Initial commit: AI Dungeon clone (FastAPI backend + React frontend)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KFsGHju9szibJJa2YJcdbg
2026-07-06 16:08:19 +05:30
commit db9f904222
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+"""AI Dungeon-compatible script execution in an embedded QuickJS sandbox.
+
+Each hook run is fully isolated (fresh Context), capped at 16 MB memory and
+2 seconds CPU, with no filesystem/network/process access (QuickJS has none by
+default). Scripts follow the AI Dungeon contract: define a `modifier(text)`
+and call it as the last line; its return value `{ text, stop }` is the result.
+"""
+
+import json
+from dataclasses import dataclass, field
+
+import quickjs
+
+MEMORY_LIMIT = 16 * 1024 * 1024
+TIME_LIMIT_SECONDS = 2
+HISTORY_WINDOW = 100  # recent actions exposed as `history`
+
+# Globals per the official docs: text, state, history, storyCards, info,
+# log/console.log, story card functions, plus legacy worldInfo aliases.
+PRELUDE = """
+"use strict";
+var __logs = [];
+var state = __DATA__.state;
+var text = __DATA__.text;
+var history = __DATA__.history;
+var storyCards = __DATA__.storyCards;
+var info = __DATA__.info;
+
+function log(msg) {
+  __logs.push(typeof msg === "string" ? msg : JSON.stringify(msg));
+}
+var console = { log: log };
+
+function addStoryCard(keys, entry, type) {
+  for (var i = 0; i < storyCards.length; i++) {
+    if (storyCards[i].keys === keys) return false;
+  }
+  storyCards.push({ id: null, keys: keys || "", entry: entry || "", type: type || "" });
+  return storyCards.length - 1;
+}
+function updateStoryCard(index, keys, entry, type) {
+  var card = storyCards[index];
+  if (!card) throw new Error("Story card not found");
+  card.keys = keys;
+  card.entry = entry;
+  card.type = type;
+}
+function removeStoryCard(index) {
+  if (!storyCards[index]) throw new Error("Story card not found");
+  storyCards.splice(index, 1);
+}
+
+// Legacy aliases used by older AI Dungeon scripts.
+var worldInfo = storyCards;
+var worldEntries = storyCards;
+function addWorldEntry(keys, entry) { return addStoryCard(keys, entry, ""); }
+function updateWorldEntry(index, keys, entry) {
+  var card = storyCards[index];
+  if (!card) throw new Error("World entry not found");
+  card.keys = keys;
+  card.entry = entry;
+}
+function removeWorldEntry(index) { return removeStoryCard(index); }
+"""
+
+COLLECT = """
+JSON.stringify({
+  result: (typeof __result === "undefined" || __result === null) ? null : __result,
+  state: state,
+  storyCards: storyCards,
+  logs: __logs
+})
+"""
+
+
+@dataclass
+class HookResult:
+    text: str
+    stop: bool = False
+    state: dict = field(default_factory=dict)
+    story_cards: list = field(default_factory=list)
+    logs: list = field(default_factory=list)
+    error: str | None = None
+
+
+def run_hook(
+    library_js: str,
+    hook_js: str,
+    text: str,
+    state: dict,
+    history: list[dict],
+    story_cards: list[dict],
+    info: dict,
+) -> HookResult:
+    """Run one modifier hook. Never raises: failures come back as .error with
+    text/state/cards unchanged, so a bad script can't break a turn."""
+    unchanged = HookResult(text=text, state=state, story_cards=story_cards)
+    source = f"{library_js}\n;\n{hook_js}" if library_js.strip() else hook_js
+    if not source.strip():
+        return unchanged
+
+    data = {
+        "state": state,
+        "text": text,
+        "history": history[-HISTORY_WINDOW:],
+        "storyCards": story_cards,
+        "info": info,
+    }
+    try:
+        ctx = quickjs.Context()
+        ctx.set_memory_limit(MEMORY_LIMIT)
+        ctx.set_time_limit(TIME_LIMIT_SECONDS)
+        ctx.eval(f"var __DATA__ = {json.dumps(data)};")
+        ctx.eval(PRELUDE)
+        ctx.eval(f"var __SRC__ = {json.dumps(source)};")
+        # Indirect eval keeps the script in global scope, so `modifier(text)` as the
+        # script's final expression statement becomes the completion value.
+        ctx.eval("var __result = (0, eval)(__SRC__);")
+        collected = json.loads(ctx.eval(COLLECT))
+    except quickjs.JSException as exc:
+        unchanged.error = f"Script error: {exc}"
+        return unchanged
+    except Exception as exc:  # memory limit, invalid JSON state, engine faults
+        unchanged.error = f"Script execution failed: {exc}"
+        return unchanged
+
+    result = collected.get("result")
+    new_text, stop = text, False
+    if isinstance(result, dict):
+        if isinstance(result.get("text"), str):
+            new_text = result["text"]
+        stop = bool(result.get("stop"))
+    elif isinstance(result, str):
+        new_text = result
+
+    new_state = collected.get("state")
+    return HookResult(
+        text=new_text,
+        stop=stop,
+        state=new_state if isinstance(new_state, dict) else {},
+        story_cards=collected.get("storyCards") or [],
+        logs=collected.get("logs") or [],
+    )