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
+}