FEAT: Discovery Video Service Subscription

discovery/internal/db/repositories/errors.go

@@ -0,0 +1,9 @@
+package repositories
+
+import "errors"
+
+// Sentinel errors the repositories return so handlers can tell "there is no
+// such row" from "the query failed", without importing database/sql to do it.
+
+// ErrVideoNotFound reports that the catalogue holds no video with that id.
+var ErrVideoNotFound = errors.New("video not found")

discovery/internal/db/repositories/videos.go

@@ -0,0 +1,59 @@
+package repositories
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"thamanyah/discovery/internal/models"
+
+	"github.com/lib/pq"
+)
+
+type VideoRepository struct {
+	SQLDB *sql.DB
+}
+
+var VideoRepo VideoRepository
+
+// SaveVideo records an announced video, replacing what the catalogue already
+// held for that id.
+//
+// The upsert is what makes the consumer safe to retry: the catalogue topic
+// delivers at-least-once, so the same announcement can arrive twice, and a
+// plain INSERT would fail the second time on the primary key. Re-announcing a
+// video is also how it is corrected — a later announcement wins, which is why
+// every column is overwritten rather than merged.
+func (svc VideoRepository) SaveVideo(ctx context.Context, v models.Video) error {
+	_, err := svc.SQLDB.ExecContext(ctx, `
+		INSERT INTO videos (id, title, playback_url, categories)
+		VALUES ($1, $2, $3, $4)
+		ON CONFLICT (id) DO UPDATE
+		SET title = EXCLUDED.title,
+		    playback_url = EXCLUDED.playback_url,
+		    categories = EXCLUDED.categories,
+		    updated_at = now()
+	`, v.ID, v.Title, v.PlaybackURL, pq.Array(v.Categories))
+	return err
+}
+
+// GetVideoByID reads the catalogue's copy of one video. It returns
+// ErrVideoNotFound when the catalogue has not heard about it — which, for a
+// video cms has only just made ready, is a matter of timing rather than a
+// mistake.
+func (svc VideoRepository) GetVideoByID(ctx context.Context, id string) (models.Video, error) {
+	var v models.Video
+
+	err := svc.SQLDB.QueryRowContext(ctx, `
+		SELECT id, title, playback_url, categories, created_at, updated_at
+		FROM videos
+		WHERE id = $1
+	`, id).Scan(&v.ID, &v.Title, &v.PlaybackURL, pq.Array(&v.Categories), &v.CreatedAt, &v.UpdatedAt)
+	if errors.Is(err, sql.ErrNoRows) {
+		return models.Video{}, ErrVideoNotFound
+	}
+	if err != nil {
+		return models.Video{}, err
+	}
+
+	return v, nil
+}