Details pane: director and cast from Trakt

With a Trakt client ID, the details of a movie or series show the
director(s) or creators and up to 8 cast members with their roles below
the plot, in every view. The title is found on Trakt by its TMDb/TVDB
(else IMDb) id, then its people are read. Casts are cached and, like
posters, only loaded once the selection rests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ui/people.go

@@ -0,0 +1,112 @@
+package ui
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"git.stinnesbeck.com/nils/arr-tui/internal/trakt"
+)
+
+const (
+	maxPeopleCache  = 500
+	peopleRetryWait = 2 * time.Minute // a failed lookup is not repeated sooner
+)
+
+// peopleCache holds the casts loaded from Trakt and the lookups in flight.
+// UI goroutine only.
+type peopleCache struct {
+	done    map[string]trakt.People
+	failed  map[string]time.Time
+	waiting map[string][]func(trakt.People, error)
+}
+
+func newPeopleCache() *peopleCache {
+	return &peopleCache{done: map[string]trakt.People{}, failed: map[string]time.Time{}, waiting: map[string][]func(trakt.People, error){}}
+}
+
+// loadPeople delivers the cast of a title to done on the UI goroutine,
+// asking Trakt in the background when it is not cached. A title Trakt does
+// not know is remembered as having no cast.
+func (a *App) loadPeople(r trakt.Ref, done func(trakt.People, error)) {
+	c, key := a.people, r.Key()
+	if p, ok := c.done[key]; ok {
+		done(p, nil)
+		return
+	}
+	if t, ok := c.failed[key]; ok && time.Since(t) < peopleRetryWait {
+		done(trakt.People{}, errors.New("cast not available"))
+		return
+	}
+	if _, inflight := c.waiting[key]; inflight {
+		c.waiting[key] = append(c.waiting[key], done)
+		return
+	}
+	c.waiting[key] = []func(trakt.People, error){done}
+	go func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+		defer cancel()
+		p, err := a.trakt.People(ctx, r)
+		if errors.Is(err, trakt.ErrNotFound) {
+			p, err = trakt.People{}, nil
+		}
+		a.post(func() {
+			if a.people != c {
+				return // dropped meanwhile (the client ID changed)
+			}
+			waiters := c.waiting[key]
+			delete(c.waiting, key)
+			if err != nil {
+				c.failed[key] = time.Now()
+			} else {
+				if len(c.done) >= maxPeopleCache {
+					c.done = map[string]trakt.People{}
+				}
+				c.done[key] = p
+			}
+			for _, w := range waiters {
+				w(p, err)
+			}
+		})
+	}()
+}
+
+// showPeople loads the cast of the title the pane shows, once the selection
+// rests (like the poster: holding an arrow key must not send a request per
+// step, Trakt allows 500 per five minutes).
+func (d *detailPane) showPeople(r trakt.Ref) {
+	key := r.Key()
+	if key == d.castKey {
+		return // the same title again (a refresh): keep what is shown
+	}
+	if d.castSettle != nil {
+		d.castSettle.Stop()
+	}
+	d.castKey, d.cast = key, ""
+	if key == "" || !d.app.trakt.Configured() {
+		return
+	}
+	now := time.Now()
+	moving := now.Sub(d.castShown) < posterSettle
+	d.castShown = now
+	load := func() {
+		d.app.loadPeople(r, func(p trakt.People, err error) {
+			if d.castKey != key || err != nil {
+				return
+			}
+			d.cast = peopleText(p, r.Kind)
+			d.laidOut.valid = false
+		})
+	}
+	if moving {
+		d.castSettle = time.AfterFunc(posterSettle, func() {
+			d.app.post(func() {
+				if d.castKey == key {
+					load()
+				}
+			})
+		})
+		return
+	}
+	load()
+}