Refactor error classification in shannon: use idiomatic errors.Is/As instead of string matching

protocol/shannon/errors.go

@@ -2,8 +2,10 @@ package shannon
 
 import (
 	"context"
+	"crypto/x509"
 	"errors"
-	"strings"
+	"crypto/tls"
+	"net"
 
 	pathhttp "github.com/pokt-network/path/network/http"
 	protocolobservations "github.com/pokt-network/path/observation/protocol"
@@ -13,80 +15,39 @@ var (
 	// Unsupported gateway mode
 	errProtocolContextSetupUnsupportedGatewayMode = errors.New("unsupported gateway mode")
 
-	// ** Network errors **
-	// endpoint configuration error:
-	// - TLS certificate verification error.
-	// - DNS error on lookup of endpoint URL.
-	errRelayEndpointConfig = errors.New("endpoint configuration error")
-
-	// endpoint timeout
-	errRelayEndpointTimeout = errors.New("timeout waiting for endpoint response")
-	// PATH manually canceled the context for the request.
-	// E.g. Parallel requests were made and one succeeded so the other was canceled.
-	errContextCanceled = errors.New("context canceled manually")
-
-	// HTTP relay request failed - wraps net/http package errors
-	errSendHTTPRelay = errors.New("HTTP relay request failed")
-
-	// ** Centralized gateway mode errors **
-
-	// Centralized gateway mode: Error getting onchain data for app
-	errProtocolContextSetupCentralizedAppFetchErr = errors.New("error getting onchain data for app owned by the gateway")
-	// Centralized gateway mode app does not delegate to the gateway.
-	errProtocolContextSetupCentralizedAppDelegation = errors.New("centralized gateway mode app does not delegate to the gateway")
-	// Centralized gateway mode: no active sessions could be retrieved for the service.
-	errProtocolContextSetupCentralizedNoSessions = errors.New("no active sessions could be retrieved for the service")
-	// Centralized gateway mode: no owned apps found for the service.
+	// === Network & relay errors ===
+	errRelayEndpointConfig       = errors.New("endpoint configuration error")                  // TLS/DNS/config issues
+	errRelayEndpointTimeout      = errors.New("timeout waiting for endpoint response")
+	errContextCanceled           = errors.New("context canceled manually")                      // PATH-initiated cancel
+	errSendHTTPRelay             = errors.New("HTTP relay request failed")
+	errMalformedEndpointPayload  = errors.New("endpoint returned malformed payload")
+
+	// === Gateway mode errors ===
+	errProtocolContextSetupCentralizedAppFetchErr      = errors.New("error getting onchain data for app owned by the gateway")
+	errProtocolContextSetupCentralizedAppDelegation    = errors.New("centralized gateway mode app does not delegate to the gateway")
+	errProtocolContextSetupCentralizedNoSessions       = errors.New("no active sessions could be retrieved for the service")
 	errProtocolContextSetupCentralizedNoAppsForService = errors.New("ZERO owned apps found for service")
-
-	// Delegated gateway mode: could not extract app from HTTP request.
-	errProtocolContextSetupGetAppFromHTTPReq = errors.New("error getting the selected app from the HTTP request")
-	// Delegated gateway mode: could not fetch session for app from the full node
-	errProtocolContextSetupFetchSession = errors.New("error getting a session from the full node for app")
-	// Delegated gateway mode: gateway does not have delegation for the app.
-	errProtocolContextSetupAppDoesNotDelegate = errors.New("gateway does not have delegation for app")
-	// Delegated gateway mode: app is not staked for the service.
-	errProtocolContextSetupAppNotStaked = errors.New("app is not staked for the service")
-
-	// ** Request context setup errors **
-
-	// No endpoints available for the service.
-	// Can be due to one or more of the following:
-	// - Any of the gateway mode errors above.
-	// - Error fetching a session for an app.
-	errProtocolContextSetupNoEndpoints = errors.New("no endpoints found for service: relay request will fail")
-	// Selected endpoint is no longer available.
-	// Can happen due to:
-	// - Bug in endpoint selection logic.
-	// - Endpoint sanctioned due to an observation while selection logic was running.
-	errRequestContextSetupInvalidEndpointSelected = errors.New("selected endpoint is not available: relay request will fail")
-	// Error initializing a signer for the current gateway mode.
-	errRequestContextSetupErrSignerSetup = errors.New("error getting the permitted signer: relay request will fail")
-
-	// The endpoint returned a malformed payload.
-	// Helps track more fine-grained metrics on endpoint errors.
-	errMalformedEndpointPayload = errors.New("endpoint returned malformed payload")
-
-	// The endpoint returned a non-2XX response.
-	errEndpointNon2XXHTTPStatusCode = errors.New("endpoint returned non-2xx HTTP status code")
-
-	// ** Websocket errors **
-
-	// Error creating a Websocket connection.
-	errCreatingWebSocketConnection = errors.New("error creating Websocket connection")
-
-	// Error signing the relay request in a websocket message.
-	errRelayRequestWebsocketMessageSigningFailed = errors.New("error signing relay request in websocket message")
-
-	// Error validating the relay response in a websocket message.
+	errProtocolContextSetupGetAppFromHTTPReq           = errors.New("error getting the selected app from the HTTP request")
+	errProtocolContextSetupFetchSession                = errors.New("error getting a session from the full node for app")
+	errProtocolContextSetupAppDoesNotDelegate          = errors.New("gateway does not have delegation for app")
+	errProtocolContextSetupAppNotStaked                = errors.New("app is not staked for the service")
+
+	// === Request context setup errors ===
+	errProtocolContextSetupNoEndpoints                = errors.New("no endpoints found for service: relay request will fail")
+	errRequestContextSetupInvalidEndpointSelected     = errors.New("selected endpoint is not available: relay request will fail")
+	errRequestContextSetupErrSignerSetup              = errors.New("error getting the permitted signer: relay request will fail")
+
+	// === Websocket errors ===
+	errCreatingWebSocketConnection                    = errors.New("error creating Websocket connection")
+	errRelayRequestWebsocketMessageSigningFailed      = errors.New("error signing relay request in websocket message")
 	errRelayResponseInWebsocketMessageValidationFailed = errors.New("error validating relay response in websocket message")
 )
 
 // extractErrFromRelayError:
 // • Analyzes errors returned during relay operations
 // • Matches errors to predefined types through:
-//   - Primary: Error comparison (with unwrapping)
-//   - Fallback: String analysis for unrecognized types
+//   - Primary: errors.Is / errors.As (robust, works with wrapped errors)
+//   - Secondary: Type-specific matching for network/config errors
 //
 // • Centralizes error recognition logic to avoid duplicate string matching
 // • Provides fine-grained HTTP error classification
@@ -101,17 +62,16 @@ func extractErrFromRelayError(err error) error {
 		return errRelayEndpointConfig
 	}
 
-	// http endpoint timeout
-	if strings.Contains(err.Error(), context.DeadlineExceeded.Error()) { // "context deadline exceeded"
+	// Context-based errors (robust, works recursively through wrapped errors)
+	if errors.Is(err, context.DeadlineExceeded) {
 		return errRelayEndpointTimeout
 	}
 
-	// Endpoint's backend service returned a non 2xx HTTP status code.
-	if strings.Contains(err.Error(), "non 2xx HTTP status code") {
+	if errors.Is(err, pathhttp.ErrRelayEndpointHTTPError) {
 		return pathhttp.ErrRelayEndpointHTTPError
 	}
-	// context canceled manually
-	if strings.Contains(err.Error(), "context canceled") {
+
+	if errors.Is(err, context.Canceled) {
 		return errContextCanceled
 	}
 
@@ -126,15 +86,38 @@ func extractErrFromRelayError(err error) error {
 // - Error verifying endpoint's TLS certificate
 // - Error on DNS lookup of endpoint's URL.
 func isEndpointNetworkConfigError(err error) bool {
-	errStr := err.Error()
-	switch {
-	case strings.Contains(errStr, "dial tcp: lookup"):
+	// Use errors.As for robust type matching (works with wrapped errors)
+	// Covers common DNS, connection, and TLS issues
+
+	// DNS resolution errors
+	if errors.As(err, &net.DNSError{}) {
 		return true
-	case strings.Contains(errStr, "tls: failed to verify certificate"):
+	}
+
+	// General network operation errors (dial, read, write, connect, etc.)
+	var opErr *net.OpError
+	if errors.As(err, &opErr) {
+		return true
+	}
+
+	// Common x509 certificate validation errors
+	if errors.As(err, &x509.HostnameError{}) {
+		return true
+	}
+	if errors.As(err, &x509.UnknownAuthorityError{}) {
+		return true
+	}
+	if errors.As(err, &x509.CertificateInvalidError{}) {
 		return true
-	default:
-		return false
 	}
+
+	// TLS handshake / record-level errors not covered by x509
+	var tlsRecordErr *tls.RecordHeaderError
+	if errors.As(err, &tlsRecordErr) {
+		return true
+	}
+
+	return false
 }
 
 // isMalformedEndpointPayloadError returns true if the error indicates a malformed endpoint payload.