package unit;

import java.util.*;

/**
 * CWE-407 unit test: cmake-0004
 * AddSource — O(n²) std::find_if per call in Unity build loop vs O(n) set guard.
 *
 * Simulates cmTarget::AddSource called in loop over unity_files:
 *   slow: scan Sources.Entries vector (find_if) for each add → O(n²)
 *   fast: use HashSet shadow, skip scan if already present → O(n)
 */
public class AddSourceAlgorithm {

    // Slow: O(n^2) — find_if scan per AddSource call (mirrors TargetPropertyEntryFinder)
    static long slowAddSources(List<String> unityFiles) {
        long ops = 0;
        List<String> sourcesEntries = new ArrayList<>();
        for (String src : unityFiles) {
            boolean found = false;
            for (String existing : sourcesEntries) { // O(n) scan
                ops++;
                if (existing.equals(src)) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                sourcesEntries.add(src);
            }
        }
        return ops;
    }

    // Fast: HashSet shadow for O(1) check, O(n) total
    static long fastAddSources(List<String> unityFiles) {
        long ops = 0;
        Set<String> sourcePathsSet = new HashSet<>();
        List<String> sourcesEntries = new ArrayList<>();
        for (String src : unityFiles) {
            ops++;
            if (sourcePathsSet.add(src)) {
                sourcesEntries.add(src);
            }
        }
        return ops;
    }

    public static void main(String[] args) {
        int[] sizes = {200, 500, 1000, 2000};
        int passed = 0, total = 0;

        for (int S : sizes) {
            // S unity source files, 20% duplicates (re-added after PCH generation)
            List<String> unityFiles = new ArrayList<>(S + S / 5);
            for (int i = 0; i < S; i++) {
                unityFiles.add("/src/unity_" + i + ".cpp");
            }
            for (int i = 0; i < S / 5; i++) {
                unityFiles.add("/src/unity_" + i + ".cpp"); // duplicate
            }

            long slowOps = slowAddSources(unityFiles);
            long fastOps = fastAddSources(unityFiles);
            double ratio = (double) slowOps / fastOps;

            total++;
            System.out.printf("S=%4d  slow=%8d  fast=%6d  ratio=%.1fx%n",
                S, slowOps, fastOps, ratio);
            // At S=2000: slow is O(S^2/2) ~ 2M, fast is O(S) ~ 2000 → >100x
            assert ratio > 20.0 : "Expected ratio > 20 at S=" + S + ", got " + ratio;
            passed++;
        }

        // Correctness: same unique list preserved
        List<String> input = Arrays.asList("a.cpp", "b.cpp", "a.cpp", "c.cpp");
        List<String> slowOut = new ArrayList<>();
        for (String s : input) {
            if (!slowOut.contains(s)) slowOut.add(s);
        }
        Set<String> fastOut = new LinkedHashSet<>();
        fastOut.addAll(input);
        assert new ArrayList<>(fastOut).equals(slowOut) :
            "Correctness: " + fastOut + " vs " + slowOut;
        passed++; total++;

        System.out.printf("%d/%d PASS%n", passed, total);
    }
}