From cac17756c6e473c5e03f8c11fc6d500393188fd0 Mon Sep 17 00:00:00 2001
From: Michael Schoonmaker <hello@schoonology.com>
Date: Sun, 17 Sep 2023 22:43:18 -0400
Subject: [PATCH 1/2] API: Add server-only route to fetch replay files.

Uses a single environment variable and a GET /replays/{id} with two
fields: `info` metadata and `frames` replay.
---
 src/routes/replays/[id]/+server.ts | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 src/routes/replays/[id]/+server.ts

diff --git a/src/routes/replays/[id]/+server.ts b/src/routes/replays/[id]/+server.ts
new file mode 100644
index 0000000..61aca0b
--- /dev/null
+++ b/src/routes/replays/[id]/+server.ts
@@ -0,0 +1,30 @@
+import { readFile } from "node:fs/promises";
+import { join } from "node:path";
+import type { RequestHandler } from "./$types";
+
+const ROOT_DIR = process.env.REPLAYS_DIR ?? process.cwd();
+
+export const GET: RequestHandler = async ({ params }) => {
+  // Load the local NDJSON 'replay' file.
+  // TODO(schoon): Once we decide on a real extension, use that here.
+  // Check that the file exists, and return a 404 otherwise.
+  const replayFile = await readFile(join(ROOT_DIR, `${params.id}.ndjson`), "utf-8");
+  const replayLines = replayFile.split("\n").filter((line) => line.trim().length);
+
+  // TODO(schoon): This would be much better with a clear delimiter,
+  // not just a gentlemen's agreement that the first line is special.
+  const info = JSON.parse(replayLines[0]);
+  const frames = replayLines.slice(1).map((line) => JSON.parse(line));
+
+  return new Response(
+    JSON.stringify({
+      frames,
+      info
+    }),
+    {
+      headers: {
+        "Content-Type": "application/json"
+      }
+    }
+  );
+};

From 262f108242097ad5d000170463c177e8d53548a7 Mon Sep 17 00:00:00 2001
From: Michael Schoonmaker <hello@schoonology.com>
Date: Sun, 17 Sep 2023 22:44:16 -0400
Subject: [PATCH 2/2] Board: Replay from files with 'local' engine URL.

---
 src/lib/playback/engine.ts | 60 +++++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 20 deletions(-)

diff --git a/src/lib/playback/engine.ts b/src/lib/playback/engine.ts
index aa89617..b8de662 100644
--- a/src/lib/playback/engine.ts
+++ b/src/lib/playback/engine.ts
@@ -26,6 +26,45 @@ export function fetchGame(
 ) {
   console.debug(`[playback] loading game ${gameID}`);
 
+  /**
+   * Helper function to add a single frame, whether via live Websocket
+   * or replay JSON.
+   */
+  // TODO(schoon): Real types for these arguments.
+  function ingestFrame(gameInfo: any, engineEvent: any) {
+    if (engineEvent.Type == "frame" && !loadedFrames.has(engineEvent.Data.Turn)) {
+      loadedFrames.add(engineEvent.Data.Turn);
+
+      const frame = engineEventToFrame(gameInfo, engineEvent.Data);
+      frames.push(frame);
+      frames.sort((a: Frame, b: Frame) => a.turn - b.turn);
+
+      // Fire frame callback
+      if (engineEvent.Data.Turn == 0) {
+        console.debug("[playback] received first frame");
+      }
+      onFrameLoad(frame);
+    } else if (engineEvent.Type == "game_end") {
+      console.debug("[playback] received final frame");
+      if (ws) ws.close();
+
+      // Flag last frame as the last one and fire callback
+      frames[frames.length - 1].isFinalFrame = true;
+      onFinalFrame(frames[frames.length - 1]);
+    }
+  }
+
+  // Special "url" for local files.
+  if (engineURL === "local") {
+    console.log("Using local playback engine...");
+    fetchFunc(`/replays/${gameID}`)
+      .then((response) => response.json())
+      .then(({ info, frames }) => {
+        frames.forEach((frame: unknown) => ingestFrame(info, frame));
+      });
+    return;
+  }
+
   // Reset
   if (ws) ws.close();
   loadedFrames = new Set();
@@ -51,26 +90,7 @@ export function fetchGame(
       ws.onmessage = (message) => {
         const engineEvent = JSON.parse(message.data);
 
-        if (engineEvent.Type == "frame" && !loadedFrames.has(engineEvent.Data.Turn)) {
-          loadedFrames.add(engineEvent.Data.Turn);
-
-          const frame = engineEventToFrame(gameInfo, engineEvent.Data);
-          frames.push(frame);
-          frames.sort((a: Frame, b: Frame) => a.turn - b.turn);
-
-          // Fire frame callback
-          if (engineEvent.Data.Turn == 0) {
-            console.debug("[playback] received first frame");
-          }
-          onFrameLoad(frame);
-        } else if (engineEvent.Type == "game_end") {
-          console.debug("[playback] received final frame");
-          if (ws) ws.close();
-
-          // Flag last frame as the last one and fire callback
-          frames[frames.length - 1].isFinalFrame = true;
-          onFinalFrame(frames[frames.length - 1]);
-        }
+        ingestFrame(gameInfo, engineEvent);
       };
 
       ws.onclose = () => {