0.2.72 - Magic button, Next up fixes

server/internal/api/magic.go

@@ -0,0 +1,90 @@
+package api
+
+import (
+	"encoding/json"
+	"math/rand"
+	"net/http"
+	"strings"
+
+	"github.com/ponzischeme89/memby/server/internal/recommend"
+	"github.com/ponzischeme89/memby/server/internal/store"
+)
+
+// magicResponse is one drawn title and the wording that goes with it.
+//
+// The item rides as Emby's own JSON, the convention every other row and detail response
+// takes, so the television parses it with the single BaseItem model it already has and a
+// field added to the catalogue tomorrow needs nothing here. [recommend.MagicSelection]
+// carries a parsed item rather than raw bytes, so the handler re-reads it — one lookup on a
+// button press, against a pick the viewer is about to watch for two hours.
+type magicResponse struct {
+	Item json.RawMessage `json:"item"`
+	// Reasons is the same explanation layer a detail page uses. The television prints the
+	// title; these are what let it say *why* without the server having to word a sentence
+	// the client's copy conventions would then have to match.
+	Reasons []string `json:"reasons,omitempty"`
+}
+
+// magicRequest is what the player knows and the server does not: the film playing right now
+// and the last few this button already offered. Repetition protection lives with the caller
+// because it is the caller that knows what it has already put in front of somebody.
+type magicRequest struct {
+	ExcludeIDs []string `json:"excludeIds"`
+	// AvailableMinutes is zero for no limit. Nothing sends it yet; it is on the wire because
+	// "I have an hour" is the obvious next thing to ask and the picker already takes it.
+	AvailableMinutes int `json:"availableMinutes"`
+}
+
+// handleMagic answers "put something good on".
+//
+// Deliberately a POST with a body rather than a GET with a query string: the exclusion list
+// grows with every press, and a URL that lengthens each time is one a proxy or an access log
+// eventually truncates — which would silently start repeating films.
+//
+// It is never cached. The whole point of the button is that pressing it twice gives two
+// answers, and a cached one would give the same film until the entry expired.
+func (s *Server) handleMagic(w http.ResponseWriter, r *http.Request, sess store.Session) {
+	ctx := r.Context()
+
+	var req magicRequest
+	if r.Body != nil {
+		// A body that will not parse is an empty one: the exclusions are an optimisation,
+		// and refusing the press over them would trade a slightly worse pick for no pick.
+		_ = json.NewDecoder(r.Body).Decode(&req)
+	}
+
+	selection, ok := s.recommender.MagicPick(ctx, credentials(sess), recommend.MagicOptions{
+		ExcludeIDs:       req.ExcludeIDs,
+		AvailableMinutes: req.AvailableMinutes,
+		// The one non-deterministic thing about the feature, named in one place.
+		Roll: rand.Float64(),
+	})
+	if !ok {
+		// A household that has run out of unseen library is not an error, and the television
+		// says so quietly rather than showing a failure over somebody's film.
+		s.loggerFor(ctx).Debug("magic found nothing", "excluded", len(req.ExcludeIDs))
+		writeError(w, http.StatusNotFound, "nothing to suggest")
+		return
+	}
+
+	item, err := s.emby.Item(ctx, credentials(sess), selection.Item.ID, fieldsDetail)
+	if err != nil {
+		s.writeUpstreamError(ctx, w, err, "could not load the suggestion")
+		return
+	}
+	decorated := []json.RawMessage{item}
+	s.decorateItemRatings(ctx, decorated)
+
+	s.loggerFor(ctx).Info("magic picked",
+		"item", selection.Item.ID,
+		"title", selection.Item.Name,
+		"score", selection.Score,
+		"pool", selection.PoolSize,
+		"signals", strings.Join(selection.Signals, ","),
+	)
+
+	writeJSON(w, http.StatusOK, magicResponse{
+		Item:    decorated[0],
+		Reasons: selection.Reasons,
+	})
+}