backend/app.py

import sys
import os
from pathlib import Path
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel

# Add parent directory to path so we can import the RL modules
ROOT_DIR = Path(__file__).parent.parent
sys.path.append(str(ROOT_DIR))

import config as cfg
from environment import TrafficEnvironment

# We will try to load DQN since it performed best
try:
    from agent import DQNAgent
    DQN_AVAILABLE = True
except ImportError:
    DQN_AVAILABLE = False

app = FastAPI(title="Traffic RL Simulation API")

# Allow CORS for frontend
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Serve static files from the frontend/dist directory
# This must be after the API routes for correct routing, but we can define it here 
# if we mount it at the end. Actually, better to define it after all routes.

# Global instances
env = TrafficEnvironment(cfg)
agent = None

# Try to load DQN agent
if DQN_AVAILABLE:
    agent = DQNAgent(cfg.STATE_SIZE, cfg.ACTION_SIZE, cfg.DQN_CONFIG)
    model_path = ROOT_DIR / "models" / "dqn_best.pth"
    if model_path.exists():
        agent.load(str(model_path))
        print("Backend: Loaded DQN Model successfully.")
    else:
        print("Backend: DQN Model file not found, using untrained agent.")
else:
    # Fallback to QLearning
    from agent import QLearningAgent
    agent = QLearningAgent(cfg.STATE_SIZE, cfg.ACTION_SIZE, cfg.Q_LEARNING_CONFIG)
    model_path = ROOT_DIR / "models" / "q_learning_best.pth"
    if model_path.exists():
        agent.load(str(model_path))
        print("Backend: Loaded Q-Learning Model successfully.")
    else:
        print("Backend: Q-Learning Model file not found.")

class StateResponse(BaseModel):
    queues: list[float]
    phase: int
    reward: float
    vehicles_passed: int
    step: int
    total_reward: float
    is_done: bool

current_state, _ = env.reset()
total_reward = 0.0

@app.post("/api/reset", response_model=StateResponse)
def reset_env():
    global current_state, total_reward
    current_state, _ = env.reset()
    total_reward = 0.0
    return {
        "queues": env.queue_lengths.tolist(),
        "phase": env.current_phase,
        "reward": 0.0,
        "vehicles_passed": env.vehicles_passed,
        "step": env.current_step,
        "total_reward": total_reward,
        "is_done": False
    }

@app.post("/api/step", response_model=StateResponse)
def step_env():
    global current_state, total_reward
    
    # Get action from the loaded agent (evaluation mode)
    action = agent.select_action(current_state, training=False)
    
    # Step the environment
    next_state, reward, terminated, truncated, info = env.step(action)
    done = terminated or truncated
    
    current_state = next_state
    total_reward += reward
    
    response = {
        "queues": env.queue_lengths.tolist(),
        "phase": env.current_phase,
        "reward": reward,
        "vehicles_passed": env.vehicles_passed,
        "step": env.current_step,
        "total_reward": total_reward,
        "is_done": done
    }
    
    if done:
        # Reset for next call if done
        current_state, _ = env.reset()
        total_reward = 0.0
        
    return response

# Mount the static files at the root
# Note: Ensure this is the last route defined
frontend_path = ROOT_DIR / "frontend" / "dist"
if frontend_path.exists():
    app.mount("/", StaticFiles(directory=str(frontend_path), html=True), name="static")

if __name__ == "__main__":
    import uvicorn
    # Use port 7860 for Hugging Face Spaces compatibility
    port = int(os.environ.get("PORT", 7860))
    uvicorn.run("app:app", host="0.0.0.0", port=port, reload=False)
    # Restart to load fixed working 9D model