{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Delete Strategies\n",
    "\n",
    "This notebook demonstrates the three deletion strategies supported by `deleteNode()`:\n",
    "\n",
    "- **`\"cascade\"`** (default): ON DELETE CASCADE — delete the node and all connected edges.\n",
    "- **`\"restrict\"`**: ON DELETE RESTRICT — refuse to delete if the node has connected edges.\n",
    "- **`\"set_null\"`**: ON DELETE SET NULL — delete the node and its edges, but keep neighbor nodes.\n",
    "\n",
    "It also covers cascade delete through `WeakNode` hierarchies via the `propagation` flag."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import importlib.util\n",
    "\n",
    "package_to_check = 'drm'\n",
    "spec = importlib.util.find_spec(package_to_check)\n",
    "\n",
    "if spec is None:\n",
    "    print(f'⚠️ {package_to_check} no està instal·lat. Iniciant instal·lació...')\n",
    "    %pip install -q --upgrade drm-tools\n",
    "    print(\"✅ Instal·lació completada. L'estat del kernel PODRIA requerir un reinici.\")\n",
    "else:\n",
    "    print(f'✅ {package_to_check} ja està present al sistema. Saltant instal·lació.')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from drm import NetworkXGraph, Node, WeakNode, Relation\n",
    "\n",
    "graph = NetworkXGraph()\n",
    "\n",
    "# Create a small graph:\n",
    "#   Alice --WROTE--> Paper1 --CITES--> Paper2\n",
    "#   Bob    --WROTE--> Paper1\n",
    "#\n",
    "#   Document1\n",
    "#     |--CONTAINS--> Section1 (WeakNode)\n",
    "#                        |--CONTAINS--> Page1 (WeakNode of Section1)\n",
    "\n",
    "doc = Node(pk={\"doc\": \"DOC-001\"}, main_label=\"Document\")\n",
    "section = WeakNode(parent=doc, pk={\"section\": 1}, main_label=\"Section\")\n",
    "page = WeakNode(parent=section, pk={\"page\": 1}, main_label=\"Page\")\n",
    "\n",
    "alice = Node(pk={\"name\": \"Alice\"}, main_label=\"Author\")\n",
    "bob = Node(pk={\"name\": \"Bob\"}, main_label=\"Author\")\n",
    "paper1 = Node(pk={\"title\": \"P1\"}, main_label=\"Paper\")\n",
    "paper2 = Node(pk={\"title\": \"P2\"}, main_label=\"Paper\")\n",
    "\n",
    "# Insert all nodes\n",
    "graph.insertNode(doc)\n",
    "graph.insertNode(section, insert_parent=True)\n",
    "graph.insertNode(page, insert_parent=True)\n",
    "graph.insertNode(alice)\n",
    "graph.insertNode(bob)\n",
    "graph.insertNode(paper1)\n",
    "graph.insertNode(paper2)\n",
    "\n",
    "# Create relations\n",
    "graph.insertRelation(Relation(alice, paper1, \"WROTE\"))\n",
    "graph.insertRelation(Relation(bob, paper1, \"WROTE\"))\n",
    "graph.insertRelation(Relation(paper1, paper2, \"CITES\"))\n",
    "\n",
    "def show_state(label):\n",
    "    print(f\"\\n=== {label} ===\")\n",
    "    print(f\"Nodes: {graph.get_node_ids()}\")\n",
    "    print(f\"Edges: {graph.get_edges()}\")\n",
    "\n",
    "show_state(\"Initial state\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Strategy 1: CASCADE (default)\n",
    "\n",
    "`on_delete=\"cascade\"` deletes the node and all connected edges.\n",
    "Neighbor nodes remain as standalone entities."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"Before deleting paper1:\")\n",
    "show_state(\"Before CASCADE delete of paper1\")\n",
    "\n",
    "# Delete paper1 with cascade (default)\n",
    "result = graph.deleteNode(paper1, on_delete=\"cascade\")\n",
    "print(f\"deleteNode returned: {result}\")\n",
    "\n",
    "print(\"\\nAfter deleting paper1 (CASCADE):\")\n",
    "show_state(\"After CASCADE delete of paper1\")\n",
    "print(\"Note: Alice, Bob, and paper2 still exist, but edges are gone.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Strategy 2: RESTRICT\n",
    "\n",
    "`on_delete=\"restrict\"` refuses to delete if the node has any connected edges.\n",
    "This is useful for enforcing referential integrity."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"Before trying to delete alice (who has edges):\")\n",
    "show_state(\"Before RESTRICT delete attempt on alice\")\n",
    "\n",
    "try:\n",
    "    graph.deleteNode(alice, on_delete=\"restrict\")\n",
    "    print(\"ERROR: Should have raised RuntimeError!\")\n",
    "except RuntimeError as e:\n",
    "    print(f\"Caught expected error: {e}\")\n",
    "\n",
    "print(\"\\nGraph unchanged (alice was not deleted):\")\n",
    "show_state(\"After RESTRICT attempt (unchanged)\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Strategy 3: SET NULL\n",
    "\n",
    "`on_delete=\"set_null\"` deletes the node and its edges, but keeps\n",
    "neighbor nodes as standalone entities. Functionally similar to cascade\n",
    "for the graph structure, but with a different semantic meaning."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"Before deleting bob:\")\n",
    "show_state(\"Before SET NULL delete of bob\")\n",
    "\n",
    "result = graph.deleteNode(bob, on_delete=\"set_null\")\n",
    "print(f\"deleteNode returned: {result}\")\n",
    "\n",
    "print(\"\\nAfter deleting bob (SET NULL):\")\n",
    "show_state(\"After SET NULL delete of bob\")\n",
    "print(\"Note: alice and paper1 still exist, edges removed.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Cascade delete through WeakNode hierarchies\n",
    "\n",
    "When `propagation=True`, deleting a parent node also deletes all\n",
    "child WeakNodes connected via edges with `_propagate=True`.\n",
    "This is the default behavior for WeakNode relations."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Reset: create a fresh graph with a WeakNode hierarchy\n",
    "graph2 = NetworkXGraph()\n",
    "\n",
    "doc2 = Node(pk={\"doc\": \"DOC-002\"}, main_label=\"Document\")\n",
    "section2 = WeakNode(parent=doc2, pk={\"section\": 1}, main_label=\"Section\")\n",
    "page2 = WeakNode(parent=section2, pk={\"page\": 1}, main_label=\"Page\")\n",
    "\n",
    "graph2.insertNode(doc2)\n",
    "graph2.insertNode(section2, insert_parent=True)\n",
    "graph2.insertNode(page2, insert_parent=True)\n",
    "\n",
    "print(\"Before deleting the document:\")\n",
    "show_state(\"Before cascade delete of Document\")\n",
    "print(\"Hierarchy: Document -> Section -> Page\")\n",
    "\n",
    "# Delete the parent document with propagation\n",
    "# This cascades to Section and Page\n",
    "result = graph2.deleteNode(doc2, propagation=True, detach=True)\n",
    "print(f\"\\ndeleteNode returned: {result}\")\n",
    "\n",
    "print(\"\\nAfter deleting Document with propagation=True:\")\n",
    "show_state(\"After cascade delete of Document\")\n",
    "print(\"All nodes (Document, Section, Page) were deleted.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Summary table\n",
    "\n",
    "| Strategy | Deletes node | Deletes edges | Keeps neighbors | Raises on edges |\n",
    "|---|---|---|---|---|\n",
    "| `\"cascade\"` (default) | ✅ | ✅ | ✅ (standalone) | ❌ |\n",
    "| `\"restrict\"` | ❌ | ❌ | — | ✅ (RuntimeError) |\n",
    "| `\"set_null\"` | ✅ | ✅ | ✅ (standalone) | ❌ |\n",
    "\n",
    "With `propagation=True`, cascade/delete also removes child WeakNodes."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Cleanup"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "graph.close()\n",
    "graph2.close()\n",
    "print(\"All graphs closed.\")"
   ]
  }
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