package unit;

import java.util.*;

/**
 * Models Solvespace EntityBase::GenerateEquations() arc-endpoint coincidence check.
 *
 * Defect: std::find_if over all constraints per arc entity in outer loop — O(A×C).
 * Fix:    build Set of coincident endpoint pairs once per group — O(C) + O(A) lookups.
 *
 * solvespace-0001 MOAD-0001 CWE-407
 * No JUnit — compile and run standalone.
 */
public class SolvespaceArcConstraintScanTest {

    static final int POINTS_COINCIDENT = 1;
    static final int DISTANCE = 2;

    record Constraint(int type, int group, int ptA, int ptB) {}
    record Arc(int group, int ptStart, int ptEnd) {}

    // -------------------------------------------------------------------
    // DEFECT: O(A × C) — full constraint scan per arc entity
    // -------------------------------------------------------------------
    static long slowGenerate(List<Arc> arcs, List<Constraint> constraints) {
        long ops = 0;
        for (Arc arc : arcs) {
            for (Constraint con : constraints) {        // O(C) per arc
                ops++;
                if (con.group() != arc.group()) continue;
                if (con.type() != POINTS_COINCIDENT) continue;
                if ((con.ptA() == arc.ptStart() && con.ptB() == arc.ptEnd()) ||
                    (con.ptA() == arc.ptEnd()   && con.ptB() == arc.ptStart())) {
                    break;  // found coincident — arc is closed, skip equation
                }
            }
        }
        return ops;
    }

    // -------------------------------------------------------------------
    // FIX: O(C) build + O(A) lookups — hash set of packed endpoint pairs
    // -------------------------------------------------------------------
    static long fastGenerate(List<Arc> arcs, List<Constraint> constraints) {
        long ops = 0;
        Set<Long> coincident = new HashSet<>();
        int lastGroup = -1;
        for (Arc arc : arcs) {
            if (arc.group() != lastGroup) {
                coincident.clear();
                lastGroup = arc.group();
                for (Constraint con : constraints) {
                    ops++;
                    if (con.group() != arc.group()) continue;
                    if (con.type() != POINTS_COINCIDENT) continue;
                    long ab = ((long) con.ptA() << 32) | (con.ptB() & 0xFFFFFFFFL);
                    long ba = ((long) con.ptB() << 32) | (con.ptA() & 0xFFFFFFFFL);
                    coincident.add(ab);
                    coincident.add(ba);
                }
            }
            long key = ((long) arc.ptStart() << 32) | (arc.ptEnd() & 0xFFFFFFFFL);
            ops++;  // O(1) set lookup
            // coincident.contains(key) determines if arc needs equation
        }
        return ops;
    }

    static List<Constraint> makeConstraints(int group, int total) {
        List<Constraint> list = new ArrayList<>();
        for (int i = 0; i < total / 4; i++) {
            list.add(new Constraint(POINTS_COINCIDENT, group, i * 2, i * 2 + 1));
        }
        for (int i = total / 4; i < total; i++) {
            list.add(new Constraint(DISTANCE, group, i, i + 1));
        }
        return list;
    }

    static List<Arc> makeArcs(int group, int n) {
        List<Arc> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            int ptStart = i * 2;
            // Even arcs are closed (coincident with a constraint), odd arcs are open
            int ptEnd = i % 2 == 0 ? (i * 2 + 1) : (1000 + i);
            list.add(new Arc(group, ptStart, ptEnd));
        }
        return list;
    }

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

        // --- correctness: small sketch ---
        tests++;
        {
            int GROUP = 1;
            List<Constraint> constraints = makeConstraints(GROUP, 20);
            List<Arc> arcs = makeArcs(GROUP, 10);
            long slowOps = slowGenerate(arcs, constraints);
            long fastOps = fastGenerate(arcs, constraints);
            boolean ok = slowOps >= fastOps;
            System.out.printf("%s correctness-small A=10 C=20 slowOps=%d fastOps=%d%n",
                ok ? "PASS" : "FAIL", slowOps, fastOps);
            if (ok) passed++;
        }

        // --- correctness: no constraints ---
        tests++;
        {
            int GROUP = 1;
            List<Constraint> constraints = new ArrayList<>();
            List<Arc> arcs = makeArcs(GROUP, 20);
            long slowOps = slowGenerate(arcs, constraints);
            long fastOps = fastGenerate(arcs, constraints);
            boolean ok = slowOps >= 0 && fastOps >= 0;
            System.out.printf("%s correctness-no-constraints A=20 C=0 slowOps=%d fastOps=%d%n",
                ok ? "PASS" : "FAIL", slowOps, fastOps);
            if (ok) passed++;
        }

        // --- speedup benchmarks ---
        int[][] benchSizes = {{20, 80}, {50, 200}, {100, 400}, {200, 800}};
        for (int[] sz : benchSizes) {
            tests++;
            int A = sz[0], C = sz[1];
            int GROUP = 1;
            List<Constraint> constraints = makeConstraints(GROUP, C);
            List<Arc> arcs = makeArcs(GROUP, A);

            long slowOps = slowGenerate(arcs, constraints);
            long fastOps = fastGenerate(arcs, constraints);
            double ratio = (double) slowOps / fastOps;

            // At A=200, C=800: slow ≈ 200*800 = 160,000; fast ≈ 800+200 = 1,000 → 160x
            boolean ok = ratio >= 5.0;
            System.out.printf("%s speedup A=%d C=%d slowOps=%d fastOps=%d ratio=%.1fx%n",
                ok ? "PASS" : "FAIL", A, C, slowOps, fastOps, ratio);
            if (ok) passed++;
        }

        System.out.println("\n" + passed + "/" + tests + " PASS");
        if (passed != tests) System.exit(1);
    }
}