fix: add server/app.py for openenv validate

server/app.py

@@ -0,0 +1,103 @@
+"""
+FastAPI server exposing OpenEnv interface over HTTP.
+Endpoints: POST /reset, POST /step, GET /state, GET /health, GET /tasks
+"""
+
+import sys
+import os
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from fastapi import FastAPI, Request, HTTPException
+from fastapi.middleware.cors import CORSMiddleware
+from pydantic import BaseModel
+from typing import Optional
+import uvicorn
+
+from env.cache import CDNCacheEnv, TASK_CONFIGS
+from env.models import Action, StepResult
+
+app = FastAPI(title="CDN Cache Optimizer - OpenEnv", version="1.0.0")
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+_env: Optional[CDNCacheEnv] = None
+
+
+@app.get("/health")
+def health():
+    return {"status": "ok", "env": "cdn-cache-optimizer"}
+
+@app.post("/health")
+def health_post():
+    return {"status": "ok", "env": "cdn-cache-optimizer"}
+
+@app.get("/tasks")
+def list_tasks():
+    return {
+        task_id: {
+            "name": cfg.name,
+            "difficulty": cfg.difficulty,
+            "description": cfg.description,
+            "cache_capacity_mb": cfg.cache_capacity_mb,
+            "episode_length": cfg.episode_length,
+        }
+        for task_id, cfg in TASK_CONFIGS.items()
+    }
+
+@app.post("/reset")
+async def reset(request: Request):
+    global _env
+    task_id = "task_easy"
+    seed = 42
+    try:
+        body = await request.json()
+        task_id = body.get("task_id", "task_easy")
+        seed = body.get("seed", 42)
+    except Exception:
+        pass
+    if task_id not in TASK_CONFIGS:
+        raise HTTPException(status_code=400, detail=f"Unknown task_id '{task_id}'.")
+    _env = CDNCacheEnv(task_id=task_id, seed=seed)
+    obs = _env.reset()
+    return {"observation": obs.dict(), "task": _env.config.dict()}
+
+@app.post("/step")
+async def step(request: Request):
+    global _env
+    if _env is None:
+        raise HTTPException(status_code=400, detail="Call /reset first.")
+    if _env._done:
+        raise HTTPException(status_code=400, detail="Episode done. Call /reset.")
+    evict_file_id = None
+    try:
+        body = await request.json()
+        evict_file_id = body.get("evict_file_id", None)
+    except Exception:
+        pass
+    action = Action(evict_file_id=evict_file_id)
+    result: StepResult = _env.step(action)
+    return result.dict()
+
+@app.get("/state")
+def state():
+    global _env
+    if _env is None:
+        raise HTTPException(status_code=400, detail="Call /reset first.")
+    return _env.state()
+
+@app.get("/")
+def root():
+    return {
+        "name": "CDN Cache Optimizer",
+        "spec": "OpenEnv v1",
+        "endpoints": ["/reset", "/step", "/state", "/health", "/tasks"],
+        "tasks": list(TASK_CONFIGS.keys()),
+    }
+
+if __name__ == "__main__":
+    uvicorn.run("api.main:app", host="0.0.0.0", port=7860, reload=False)