java-topology/defects/terraform/unit/TfAwsCloudFormationAlgorithm.java

package unit;

import java.util.*;

/**
 * TfAwsCloudFormationAlgorithm — CWE-407 benchmark
 *
 * Models terraform-provider-aws cloudformation/stack_set_instance.go
 * findStackInstanceSummariesByFourPartKey():
 *   SLOW: slices.Contains(orgIDs, v.OrganizationalUnitId) — O(O) per summary
 *         called S times inside pagination → O(S × O) total
 *   FAST: pre-build map[string]bool from orgIDs → O(1) per summary
 *
 * tf-aws-0001
 */
public class TfAwsCloudFormationAlgorithm {

    // ------------------------------------------------------------------ nodes

    static class Node {
        String ouId;
        String stackInstanceId;
        Node(String ouId, String stackInstanceId) {
            this.ouId = ouId;
            this.stackInstanceId = stackInstanceId;
        }
    }

    // ------------------------------------------------------------------ result

    static class Result {
        List<Node> matched;
        Result(List<Node> matched) { this.matched = matched; }
    }

    // ------------------------------------------------------------------ slow (defect)

    static class DefectiveFinder {
        /**
         * For each summary across all pagination pages, scan orgIDs linearly.
         * O(S × O) where S = total summaries, O = number of org IDs.
         */
        static Result findSummaries(List<List<Node>> pages, List<String> orgIDs) {
            List<Node> output = new ArrayList<>();
            for (List<Node> page : pages) {
                for (Node v : page) {
                    // CWE-407: linear scan of orgIDs on every summary
                    if (orgIDs.contains(v.ouId)) {   // O(O)
                        output.add(v);
                    }
                }
            }
            return new Result(output);
        }
    }

    // ------------------------------------------------------------------ fast (fix)

    static class FixedFinder {
        /**
         * Pre-build a HashSet from orgIDs before the pagination loop.
         * O(S + O) total.
         */
        static Result findSummaries(List<List<Node>> pages, List<String> orgIDs) {
            // CWE-407 fix: O(1) lookup set built once before pagination
            Set<String> orgIDSet = new HashSet<>(orgIDs);
            List<Node> output = new ArrayList<>();
            for (List<Node> page : pages) {
                for (Node v : page) {
                    if (orgIDSet.contains(v.ouId)) {  // O(1)
                        output.add(v);
                    }
                }
            }
            return new Result(output);
        }
    }

    // ------------------------------------------------------------------ helpers

    static List<List<Node>> buildPages(int totalSummaries, int pageSize, int numOUs) {
        List<List<Node>> pages = new ArrayList<>();
        List<Node> page = new ArrayList<>();
        for (int i = 0; i < totalSummaries; i++) {
            String ouId = "ou-" + (i % numOUs);  // distribute across OUs
            page.add(new Node(ouId, "stack-instance-" + i));
            if (page.size() == pageSize) {
                pages.add(page);
                page = new ArrayList<>();
            }
        }
        if (!page.isEmpty()) pages.add(page);
        return pages;
    }

    static List<String> buildOrgIDs(int n) {
        List<String> ids = new ArrayList<>(n);
        for (int i = 0; i < n; i++) {
            ids.add("ou-" + i);
        }
        return ids;
    }

    static long benchSlow(int S, int O, int iters) {
        List<List<Node>> pages = buildPages(S, 100, O * 2);
        List<String> orgIDs = buildOrgIDs(O);
        long start = System.nanoTime();
        for (int i = 0; i < iters; i++) {
            DefectiveFinder.findSummaries(pages, orgIDs);
        }
        return System.nanoTime() - start;
    }

    static long benchFast(int S, int O, int iters) {
        List<List<Node>> pages = buildPages(S, 100, O * 2);
        List<String> orgIDs = buildOrgIDs(O);
        long start = System.nanoTime();
        for (int i = 0; i < iters; i++) {
            FixedFinder.findSummaries(pages, orgIDs);
        }
        return System.nanoTime() - start;
    }

    // ------------------------------------------------------------------ main

    public static void main(String[] args) {
        int passed = 0, total = 0;

        // ---- correctness
        List<Node> page1 = Arrays.asList(
            new Node("ou-1", "s1"), new Node("ou-2", "s2"), new Node("ou-3", "s3")
        );
        List<Node> page2 = Arrays.asList(
            new Node("ou-4", "s4"), new Node("ou-1", "s5")
        );
        List<List<Node>> pages = Arrays.asList(page1, page2);
        List<String> orgIDs = Arrays.asList("ou-1", "ou-3");

        Result slowR = DefectiveFinder.findSummaries(pages, orgIDs);
        Result fastR = FixedFinder.findSummaries(pages, orgIDs);

        assert slowR.matched.size() == 3 : "slow: expected 3 matches, got " + slowR.matched.size();
        assert fastR.matched.size() == 3 : "fast: expected 3 matches, got " + fastR.matched.size();
        assert slowR.matched.size() == fastR.matched.size() : "slow/fast count mismatch";
        System.out.println("Correctness: PASS (slow.matched.size == fast.matched.size == 3)");

        // ---- performance
        int ITERS = 50;
        int[][] scenarios = {{2000, 200}, {4000, 350}, {7000, 500}};
        System.out.printf("%-6s  %-6s  %-12s  %-12s  %s%n", "S", "O", "slow(ns)", "fast(ns)", "ratio");

        for (int[] sc : scenarios) {
            int S = sc[0], O = sc[1];
            // warm-up (extra iterations to stabilize JIT at larger sizes)
            benchSlow(S, O, 10); benchFast(S, O, 10);

            long slowNs = benchSlow(S, O, ITERS);
            long fastNs = benchFast(S, O, ITERS);
            double ratio = (double) slowNs / fastNs;

            System.out.printf("%-6d  %-6d  %-12d  %-12d  %.2fx%n", S, O, slowNs, fastNs, ratio);

            total++;
            if (ratio >= 5.0) {
                System.out.printf("  PASS (ratio=%.2f >= 5.0)%n", ratio);
                passed++;
            } else {
                System.out.printf("  FAIL (ratio=%.2f < 5.0)%n", ratio);
            }
        }

        System.out.printf("%nTests: %d/%d PASS%n", passed, total);
        if (passed < total) System.exit(1);
    }
}