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  {
   "cell_type": "markdown",
   "id": "2eb3034b",
   "metadata": {},
   "source": [
    "# Module 3 — Lab 3: A Random Forest Security Pipeline\n",
    "\n",
    "**Topics:** Scikit-learn Pipeline, imputation, Random Forest, fit, predict\n",
    "\n",
    "> **Instructions:** Run the cells in order. Complete every `TODO`, then run the **Self-check** cell. Do not open the Solution notebook before attempting the tasks yourself.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7bf6c5fd",
   "metadata": {},
   "source": [
    "## Learning objectives\n",
    "\n",
    "After completing this lab, you will be able to:\n",
    "\n",
    "- create one reusable preprocessing-and-model pipeline;\n",
    "- train a Random Forest binary classifier;\n",
    "- generate predictions for unseen data;\n",
    "- explain why tree models do not require feature standardization.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "c98b721f",
   "metadata": {},
   "outputs": [],
   "source": [
    "from pathlib import Path\n",
    "import numpy as np\n",
    "import pandas as pd\n",
    "\n",
    "DATA_PATH = Path(\"data/cicids2017_binary_sample.csv\")\n",
    "RANDOM_STATE = 42\n",
    "\n",
    "from sklearn.model_selection import train_test_split\n",
    "from sklearn.pipeline import Pipeline\n",
    "from sklearn.impute import SimpleImputer\n",
    "from sklearn.ensemble import RandomForestClassifier\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3888c4bb",
   "metadata": {},
   "source": [
    "## 1. Prepare the binary classification data\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "b4c28e44",
   "metadata": {},
   "outputs": [],
   "source": [
    "df = pd.read_csv(DATA_PATH)\n",
    "df.columns = df.columns.str.strip()\n",
    "df = df.drop_duplicates().replace([np.inf, -np.inf], np.nan)\n",
    "\n",
    "# TODO 1: create numeric X and binary y\n",
    "X = None\n",
    "y = None\n",
    "\n",
    "# TODO 2: create a stratified 80/20 split\n",
    "X_train, X_test, y_train, y_test = None, None, None, None\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6aad53d0",
   "metadata": {},
   "source": [
    "## 2. Build one pipeline\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e6c00af0",
   "metadata": {},
   "outputs": [],
   "source": [
    "# TODO 3: create a Pipeline with:\n",
    "# - SimpleImputer(strategy=\"median\")\n",
    "# - RandomForestClassifier with n_estimators=100, max_depth=12,\n",
    "#   random_state=42, and n_jobs=-1\n",
    "pipeline = None\n",
    "\n",
    "print(pipeline)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c2111199",
   "metadata": {},
   "source": [
    "## Why there is no `StandardScaler`\n",
    "\n",
    "Random Forest makes decisions by comparing feature values with thresholds. Scaling a column does not change the ordering of its values, so standardization is not required for this model family. The imputer remains inside the pipeline because the model needs finite values.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "16aa1030",
   "metadata": {},
   "source": [
    "## 3. Train and predict\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "59b48b8d",
   "metadata": {},
   "outputs": [],
   "source": [
    "# TODO 4: fit the complete pipeline on X_train and y_train\n",
    "\n",
    "# TODO 5: predict labels for X_test and store them in y_pred\n",
    "y_pred = None\n",
    "\n",
    "print(\"Predictions:\", None)\n",
    "print(\"Number of test samples:\", None)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c0c83354",
   "metadata": {},
   "source": [
    "## 4. Predict one flow\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e1910ac4",
   "metadata": {},
   "outputs": [],
   "source": [
    "one_flow = X_test.iloc[[0]]\n",
    "\n",
    "# TODO 6: predict one_flow and convert the result to int\n",
    "one_prediction = None\n",
    "\n",
    "print(\"Prediction:\", one_prediction)\n",
    "print(\"Meaning:\", \"ATTACK\" if one_prediction == 1 else \"BENIGN\")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a7cdf396",
   "metadata": {},
   "source": [
    "## Self-check\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "926ba101",
   "metadata": {},
   "outputs": [],
   "source": [
    "assert list(pipeline.named_steps) == [\"imputer\", \"model\"]\n",
    "assert pipeline.named_steps[\"model\"].n_estimators == 100\n",
    "assert len(y_pred) == len(y_test)\n",
    "assert set(np.unique(y_pred)).issubset({0, 1})\n",
    "assert one_prediction in {0, 1}\n",
    "print(\"✓ Lab 3 completed\")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7beedd77",
   "metadata": {},
   "source": [
    "## Reflection questions\n",
    "\n",
    "1. What problem does the imputer solve inside the pipeline?\n",
    "2. Why is a pipeline safer than manually transforming train and test data in separate cells?\n",
    "3. What does `random_state=42` contribute to the experiment?\n"
   ]
  }
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