auth-yes/forum/poc-g1/dependency_graph_poc.ts

import { assertEquals } from "https://deno.land/std@0.224.0/testing/asserts.ts";

/**
 * Proof of Concept: Dependency Graphing (Adjacency Matrices)
 *
 * Demonstrates mathematically calculating the "blast radius" of a code change
 * by representing component dependencies as an adjacency matrix and using
 * graph traversal to find impacted nodes.
 */

// Adjacency matrix for a simple app:
// Nodes: [0: Auth, 1: Database, 2: API Route, 3: UI Component]
// Matrix[i][j] = 1 means Node i depends on Node j
const matrix = [
  [0, 1, 0, 0], // Auth depends on Database
  [0, 0, 0, 0], // Database has no outgoing dependencies
  [1, 1, 0, 0], // API Route depends on Auth and Database
  [0, 0, 1, 0], // UI Component depends on API Route
];

const nodes = ["Auth", "Database", "API Route", "UI Component"];

// Find all nodes that depend on a given node (blast radius)
function calculateBlastRadius(changedNodeIndex: number): number[] {
  const impacted = new Set<number>();
  const queue = [changedNodeIndex];

  while (queue.length > 0) {
    const current = queue.shift()!;
    // Find who depends on `current`
    for (let i = 0; i < matrix.length; i++) {
      if (matrix[i][current] === 1 && !impacted.has(i)) {
        impacted.add(i);
        queue.push(i);
      }
    }
  }

  return Array.from(impacted);
}

if (import.meta.main) {
  console.log("Running Dependency Graphing PoC tests...");

  try {
    const changedNode = 1; // "Database" changed
    console.log(
      `If '${nodes[changedNode]}' changes, calculating blast radius...`,
    );

    const impactedIndices = calculateBlastRadius(changedNode);
    const impactedNames = impactedIndices.map((i) => nodes[i]);

    console.log(`Impacted components:`, impactedNames);

    // If Database changes, Auth and API Route depend on it directly.
    // UI Component depends on API Route. So all others should be impacted.
    assertEquals(impactedIndices.length, 3);
    console.log(
      "✅ Dependency Graphing PoC successful: Blast radius calculated correctly.",
    );
  } catch (err) {
    console.error("❌ Dependency Graphing PoC failed:", err);
    Deno.exit(1);
  }
}