import json
import os
from datetime import datetime

MODEL_DIR = "models"
META_FILE = os.path.join(MODEL_DIR, "metadata.json")

def load_meta():
    if not os.path.exists(META_FILE):
        return {"current": {}, "history": []}
    with open(META_FILE) as f:
        return json.load(f)

def save_meta(meta):
    os.makedirs(MODEL_DIR, exist_ok=True)
    with open(META_FILE, "w") as f:
        json.dump(meta, f, indent=2)

def register(model_type, file_name, rows):
    meta = load_meta()
    entry = {
        "type": model_type,
        "file": file_name,
        "trained_at": datetime.utcnow().isoformat() + "Z",
        "rows": rows
    }
    meta["history"].append(entry)
    meta["current"][model_type] = file_name
    save_meta(meta)
    return entry