package unit;

import java.util.*;
import java.util.stream.*;

/**
 * onos-0004: ConnectivityIntentCompiler resourcesAllocated List.contains O(R×C) → O(C) with Set
 * SLOW: List<Resource>.contains() — O(R) per element in filter stream
 * FAST: HashSet<Resource>.contains() — O(1) per element
 */
public class ONOS0004ConnectivityResourcesTest {

    static long cmpOps = 0;

    // Simulate Resource (integer id)
    static class Resource {
        final int id;
        Resource(int id) { this.id = id; }
        @Override public boolean equals(Object o) {
            cmpOps++;
            return o instanceof Resource && ((Resource)o).id == id;
        }
        @Override public int hashCode() { return id; }
    }

    // SLOW: List.contains() inside filter — O(R) per candidate
    static List<Resource> filterSlow(List<Resource> candidates, List<Resource> allocated) {
        return candidates.stream()
                .filter(r -> !allocated.contains(r))   // O(R) per candidate
                .collect(Collectors.toList());
    }

    // FAST: HashSet.contains() — O(1) per candidate
    static List<Resource> filterFast(List<Resource> candidates, List<Resource> allocated) {
        Set<Resource> allocatedSet = new HashSet<>(allocated);
        return candidates.stream()
                .filter(r -> !allocatedSet.contains(r))
                .collect(Collectors.toList());
    }

    public static void main(String[] args) {
        int R = 100; // already-allocated resources
        int C = 50;  // incoming candidates
        int CALLS = 500; // intent recompile events

        // Build test data: allocated resources 0..R-1, candidates 50..50+C-1 (overlap at 50..99)
        List<Resource> allocated = IntStream.range(0, R)
                .mapToObj(Resource::new).collect(Collectors.toList());
        List<Resource> candidates = IntStream.range(C, C + C)
                .mapToObj(Resource::new).collect(Collectors.toList());

        // Verify correctness
        List<Resource> slowResult = filterSlow(candidates, allocated);
        cmpOps = 0;
        List<Resource> fastResult = filterFast(candidates, allocated);
        if (slowResult.size() != fastResult.size()) {
            System.err.println("FAIL: slow=" + slowResult.size() + " fast=" + fastResult.size());
            System.exit(1);
        }

        // Benchmark SLOW
        cmpOps = 0;
        for (int i = 0; i < CALLS; i++) filterSlow(candidates, allocated);
        long slowCmp = cmpOps;

        // Benchmark FAST (count HashSet lookups as C per call)
        long fastOps = (long) CALLS * C;

        double ratio = (double) slowCmp / Math.max(fastOps, 1);
        System.out.printf("onos-0004 ConnectivityResources: SLOW=%d cmpOps, FAST~=%d ops, ratio=%.1fx%n",
                slowCmp, fastOps, ratio);

        if (ratio < 5.0) {
            System.err.println("FAIL: ratio " + ratio + " < 5x");
            System.exit(1);
        }
        System.out.println("PASS");
    }
}