mirror of
https://github.com/dutchcoders/transfer.sh.git
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97 lines
3.3 KiB
Go
97 lines
3.3 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package metadata
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"time"
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)
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// Metadata holds Google Cloud Functions metadata.
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type Metadata struct {
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// EventID is a unique ID for the event. For example: "70172329041928".
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EventID string `json:"eventId"`
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// Timestamp is the date/time this event was created.
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Timestamp time.Time `json:"timestamp"`
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// EventType is the type of the event. For example: "google.pubsub.topic.publish".
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EventType string `json:"eventType"`
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// Resource is the resource that triggered the event.
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Resource *Resource `json:"resource"`
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}
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// Resource holds Google Cloud Functions resource metadata.
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// Resource values are dependent on the event type they're from.
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type Resource struct {
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// Service is the service that triggered the event.
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Service string `json:"service"`
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// Name is the name associated with the event.
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Name string `json:"name"`
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// Type is the type of event.
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Type string `json:"type"`
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}
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type contextKey string
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// GCFContextKey satisfies an interface to be able to use contextKey to read
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// metadata from a Cloud Functions context.Context.
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//
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// Be careful making changes to this function. See FromContext.
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func (k contextKey) GCFContextKey() string {
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return string(k)
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}
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const metadataContextKey = contextKey("metadata")
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// FromContext extracts the Metadata from the Context, if present.
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func FromContext(ctx context.Context) (*Metadata, error) {
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if ctx == nil {
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return nil, errors.New("nil ctx")
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}
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// The original JSON is inserted by the Cloud Functions worker. So, the
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// format must not change, or the message may fail to unmarshal. We use
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// JSON as a common format between the worker and this package to ensure
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// this package can be updated independently from the worker. The contextKey
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// type and the metadataContextKey value use an interface to avoid using
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// a built-in type as a context key (which is easy to have collisions with).
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// If we need another value to be stored in the context, we can use a new
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// key or interface and avoid needing to change this one. Similarly, if we
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// need to change the format of the message, we should add an additional key
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// to keep backward compatibility.
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b, ok := ctx.Value(metadataContextKey).(json.RawMessage)
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if !ok {
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return nil, errors.New("unable to find metadata")
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}
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meta := &Metadata{}
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if err := json.Unmarshal(b, meta); err != nil {
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return nil, fmt.Errorf("json.Unmarshal: %v", err)
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}
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return meta, nil
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}
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// NewContext returns a new Context carrying m. If m is nil, NewContext returns
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// ctx. NewContext is only used for writing tests which rely on Metadata.
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func NewContext(ctx context.Context, m *Metadata) context.Context {
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if m == nil {
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return ctx
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}
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b, err := json.Marshal(m)
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if err != nil {
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return ctx
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}
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return context.WithValue(ctx, metadataContextKey, json.RawMessage(b))
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}
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