Merge p17-w3-embed-panel into dev (Phase 17 Wave 17.3: Fixed embed queue panel + collapse/resize handshake)

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor

@@ -26,7 +26,7 @@ else
                                          SkipNext="@SkipNext"
                                          SkipPrevious="@SkipPrevious"
                                          ShowQueueButton="ShowQueueButton"
-                                         QueueOpen="_queueOpen"
+                                         QueueOpen="QueueButtonOpen"
                                          QueueToggle="@ToggleQueue"
                                          Class="transport-zone"/>
 
@@ -42,6 +42,23 @@ else
                                     Class="seek-zone"/>
                 </div>
 
+                @* Fixed (embed) queue panel (§4 / AC5). A release embed shows the up-next inline below the
+                   controls as a read-only list (Editable=false → no drag handles, no remove buttons; C3).
+                   Jump-to-track is still allowed (OQ2) — routed through the same OnQueueJump as the docked
+                   overlay, which calls PlayRelease (clearing IsArmed if the embed was armed-but-not-started).
+                   Gated on ShowFixedPanel so a single-track embed (empty queue) stays panel-free (UC6). The
+                   Queue button collapses/expands this panel (OQ1 Option A); collapse hides it and posts the
+                   shrunken height to the host iframe. *@
+                @if (ShowFixedPanel && _fixedPanelOpen)
+                {
+                    <div class="deepdrft-queue-embed-panel">
+                        <QueueList Items="QueueItems"
+                                   CurrentIndex="QueueCurrentIndex"
+                                   Editable="false"
+                                   OnJump="@OnQueueJump"/>
+                    </div>
+                }
+
                 @* Minimize / close — positioned absolutely top-right *@
                 @if (!Fixed)
                 {
@@ -62,8 +79,8 @@ else
 
         @* Docked queue overlay (Phase 17 §3.2). MudOverlay portals to the body, so its position here in
            the dock subtree does not affect its screen-centered rendering. Only mounted in docked mode —
-           the Fixed embed gets its own inline panel in a later wave. *@
+           the Fixed embed renders its own inline panel inside the surface above. *@
-        @if (ShowQueueButton)
+        @if (ShowDockedOverlay)
         {
             <QueueOverlay Visible="_queueOpen"
                           Items="QueueItems"

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor.cs

@@ -40,6 +40,13 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
     private IJSObjectReference? _spacerModule;
     private bool _spacerObserved;
 
+    // Fixed-embed → host resize handshake (OQ1 Option A). When the inline panel collapses/expands we
+    // measure the player's live height and post it to the host so the iframe resizes to match. The
+    // dirty flag defers the post to OnAfterRenderAsync so the DOM reflects the new panel state first.
+    private IJSObjectReference? _embedModule;
+    private bool _embedHeightDirty;
+    private bool _embedHeightPosted;
+
     private bool IsLoaded => PlayerService?.IsLoaded ?? false;
     private bool IsLoading => PlayerService?.IsLoading ?? false;
 
@@ -64,13 +71,31 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
     private bool HasNext => QueueService?.HasNext ?? false;
     private bool HasPrevious => QueueService?.HasPrevious ?? false;
 
-    // Queue overlay state. The button (and overlay) appear only in docked mode with a non-empty queue,
+    // Queue button gating. The button appears in BOTH modes when a queue is loaded, mirroring the
-    // mirroring the skip-affordance gating (AC1): with no queue the bar is byte-for-byte its pre-queue
+    // skip-affordance gating (AC1): with no queue the bar is byte-for-byte its pre-queue self, so a
-    // self. The Fixed embed gets an inline panel in a later wave, so the docked overlay is !Fixed-only.
+    // single-track embed (empty queue) shows no button and no panel (UC6). In docked mode it toggles
-    private bool ShowQueueButton => !Fixed && (QueueService?.Items.Count ?? 0) > 0;
+    // the overlay; in Fixed mode it collapses/expands the inline panel (OQ1 Option A).
+    private bool HasQueue => (QueueService?.Items.Count ?? 0) > 0;
+    private bool ShowQueueButton => HasQueue;
+
+    // The docked overlay mounts only in docked mode; the Fixed embed renders its inline panel instead.
+    private bool ShowDockedOverlay => !Fixed && HasQueue;
+
+    // The Fixed-mode inline panel: always shown (read-only, C3) when a release embed has a queue.
+    // Gated on Fixed + non-empty so single-track embeds keep their compact, panel-free bar (UC6).
+    private bool ShowFixedPanel => Fixed && HasQueue;
+
     private IReadOnlyList<TrackDto> QueueItems => QueueService?.Items ?? [];
     private int QueueCurrentIndex => QueueService?.CurrentIndex ?? -1;
 
+    // Fixed-mode panel collapse state (OQ1 Option A). Default expanded so a release embed shows the
+    // up-next out of the box; the Queue button collapses it to let the viewer reclaim iframe space.
+    private bool _fixedPanelOpen = true;
+
+    // The Queue button's "open" state differs by mode: docked tracks the overlay, Fixed tracks the
+    // inline panel's expanded state. One button, mode-appropriate meaning.
+    private bool QueueButtonOpen => Fixed ? _fixedPanelOpen : _queueOpen;
+
     /// <summary>
     /// Display time - shows seek position while dragging, otherwise current playback time.
     /// </summary>
@@ -137,7 +162,21 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
         await QueueService.Previous();
     }
 
-    private void ToggleQueue() => _queueOpen = !_queueOpen;
+    // Docked: toggle the overlay. Fixed: collapse/expand the inline panel and flag a height re-post so
+    // the host iframe resizes to match the new panel state (OQ1 Option A). The post happens in
+    // OnAfterRenderAsync (below) once the DOM reflects the new state, then degrades safely — the host
+    // listener may simply not be present (Option B's behaviour).
+    private void ToggleQueue()
+    {
+        if (Fixed)
+        {
+            _fixedPanelOpen = !_fixedPanelOpen;
+            _embedHeightDirty = true;
+            return;
+        }
+
+        _queueOpen = !_queueOpen;
+    }
 
     private void CloseQueue() => _queueOpen = false;
 
@@ -160,7 +199,21 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
-        // The Fixed embed is already in normal flow — no spacer/clip needed.
+        // Fixed embed: post the live player height to the host so the iframe sizes to the panel. We
+        // post on the first render (so the host snaps to the expanded panel rather than the snippet's
+        // initial guess) and whenever the panel is collapsed/expanded (_embedHeightDirty). No spacer/
+        // clip here — the embed is in normal flow.
+        if (Fixed)
+        {
+            if (ShowFixedPanel && (!_embedHeightPosted || _embedHeightDirty))
+            {
+                _embedHeightDirty = false;
+                _embedHeightPosted = true;
+                await PostEmbedHeight();
+            }
+            return;
+        }
+
         // For the docked player: we observe in BOTH expanded and minimized states
         // so --player-height always reflects the live height of whichever element
         // is visible. This keeps the WaveformVisualizer clipped to the top of
@@ -169,7 +222,6 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
         //   minimized → observe _miniDock   (floating FAB container, ~56–60px)
         // The player-spacer's .minimized class uses a hardcoded height and ignores
         // the var, so publishing the FAB height here does not regress the spacer.
-        if (Fixed) return;
 
         var elementToObserve = _isMinimized ? _miniDock : _playerRoot;
         var alreadyOnThisElement = _spacerObserved && elementToObserve.Id == _lastObservedElement.Id;
@@ -198,6 +250,37 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
         }
     }
 
+    // Measure the player root's live height and post it to the host page (OQ1 Option A). Best-effort:
+    // a missing module or a host that ignores the message just means no outer resize (Option B value).
+    private async Task PostEmbedHeight()
+    {
+        var module = await GetEmbedModuleAsync();
+        if (module is null) return;
+
+        try
+        {
+            await module.InvokeVoidAsync("postHeight", _playerRoot);
+        }
+        catch (JSException)
+        {
+            // Runtime gone or element detached mid-teardown — nothing actionable.
+        }
+    }
+
+    private async Task<IJSObjectReference?> GetEmbedModuleAsync()
+    {
+        try
+        {
+            return _embedModule ??= await JsRuntime.InvokeAsync<IJSObjectReference>(
+                "import", "./js/embed/embed-frame.js");
+        }
+        catch (JSException)
+        {
+            // Module failed to load — the panel still renders and toggles; only the outer resize is lost.
+            return null;
+        }
+    }
+
     private async Task Expand() => await SetMinimized(false);
 
     /// <summary>
@@ -318,5 +401,18 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
             }
             _spacerModule = null;
         }
+
+        if (_embedModule is not null)
+        {
+            try
+            {
+                await _embedModule.DisposeAsync();
+            }
+            catch (JSException)
+            {
+                // Runtime already gone (navigation/teardown) — nothing to clean up.
+            }
+            _embedModule = null;
+        }
     }
 }

DeepDrftPublic.Client/Helpers/EmbedSnippetBuilder.cs

@@ -3,19 +3,74 @@ namespace DeepDrftPublic.Client.Helpers;
 /// <summary>
 /// Builds the iframe embed snippet the share popover copies. Two targets: a single track
 /// (<see cref="ForTrack"/> → <c>FramePlayer?TrackEntryKey=...</c>) and a whole release
-/// (<see cref="ForRelease"/> → <c>FramePlayer?ReleaseEntryKey=...</c>). The iframe chrome
+/// (<see cref="ForRelease"/> → <c>FramePlayer?ReleaseEntryKey=...</c>).
-/// (dimensions, border radius, autoplay permission) is identical across both, defined once here.
+///
+/// <para>
+/// The two snippets diverge in height by design (Phase 17 §4.1, OQ6): a single-track embed has no
+/// queue, so <see cref="ForTrack"/> stays at the compact player height; a release embed renders the
+/// always-shown queue panel below the controls, so <see cref="ForRelease"/> is taller to show it
+/// without clipping. Other iframe chrome (width, border radius, autoplay permission) is identical and
+/// defined once in <see cref="Frame"/>.
+/// </para>
+///
+/// <para>
+/// OQ1 Option A — collapse/expand resize handshake. The release snippet carries a tiny host-side
+/// listener: the embedded player posts its desired height when the viewer collapses/expands the
+/// queue panel, and the listener sizes this specific iframe to match. It is scoped to the snippet's
+/// own iframe (matched by id) and ignores any message whose shape does not match, so it cannot be
+/// driven by foreign frames. It degrades to Option B's behaviour if the host strips the script: the
+/// panel still renders and toggles inside the iframe at its default (expanded) height — only the
+/// outer resize is lost. The track snippet needs no script (no panel, no toggle).
+/// </para>
+///
+/// <para>
+/// Multi-embed isolation: each <see cref="ForRelease"/> call mints a fresh random token (8 hex
+/// chars). The token is used as the iframe id (<c>deepdrft-embed-{token}</c>) and threaded into
+/// the iframe src as <c>&amp;EmbedId={token}</c> so the iframe can learn its own id. The host-side
+/// resize script matches incoming messages on <c>embedId</c> and resizes only the iframe whose id
+/// matches the token — two releases on one host page resize independently without cross-talk. Two
+/// calls for the same release still get distinct tokens, ensuring uniqueness even when the same
+/// release is pasted twice. Older snippets that lack <c>embedId</c> in their postMessage payload are
+/// silently ignored by the script (backward-compatible degradation).
+/// </para>
+///
 /// Pure string composition so the snippet shape is unit-testable without rendering the component.
 /// </summary>
 public static class EmbedSnippetBuilder
 {
+    // Compact single-track height (the historical embed height — must not change: UC6/AC6).
+    private const int TrackHeight = 196;
+
+    // Release height: the compact player plus the queue panel (fixed, internally scrollable past N
+    // rows per OQ6). The panel collapses to the track height via the resize handshake below.
+    private const int ReleaseHeight = 384;
+
     // baseUri carries a trailing slash (NavigationManager.BaseUri), so "FramePlayer" appends cleanly.
     public static string ForTrack(string baseUri, string trackEntryKey)
-        => Frame($"{baseUri}FramePlayer?TrackEntryKey={trackEntryKey}");
+        => Frame($"{baseUri}FramePlayer?TrackEntryKey={trackEntryKey}", TrackHeight);
 
     public static string ForRelease(string baseUri, string releaseEntryKey)
-        => Frame($"{baseUri}FramePlayer?ReleaseEntryKey={releaseEntryKey}");
+    {
+        // Mint a fresh random token per call so two embeds on the same host page never share an id,
+        // even when they point at the same release.
+        var token = Guid.NewGuid().ToString("N")[..8];
+        var iframeId = $"deepdrft-embed-{token}";
+        var src = $"{baseUri}FramePlayer?ReleaseEntryKey={releaseEntryKey}&EmbedId={token}";
+        return Frame(src, ReleaseHeight, iframeId, ResizeScript(iframeId, token));
+    }
 
-    private static string Frame(string src)
+    private static string Frame(string src, int height, string iframeId = "deepdrft-embed", string trailingScript = "")
-        => $"""<iframe src="{src}" width="656" height="196" frameborder="0" style="border-radius:8px;" allow="autoplay"></iframe>""";
+        => $"""<iframe id="{iframeId}" src="{src}" width="656" height="{height}" frameborder="0" style="border-radius:8px;" allow="autoplay"></iframe>{trailingScript}""";
+
+    // Host-side listener: resize the matching iframe when the embedded player posts its panel height.
+    // The embedId field in the payload is matched against the snippet's own token so only this
+    // iframe is driven — foreign frames or other release embeds on the same page cannot interfere.
+    // The height is clamped to a sane floor so a bad payload can't collapse the player away.
+    // Messages without embedId (older snippets) are silently ignored.
+    private static string ResizeScript(string iframeId, string token) =>
+        "<script>(function(){var id=\"" + iframeId + "\",tok=\"" + token + "\";" +
+        "window.addEventListener(\"message\",function(e){var d=e.data;" +
+        "if(!d||d.type!==\"deepdrft-embed-resize\"||d.embedId!==tok)return;" +
+        "var f=document.getElementById(id);var h=Number(d.height);" +
+        "if(f&&h>=150)f.style.height=h+\"px\";});})();</script>";
 }

DeepDrftPublic/Interop/embed/embed-frame.ts

@@ -0,0 +1,55 @@
+// Embed (iframe) → host resize handshake (Phase 17 wave 17.3, OQ1 Option A).
+//
+// The Fixed-mode player renders an always-shown queue panel below the controls. A collapse/expand
+// toggle lets the embedder's viewer reclaim the panel's vertical space — but collapsing inside the
+// iframe only reclaims space if the *outer* iframe element also shrinks. The iframe cannot resize
+// itself, so it posts its desired pixel height to the host page; the embed snippet (minted by
+// EmbedSnippetBuilder.ForRelease) carries a tiny listener that sets iframe.style.height.
+//
+// Degrades safely: if the host page ignores or strips the snippet's listener (Option B's value), the
+// panel still renders and toggles inside the iframe — only the outer resize is lost. We post nothing
+// when not framed (window === parent), so the docked player is unaffected.
+//
+// Multi-embed isolation: EmbedSnippetBuilder.ForRelease mints a per-snippet random token and passes
+// it as ?EmbedId=<token> in the iframe src. We read it here from window.location.search and include
+// it in the postMessage payload as `embedId`. The host-side resize script matches on this token so
+// only the correct iframe is resized when multiple embeds share a host page. If EmbedId is absent
+// (older already-pasted snippets), embedId is omitted from the payload — those snippets' scripts
+// ignore messages without a matching embedId, so there is no cross-talk either way.
+
+const MESSAGE_TYPE = "deepdrft-embed-resize";
+
+/** Read the EmbedId query param from the iframe's own URL, if present. */
+function readEmbedId(): string | null {
+    try {
+        return new URLSearchParams(window.location.search).get("EmbedId");
+    } catch {
+        return null;
+    }
+}
+
+// Resolved once at module load — the URL does not change while the iframe is alive.
+const embedId: string | null = readEmbedId();
+
+/**
+ * Measure the live rendered height of the player element and post it to the host page so it can size
+ * the iframe to match. No-op when not embedded in a frame, or when the element is unmeasurable.
+ *
+ * targetOrigin is "*" deliberately: the embedder's origin is unknown (any blog can embed us) and the
+ * payload carries no secrets — just a height the host is free to ignore.
+ *
+ * The payload includes `embedId` when the iframe src carried an EmbedId query param. The host-side
+ * resize script matches on this field to isolate multiple embeds on the same page.
+ */
+export function postHeight(element: HTMLElement): void {
+    if (window.parent === window) return; // Not framed — nothing to resize.
+    if (!element) return;
+
+    // ceil + a hairline guard against sub-pixel rounding that would otherwise clip the bottom edge.
+    const height = Math.ceil(element.getBoundingClientRect().height) + 2;
+    if (!Number.isFinite(height) || height <= 0) return;
+
+    const payload: Record<string, unknown> = { type: MESSAGE_TYPE, height };
+    if (embedId !== null) payload.embedId = embedId;
+    window.parent.postMessage(payload, "*");
+}

DeepDrftPublic/wwwroot/styles/deepdrft-styles.css

@@ -905,3 +905,15 @@ body:has(.deepdrft-queue-overlay) {
     background: color-mix(in srgb, var(--deepdrft-green-accent) 22%, transparent);
     border-radius: 6px;
 }
+
+/* ── Fixed (embed) inline queue panel (Phase 17 §4, OQ6). ──
+   Rendered below the player controls inside the embed surface. A fixed sensible height with internal
+   scroll past N rows (NOT grow-to-cap): ~4.5 rows are visible, the rest scroll. A top hairline
+   separates it from the controls. The list rows reuse the shared .deepdrft-queue-* styles above. */
+.deepdrft-queue-embed-panel {
+    margin-top: 0.5rem;
+    padding-top: 0.5rem;
+    border-top: 1px solid var(--deepdrft-border-light);
+    max-height: 184px;
+    overflow-y: auto;
+}

DeepDrftTests/EmbedSnippetBuilderTests.cs

@@ -1,3 +1,4 @@
+using System.Text.RegularExpressions;
 using DeepDrftPublic.Client.Helpers;
 
 namespace DeepDrftTests;
@@ -5,8 +6,9 @@ namespace DeepDrftTests;
 /// <summary>
 /// Unit tests for the share-popover embed snippet (<see cref="EmbedSnippetBuilder"/>). The builder is
 /// the mode-aware half of SharePopover: track mode targets FramePlayer's TrackEntryKey param, release
-/// mode targets its ReleaseEntryKey param. The iframe chrome (dimensions, autoplay) must be identical
+/// mode targets its ReleaseEntryKey param. The two snippets share width/border/autoplay chrome but
-/// across both. Pure string composition, tested directly without rendering the component.
+/// diverge in height by design (Phase 17 §4.1, OQ6): the release embed is taller to show its queue
+/// panel; the track embed stays compact. Pure string composition, tested without rendering.
 /// </summary>
 [TestFixture]
 public class EmbedSnippetBuilderTests
@@ -27,12 +29,13 @@ public class EmbedSnippetBuilderTests
     {
         var snippet = EmbedSnippetBuilder.ForRelease(BaseUri, "rel-xyz");
 
-        Assert.That(snippet, Does.Contain(@"src=""https://deepdrft.example/FramePlayer?ReleaseEntryKey=rel-xyz"""));
+        // src contains ReleaseEntryKey; may also carry additional query params (e.g. EmbedId).
+        Assert.That(snippet, Does.Contain("ReleaseEntryKey=rel-xyz"));
         Assert.That(snippet, Does.Not.Contain("TrackEntryKey"));
     }
 
     [Test]
-    public void BothModes_ShareIdenticalIframeChrome()
+    public void BothModes_ShareIdenticalNonHeightChrome()
     {
         var track = EmbedSnippetBuilder.ForTrack(BaseUri, "k");
         var release = EmbedSnippetBuilder.ForRelease(BaseUri, "k");
@@ -43,12 +46,115 @@ public class EmbedSnippetBuilderTests
             {
                 Assert.That(snippet, Does.StartWith("<iframe "));
                 Assert.That(snippet, Does.Contain(@"width=""656"""));
-                Assert.That(snippet, Does.Contain(@"height=""196"""));
                 Assert.That(snippet, Does.Contain(@"frameborder=""0"""));
                 Assert.That(snippet, Does.Contain(@"style=""border-radius:8px;"""));
                 Assert.That(snippet, Does.Contain(@"allow=""autoplay"""));
-                Assert.That(snippet, Does.EndWith("></iframe>"));
+                Assert.That(snippet, Does.Contain("</iframe>"));
             }
         });
     }
+
+    // T14 (Phase 17 §9): the release embed is taller than the track embed (it shows a queue panel),
+    // and the track embed's height is unchanged from its historical value (UC6/AC6).
+    [Test]
+    public void ForTrack_KeepsHistoricalCompactHeight()
+    {
+        var track = EmbedSnippetBuilder.ForTrack(BaseUri, "k");
+
+        Assert.That(track, Does.Contain(@"height=""196"""));
+    }
+
+    [Test]
+    public void ForRelease_IsTallerThanForTrack_ToShowQueuePanel()
+    {
+        var trackHeight = HeightOf(EmbedSnippetBuilder.ForTrack(BaseUri, "k"));
+        var releaseHeight = HeightOf(EmbedSnippetBuilder.ForRelease(BaseUri, "k"));
+
+        Assert.That(releaseHeight, Is.GreaterThan(trackHeight));
+    }
+
+    // The release snippet carries the host-side resize listener (OQ1 Option A); the track snippet,
+    // having no panel to collapse, does not.
+    [Test]
+    public void ForRelease_IncludesResizeListenerScript()
+    {
+        var release = EmbedSnippetBuilder.ForRelease(BaseUri, "k");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(release, Does.Contain("<script>"));
+            Assert.That(release, Does.Contain("deepdrft-embed-resize"));
+        });
+    }
+
+    [Test]
+    public void ForTrack_HasNoResizeListenerScript()
+    {
+        var track = EmbedSnippetBuilder.ForTrack(BaseUri, "k");
+
+        Assert.That(track, Does.Not.Contain("<script>"));
+    }
+
+    // --- Multi-embed isolation (Phase 17 major remediation) ---
+
+    // Two ForRelease calls must produce snippets with different iframe ids so both can coexist on one
+    // host page without the host-side resize script resolving only the first via getElementById.
+    [Test]
+    public void ForRelease_TwoCalls_ProduceDifferentIframeIds()
+    {
+        var a = EmbedSnippetBuilder.ForRelease(BaseUri, "rel-xyz");
+        var b = EmbedSnippetBuilder.ForRelease(BaseUri, "rel-xyz"); // same release, different call
+
+        var idA = IframeId(a);
+        var idB = IframeId(b);
+
+        Assert.That(idA, Is.Not.EqualTo(idB),
+            "each ForRelease call must mint a distinct iframe id to prevent multi-embed cross-talk");
+    }
+
+    // The iframe id and the token embedded in the host-side resize script must be consistent within
+    // a single snippet — the script assigns the id string to a JS variable and calls getElementById
+    // with it, so the id literal must appear in the script's var initializer.
+    [Test]
+    public void ForRelease_IframeIdAndScriptToken_AreConsistentWithinOneSnippet()
+    {
+        var snippet = EmbedSnippetBuilder.ForRelease(BaseUri, "rel-abc");
+
+        var id = IframeId(snippet);
+        Assert.That(id, Does.StartWith("deepdrft-embed-"), "id must carry the expected prefix");
+
+        // The iframe element must declare the minted id.
+        Assert.That(snippet, Does.Contain($@"id=""{id}"""),
+            "iframe element must carry the minted id");
+
+        // The script stores the id in a JS var and calls getElementById(id) — confirm the id literal
+        // appears in the script's var initializer so the right iframe is targeted.
+        Assert.That(snippet, Does.Contain($@"var id=""{id}"""),
+            "resize script must initialise its id variable with the same minted id");
+    }
+
+    // The iframe src must carry EmbedId so the iframe content (embed-frame.ts) can read its own
+    // token and include it in postMessage payloads for the host-side script to match on.
+    [Test]
+    public void ForRelease_SrcCarriesEmbedIdParam()
+    {
+        var snippet = EmbedSnippetBuilder.ForRelease(BaseUri, "rel-def");
+
+        Assert.That(snippet, Does.Contain("EmbedId="),
+            "iframe src must include EmbedId query param so embed-frame.ts can read its own token");
+    }
+
+    private static int HeightOf(string snippet)
+    {
+        var match = Regex.Match(snippet, @"height=""(\d+)""");
+        Assert.That(match.Success, Is.True, "snippet must declare an iframe height");
+        return int.Parse(match.Groups[1].Value);
+    }
+
+    private static string IframeId(string snippet)
+    {
+        var match = Regex.Match(snippet, @"id=""([^""]+)""");
+        Assert.That(match.Success, Is.True, "snippet must declare an iframe id");
+        return match.Groups[1].Value;
+    }
 }