server.py

"""
server.py — FastAPI HTTP wrapper for SQLCorrectionEnv
Exposes the OpenEnv-required endpoints: /reset, /step, /state
"""

import os
from contextlib import asynccontextmanager
from typing import Optional

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel

from sql_env import SQLCorrectionEnv, SQLAction


# ── Request / Response schemas ────────────────────────────────

class ResetRequest(BaseModel):
    difficulty: Optional[str] = "easy"
    task_index: Optional[int] = None


class StepRequest(BaseModel):
    corrected_query: str


# ── App setup ─────────────────────────────────────────────────

env: Optional[SQLCorrectionEnv] = None


@asynccontextmanager
async def lifespan(app: FastAPI):
    global env
    env = SQLCorrectionEnv(difficulty="easy")
    yield
    if env:
        await env.close()


app = FastAPI(
    title="SQL Correction RL Environment",
    description="OpenEnv-compliant environment for SQL query correction tasks.",
    version="1.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)


# ── Endpoints ─────────────────────────────────────────────────

@app.post("/reset")
async def reset(request: ResetRequest = ResetRequest()):
    """Reset the environment. Returns initial observation."""
    global env
    difficulty = request.difficulty or "easy"
    if difficulty not in ("easy", "medium", "hard"):
        raise HTTPException(status_code=400, detail="difficulty must be easy, medium, or hard")

    env = SQLCorrectionEnv(
        difficulty=difficulty,
        task_index=request.task_index,
    )
    obs = await env.reset()
    return obs.model_dump()


@app.post("/step")
async def step(request: StepRequest):
    """Take one step. Returns observation, reward, done, info."""
    global env
    if env is None:
        raise HTTPException(status_code=400, detail="Call /reset first.")
    try:
        action = SQLAction(corrected_query=request.corrected_query)
        result = await env.step(action)
        return result.model_dump()
    except RuntimeError as e:
        raise HTTPException(status_code=400, detail=str(e))


@app.post("/state")
async def state():
    """Return current environment state."""
    global env
    if env is None:
        return {"status": "not_initialized"}
    return await env.state()


@app.get("/health")
async def health():
    return {"status": "ok", "service": "sql-correction-env"}


@app.get("/")
async def root():
    return {
        "name": "SQL Correction RL Environment",
        "version": "1.0.0",
        "endpoints": ["/reset", "/step", "/state", "/health"],
        "tasks": ["easy", "medium", "hard"],
    }