Show poster thumbnails in the detail panes

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

internal/arr/image.go

@@ -0,0 +1,120 @@
+package arr
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const maxImageBytes = 8 << 20
+
+// Poster returns a key identifying the poster among cached images and a
+// function that downloads it, or ok=false when there is none.
+//
+// Library items have a copy on the Radarr/Sonarr server, which is fetched
+// with the API key (preferring the small -250 variant). Titles that are not
+// in the library yet only have the remote URL of the metadata provider; that
+// is fetched without the API key.
+func (c *Client) Poster(images []Image, inLibrary bool) (key string, fetch func(ctx context.Context) ([]byte, error), ok bool) {
+	for _, img := range images {
+		if img.CoverType != "poster" {
+			continue
+		}
+		if inLibrary && img.URL != "" {
+			local := img.URL
+			return c.baseURL + "|" + local, func(ctx context.Context) ([]byte, error) {
+				// MediaCover has poster-250.jpg next to poster.jpg; fall back to the original.
+				if small := smallVariant(local); small != local {
+					if data, err := c.GetBytes(ctx, small); err == nil {
+						return data, nil
+					}
+				}
+				return c.GetBytes(ctx, local)
+			}, true
+		}
+		if img.RemoteURL != "" {
+			remote := img.RemoteURL
+			return remote, func(ctx context.Context) ([]byte, error) { return FetchURL(ctx, remote) }, true
+		}
+	}
+	return "", nil, false
+}
+
+// smallVariant turns /MediaCover/1/poster.jpg?x into /MediaCover/1/poster-250.jpg?x.
+func smallVariant(p string) string {
+	path, query, hasQuery := strings.Cut(p, "?")
+	if !strings.HasSuffix(path, "/poster.jpg") {
+		return p
+	}
+	path = strings.TrimSuffix(path, ".jpg") + "-250.jpg"
+	if hasQuery {
+		return path + "?" + query
+	}
+	return path
+}
+
+// GetBytes downloads a server-relative path such as /MediaCover/1/poster.jpg
+// from the instance, authenticated with the API key.
+func (c *Client) GetBytes(ctx context.Context, ref string) ([]byte, error) {
+	u, err := c.resolve(ref)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("X-Api-Key", c.apiKey)
+	return doImage(c.http, req)
+}
+
+// resolve joins a server-relative path to the base URL. Radarr/Sonarr include
+// their URL base in image paths, so it must not be added twice.
+func (c *Client) resolve(ref string) (string, error) {
+	base, err := url.Parse(c.baseURL)
+	if err != nil {
+		return "", err
+	}
+	if base.Path != "" && base.Path != "/" && strings.HasPrefix(ref, strings.TrimRight(base.Path, "/")+"/") {
+		return base.Scheme + "://" + base.Host + ref, nil
+	}
+	return c.baseURL + ref, nil
+}
+
+var imageClient = &http.Client{Timeout: 20 * time.Second}
+
+// FetchURL downloads a public image. No credentials are sent.
+func FetchURL(ctx context.Context, rawURL string) ([]byte, error) {
+	u, err := url.Parse(rawURL)
+	if err != nil || (u.Scheme != "http" && u.Scheme != "https") {
+		return nil, fmt.Errorf("unsupported image URL")
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	return doImage(imageClient, req)
+}
+
+func doImage(client *http.Client, req *http.Request) ([]byte, error) {
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, stripURL(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("image: HTTP %d", resp.StatusCode)
+	}
+	data, err := io.ReadAll(io.LimitReader(resp.Body, maxImageBytes+1))
+	if err != nil {
+		return nil, err
+	}
+	if len(data) > maxImageBytes {
+		return nil, fmt.Errorf("image larger than %d MB", maxImageBytes>>20)
+	}
+	return data, nil
+}

internal/arr/image_test.go

@@ -0,0 +1,96 @@
+package arr
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestSmallVariant(t *testing.T) {
+	for in, want := range map[string]string{
+		"/MediaCover/1/poster.jpg?lastWrite=5": "/MediaCover/1/poster-250.jpg?lastWrite=5",
+		"/MediaCover/1/poster.jpg":             "/MediaCover/1/poster-250.jpg",
+		"/MediaCover/1/fanart.jpg":             "/MediaCover/1/fanart.jpg",
+	} {
+		if got := smallVariant(in); got != want {
+			t.Errorf("smallVariant(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+func TestPosterLocalUsesAPIKey(t *testing.T) {
+	var paths []string
+	var keys []string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		paths = append(paths, r.URL.RequestURI())
+		keys = append(keys, r.Header.Get("X-Api-Key"))
+		if r.URL.Path == "/MediaCover/1/poster-250.jpg" {
+			http.NotFound(w, r) // no small variant: fall back to the original
+			return
+		}
+		w.Write([]byte("IMG"))
+	}))
+	defer srv.Close()
+
+	c := NewClient(srv.URL, "secret")
+	imgs := []Image{{CoverType: "fanart", URL: "/MediaCover/1/fanart.jpg"}, {CoverType: "poster", URL: "/MediaCover/1/poster.jpg?lastWrite=1", RemoteURL: "https://remote/p.jpg"}}
+	key, fetch, ok := c.Poster(imgs, true)
+	if !ok || key == "" {
+		t.Fatal("no poster")
+	}
+	data, err := fetch(context.Background())
+	if err != nil || string(data) != "IMG" {
+		t.Fatalf("data=%q err=%v", data, err)
+	}
+	if len(paths) != 2 || paths[0] != "/MediaCover/1/poster-250.jpg?lastWrite=1" || paths[1] != "/MediaCover/1/poster.jpg?lastWrite=1" {
+		t.Errorf("requests = %v", paths)
+	}
+	for _, k := range keys {
+		if k != "secret" {
+			t.Errorf("api key header = %q", k)
+		}
+	}
+}
+
+func TestPosterRemoteSendsNoAPIKey(t *testing.T) {
+	var got string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		got = r.Header.Get("X-Api-Key")
+		w.Write([]byte("IMG"))
+	}))
+	defer srv.Close()
+
+	c := NewClient("http://radarr.invalid", "secret")
+	key, fetch, ok := c.Poster([]Image{{CoverType: "poster", URL: "/MediaCover/0/poster.jpg", RemoteURL: srv.URL + "/p.jpg"}}, false)
+	if !ok || key != srv.URL+"/p.jpg" {
+		t.Fatalf("key=%q ok=%v", key, ok)
+	}
+	if _, err := fetch(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+	if got != "" {
+		t.Errorf("the API key leaked to a remote image host: %q", got)
+	}
+	if _, _, ok := c.Poster([]Image{{CoverType: "banner", RemoteURL: "x"}}, false); ok {
+		t.Error("only posters count")
+	}
+	if _, err := FetchURL(context.Background(), "file:///etc/passwd"); err == nil {
+		t.Error("non-http schemes must be refused")
+	}
+}
+
+func TestResolveURLBase(t *testing.T) {
+	c := NewClient("http://host:7878/radarr", "k")
+	for ref, want := range map[string]string{
+		"/radarr/MediaCover/1/poster.jpg": "http://host:7878/radarr/MediaCover/1/poster.jpg",
+		"/MediaCover/1/poster.jpg":        "http://host:7878/radarr/MediaCover/1/poster.jpg",
+	} {
+		if got, _ := c.resolve(ref); got != want {
+			t.Errorf("resolve(%q) = %q, want %q", ref, got, want)
+		}
+	}
+	if got, _ := NewClient("http://host", "k").resolve("/MediaCover/1/poster.jpg"); got != "http://host/MediaCover/1/poster.jpg" {
+		t.Errorf("no url base: %q", got)
+	}
+}

internal/config/config.go

@@ -28,8 +28,15 @@ type Arr struct {
 // UI holds interface settings.
 type UI struct {
 	RefreshSeconds int `json:"refresh_seconds,omitempty"`
+	// Covers shows poster thumbnails in the detail panes (default true).
+	// Posters of titles that are not in the library yet are downloaded from
+	// the public image hosts Radarr/Sonarr point to (TMDb, TheTVDB).
+	Covers *bool `json:"covers,omitempty"`
 }
 
+// ShowCovers reports whether poster thumbnails are enabled.
+func (u UI) ShowCovers() bool { return u.Covers == nil || *u.Covers }
+
 // Config is the full application configuration.
 type Config struct {
 	Radarr  Arr     `json:"radarr"`

internal/config/config_test.go

@@ -76,3 +76,24 @@ func TestLoadPermissionWarning(t *testing.T) {
 		t.Fatalf("unexpected warnings: %v", warnings)
 	}
 }
+
+func TestShowCovers(t *testing.T) {
+	base := `{"radarr":{"url":"http://r","apikey":"k"},"sonarr":{"url":"http://s","apikey":"k"},"sabnzbd":{"url":"http://a","apikey":"k"}`
+	for _, tc := range []struct {
+		ui   string
+		want bool
+	}{
+		{``, true},
+		{`,"ui":{}`, true},
+		{`,"ui":{"covers":true}`, true},
+		{`,"ui":{"covers":false}`, false},
+	} {
+		cfg, err := Parse([]byte(base + tc.ui + `}`))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got := cfg.UI.ShowCovers(); got != tc.want {
+			t.Errorf("%q: ShowCovers = %v, want %v", tc.ui, got, tc.want)
+		}
+	}
+}

internal/ui/app.go

@@ -42,6 +42,9 @@ type App struct {
 	services *tview.TextView
 	state    map[string]serviceState // keyed by service name
 	probes   []probe
+
+	covers     bool // poster thumbnails enabled
+	coverCache *coverCache
 }
 
 // probe checks that one service answers; it returns its version.
@@ -84,6 +87,9 @@ func New(cfg *config.Config) *App {
 
 		services: tview.NewTextView().SetDynamicColors(true).SetTextAlign(tview.AlignRight),
 		state:    map[string]serviceState{},
+
+		covers:     cfg.UI.ShowCovers(),
+		coverCache: newCoverCache(),
 	}
 
 	radarrClient := radarr.NewClient(cfg.Radarr.URL, cfg.Radarr.APIKey)

internal/ui/backend.go

@@ -19,6 +19,7 @@ type result interface {
 	details() string
 	inLibrary() bool
 	withID(id int) result // copy flagged as added to the library
+	cover() coverRef
 }
 
 // monitorMode is a Sonarr-style "which episodes to monitor" choice.
@@ -50,13 +51,17 @@ type backend interface {
 
 // --- Radarr ---
 
-type movieResult struct{ radarr.Movie }
+type movieResult struct {
+	radarr.Movie
+	poster coverRef
+}
 
 func (m movieResult) key() string     { return radarr.TMDBTerm(m.TMDBID) }
 func (m movieResult) title() string   { return m.Title }
 func (m movieResult) label() string   { return movieLabel(m.Movie) }
 func (m movieResult) details() string { return movieDetails(m.Movie) }
 func (m movieResult) inLibrary() bool { return m.InLibrary() }
+func (m movieResult) cover() coverRef { return m.poster }
 func (m movieResult) withID(id int) result {
 	m.ID = id
 	return m
@@ -73,7 +78,7 @@ func (b radarrBackend) search(ctx context.Context, term string) ([]result, error
 	movies, err := b.c.Lookup(ctx, term)
 	out := make([]result, len(movies))
 	for i, m := range movies {
-		out[i] = movieResult{m}
+		out[i] = movieResult{Movie: m, poster: coverFor(b.c.Client, m.Images, m.InLibrary())}
 	}
 	return out, err
 }
@@ -97,13 +102,17 @@ func (b radarrBackend) interactive(v *searchView, r result) {
 
 // --- Sonarr ---
 
-type seriesResult struct{ sonarr.Series }
+type seriesResult struct {
+	sonarr.Series
+	poster coverRef
+}
 
 func (s seriesResult) key() string     { return "tvdb:" + itoa(s.TVDBID) }
 func (s seriesResult) title() string   { return s.Title }
 func (s seriesResult) label() string   { return seriesLabel(s.Series) }
 func (s seriesResult) details() string { return seriesDetails(s.Series) }
 func (s seriesResult) inLibrary() bool { return s.InLibrary() }
+func (s seriesResult) cover() coverRef { return s.poster }
 func (s seriesResult) withID(id int) result {
 	s.ID = id
 	return s
@@ -130,7 +139,7 @@ func (b sonarrBackend) search(ctx context.Context, term string) ([]result, error
 	series, err := b.c.Lookup(ctx, term)
 	out := make([]result, len(series))
 	for i, s := range series {
-		out[i] = seriesResult{s}
+		out[i] = seriesResult{Series: s, poster: coverFor(b.c.Client, s.Images, s.InLibrary())}
 	}
 	return out, err
 }

internal/ui/cover.go

@@ -0,0 +1,204 @@
+package ui
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"image"
+	_ "image/jpeg" // poster formats
+	_ "image/png"
+	"time"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/tview"
+
+	"git.stinnesbeck.com/nils/arr-tui/internal/arr"
+)
+
+const (
+	maxCoverPixels    = 25_000_000 // refuse decompression bombs
+	storedCoverHeight = 160        // a small copy is plenty for a terminal thumbnail
+	coverFailureTTL   = 2 * time.Minute
+	maxCoverCache     = 300
+	coverFetchLimit   = 4
+)
+
+// decodeCover decodes a JPEG or PNG poster and keeps a small copy.
+func decodeCover(data []byte) (*image.RGBA, error) {
+	cfg, _, err := image.DecodeConfig(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("not a supported image: %w", err)
+	}
+	if cfg.Width <= 0 || cfg.Height <= 0 || cfg.Width*cfg.Height > maxCoverPixels {
+		return nil, fmt.Errorf("image dimensions %dx%d not supported", cfg.Width, cfg.Height)
+	}
+	img, _, err := image.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	b := img.Bounds()
+	if b.Dy() <= storedCoverHeight {
+		return boxScale(img, b.Dx(), b.Dy()), nil
+	}
+	return boxScale(img, max(1, b.Dx()*storedCoverHeight/b.Dy()), storedCoverHeight), nil
+}
+
+// boxScale resizes src to w×h by averaging the source pixels under every
+// target pixel (good for shrinking; upscaling degrades to nearest neighbour).
+func boxScale(src image.Image, w, h int) *image.RGBA {
+	b := src.Bounds()
+	dst := image.NewRGBA(image.Rect(0, 0, w, h))
+	for y := 0; y < h; y++ {
+		y0 := b.Min.Y + y*b.Dy()/h
+		y1 := max(b.Min.Y+(y+1)*b.Dy()/h, y0+1)
+		for x := 0; x < w; x++ {
+			x0 := b.Min.X + x*b.Dx()/w
+			x1 := max(b.Min.X+(x+1)*b.Dx()/w, x0+1)
+			var r, g, bl, n uint64
+			for sy := y0; sy < y1; sy++ {
+				for sx := x0; sx < x1; sx++ {
+					pr, pg, pb, _ := src.At(sx, sy).RGBA()
+					r, g, bl, n = r+uint64(pr), g+uint64(pg), bl+uint64(pb), n+1
+				}
+			}
+			i := dst.PixOffset(x, y)
+			dst.Pix[i], dst.Pix[i+1], dst.Pix[i+2], dst.Pix[i+3] = uint8(r/n>>8), uint8(g/n>>8), uint8(bl/n>>8), 255
+		}
+	}
+	return dst
+}
+
+// coverView draws a poster with half-block characters: every cell shows two
+// vertically stacked pixels (foreground = upper, background = lower), so it
+// works in any terminal with colors, also over SSH.
+type coverView struct {
+	*tview.Box
+	img  *image.RGBA
+	note string // shown instead of the image: "loading…", "no cover"
+
+	scaled *image.RGBA // cache of img at the last drawn size
+}
+
+func newCoverView() *coverView { return &coverView{Box: tview.NewBox()} }
+
+func (c *coverView) setImage(img *image.RGBA) { c.img, c.note, c.scaled = img, "", nil }
+func (c *coverView) setNote(note string)      { c.img, c.note, c.scaled = nil, note, nil }
+
+func (c *coverView) Draw(screen tcell.Screen) {
+	c.Box.DrawForSubclass(screen, c)
+	x, y, w, h := c.GetInnerRect()
+	if w < 1 || h < 1 {
+		return
+	}
+	if c.img == nil {
+		if c.note != "" {
+			tview.Print(screen, "[gray]"+c.note, x, y, w, tview.AlignLeft, tcell.ColorGray)
+		}
+		return
+	}
+
+	// Fit the poster into w columns by 2h pixel rows, keeping its aspect.
+	b := c.img.Bounds()
+	tw := w
+	th := tw * b.Dy() / b.Dx()
+	if th > 2*h {
+		th = 2 * h
+		tw = th * b.Dx() / b.Dy()
+	}
+	th &^= 1
+	if tw < 1 || th < 2 {
+		return
+	}
+	if c.scaled == nil || c.scaled.Bounds().Dx() != tw || c.scaled.Bounds().Dy() != th {
+		c.scaled = boxScale(c.img, tw, th)
+	}
+	px := func(px, py int) tcell.Color {
+		i := c.scaled.PixOffset(px, py)
+		return tcell.NewRGBColor(int32(c.scaled.Pix[i]), int32(c.scaled.Pix[i+1]), int32(c.scaled.Pix[i+2]))
+	}
+	for row := 0; row < th/2; row++ {
+		for col := 0; col < tw; col++ {
+			style := tcell.StyleDefault.Foreground(px(col, 2*row)).Background(px(col, 2*row+1))
+			screen.SetContent(x+col, y+row, '▀', nil, style)
+		}
+	}
+}
+
+// coverRef says where a poster comes from. The zero value means "no poster".
+type coverRef struct {
+	key   string // identifies the poster in the cache
+	fetch func(ctx context.Context) ([]byte, error)
+}
+
+// coverFor builds the poster reference of a title from its image list.
+func coverFor(c *arr.Client, images []arr.Image, inLibrary bool) coverRef {
+	key, fetch, ok := c.Poster(images, inLibrary)
+	if !ok {
+		return coverRef{}
+	}
+	return coverRef{key: key, fetch: fetch}
+}
+
+// coverCache holds decoded posters and the downloads in flight. UI goroutine only.
+type coverCache struct {
+	imgs    map[string]*image.RGBA
+	failed  map[string]time.Time
+	waiting map[string][]func(*image.RGBA, error)
+	slots   chan struct{}
+}
+
+func newCoverCache() *coverCache {
+	return &coverCache{
+		imgs:    map[string]*image.RGBA{},
+		failed:  map[string]time.Time{},
+		waiting: map[string][]func(*image.RGBA, error){},
+		slots:   make(chan struct{}, coverFetchLimit),
+	}
+}
+
+// loadCover delivers the poster to done on the UI goroutine, downloading it in
+// the background when it is not cached. Failures are remembered for a while so
+// an unreachable image host is not retried on every selection.
+func (a *App) loadCover(ref coverRef, done func(*image.RGBA, error)) {
+	c := a.coverCache
+	if img, ok := c.imgs[ref.key]; ok {
+		done(img, nil)
+		return
+	}
+	if t, ok := c.failed[ref.key]; ok && time.Since(t) < coverFailureTTL {
+		done(nil, fmt.Errorf("no cover"))
+		return
+	}
+	if _, inflight := c.waiting[ref.key]; inflight {
+		c.waiting[ref.key] = append(c.waiting[ref.key], done)
+		return
+	}
+	c.waiting[ref.key] = []func(*image.RGBA, error){done}
+
+	go func() {
+		c.slots <- struct{}{}
+		defer func() { <-c.slots }()
+		ctx, cancel := context.WithTimeout(context.Background(), 25*time.Second)
+		defer cancel()
+		var img *image.RGBA
+		data, err := ref.fetch(ctx)
+		if err == nil {
+			img, err = decodeCover(data)
+		}
+		a.post(func() {
+			waiters := c.waiting[ref.key]
+			delete(c.waiting, ref.key)
+			if err != nil {
+				c.failed[ref.key] = time.Now()
+			} else {
+				if len(c.imgs) >= maxCoverCache {
+					c.imgs = map[string]*image.RGBA{} // simple bound; posters are cheap to fetch again
+				}
+				c.imgs[ref.key] = img
+			}
+			for _, w := range waiters {
+				w(img, err)
+			}
+		})
+	}()
+}

internal/ui/cover_test.go

@@ -0,0 +1,149 @@
+package ui
+
+import (
+	"bytes"
+	"context"
+	"image"
+	"image/color"
+	"image/jpeg"
+	"image/png"
+	"testing"
+	"time"
+
+	"github.com/gdamore/tcell/v2"
+)
+
+// stripes returns a w×h image whose top half is red and bottom half blue.
+func stripes(w, h int) *image.RGBA {
+	img := image.NewRGBA(image.Rect(0, 0, w, h))
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			c := color.RGBA{255, 0, 0, 255}
+			if y >= h/2 {
+				c = color.RGBA{0, 0, 255, 255}
+			}
+			img.SetRGBA(x, y, c)
+		}
+	}
+	return img
+}
+
+func TestBoxScaleAverages(t *testing.T) {
+	src := image.NewRGBA(image.Rect(0, 0, 2, 2))
+	src.SetRGBA(0, 0, color.RGBA{200, 0, 0, 255})
+	src.SetRGBA(1, 0, color.RGBA{0, 0, 0, 255})
+	src.SetRGBA(0, 1, color.RGBA{0, 0, 0, 255})
+	src.SetRGBA(1, 1, color.RGBA{0, 0, 0, 255})
+	got := boxScale(src, 1, 1).RGBAAt(0, 0)
+	if got.R < 49 || got.R > 51 || got.G != 0 || got.A != 255 {
+		t.Errorf("average = %+v, want R≈50", got)
+	}
+	// Upscaling must not leave holes.
+	up := boxScale(stripes(1, 2), 3, 4)
+	if up.RGBAAt(2, 0).R != 255 || up.RGBAAt(2, 3).B != 255 {
+		t.Errorf("upscaled corners: %+v %+v", up.RGBAAt(2, 0), up.RGBAAt(2, 3))
+	}
+}
+
+func TestDecodeCover(t *testing.T) {
+	var buf bytes.Buffer
+	if err := jpeg.Encode(&buf, stripes(300, 450), nil); err != nil {
+		t.Fatal(err)
+	}
+	img, err := decodeCover(buf.Bytes())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b := img.Bounds(); b.Dy() != storedCoverHeight || b.Dx() != 106 {
+		t.Errorf("stored size %v, want 106x%d", b, storedCoverHeight)
+	}
+
+	buf.Reset()
+	if err := png.Encode(&buf, stripes(20, 30)); err != nil {
+		t.Fatal(err)
+	}
+	if img, err := decodeCover(buf.Bytes()); err != nil || img.Bounds().Dy() != 30 {
+		t.Errorf("small png kept as is: %v %v", img, err)
+	}
+
+	if _, err := decodeCover([]byte("<html>not an image</html>")); err == nil {
+		t.Error("garbage must be rejected")
+	}
+	// A header that promises a huge image is refused before decoding it.
+	var huge bytes.Buffer
+	huge.Write([]byte("\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x27\x10\x00\x00\x27\x10\x08\x02\x00\x00\x00"))
+	if _, err := decodeCover(huge.Bytes()); err == nil {
+		t.Error("oversized image must be rejected")
+	}
+}
+
+func TestCoverViewDrawsHalfBlocks(t *testing.T) {
+	screen := tcell.NewSimulationScreen("")
+	if err := screen.Init(); err != nil {
+		t.Fatal(err)
+	}
+	defer screen.Fini()
+	screen.SetSize(20, 10)
+
+	c := newCoverView()
+	c.setImage(stripes(40, 60)) // 2:3 poster
+	c.SetRect(0, 0, 20, 10)     // 20 columns × 20 pixel rows: a 13×20 pixel poster
+	c.Draw(screen)
+
+	// Row 0 holds pixel rows 0 (top) and 1: both red. The middle cell row
+	// (index 4/5) crosses into blue; the last row is blue on both halves.
+	rgba := func(c tcell.Color) color.RGBA {
+		r, g, b := c.RGB()
+		return color.RGBA{uint8(r), uint8(g), uint8(b), 255}
+	}
+	check := func(row int, wantFg, wantBg color.RGBA) {
+		t.Helper()
+		ch, _, style, _ := screen.GetContent(0, row)
+		fg, bg, _ := style.Decompose()
+		if ch != '▀' || rgba(fg) != wantFg || rgba(bg) != wantBg {
+			t.Errorf("row %d: %q fg=%v bg=%v", row, ch, rgba(fg), rgba(bg))
+		}
+	}
+	red, blue := color.RGBA{255, 0, 0, 255}, color.RGBA{0, 0, 255, 255}
+	check(0, red, red)
+	check(9, blue, blue)
+	// Beyond the poster's width nothing is drawn.
+	if ch, _, _, _ := screen.GetContent(19, 0); ch == '▀' {
+		t.Error("poster stretched beyond its aspect ratio")
+	}
+}
+
+func TestLoadCoverCachesAndDedupes(t *testing.T) {
+	a := newTestApp(t)
+	fetches := 0
+	var buf bytes.Buffer
+	png.Encode(&buf, stripes(10, 20))
+	ref := coverRef{key: "k", fetch: func(context.Context) ([]byte, error) {
+		fetches++
+		return buf.Bytes(), nil
+	}}
+
+	// Run posted callbacks inline instead of through the (not running) event loop.
+	delivered := make(chan error, 2)
+	a.loadCover(ref, func(_ *image.RGBA, err error) { delivered <- err })
+	a.loadCover(ref, func(_ *image.RGBA, err error) { delivered <- err }) // joins the request in flight
+	if len(a.coverCache.waiting["k"]) != 2 {
+		t.Fatalf("waiters = %d, want 2", len(a.coverCache.waiting["k"]))
+	}
+	if fetches > 1 {
+		t.Errorf("fetched %d times", fetches)
+	}
+}
+
+func TestLoadCoverRemembersFailures(t *testing.T) {
+	a := newTestApp(t)
+	a.coverCache.failed["bad"] = time.Now()
+	var gotErr error
+	a.loadCover(coverRef{key: "bad", fetch: func(context.Context) ([]byte, error) {
+		t.Error("a recent failure must not be retried")
+		return nil, nil
+	}}, func(_ *image.RGBA, err error) { gotErr = err })
+	if gotErr == nil {
+		t.Error("expected an error for a recently failed cover")
+	}
+}

internal/ui/detail.go

@@ -0,0 +1,82 @@
+package ui
+
+import (
+	"image"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/tview"
+)
+
+const (
+	coverRows    = 18 // poster height in terminal rows (36 pixels)
+	minCoverRows = 6  // a smaller poster is not worth showing
+	minTextRows  = 10 // the poster never takes these rows from the text
+)
+
+// detailPane shows a poster above a text. The poster shrinks on short panes
+// and is dropped when the text would get too little room.
+type detailPane struct {
+	*tview.Flex
+	app   *App
+	cover *coverView
+	text  *tview.TextView
+
+	want      string // key of the poster that should be shown
+	hasCover  bool   // a poster (or its loading note) is part of the content
+	coverSize int    // rows currently given to the poster
+}
+
+func newDetailPane(app *App) *detailPane {
+	d := &detailPane{
+		Flex:  tview.NewFlex().SetDirection(tview.FlexRow),
+		app:   app,
+		cover: newCoverView(),
+		text:  tview.NewTextView().SetDynamicColors(true).SetWordWrap(true),
+	}
+	d.AddItem(d.cover, 0, 0, false).AddItem(d.text, 0, 1, false)
+	d.SetBorder(true).SetTitle(" Details ")
+	return d
+}
+
+// Show displays the text and, if there is one, the poster.
+func (d *detailPane) Show(text string, ref coverRef) {
+	d.text.SetText(text).ScrollToBeginning()
+	if !d.app.covers || ref.fetch == nil {
+		d.want, d.hasCover = "", false
+		d.cover.setImage(nil)
+		return
+	}
+	d.want, d.hasCover = ref.key, true
+	d.cover.setNote("loading cover…")
+	want := ref.key
+	d.app.loadCover(ref, func(img *image.RGBA, err error) {
+		if d.want != want {
+			return // the selection moved on
+		}
+		if err != nil {
+			d.hasCover = false // nothing to show: give the room back to the text
+			d.cover.setImage(nil)
+			return
+		}
+		d.cover.setImage(img)
+	})
+}
+
+// Clear empties the pane.
+func (d *detailPane) Clear() { d.Show("", coverRef{}) }
+
+func (d *detailPane) Draw(screen tcell.Screen) {
+	_, _, _, h := d.GetInnerRect()
+	rows := 0
+	if d.hasCover {
+		rows = min(coverRows, h-minTextRows)
+		if rows < minCoverRows {
+			rows = 0
+		}
+	}
+	if rows != d.coverSize {
+		d.coverSize = rows
+		d.ResizeItem(d.cover, rows, 0)
+	}
+	d.Flex.Draw(screen)
+}

internal/ui/format_test.go

@@ -75,14 +75,14 @@ func TestSeriesLabelAndDetails(t *testing.T) {
 }
 
 func TestResultKeysAndWithID(t *testing.T) {
-	var r result = movieResult{radarr.Movie{TMDBID: 603, Title: "x"}}
+	var r result = movieResult{Movie: radarr.Movie{TMDBID: 603, Title: "x"}}
 	if r.key() != "tmdb:603" || r.inLibrary() {
 		t.Fatalf("movie key/inLibrary: %q %v", r.key(), r.inLibrary())
 	}
 	if added := r.withID(5); !added.inLibrary() || r.inLibrary() {
 		t.Error("withID must return a flagged copy and leave the original alone")
 	}
-	r = seriesResult{sonarr.Series{TVDBID: 81189}}
+	r = seriesResult{Series: sonarr.Series{TVDBID: 81189}}
 	if r.key() != "tvdb:81189" {
 		t.Errorf("series key = %q", r.key())
 	}

internal/ui/library.go

@@ -47,6 +47,7 @@ type libItem struct {
 	status    string
 	size      string
 	details   string
+	cover     coverRef
 	movie     *radarr.Movie
 	series    *sonarr.Series
 	// File properties for the attribute filter. For series they are fetched on
@@ -199,7 +200,7 @@ type libraryView struct {
 	root    *tview.Flex
 	header  *tview.TextView
 	input   *tview.InputField
-	details *tview.TextView
+	details *detailPane
 	panes   [2]*libPane
 
 	// UI-goroutine state.
@@ -225,11 +226,10 @@ func newLibraryView(app *App, r *radarr.Client, s *sonarr.Client) *libraryView {
 		app: app, radarr: r, sonarr: s,
 		header:  tview.NewTextView().SetDynamicColors(true),
 		input:   tview.NewInputField().SetLabel("Filter Movies: ").SetFieldWidth(0),
-		details: tview.NewTextView().SetDynamicColors(true).SetWordWrap(true),
+		details: newDetailPane(app),
 
 		seriesFiles: map[int]seriesFiles{},
 	}
-	v.details.SetBorder(true).SetTitle(" Details ")
 
 	lists := tview.NewFlex().SetDirection(tview.FlexRow) // movies above series
 	for _, kind := range []libKind{kindMovies, kindSeries} {
@@ -326,14 +326,18 @@ func (v *libraryView) reloadPane(p *libPane) {
 			var movies []radarr.Movie
 			if movies, err = v.radarr.Movies(ctx); err == nil {
 				for _, m := range movies {
-					items = append(items, newMovieItem(m))
+					it := newMovieItem(m)
+					it.cover = coverFor(v.radarr.Client, m.Images, true)
+					items = append(items, it)
 				}
 			}
 		} else {
 			var series []sonarr.Series
 			if series, err = v.sonarr.Series(ctx); err == nil {
 				for _, s := range series {
-					items = append(items, v.withCachedFiles(newSeriesItem(s)))
+					it := newSeriesItem(s)
+					it.cover = coverFor(v.sonarr.Client, s.Images, true)
+					items = append(items, v.withCachedFiles(it))
 				}
 			}
 		}
@@ -423,11 +427,10 @@ func (v *libraryView) renderPane(p *libPane) {
 
 func (v *libraryView) renderDetails() {
 	if it, ok := v.selected(); ok {
-		v.details.SetText(it.details)
-		v.details.ScrollToBeginning()
+		v.details.Show(it.details, it.cover)
 		return
 	}
-	v.details.SetText("")
+	v.details.Clear()
 }
 
 // open starts the interactive search (movie) or the episode drill-down (series).

internal/ui/search.go

@@ -30,7 +30,7 @@ type searchView struct {
 	root    *tview.Flex
 	input   *tview.InputField
 	list    *tview.List
-	details *tview.TextView
+	details *detailPane
 
 	// UI-goroutine state.
 	results []result
@@ -53,10 +53,9 @@ func newSearchView(app *App, be backend, cfg config.Arr) *searchView {
 		cfg:     cfg,
 		input:   tview.NewInputField().SetLabel("Search: "),
 		list:    tview.NewList().ShowSecondaryText(false),
-		details: tview.NewTextView().SetDynamicColors(true).SetWordWrap(true),
+		details: newDetailPane(app),
 	}
 	v.list.SetBorder(true).SetTitle(" " + be.noun() + " ")
-	v.details.SetBorder(true).SetTitle(" Details ")
 
 	left := tview.NewFlex().SetDirection(tview.FlexRow).
 		AddItem(v.input, 1, 0, true).
@@ -231,7 +230,7 @@ func (v *searchView) render(sel int) {
 		v.list.AddItem(r.label(), "", 0, nil)
 	}
 	if len(v.results) == 0 {
-		v.details.SetText("")
+		v.details.Clear()
 		return
 	}
 	sel = min(max(sel, 0), len(v.results)-1)
@@ -241,10 +240,10 @@ func (v *searchView) render(sel int) {
 
 func (v *searchView) showDetails(i int) {
 	if i < 0 || i >= len(v.results) {
-		v.details.SetText("")
+		v.details.Clear()
 		return
 	}
-	v.details.SetText(v.results[i].details()).ScrollToBeginning()
+	v.details.Show(v.results[i].details(), v.results[i].cover())
 }
 
 // interactive opens the release list for the result at index i.