import os
from flask import request as flask_request, Response

# Absolute path avoids relative-path confusion in Docker
os.environ.setdefault("MLFLOW_TRACKING_URI", "./mlruns")
os.environ.setdefault("MLFLOW_DEFAULT_ARTIFACT_ROOT", "/app/mlartifacts")

# Pre-initialize the MLflow store on the main thread before Flask starts.
# Without this, threaded Flask lets multiple requests race against the SQLite
# migration, causing "NoneType has no len()" errors on _search_experiments.
import mlflow
mlflow.set_tracking_uri(os.environ["MLFLOW_TRACKING_URI"])
try:
    mlflow.search_experiments()
except Exception:
    pass

from mlflow.server import app  # Flask app do MLflow

# ── CORS ──────────────────────────────────────────────────────────────────────

CORS_HEADERS = {
    "Access-Control-Allow-Origin":  "*",
    "Access-Control-Allow-Headers": "Content-Type, Authorization, X-Requested-With",
    "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, PATCH, OPTIONS",
}

@app.before_request
def handle_preflight():
    """Responde imediatamente às requisições OPTIONS (preflight)."""
    if flask_request.method == "OPTIONS":
        res = Response(status=200)
        for k, v in CORS_HEADERS.items():
            res.headers[k] = v
        return res

@app.after_request
def add_cors_headers(response):
    """Adiciona CORS headers em todas as respostas."""
    for k, v in CORS_HEADERS.items():
        response.headers[k] = v
    return response

# ─────────────────────────────────────────────────────────────────────────────

if __name__ == "__main__":
    # threaded=False prevents concurrent SQLite access races
    app.run(host="0.0.0.0", port=7860, debug=False, threaded=False)