package ws

import (
	"context"
	"encoding/json"
	"sync"
	"testing"
	"time"

	"github.com/oklog/ulid/v2"

	"gitea.dcglab.co.uk/steve/restic-manager/internal/api"
)

// TestRPCRegistryRoundTrip: register a waiter, resolve it, get the
// envelope back. Cover the no-waiter and double-resolve cases too.
func TestRPCRegistryRoundTrip(t *testing.T) {
	t.Parallel()
	var r rpcRegistry
	id := ulid.Make().String()
	ch := r.register(id)

	want := api.Envelope{Type: api.MsgTreeListResult, ID: id, Payload: json.RawMessage(`{"path":"/"}`)}
	if !r.resolve(id, want) {
		t.Fatal("resolve: returned false for registered id")
	}
	got := <-ch
	if got.ID != id {
		t.Fatalf("id mismatch: got %q want %q", got.ID, id)
	}

	// A second resolve for the same id has no waiter and should not panic.
	if r.resolve(id, want) {
		t.Fatal("resolve: returned true for already-resolved id")
	}
}

// TestRPCRegistryRelease: release abandons the waiter; a subsequent
// resolve is a no-op (no goroutine leak, no panic).
func TestRPCRegistryRelease(t *testing.T) {
	t.Parallel()
	var r rpcRegistry
	id := ulid.Make().String()
	_ = r.register(id)
	r.release(id)
	if r.resolve(id, api.Envelope{ID: id}) {
		t.Fatal("resolve after release: should be no-op")
	}
}

// TestRPCRegistryConcurrent: many waiters in flight concurrently get
// only their own reply. This catches buggy keying/locking.
func TestRPCRegistryConcurrent(t *testing.T) {
	t.Parallel()
	var r rpcRegistry
	const n = 64

	ids := make([]string, n)
	chs := make([]chan api.Envelope, n)
	for i := 0; i < n; i++ {
		ids[i] = ulid.Make().String()
		chs[i] = r.register(ids[i])
	}

	// Resolve in random-ish order from many goroutines.
	var wg sync.WaitGroup
	for i := 0; i < n; i++ {
		wg.Add(1)
		go func(idx int) {
			defer wg.Done()
			r.resolve(ids[idx], api.Envelope{ID: ids[idx], Type: api.MsgTreeListResult})
		}(i)
	}
	wg.Wait()

	for i := 0; i < n; i++ {
		select {
		case got := <-chs[i]:
			if got.ID != ids[i] {
				t.Fatalf("waiter %d: got id %q want %q", i, got.ID, ids[i])
			}
		case <-time.After(2 * time.Second):
			t.Fatalf("waiter %d: timed out", i)
		}
	}
}

// TestSendRPCContextCancelReleases ensures that canceling the caller's
// ctx releases the registry entry so a stray late reply is harmlessly
// dropped. Skips if the hub isn't reachable for direct access — this
// is purely a unit test on the registry path inside SendRPC.
func TestSendRPCContextCancelReleases(t *testing.T) {
	t.Parallel()
	h := NewHub()

	// No host registered, so Hub.Send returns "host offline" and
	// SendRPC bails without ever waiting. We test the timeout/ctx
	// path by going through register() directly.
	id := ulid.Make().String()
	ch := h.rpcs.register(id)

	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		time.Sleep(20 * time.Millisecond)
		cancel()
	}()

	// Simulate the SendRPC select: ctx wins.
	select {
	case <-ch:
		t.Fatal("unexpected reply")
	case <-ctx.Done():
		h.rpcs.release(id)
	}

	// Now a late reply should not block (ch is still open but no
	// receiver — buffered size 1 absorbs it).
	resolved := h.rpcs.resolve(id, api.Envelope{ID: id})
	if resolved {
		t.Fatal("resolve after release should return false")
	}
}