json/helloptr", httprc.JSONTransformer[*Hello]())
				if err != nil {
					return nil, err
				}
				r.SetMinInterval(time.Second)
				return r, nil
			},
			Expected:  &Hello{Hello: "world"},
			Expected2: &Hello{Hello: "world2"},
		},
		{
			URL: srv.URL + "/json/hello",
			Create: func() (httprc.Resource, error) {
				r, err := httprc.NewResource[Hello](srv.URL+"/json/hello", httprc.JSONTransformer[Hello]())
				if err != nil {
					return nil, err
				}
				r.SetMinInterval(time.Second)
				return r, nil
			},
			Expected:  Hello{Hello: "world"},
			Expected2: Hello{Hello: "world2"},
		},
		{
			URL: srv.URL + "/json/hellomap",
			Create: func() (httprc.Resource, error) {
				r, err := httprc.NewResource[map[string]any](srv.URL+"/json/hellomap", httprc.JSONTransformer[map[string]any]())
				if err != nil {
					return nil, err
				}
				r.SetMinInterval(time.Second)
				return r, nil
			},
			Expected:  map[string]any{"hello": "world"},
			Expected2: map[string]any{"hello": "world2"},
		},
		{
			URL: srv.URL + "/int",
			Create: func() (httprc.Resource, error) {
				return httprc.NewResource[int](srv.URL+"/int", httprc.TransformFunc[int](func(_ context.Context, res *http.Response) (int, error) {
					buf, err := io.ReadAll(res.Body)
					if err != nil {
						return 0, err
					}
					return strconv.Atoi(string(buf))
				}))
			},
			Expected: 42,
		},
		{
			URL: srv.URL + "/string",
			Create: func() (httprc.Resource, error) {
				return httprc.NewResource[string](srv.URL+"/string", httprc.TransformFunc[string](func(_ context.Context, res *http.Response) (string, error) {
					buf, err := io.ReadAll(res.Body)
					if err != nil {
						return "", err
					}
					return string(buf), nil
				}))
			},
			Expected: "Lorem ipsum dolor sit amet",
		},
	}

	for _, tc := range testcases {
		t.Run(tc.URL, func(t *testing.T) {
			r, err := tc.Create()
			require.NoError(t, err, `NewResource should succeed`)

			require.NoError(t, ctrl.Add(ctx, r), `ctrl.Add should succeed`)
			require.NoError(t, r.Ready(ctx), `r.Ready should succeed`)

			var dst any
			require.NoError(t, r.Get(&dst), `r.Get should succeed`)

			require.Equal(t, tc.Expected, dst, `r.Get should return expected value`)
		})
	}

	time.Sleep(6 * time.Second)
	for _, tc := range testcases {
		t.Run("Lookup "+tc.URL, func(t *testing.T) {
			r, err := ctrl.Lookup(ctx, tc.URL)
			require.NoError(t, err, `ctrl.Lookup should succeed`)
			require.Equal(t, tc.URL, r.URL(), `r.URL should return expected value`)

			var dst any
			require.NoError(t, r.Get(&dst), `r.Get should succeed`)

			expected := tc.Expected2
			if expected == nil {
				expected = tc.Expected
			}
			require.Equal(t, expected, dst, `r.Resource should return expected value`)
		})
	}
}

func TestRefresh(t *testing.T) {
	count := 0
	var mu sync.Mutex
	h := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		mu.Lock()
		defer mu.Unlock()
		count++
		json.NewEncoder(w).Encode(map[string]any{"count": count})
	})
	srv := httptest.NewServer(h)
	defer srv.Close()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	options := []httprc.NewClientOption{
		httprc.WithWhitelist(httprc.NewInsecureWhitelist()),
	}
	cl := httprc.NewClient(options...)
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err, `cl.Run should succeed`)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	r, err := httprc.NewResource[map[string]int](srv.URL, httprc.JSONTransformer[map[string]int]())
	require.NoError(t, err, `NewResource should succeed`)

	require.NoError(t, ctrl.Add(ctx, r), `ctrl.Add should succeed`)

	require.NoError(t, r.Ready(ctx), `r.Ready should succeed`)

	for i := 1; i <= 5; i++ {
		m := r.Resource()
		require.Equal(t, i, m["count"], `r.Resource should return expected value`)
		require.NoError(t, ctrl.Refresh(ctx, srv.URL), `r.Refresh should succeed`)
	}
}

func Test_gh74(t *testing.T) {
	// Test server that returns simple JSON data
	testData := `{"test": "data"}`
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = w.Write([]byte(testData))
	}))
	t.Cleanup(func() { server.Close() })

	// Create httprc client with trace logging
	client := httprc.NewClient(
		httprc.WithTraceSink(
			tracesink.NewSlog(slog.New(slog.NewJSONHandler(os.Stdout, nil)))),
	)

	// Create a resource that transforms bytes
	resource, err := httprc.NewResource[[]byte](server.URL, httprc.BytesTransformer())
	require.NoError(t, err, "failed to create resource")

	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
	defer cancel()

	// Start the client to get a controller
	ctrl, err := client.Start(ctx)
	require.NoError(t, err, "failed to start client")
	defer func() {
		_ = ctrl.Shutdown(time.Second)
	}()

	// Test the original issue: Add with WithWaitReady(false) followed by Refresh calls
	// This would block before the fix
	require.NoError(t, ctrl.Add(ctx, resource, httprc.WithWaitReady(false)), "Add should succeed")

	// These refresh calls would block indefinitely before the fix
	for i := range 10 {
		err = ctrl.Refresh(ctx, server.URL)
		require.NoError(t, err, "refresh should succeed on iteration %d", i)

		// Verify we can lookup the resource
		res, err := ctrl.Lookup(ctx, server.URL)
		require.NoError(t, err, "lookup should succeed")
		require.NotNil(t, res, "resource should not be nil")
	}
}

// TestAdd_returns_err_not_ready_when_ready_fails tests that ErrNotReady is returned
// when Ready() fails but registration succeeded
func TestAdd_returns_err_not_ready_when_ready_fails(t *testing.T) {
	t.Parallel()

	// Setup: Create mock HTTP server that returns invalid JSON
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(`{invalid json`))
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]any](
		server.URL,
		httprc.JSONTransformer[map[string]any](),
	)
	require.NoError(t, err)

	// Act: Add with timeout (will fail on Ready due to invalid JSON)
	addCtx, cancel := context.WithTimeout(ctx, 1*time.Second)
	defer cancel()

	err = ctrl.Add(addCtx, resource)

	// Assert: Should return ErrNotReady
	require.Error(t, err, "expected error when Ready() fails")
	require.ErrorIs(t, err, httprc.ErrNotReady(), "expected ErrNotReady")

	// Verify resource IS in backend
	existing, lookupErr := ctrl.Lookup(ctx, server.URL)
	require.NoError(t, lookupErr, "resource should be in backend after ErrNotReady")
	require.NotNil(t, existing, "resource should exist in backend")
}

// TestAdd_does_not_return_err_not_ready_when_registration_fails tests that ErrNotReady
// is NOT returned when registration fails (before Ready() is called)
func TestAdd_does_not_return_err_not_ready_when_registration_fails(t *testing.T) {
	t.Parallel()

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	// Add first resource
	resource1, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
	)
	require.NoError(t, err)
	require.NoError(t, ctrl.Add(ctx, resource1, httprc.WithWaitReady(false)))

	// Try to add duplicate
	resource2, err := httprc.NewResource[map[string]string](
		server.URL, // Same URL
		httprc.JSONTransformer[map[string]string](),
	)
	require.NoError(t, err)

	err = ctrl.Add(ctx, resource2)

	// Assert: Should NOT be ErrNotReady (registration failed before Ready)
	require.Error(t, err, "expected error for duplicate URL")
	require.NotErrorIs(t, err, httprc.ErrNotReady(), "should not return ErrNotReady for registration failure")
}

// TestAdd_with_wait_ready_false_never_returns_err_not_ready tests that WithWaitReady(false)
// never returns ErrNotReady because Ready() is not called
func TestAdd_with_wait_ready_false_never_returns_err_not_ready(t *testing.T) {
	t.Parallel()

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(`{invalid json`))
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]any](
		server.URL,
		httprc.JSONTransformer[map[string]any](),
	)
	require.NoError(t, err)

	// Act: Add with WithWaitReady(false)
	err = ctrl.Add(ctx, resource, httprc.WithWaitReady(false))

	// Assert: Should succeed (no error) because we didn't wait for Ready
	require.NoError(t, err, "expected no error with WithWaitReady(false)")

	// Verify resource is in backend
	existing, lookupErr := ctrl.Lookup(ctx, server.URL)
	require.NoError(t, lookupErr, "resource should be in backend")
	require.NotNil(t, existing, "expected resource in backend")

	// Verify Ready() will fail separately
	readyCtx, cancel := context.WithTimeout(ctx, 1*time.Second)
	defer cancel()

	readyErr := resource.Ready(readyCtx)
	require.Error(t, readyErr, "expected Ready() to fail with invalid JSON")
}

// TestErrNotReady_wraps_underlying_error tests that ErrNotReady wraps the
// underlying error using Go 1.20+ multi-error wrapping
func TestErrNotReady_wraps_underlying_error(t *testing.T) {
	t.Parallel()

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		time.Sleep(2 * time.Second) // Longer than context timeout
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
	)
	require.NoError(t, err)

	// Add with short timeout
	addCtx, cancel := context.WithTimeout(ctx, 500*time.Millisecond)
	defer cancel()

	err = ctrl.Add(addCtx, resource)

	// Assert: Should be ErrNotReady wrapping DeadlineExceeded
	require.ErrorIs(t, err, httprc.ErrNotReady(), "expected ErrNotReady")
	require.ErrorIs(t, err, context.DeadlineExceeded, "expected wrapped DeadlineExceeded")
}

// TestAdd_whitelist_blocked_not_err_not_ready tests that whitelist blocking
// returns a non-ErrNotReady error
func TestAdd_whitelist_blocked_not_err_not_ready(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	cl := httprc.NewClient(httprc.WithWhitelist(httprc.WhitelistFunc(func(_ string) bool {
		return false // Block everything
	})))
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]any](
		"https://example.com",
		httprc.JSONTransformer[map[string]any](),
	)
	require.NoError(t, err)

	err = ctrl.Add(ctx, resource)

	// Assert: Should return whitelist error, not ErrNotReady
	require.Error(t, err, "expected whitelist error")
	require.NotErrorIs(t, err, httprc.ErrNotReady(), "whitelist blocking should not return ErrNotReady")
	require.ErrorIs(t, err, httprc.ErrBlockedByWhitelist(), "expected ErrBlockedByWhitelist")
}

// TestAdd_context_cancelled_before_send_backend_not_err_not_ready tests that context
// cancellation before registration completes returns non-ErrNotReady
func TestAdd_context_cancelled_before_send_backend_not_err_not_ready(t *testing.T) {
	t.Parallel()

	ctx, cancel := context.WithCancel(context.Background())
	cancel() // Cancel immediately

	cl := httprc.NewClient()
	ctrl, err := cl.Start(context.Background())
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]any](
		"https://example.com",
		httprc.JSONTransformer[map[string]any](),
	)
	require.NoError(t, err)

	err = ctrl.Add(ctx, resource)

	// Assert: Should return context error, not ErrNotReady
	require.Error(t, err, "expected context error")
	require.NotErrorIs(t, err, httprc.ErrNotReady(), "context cancellation should not return ErrNotReady")
	require.ErrorIs(t, err, context.Canceled, "expected context.Canceled")
}

// TestAdd_retry_logic_distinguishes_errors tests that retry logic can properly
// distinguish between registration failures and ErrNotReady
func TestAdd_retry_logic_distinguishes_errors(t *testing.T) {
	t.Parallel()

	// Server returns valid data after 2 seconds
	callCount := 0
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		callCount++
		if callCount == 1 {
			time.Sleep(2 * time.Second) // First call times out
		}
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	// First attempt: times out
	resource1, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
	)
	require.NoError(t, err)

	ctx1, cancel1 := context.WithTimeout(ctx, 500*time.Millisecond)
	defer cancel1()

	err1 := ctrl.Add(ctx1, resource1)
	require.ErrorIs(t, err1, httprc.ErrNotReady(), "first attempt should return ErrNotReady")

	// Verify resource is in backend - should NOT retry Add()
	existing, lookupErr := ctrl.Lookup(ctx, server.URL)
	require.NoError(t, lookupErr, "resource should be in backend")
	require.NotNil(t, existing)

	// Second attempt: should fail with duplicate URL (correct behavior)
	resource2, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
	)
	require.NoError(t, err)

	err2 := ctrl.Add(ctx, resource2)
	require.Error(t, err2, "second Add should fail with duplicate URL")
	require.NotErrorIs(t, err2, httprc.ErrNotReady(), "duplicate URL should not return ErrNotReady")

	// Instead, wait for existing resource to be ready
	ctx3, cancel3 := context.WithTimeout(ctx, 5*time.Second)
	defer cancel3()

	err3 := existing.Ready(ctx3)
	require.NoError(t, err3, "existing resource should become ready")
}

// controlledHandler implements a deterministic HTTP handler for testing
// retry logic. It uses an atomic counter to control exactly when to
// transition from failure (invalid JSON) to success (valid JSON).
// See DESIGN_SYNC_TEST.md for detailed design rationale.
type controlledHandler struct {
	failuresRemaining atomic.Int32
}

func (h *controlledHandler) ServeHTTP(w http.ResponseWriter, _ *http.Request) {
	w.WriteHeader(http.StatusOK)

	// Atomically decrement and check if we should still fail
	if remaining := h.failuresRemaining.Add(-1); remaining >= 0 {
		// Still have failures remaining, return invalid JSON
		w.Write([]byte(`{invalid json`))
	} else {
		// No more failures needed, return valid JSON
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	}
}

// TestIntegration_invalid_json_background_retry tests the end-to-end flow
// when a server initially returns invalid JSON, then valid JSON on retry
func TestIntegration_invalid_json_background_retry(t *testing.T) {
	t.Parallel()

	// Test configuration
	const (
		minInterval = 100 * time.Millisecond
		timeout     = 500 * time.Millisecond
	)

	// Validate preconditions
	require.Greater(t, timeout, minInterval,
		"timeout must be greater than minInterval to allow at least one fetch")

	// Setup controlled server
	// Calculate failures needed with 2x safety margin to guarantee timeout
	// Formula: (timeout / minInterval) * 2
	// Note: Integer division truncates, making this calculation conservative
	// Example: (500ms / 100ms) * 2 = 5 * 2 = 10 failures
	failuresNeeded := int32((timeout / minInterval) * 2)

	handler := &controlledHandler{}
	handler.failuresRemaining.Store(failuresNeeded)
	server := httptest.NewServer(handler)
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
		httprc.WithMinInterval(minInterval),
	)
	require.NoError(t, err)

	// Add resource with timeout
	// Server is configured to fail enough times that timeout will fire
	addCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	err = ctrl.Add(addCtx, resource)

	// Assert ErrNotReady returned
	// Guaranteed because server will keep failing until we change the counter
	require.ErrorIs(t, err, httprc.ErrNotReady(), "expected ErrNotReady")

	// Verify resource is in backend (registration succeeded)
	existing, lookupErr := ctrl.Lookup(ctx, server.URL)
	require.NoError(t, lookupErr, "resource should be in backend")
	require.NotNil(t, existing, "resource should exist")

	// Allow server to succeed on next fetch
	// Safe to modify counter now because:
	// - Previous fetch failed (we got ErrNotReady)
	// - Next fetch won't start until minInterval elapses
	// - No concurrent access to the counter at this moment
	handler.failuresRemaining.Store(0)

	// Wait for background retry to make resource ready
	// The next fetch attempt will succeed and close the ready channel
	readyCtx, readyCancel := context.WithTimeout(ctx, 5*time.Second)
	defer readyCancel()

	err = resource.Ready(readyCtx)
	require.NoError(t, err, "resource should become ready after background retry")

	// Verify data is available
	var data map[string]string
	err = resource.Get(&data)
	require.NoError(t, err, "should be able to get data")
	require.Equal(t, "ok", data["status"], "data should have correct status")
}

// TestGH1551 reproduces the deadlock described in
// https://github.com/lestrrat-go/jwx/issues/1551.
//
// When manual Refresh() calls fail (e.g. HTTP 500), each failure kills the
// worker goroutine that processed it (worker.go returns on sync error).
// After N failures (where N = number of workers), all workers are dead and
// subsequent Refresh() calls block forever because nobody drains the
// syncoutgoing channel.
func TestGH1551(t *testing.T) {
	t.Parallel()

	t.Run("sync refresh deadlock", func(t *testing.T) {
		t.Parallel()

		const numWorkers = 3

		// Server that always returns HTTP 500
		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		}))
		t.Cleanup(srv.Close)

		ctx, cancel := context.WithCancel(context.Background())
		t.Cleanup(cancel)

		traceDst := io.Discard
		if testing.Verbose() {
			traceDst = os.Stderr
		}

		cl := httprc.NewClient(
			httprc.WithWorkers(numWorkers),
			httprc.WithTraceSink(tracesink.NewSlog(slog.New(slog.NewJSONHandler(traceDst, nil)))),
		)
		ctrl, err := cl.Start(ctx)
		require.NoError(t, err)
		t.Cleanup(func() { ctrl.Shutdown(time.Second) })

		// Register a resource without waiting for it to become ready
		// (since it will never succeed with a 500 server)
		resource, err := httprc.NewResource[[]byte](
			srv.URL,
			httprc.BytesTransformer(),
			httprc.WithConstantInterval(time.Hour), // prevent periodic refresh from interfering
		)
		require.NoError(t, err)
		require.NoError(t, ctrl.Add(ctx, resource, httprc.WithWaitReady(false)))

		// Fire numWorkers Refresh() calls that all fail. Each one kills a worker.
		for i := range numWorkers {
			refreshCtx, refreshCancel := context.WithTimeout(ctx, 5*time.Second)
			err := ctrl.Refresh(refreshCtx, srv.URL)
			refreshCancel()
			// The refresh should return an error (HTTP 500), not hang.
			require.Error(t, err, "Refresh #%d should return an error", i)
			t.Logf("Refresh #%d failed as expected: %v", i, err)
		}

		// At this point all workers should be dead (before the fix).
		// The next Refresh() call will deadlock because no worker is alive
		// to drain the syncoutgoing channel.
		t.Log("All workers should have failed. Attempting one more Refresh()...")

		deadlockCtx, deadlockCancel := context.WithTimeout(ctx, 5*time.Second)
		defer deadlockCancel()

		err = ctrl.Refresh(deadlockCtx, srv.URL)
		// Before the fix: this blocks until deadlockCtx expires (context.DeadlineExceeded).
		// After the fix: this should return promptly with the HTTP 500 error.
		require.Error(t, err, "Refresh after all workers failed should still return an error")
		require.NotErrorIs(t, err, context.DeadlineExceeded,
			"Refresh should not deadlock (got context deadline exceeded, indicating workers are stuck)")
		t.Logf("Post-failure Refresh returned: %v", err)
	})

	// Verify that periodic (async) refresh continues to function even after
	// synchronous Refresh() calls have failed. Before the fix, dead workers
	// meant async refreshes also stopped being processed.
	t.Run("async refresh still works after sync failures", func(t *testing.T) {
		t.Parallel()

		const numWorkers = 2

		// Server that starts returning 500, then switches to 200
		var shouldFail atomic.Bool
		shouldFail.Store(true)

		var successCount atomic.Int64
		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
			if shouldFail.Load() {
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
				return
			}
			successCount.Add(1)
			w.Header().Set("Content-Type", "application/octet-stream")
			w.Write([]byte("ok"))
		}))
		t.Cleanup(srv.Close)

		ctx, cancel := context.WithCancel(context.Background())
		t.Cleanup(cancel)

		traceDst := io.Discard
		if testing.Verbose() {
			traceDst = os.Stderr
		}

		cl := httprc.NewClient(
			httprc.WithWorkers(numWorkers),
			httprc.WithTraceSink(tracesink.NewSlog(slog.New(slog.NewJSONHandler(traceDst, nil)))),
		)
		ctrl, err := cl.Start(ctx)
		require.NoError(t, err)
		t.Cleanup(func() { ctrl.Shutdown(time.Second) })

		resource, err := httprc.NewResource[[]byte](
			srv.URL,
			httprc.BytesTransformer(),
			httprc.WithConstantInterval(500*time.Millisecond), // short interval for async refresh
		)
		require.NoError(t, err)
		require.NoError(t, ctrl.Add(ctx, resource, httprc.WithWaitReady(false)))

		// Let the initial async fetch (triggered by Add) complete before
		// starting sync refreshes, to avoid a race between the async
		// dispatch and the synchronous Refresh calls.
		time.Sleep(time.Second)

		// Kill all workers via failed sync refreshes
		for i := range numWorkers {
			refreshCtx, refreshCancel := context.WithTimeout(ctx, 5*time.Second)
			err := ctrl.Refresh(refreshCtx, srv.URL)
			refreshCancel()
			require.Error(t, err, "Refresh #%d should fail", i)
		}

		// Now make the server return 200
		shouldFail.Store(false)
		countBefore := successCount.Load()

		// Wait for async refreshes to pick up the resource
		time.Sleep(3 * time.Second)

		countAfter := successCount.Load()
		require.Greater(t, countAfter, countBefore,
			"Async refresh should still work after sync refresh failures killed workers. "+
				"No successful requests were made, indicating workers are dead.")
	})
}

// TestIntegration_multiple_ready_calls_after_err_not_ready tests that multiple
// Ready() calls work correctly after ErrNotReady
func TestIntegration_multiple_ready_calls_after_err_not_ready(t *testing.T) {
	t.Parallel()

	// Setup: Server returns invalid JSON first, then valid JSON
	callCount := 0
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		callCount++
		w.WriteHeader(http.StatusOK)
		if callCount == 1 {
			w.Write([]byte(`{invalid json`)) // First call: invalid
		} else {
			json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
		}
	}))
	t.Cleanup(server.Close)

	ctx := context.Background()
	cl := httprc.NewClient()
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	resource, err := httprc.NewResource[map[string]string](
		server.URL,
		httprc.JSONTransformer[map[string]string](),
		httprc.WithMinInterval(100*time.Millisecond),
	)
	require.NoError(t, err)

	// First Add() - returns ErrNotReady
	ctx1, cancel1 := context.WithTimeout(ctx, 100*time.Millisecond)
	defer cancel1()

	err1 := ctrl.Add(ctx1, resource)
	require.ErrorIs(t, err1, httprc.ErrNotReady(), "expected ErrNotReady")

	// Verify resource is in backend
	existing, lookupErr := ctrl.Lookup(ctx, server.URL)
	require.NoError(t, lookupErr, "resource should be in backend")
	require.NotNil(t, existing)

	// Call Ready() again - should eventually succeed after backend retries
	ctx2, cancel2 := context.WithTimeout(ctx, 5*time.Second)
	defer cancel2()

	err2 := resource.Ready(ctx2)
	require.NoError(t, err2, "second Ready() should succeed after backend retry")

	// Verify data is now available
	var data1 map[string]string
	err = resource.Get(&data1)
	require.NoError(t, err, "should be able to get data")
	require.Equal(t, "ok", data1["status"])

	// Subsequent Ready() calls should succeed immediately
	ctx3, cancel3 := context.WithTimeout(ctx, 100*time.Millisecond)
	defer cancel3()

	err3 := existing.Ready(ctx3)
	require.NoError(t, err3, "subsequent Ready() should succeed immediately")

	// Data should still be available
	var data2 map[string]string
	err = existing.Get(&data2)
	require.NoError(t, err, "should still be able to get data")
	require.Equal(t, "ok", data2["status"])
}

// TestPeriodicCheckDeadlock reproduces the deadlock described in
// https://github.com/lestrrat-go/httprc/issues/113
//
// The deadlock occurs when:
//  1. A periodic check in the controller iterates ready resources and
//     queues work for them by sending items on c.outgoing.
//  2. c.outgoing is a buffered channel with capacity numWorkers+1. With
//     numWorkers=1, it can hold 2 items. With 1 worker and N>2 ready
//     resources, the controller eventually blocks trying to send the 3rd
//     item to c.outgoing once the buffer is full.
//  3. The worker that picked up the 1st item finishes and attempts to send
//     a control message (such as an interval adjustment) to w.incoming
//     (= c.incoming).
//  4. But c.incoming is read by the controller loop, which is currently
//     blocked trying to send to c.outgoing.
//  5. Circular wait → deadlock.
//
// The test registers multiple resources with 1 worker and short refresh
// intervals, waits for a periodic check to fire, then attempts to register
// a new resource (which also sends to c.incoming). If the deadlock is
// present, the new registration will hang until the context deadline.
func TestPeriodicCheckDeadlock(t *testing.T) {
	t.Parallel()

	const (
		numResources       = 6
		numWorkers         = 1
		minRefreshInterval = time.Second
		maxRefreshInterval = 2 * time.Second
	)

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.Write([]byte(`{"status":"ok"}`))
	}))
	t.Cleanup(srv.Close)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	traceDst := io.Discard
	if testing.Verbose() {
		traceDst = os.Stderr
	}

	cl := httprc.NewClient(
		httprc.WithWorkers(numWorkers),
		httprc.WithTraceSink(tracesink.NewSlog(slog.New(slog.NewJSONHandler(traceDst, nil)))),
	)
	ctrl, err := cl.Start(ctx)
	require.NoError(t, err)
	t.Cleanup(func() { ctrl.Shutdown(time.Second) })

	// Register N resources, all with the same short refresh interval.
	// Each resource uses a distinct URL path so they are treated as separate items.
	for i := range numResources {
		url := srv.URL + "/resource/" + strconv.Itoa(i)
		r, err := httprc.NewResource[map[string]string](
			url,
			httprc.JSONTransformer[map[string]string](),
			httprc.WithMinInterval(minRefreshInterval),
			httprc.WithMaxInterval(maxRefreshInterval),
		)
		require.NoError(t, err, "NewResource should succeed for resource %d", i)

		addCtx, addCancel := context.WithTimeout(ctx, 10*time.Second)
		err = ctrl.Add(addCtx, r)
		addCancel()
		require.NoError(t, err, "Add should succeed for resource %d", i)
	}

	// Wait long enough for all resources to become due for periodic refresh.
	// maxRefreshInterval + 1s gives headroom for the tick to fire.
	time.Sleep(maxRefreshInterval + time.Second)

	// Now attempt to register a new resource. This sends an addRequest to
	// c.incoming. If the deadlock is present, periodicCheck is blocked
	// sending to c.outgoing while the worker is blocked sending to
	// c.incoming, so this Add will hang.
	newURL := srv.URL + "/resource/new"
	newR, err := httprc.NewResource[map[string]string](
		newURL,
		httprc.JSONTransformer[map[string]string](),
		httprc.WithMinInterval(minRefreshInterval),
		httprc.WithMaxInterval(maxRefreshInterval),
	)
	require.NoError(t, err, "NewResource should succeed for new resource")

	addCtx, addCancel := context.WithTimeout(ctx, 5*time.Second)
	defer addCancel()

	// Use WithWaitReady(false) so that a timeout here can only be caused by
	// the controller deadlock, not by a slow initial fetch under backlog.
	err = ctrl.Add(addCtx, newR, httprc.WithWaitReady(false))

	// Before fix: context.DeadlineExceeded (Add hangs for 5s, then times out)
	// After fix: succeeds promptly
	require.NoError(t, err, "Add should not deadlock; got timeout indicating periodicCheck deadlock (issue #113)")

	// Verify the new resource is accessible
	existing, lookupErr := ctrl.Lookup(ctx, newURL)
	require.NoError(t, lookupErr, "Lookup should find the newly added resource")
	require.Equal(t, newURL, existing.URL())
}