feat: add Export GIF link to finished game pages (BS-c23cac20c43944fe)

Links to exporter.battlesnake.com with engine_url={BASE_URL}/api so the
exporter pulls frames from the engine-compatible endpoint shipped in
PR #127. Rendered only for finished games, as the last action in the
theater row, for anonymous and authenticated viewers alike.

Author: byte-the-bot

e2e/tests/game-public-view.spec.ts

@@ -3,12 +3,15 @@ import { query } from '../fixtures/db';
 
 test.describe('Public Game Viewing', () => {
   // Helper: create a game via the API using an authenticated page, return game_id
-  async function createGameViaDb(): Promise<string> {
+  async function createGameViaDb(
+    status: 'waiting' | 'running' | 'finished' | 'failed' = 'finished'
+  ): Promise<string> {
     // Insert a minimal game directly in the DB for testing view access
     const result = await query<{ game_id: string }>(
       `INSERT INTO games (board_size, game_type, status, created_at, updated_at)
-       VALUES ('small', 'standard', 'finished', NOW(), NOW())
-       RETURNING game_id::text AS game_id`
+       VALUES ('small', 'standard', $1, NOW(), NOW())
+       RETURNING game_id::text AS game_id`,
+      [status]
     );
     return result[0].game_id;
   }
@@ -140,6 +143,33 @@ test.describe('Public Game Viewing', () => {
     await expect(meta.getByText('Survived to the 5,000-turn limit')).toBeVisible();
     await expect(meta.getByText('Cause of Death', { exact: true })).not.toBeVisible();
   });
+
+  test('finished game page shows an Export GIF link pointing at the exporter', async ({ page }) => {
+    const gameId = await createGameViaDb();
+
+    await page.goto(`/games/${gameId}`);
+
+    // The e2e server env does not set BASE_URL, so the app falls back to its
+    // default origin — the exporter href embeds that default.
+    const link = page.getByRole('link', { name: 'Export GIF' });
+    await expect(link).toHaveCount(1);
+    await expect(link).toHaveAttribute(
+      'href',
+      `https://exporter.battlesnake.com/games/${gameId}/gif?engine_url=http://localhost:3000/api`
+    );
+    await expect(link).toHaveAttribute('target', '_blank');
+    await expect(link).toHaveAttribute('rel', 'noopener');
+  });
+
+  test('unfinished game pages show no Export GIF link', async ({ page }) => {
+    for (const status of ['waiting', 'running', 'failed'] as const) {
+      const gameId = await createGameViaDb(status);
+
+      await page.goto(`/games/${gameId}`);
+
+      await expect(page.getByRole('link', { name: 'Export GIF' })).toHaveCount(0);
+    }
+  });
 });
 
 test.describe('Homepage Leaderboard Link for Unauthenticated Users', () => {

server/src/routes/game/view.rs

@@ -197,6 +197,13 @@ pub async fn view_game(
                             a href="/leaderboards" class="btn" { "View Leaderboards" }
                             a href="/" class="btn" { "Back to Home" }
                         }
+                        @if finished {
+                            a
+                                href=(export_gif_url(&state.config.base_url, game_id))
+                                class="btn"
+                                target="_blank"
+                                rel="noopener" { "Export GIF" }
+                        }
                     }
                 }
 
@@ -383,6 +390,14 @@ fn append_show_spoilers(url: String, show_spoilers: bool) -> String {
     format!("{url}{sep}showSpoilers=true")
 }
 
+/// Build the exporter.battlesnake.com GIF URL for a game. The exporter
+/// fetches frame history from `{base_url}/api/games/{game_id}/frames`, so the
+/// `/api` suffix is load-bearing: dropping it silently sends the exporter to
+/// its default engine, which contains no Arena games.
+fn export_gif_url(base_url: &str, game_id: Uuid) -> String {
+    format!("https://exporter.battlesnake.com/games/{game_id}/gif?engine_url={base_url}/api")
+}
+
 fn ordinal_place(n: i32) -> String {
     let suffix = match (n % 10, n % 100) {
         (_, 11..=13) => "th",
@@ -528,6 +543,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn export_gif_url_is_full_exporter_url_with_api_engine() {
+        let url = export_gif_url("https://arena.example.com", game_id());
+        assert_eq!(
+            url,
+            "https://exporter.battlesnake.com/games/6f9422eb-cd95-4a17-b0a2-a3fefe4f47b1/gif?engine_url=https://arena.example.com/api"
+        );
+    }
+
     fn params(value: Option<&str>) -> ViewGameParams {
         ViewGameParams {
             show_spoilers: value.map(str::to_string),