Show poster thumbnails in the detail panes

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

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)
+}