FahdShalhoub
76 lines
2.5 KiB
Go
76 lines
2.5 KiB
Go
package services
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import (
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"context"
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"encoding/json"
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"fmt"
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"github.com/aws/aws-sdk-go-v2/aws"
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"github.com/aws/aws-sdk-go-v2/service/sns"
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)
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var CatalogueClient Catalogue
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// CatalogueVideo is what cms announces when a video becomes ready. It is a
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// published contract — every subscriber of the catalogue topic decodes it —
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// so the JSON names here are as much an API as the ones in internal/api, and
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// changing one is a change every subscriber sees.
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//
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// Categories are named rather than numbered on purpose: the ids are cms's
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// own, and a consumer holding a name needs nothing from cms to make sense
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// of it.
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type CatalogueVideo struct {
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VideoID string `json:"videoId"`
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Title string `json:"title"`
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PlaybackURL string `json:"playbackUrl"`
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Categories []string `json:"categories"`
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}
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type Catalogue interface {
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AnnounceVideo(ctx context.Context, video CatalogueVideo) error
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}
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type CatalogueConcrete struct {
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SNSClient *sns.Client
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TopicARN string
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}
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// AnnounceVideo publishes one video to the catalogue topic, which fans it out
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// to whatever has subscribed. Delivery is at-least-once: the caller
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// republishes when a later step fails, so a subscriber has to tolerate seeing
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// the same video twice.
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//
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// A topic delivers only to the subscriptions that exist at the moment it
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// publishes, so a subscriber that wants the backlog needs its queue in place
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// before the announcement, not after.
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func (svc CatalogueConcrete) AnnounceVideo(ctx context.Context, video CatalogueVideo) error {
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// A nil slice marshals to null, which would make "has no categories" and
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// "categories unknown" indistinguishable to a reader. An empty list says
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// the first, which is what an unfiled video means.
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if video.Categories == nil {
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video.Categories = []string{}
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}
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body, err := json.Marshal(video)
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if err != nil {
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return err
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}
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_, err = svc.SNSClient.Publish(ctx, &sns.PublishInput{
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TopicArn: aws.String(svc.TopicARN),
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Message: aws.String(string(body)),
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})
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return err
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}
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// AssertSuccessfulConnection verifies the topic exists and is readable with
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// the configured credentials. It panics on failure: a service that cannot
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// announce would transcode videos the catalogue never hears about.
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func (svc CatalogueConcrete) AssertSuccessfulConnection(ctx context.Context) {
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if _, err := svc.SNSClient.GetTopicAttributes(ctx, &sns.GetTopicAttributesInput{
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TopicArn: aws.String(svc.TopicARN),
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}); err != nil {
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panic(fmt.Errorf("sns: cannot connect to catalogue topic %q: %w", svc.TopicARN, err))
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}
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}
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