server/app.py

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
import json, os, random, subprocess, tempfile, sys, time
from typing import Optional, List

from server.executor import run_code_with_tests
from server.grader import calculate_codearena_reward

app = FastAPI(title="CodeArena RL Environment")

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

# -- State ------------------------------------------------
current_task = {}
step_count = 0
previous_attempts = []
episode_rewards = []
TASKS_DIR = os.path.join(os.path.dirname(__file__), "..", "tasks")

# -- Models -----------------------------------------------
class ResetRequest(BaseModel):
    task_id: str = "easy"
    buggy_code: Optional[str] = None

class StepRequest(BaseModel):
    proposed_fix: str


class AgentPerformanceTracker:
    def __init__(self):
        self.episode_rewards = []
        self.current_difficulty = "easy"
        self.steps_at_difficulty = 0

    def record_episode(self, avg_reward: float):
        self.episode_rewards.append(round(avg_reward, 4))
        if len(self.episode_rewards) > 10:
            self.episode_rewards.pop(0)
        self.steps_at_difficulty += 1
        self._maybe_escalate()

    def _maybe_escalate(self):
        if self.steps_at_difficulty < 3:
            return
        if not self.episode_rewards:
            return
        avg = sum(self.episode_rewards) / len(self.episode_rewards)
        old = self.current_difficulty
        if avg > 0.80 and self.current_difficulty == "easy":
            self.current_difficulty = "medium"
            self.steps_at_difficulty = 0
        elif avg > 0.75 and self.current_difficulty == "medium":
            self.current_difficulty = "hard"
            self.steps_at_difficulty = 0
        elif avg < 0.35 and self.current_difficulty == "hard":
            self.current_difficulty = "medium"
            self.steps_at_difficulty = 0
        elif avg < 0.35 and self.current_difficulty == "medium":
            self.current_difficulty = "easy"
            self.steps_at_difficulty = 0
        if self.current_difficulty != old:
            print(
                f"[CURRICULUM] {old} -> {self.current_difficulty} "
                f"after avg={avg:.3f}"
            )

    def get_difficulty(self) -> str:
        return self.current_difficulty

    def get_stats(self) -> dict:
        avg = (
            sum(self.episode_rewards) / len(self.episode_rewards)
            if self.episode_rewards else 0.0
        )
        return {
            "current_difficulty": self.current_difficulty,
            "recent_avg_reward": round(avg, 3),
            "episodes_tracked": len(self.episode_rewards),
            "steps_at_current_difficulty": self.steps_at_difficulty
        }


tracker = AgentPerformanceTracker()

# -- Helpers ----------------------------------------------
def load_random_task(difficulty: str):
    folder = os.path.join(TASKS_DIR, difficulty)
    files = [f for f in os.listdir(folder) if f.endswith(".json")]
    if not files:
        raise ValueError(f"No tasks found in {folder}")
    path = os.path.join(folder, random.choice(files))
    with open(path) as f:
        return json.load(f)

def run_tests(code: str, tests: list):
    passed = 0
    total = len(tests)
    compile_ok = True
    error_log = ""
    start_time = time.time()

    with tempfile.NamedTemporaryFile(mode="w", suffix=".py",
                                     delete=False, dir=tempfile.gettempdir()) as tmp:
        tmp.write(code)
        tmp_path = tmp.name

    try:
        for test in tests:
            inp = test["input"]
            expected = test["expected"]

            # Build a test runner script
            test_script = f"""
import sys
sys.path.insert(0, '')
exec(open(r'{tmp_path}').read())

inp = {repr(inp)}
if isinstance(inp, list):
    result = list(locals().values())[-1](*inp) if callable(list(locals().values())[-1]) else None
    # find the function
    import types
    funcs = {{k:v for k,v in locals().items() if isinstance(v, types.FunctionType)}}
    if funcs:
        fn = list(funcs.values())[0]
        result = fn(*inp)
    else:
        result = None
else:
    result = None

expected = {repr(expected)}
print('PASS' if result == expected else f'FAIL got {{result}} expected {{expected}}')
"""
            runner = tempfile.NamedTemporaryFile(mode="w", suffix=".py",
                                                  delete=False, dir=tempfile.gettempdir())
            runner.write(test_script)
            runner.close()

            try:
                proc = subprocess.run(
                    [sys.executable, runner.name],
                    capture_output=True, text=True, timeout=5
                )
                if "PASS" in proc.stdout:
                    passed += 1
                elif proc.returncode != 0:
                    compile_ok = False
                    error_log = proc.stderr[:300]
            except subprocess.TimeoutExpired:
                error_log = "Timeout"
            finally:
                os.unlink(runner.name)

    finally:
        os.unlink(tmp_path)

    return compile_ok, passed, total, error_log, time.time() - start_time

def evaluate_fix(code: str, task: dict):
    if "test_code" in task:
        result = run_code_with_tests(
            code=code,
            test_code=task.get("test_code", ""),
            timeout=max(float(task.get("optimal_time_seconds", 0.05)) * 10, 2.0),
        )
        return (
            result.compile_success,
            result.test_passed,
            max(result.test_total, 1),
            result.runtime_errors,
            result.execution_time_seconds,
        )

    return run_tests(code, task.get("tests", []))

# -- Endpoints --------------------------------------------
@app.get("/")
def health():
    return {"status": "ok", "environment": "CodeArena"}

@app.post("/reset")
def reset(req: ResetRequest):
    global current_task, step_count, previous_attempts, episode_rewards

    step_count = 0
    previous_attempts = []
    episode_rewards = []

    if req.buggy_code:
        # Custom mode -- user pasted their own broken code
        current_task = {
            "task_id": "custom",
            "buggy_code": req.buggy_code,
            "description": "User-provided code -- fix the bug",
            "tests": [
                {"input": [1, 2], "expected": None},
                {"input": [0, 0], "expected": None},
                {"input": [5, 5], "expected": None}
            ]
        }
    elif req.task_id in ("easy", "medium", "hard", "type_errors", "security_bugs"):
        current_task = load_random_task(req.task_id)
    elif req.task_id == "auto":
        current_task = load_random_task(tracker.get_difficulty())
    else:
        current_task = load_random_task("easy")

    tests_count = len(current_task.get("tests", []))
    if "test_code" in current_task:
        tests_count = 1

    return {
        "task_id": current_task["task_id"],
        "curriculum_info": tracker.get_stats(),
        "observation": {
            "buggy_code": current_task["buggy_code"],
            "error_log": "",
            "test_results": f"0/{tests_count} tests passing",
            "previous_attempts": []
        }
    }

@app.post("/step")
def step(req: StepRequest):
    global step_count, previous_attempts, episode_rewards

    step_count += 1
    is_repeated_fix = req.proposed_fix in previous_attempts

    tests = current_task.get("tests", [])
    
    # For custom tasks with no expected values, just check compile + run
    if current_task["task_id"] == "custom":
        compile_ok, passed, total, error_log, execution_time_seconds = True, 0, 1, "", 0.0
        try:
            with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
                f.write(req.proposed_fix)
                tmp_path = f.name
            start_time = time.time()
            proc = subprocess.run([sys.executable, tmp_path],
                                   capture_output=True, text=True, timeout=5)
            execution_time_seconds = time.time() - start_time
            compile_ok = proc.returncode == 0
            passed = 1 if compile_ok else 0
            error_log = proc.stderr[:300] if not compile_ok else ""
            os.unlink(tmp_path)
        except Exception as e:
            compile_ok = False
            error_log = str(e)
    else:
        compile_ok, passed, total, error_log, execution_time_seconds = evaluate_fix(
            req.proposed_fix,
            current_task,
        )
        total = max(total, 1)

    reward, reward_components = calculate_codearena_reward(
        compile_ok=compile_ok,
        passed=passed,
        total=total,
        execution_time_seconds=execution_time_seconds,
        optimal_time_seconds=float(current_task.get("optimal_time_seconds", 0.05)),
        buggy_code=current_task.get("buggy_code", ""),
        proposed_fix=req.proposed_fix,
        task_category=current_task.get("difficulty", current_task.get("task_id", "easy").split("-")[0]),
        step_count=step_count,
        is_repeated_fix=is_repeated_fix,
    )
    episode_rewards.append(reward)
    previous_attempts.append(req.proposed_fix)
    done = (reward > 0.95) or (step_count >= 5)
    if done and episode_rewards:
        tracker.record_episode(sum(episode_rewards) / len(episode_rewards))

    tests_total = len(tests) if tests else total

    return {
        "reward": reward,
        "done": done,
        "reward_components": reward_components,
        "curriculum_info": tracker.get_stats(),
        "observation": {
            "buggy_code": current_task["buggy_code"],
            "error_log": error_log,
            "test_results": f"{passed}/{tests_total} tests passing",
            "previous_attempts": previous_attempts[-3:]
        }
    }

@app.get("/state")
def state():
    return {
        "task_id": current_task.get("task_id", "none"),
        "step_count": step_count,
        "observation": {
            "buggy_code": current_task.get("buggy_code", ""),
            "error_log": "",
            "test_results": "",
            "previous_attempts": previous_attempts
        }
    }

@app.get("/curriculum")
async def get_curriculum():
    return tracker.get_stats()