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adapter.go
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adapter.go
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//go:build !noclibs
package xslttransformation
import (
"context"
"errors"
"fmt"
"runtime"
xslt "github.com/wamuir/go-xslt"
"go.uber.org/zap"
cloudevents "github.com/cloudevents/sdk-go/v2"
pkgadapter "knative.dev/eventing/pkg/adapter/v2"
"knative.dev/pkg/logging"
"github.com/zeiss/typhoon/pkg/apis/flow"
"github.com/zeiss/typhoon/pkg/apis/flow/v1alpha1"
"github.com/zeiss/typhoon/pkg/metrics"
targetce "github.com/zeiss/typhoon/pkg/targets/adapter/cloudevents"
)
var _ pkgadapter.Adapter = (*xsltTransformAdapter)(nil)
type xsltTransformAdapter struct {
defaultXSLT *xslt.Stylesheet
xsltOverride bool
replier *targetce.Replier
ceClient cloudevents.Client
logger *zap.SugaredLogger
sink string
mt *pkgadapter.MetricTag
sr *metrics.EventProcessingStatsReporter
}
// NewTarget adapter implementation
func NewTarget(ctx context.Context, envAcc pkgadapter.EnvConfigAccessor, ceClient cloudevents.Client) pkgadapter.Adapter {
logger := logging.FromContext(ctx)
mt := &pkgadapter.MetricTag{
ResourceGroup: flow.XSLTTransformationResource.String(),
Namespace: envAcc.GetNamespace(),
Name: envAcc.GetName(),
}
metrics.MustRegisterEventProcessingStatsView()
env := envAcc.(*envAccessor)
if err := env.validate(); err != nil {
logger.Panicf("Configuration error: %v", err)
}
replier, err := targetce.New(env.Component, logger.Named("replier"),
targetce.ReplierWithStatefulHeaders(env.BridgeIdentifier),
targetce.ReplierWithStaticDataContentType(cloudevents.ApplicationXML),
targetce.ReplierWithStaticErrorDataContentType(*cloudevents.StringOfApplicationJSON()),
targetce.ReplierWithPayloadPolicy(targetce.PayloadPolicy(targetce.PayloadPolicyAlways)))
if err != nil {
logger.Panicf("Error creating CloudEvents replier: %v", err)
}
adapter := &xsltTransformAdapter{
xsltOverride: env.AllowXSLTOverride,
replier: replier,
ceClient: ceClient,
logger: logger,
sink: env.Sink,
mt: mt,
sr: metrics.MustNewEventProcessingStatsReporter(mt),
}
if env.XSLT != "" {
adapter.defaultXSLT, err = xslt.NewStylesheet([]byte(env.XSLT))
if err != nil {
logger.Panicf("XSLT validation error: %v", err)
}
runtime.SetFinalizer(adapter.defaultXSLT, (*xslt.Stylesheet).Close)
}
return adapter
}
// Start is a blocking function and will return if an error occurs
// or the context is cancelled.
func (a *xsltTransformAdapter) Start(ctx context.Context) error {
a.logger.Info("Starting XSLT transformer")
ctx = pkgadapter.ContextWithMetricTag(ctx, a.mt)
return a.ceClient.StartReceiver(ctx, a.dispatch)
}
func (a *xsltTransformAdapter) dispatch(ctx context.Context, event cloudevents.Event) (*cloudevents.Event, cloudevents.Result) {
isStructuredTransform := event.Type() == v1alpha1.EventTypeXSLTTransformation
if isStructuredTransform && !a.xsltOverride {
return a.replier.Error(&event, targetce.ErrorCodeRequestValidation,
errors.New("it is not allowed to override XSLT per CloudEvent"), nil)
}
isXML := event.DataMediaType() == cloudevents.ApplicationXML
var style *xslt.Stylesheet
var xmlin []byte
var err error
switch {
case isStructuredTransform:
req := &XSLTTransformationStructuredRequest{}
if err := event.DataAs(req); err != nil {
return a.replier.Error(&event, targetce.ErrorCodeRequestParsing, err, nil)
}
xmlin = []byte(req.XML)
style, err = xslt.NewStylesheet([]byte(req.XSLT))
if err != nil {
return a.replier.Error(&event, targetce.ErrorCodeRequestParsing, err, nil)
}
defer style.Close()
case isXML:
xmlin = event.DataEncoded
style = a.defaultXSLT
default:
return a.replier.Error(&event, targetce.ErrorCodeRequestValidation,
errors.New("unexpected type or media-type for the incoming event"), nil)
}
res, err := style.Transform(xmlin)
if err != nil {
return a.replier.Error(&event, targetce.ErrorCodeRequestValidation,
fmt.Errorf("error processing XML with XSLT: %v", err), nil)
}
if a.sink != "" {
event.SetType(event.Type() + ".response")
if err := event.SetData(cloudevents.ApplicationXML, res); err != nil {
return a.replier.Error(&event, targetce.ErrorCodeAdapterProcess, err, nil)
}
if result := a.ceClient.Send(ctx, event); !cloudevents.IsACK(result) {
return a.replier.Error(&event, targetce.ErrorCodeAdapterProcess, err, "sending the cloudevent to the sink")
}
return nil, cloudevents.ResultACK
}
return a.replier.Ok(&event, res, targetce.ResponseWithDataContentType(cloudevents.ApplicationXML))
}