Websocket: Restructure files and types (#1859)

* Websocket: Rename stream package

* Websocket: Rename Websocket to Manager

* Websocket: Replace explicit errs with common.NilGuard

* Websocket: Move websocket_types.go to types.go

* Websocket: Minor field comment and alignment in types

* Webosocket: Rename WebsocketConnection to Connection

* Alphapoint: Make gorilla ws import explicit

Just to avoid confusion with our own packages.

* Websocket: Move stream_match to match

* Websocket: Move websocket_connection to connection

* Websocket: Move websocket.go to manager.go

* Websocket: Break out all subscription methods into subscriptions.go

* Websocket: Move connection type into its file

* Websocket: Remove PositionUpdated

Type is not used anywhere

* Kraken: Use local constant for pong

Was the only use of websocket.Pong and doesn't really feel right to
represent kraken's api resp in one of our packages

* Websocket: Move connection sub-types to connection package

* Websocket: Move manager types into manager

* Websocket: Move ConnectionWrapper into manager

* Websocket: Move websocket_test to manager_test

* Websocket: Privatise connectionWrapper

* Websocket: Remaining types into types.go

These really belong somewhere else mostly, but this will do for now

* Websocket: Tidy up connection method vars

* Gofumpt: Moving package imports around

* Websocket: Rename errDuplicateConnectionSetup

* Websocket: Fix duplicate import of gws

* Websocket: Fix gofumpt -extra

* Websocket: Standardise import of gws across other pkgs

* Kraken: Remove unused sub conf consts

These were replaced by the generic Levels and Depth fields on all subs

* Websocket: Privitise ConnectioWrapper fields

* Websocket: inline single use var WebsocketNotAuthenticatedUsingRest

* Websocket: Move documentation to template

* Bithumb: Assertify TestWsHandleData

common/common.go

@@ -21,6 +21,7 @@ import (
 	"sync/atomic"
 	"time"
 	"unicode"
+	"unsafe"
 
 	"github.com/thrasher-corp/gocryptotrader/common/file"
 	"github.com/thrasher-corp/gocryptotrader/log"
@@ -80,6 +81,22 @@ var (
 	errHTTPClientInvalid       = errors.New("custom http client cannot be nil")
 )
 
+// NilGuard returns an ErrNilPointer with the type of the first nil argument
+func NilGuard(ptrs ...any) (errs error) {
+	for _, p := range ptrs {
+		/* 	Internally interfaces contain a type and a value address
+		Obviously can't compare to nil, since the types won't match, so we look into the interface
+		eface is the internal representation of any; e(mpty-inter)face
+		See: https://cs.opensource.google/go/go/+/refs/tags/go1.24.1:src/runtime/runtime2.go;l=184-187
+		We optimize here by converting to [2]uintptr and just checking the address, instead of casting to a local eface type
+		*/
+		if (*[2]uintptr)(unsafe.Pointer(&p))[1] == 0 {
+			errs = AppendError(errs, fmt.Errorf("%w: %T", ErrNilPointer, p))
+		}
+	}
+	return errs
+}
+
 // MatchesEmailPattern ensures that the string is an email address by regexp check
 func MatchesEmailPattern(value string) bool {
 	if len(value) < 3 || len(value) > 254 {

common/common_test.go

@@ -722,3 +722,26 @@ func BenchmarkCounter(b *testing.B) {
 		c.IncrementAndGet()
 	}
 }
+
+func TestNilGuard(t *testing.T) {
+	t.Parallel()
+	err := NilGuard((*int)(nil))
+	assert.ErrorIs(t, err, ErrNilPointer)
+	assert.ErrorContains(t, err, "*int")
+
+	s := "normal input"
+	err = NilGuard(&s, 2, &[]int{4, 5, 6}, []int{1, 2, 3}, new(A))
+	assert.NoError(t, err)
+
+	err = NilGuard(&s, nil, (*int)(nil))
+	assert.ErrorIs(t, err, ErrNilPointer)
+	assert.ErrorContains(t, err, "*int")
+	var mErr *multiError
+	require.ErrorAs(t, err, &mErr, "err must be a multiError")
+	assert.Len(t, mErr.Unwrap(), 2, "Should get 2 errors back")
+
+	assert.ErrorIs(t, NilGuard(nil), ErrNilPointer, "Unusual input of an untyped nil should still error correctly")
+
+	err = NilGuard()
+	require.NoError(t, err, "NilGuard with no arguments should not panic")
+}