package unit;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;

/**
 * hadoop-0003: StoragePolicySatisfier.findTargetNode() — ArrayList.contains() O(E)
 * called inside nested loops over storage types and candidate nodes.
 * Total complexity: O(T * N * E) where T=storageTypes, N=nodesPerType, E=excludedNodes.
 *
 * Standalone unit test — no JUnit required.
 * Compile: javac -d . HadoopStoragePolicySatisfierTest.java
 * Run:     java -ea unit.HadoopStoragePolicySatisfierTest
 */
public class HadoopStoragePolicySatisfierTest {

    static long slowOps;
    static long fastOps;

    /**
     * Simulates findTargetNode() with ArrayList excludeNodes — O(E) per candidate.
     * Returns count of valid targets found (to verify correctness).
     */
    static int slowFindTargets(int numStorageTypes, int nodesPerType, List<Integer> excludeNodes) {
        slowOps = 0;
        int validTargets = 0;
        for (int t = 0; t < numStorageTypes; t++) {          // outer: storage types O(T)
            for (int n = 0; n < nodesPerType; n++) {         // inner: candidate nodes O(N)
                slowOps++;
                int nodeId = t * nodesPerType + n;
                for (Integer ex : excludeNodes) {            // ArrayList.contains() scan O(E)
                    slowOps++;
                    if (ex.equals(nodeId)) break;
                }
                if (!excludeNodes.contains(nodeId)) {
                    validTargets++;
                }
            }
        }
        return validTargets;
    }

    /**
     * Patched: HashSet excludeNodes — O(1) contains().
     */
    static int fastFindTargets(int numStorageTypes, int nodesPerType, Collection<Integer> excludeNodes) {
        fastOps = 0;
        int validTargets = 0;
        for (int t = 0; t < numStorageTypes; t++) {
            for (int n = 0; n < nodesPerType; n++) {
                fastOps++;
                int nodeId = t * nodesPerType + n;
                fastOps++;  // O(1) HashSet.contains()
                if (!excludeNodes.contains(nodeId)) {
                    validTargets++;
                }
            }
        }
        return validTargets;
    }

    static void run(int T, int N, int E, int expectedRatio) {
        // Exclude nodes: first E node IDs
        List<Integer> slowExclude = new ArrayList<>();
        HashSet<Integer> fastExclude = new HashSet<>();
        for (int i = 0; i < E; i++) {
            slowExclude.add(i);
            fastExclude.add(i);
        }

        int slowResult = slowFindTargets(T, N, slowExclude);
        int fastResult = fastFindTargets(T, N, fastExclude);

        boolean resultsMatch = (slowResult == fastResult);
        boolean quadraticWorse = slowOps > fastOps * expectedRatio;
        boolean pass = resultsMatch && quadraticWorse;

        System.out.printf("T=%-3d N=%-4d E=%-4d  slow=%8d  fast=%6d  ratio=%6.1fx  match=%b  PASS=%b%n",
            T, N, E, slowOps, fastOps, (double) slowOps / fastOps, resultsMatch, pass);

        if (!pass) {
            throw new AssertionError(
                "FAIL T=" + T + " N=" + N + " E=" + E +
                " resultsMatch=" + resultsMatch +
                " slowOps=" + slowOps + " fastOps=" + fastOps +
                " needed ratio>" + expectedRatio);
        }
    }

    public static void main(String[] args) {
        System.out.println("=== hadoop-0003: StoragePolicySatisfier.findTargetNode() O(T*N*E) vs O(T*N) ===");
        run(3,  100, 20,  5);
        run(5,  200, 50,  15);
        run(5,  300, 100, 25);
        System.out.println("3/3 PASS");
    }
}