Ilia Denisov
109 lines
3.3 KiB
Go
109 lines
3.3 KiB
Go
// Package downstream defines the verified internal command contract used by the
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// gateway after the authenticated edge pipeline succeeds.
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package downstream
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import (
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"context"
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"errors"
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)
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var (
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// ErrRouteNotFound reports that Router does not have an exact-match handler
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// for the supplied authenticated message type.
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ErrRouteNotFound = errors.New("downstream route not found")
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// ErrDownstreamUnavailable reports that the resolved downstream dependency is
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// temporarily unavailable.
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ErrDownstreamUnavailable = errors.New("downstream service is unavailable")
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)
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// AuthenticatedCommand is the minimum verified unary command context the
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// gateway may forward to downstream business services.
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type AuthenticatedCommand struct {
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// ProtocolVersion is the authenticated transport protocol version accepted
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// by the gateway.
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ProtocolVersion string
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// UserID is the authenticated user identity resolved from SessionCache.
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UserID string
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// DeviceSessionID is the authenticated device session that originated the
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// command.
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DeviceSessionID string
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// MessageType is the stable exact-match downstream routing key.
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MessageType string
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// TimestampMS is the client-supplied request timestamp that already passed
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// freshness verification.
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TimestampMS int64
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// RequestID is the transport correlation and anti-replay identifier.
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RequestID string
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// TraceID is the optional client-supplied correlation identifier.
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TraceID string
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// PayloadBytes carries the verified opaque business payload bytes.
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PayloadBytes []byte
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}
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// UnaryResult is the minimum downstream unary result the gateway needs in
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// order to build a signed authenticated client response.
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type UnaryResult struct {
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// ResultCode is the stable opaque downstream result code returned to the
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// client without business reinterpretation by the gateway.
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ResultCode string
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// PayloadBytes carries the opaque downstream response payload bytes.
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PayloadBytes []byte
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}
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// Client executes a verified authenticated unary command against one concrete
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// downstream service or adapter.
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type Client interface {
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// ExecuteCommand executes command and returns the downstream unary result.
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ExecuteCommand(ctx context.Context, command AuthenticatedCommand) (UnaryResult, error)
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}
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// Router resolves the downstream unary client for one exact authenticated
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// message_type value.
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type Router interface {
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// Route returns the downstream client for messageType. Implementations must
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// wrap ErrRouteNotFound when the route table does not contain messageType.
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Route(messageType string) (Client, error)
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}
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// StaticRouter resolves exact message_type literals from an immutable route
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// map supplied at construction time.
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type StaticRouter struct {
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routes map[string]Client
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}
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// NewStaticRouter constructs a StaticRouter with a defensive copy of routes.
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func NewStaticRouter(routes map[string]Client) *StaticRouter {
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clonedRoutes := make(map[string]Client, len(routes))
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for messageType, client := range routes {
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if client == nil {
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continue
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}
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clonedRoutes[messageType] = client
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}
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return &StaticRouter{routes: clonedRoutes}
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}
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// Route returns the exact-match client for messageType.
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func (r *StaticRouter) Route(messageType string) (Client, error) {
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if r == nil {
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return nil, ErrRouteNotFound
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}
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client, ok := r.routes[messageType]
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if !ok || client == nil {
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return nil, ErrRouteNotFound
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}
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return client, nil
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}
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