import java.util.*;

/**
 * CWE-407 unit test for three.js NodeBuilder defect.
 *
 * three-0001: src/nodes/core/NodeBuilder.js addNode() / addSequentialNode()
 *             src/nodes/core/StackNode.js generate()
 *
 *   NodeBuilder.addNode() guards deduplication with:
 *     if ( this.nodes.includes( node ) === false ) { ... }
 *   Array.includes() is O(N).  It is called once per node during the shader
 *   build traversal (Node.build → builder.addNode), making the full build
 *   O(N²) in the number of unique nodes.
 *
 *   addSequentialNode() has the identical pattern with sequentialNodes.
 *
 *   StackNode.generate() compounds this:
 *     const newNodes = this.nodes.filter( n => nodes.indexOf(n) === -1 );
 *   filter is O(N), indexOf is O(N) per element → O(N²) to compute the
 *   newly-added-node delta.
 *
 *   Fix: shadow Array with Set for O(1) has() checks.
 *
 * Severity: MEDIUM — called during shader compilation (material first-frame
 *   or material.needsUpdate).  Complex scenes with N=300+ nodes (particles,
 *   post-processing chains) stall on first render due to quadratic build cost.
 *
 * Speedup: O(N²) → O(N); measured ~250x op-count reduction at N=500.
 */
public class ThreeJsTest {

    // --- defect simulation: Array.includes dedup (O(N) per call) ---

    static void addNode_array(List<Object> nodes, Object node) {
        if (!nodes.contains(node)) {   // O(N)
            nodes.add(node);
        }
    }

    // Build simulation: traverse N nodes, each calling addNode
    static long buildShader_array(List<Object> allNodes) {
        List<Object> visited = new ArrayList<>();
        long ops = 0;
        for (Object node : allNodes) {
            // simulate nodes.includes(node): scan visited
            boolean found = false;
            for (Object v : visited) { ops++; if (v == node) { found = true; break; } }
            if (!found) {
                visited.add(node);
                ops++;  // the push
            }
        }
        return ops;
    }

    // --- fix simulation: Set.has dedup (O(1) per call) ---

    static void addNode_set(List<Object> nodes, Set<Object> nodeSet, Object node) {
        if (!nodeSet.contains(node)) {  // O(1)
            nodes.add(node);
            nodeSet.add(node);
        }
    }

    static long buildShader_set(List<Object> allNodes) {
        List<Object> visited = new ArrayList<>();
        Set<Object> visitedSet = new HashSet<>();
        long ops = 0;
        for (Object node : allNodes) {
            ops++;  // O(1) set lookup
            if (!visitedSet.contains(node)) {
                visited.add(node);
                visitedSet.add(node);
            }
        }
        return ops;
    }

    // --- filter delta simulation: nodes.indexOf vs Set.has ---

    static long filterDelta_indexOf(List<Object> allNodes, List<Object> snapshot) {
        long ops = 0;
        List<Object> newNodes = new ArrayList<>();
        for (Object node : allNodes) {
            // indexOf O(N) per element
            boolean found = false;
            for (Object s : snapshot) { ops++; if (s == node) { found = true; break; } }
            if (!found) newNodes.add(node);
        }
        return ops;
    }

    static long filterDelta_set(List<Object> allNodes, List<Object> snapshot) {
        long ops = 0;
        Set<Object> snapshotSet = new HashSet<>(snapshot);
        List<Object> newNodes = new ArrayList<>();
        for (Object node : allNodes) {
            ops++;  // O(1) set lookup
            if (!snapshotSet.contains(node)) newNodes.add(node);
        }
        return ops;
    }

    static void testThree0001() throws Exception {
        int N = 500;

        // Build N unique node objects
        List<Object> allNodes = new ArrayList<>();
        for (int i = 0; i < N; i++) allNodes.add(new Object());

        // Shader build dedup
        long arrayOps = buildShader_array(allNodes);
        long setOps   = buildShader_set(allNodes);

        double buildRatio = (double) arrayOps / setOps;
        System.out.printf("three-0001 addNode  N=%d  array_ops=%d  set_ops=%d  ratio=%.1fx%n",
                N, arrayOps, setOps, buildRatio);
        if (buildRatio < 2.0) {
            throw new Exception("FAIL: addNode ratio expected >= 2x, got " + buildRatio);
        }

        // StackNode.generate filter-delta
        // snapshot = first half of nodes, allNodes = all N
        List<Object> snapshot = new ArrayList<>(allNodes.subList(0, N / 2));
        long idxOps  = filterDelta_indexOf(allNodes, snapshot);
        long setOps2 = filterDelta_set(allNodes, snapshot);

        double filterRatio = (double) idxOps / setOps2;
        System.out.printf("three-0001 filter   N=%d  indexOf_ops=%d  set_ops=%d  ratio=%.1fx%n",
                N, idxOps, setOps2, filterRatio);
        if (filterRatio < 2.0) {
            throw new Exception("FAIL: filter ratio expected >= 2x, got " + filterRatio);
        }

        // Correctness: final visited sets must be equal
        List<Object> arrayVisited = new ArrayList<>();
        List<Object> setVisited   = new ArrayList<>();
        Set<Object>  setMirror    = new HashSet<>();
        for (Object node : allNodes) {
            addNode_array(arrayVisited, node);
            addNode_set(setVisited, setMirror, node);
        }
        if (!new HashSet<>(arrayVisited).equals(new HashSet<>(setVisited))) {
            throw new Exception("FAIL: visited sets differ between array and set implementations");
        }

        System.out.println("three-0001 PASS");
    }

    public static void main(String[] args) throws Exception {
        testThree0001();
        System.out.println("All three.js tests PASS");
    }
}