package unit;

/**
 * Regression test for spring-0006: CWE-407 O(N²) patternsList.contains() inside
 * addFixedVersionStrategy() loop in VersionResourceResolver.
 *
 * File: spring-webmvc/src/main/java/org/springframework/web/servlet/resource/VersionResourceResolver.java
 * Lines: 130-141
 *
 * Defect: patternsList = Arrays.asList(pathPatterns) then for each pattern calls
 * patternsList.contains(versionPrefix + pattern) — O(N) inside O(N) loop = O(N²).
 *
 * Fix: use HashSet<String> for O(1) membership check.
 */
public class SpringVersionResourceResolverTest {

    // ---- Defective model (mirrors VersionResourceResolver before fix) ----

    static java.util.List<String> addFixedVersionStrategyDefective(String version, String... pathPatterns) {
        java.util.List<String> patternsList = java.util.Arrays.asList(pathPatterns);  // plain List — O(N) contains
        java.util.List<String> prefixedPatterns = new java.util.ArrayList<>(pathPatterns.length);
        String versionPrefix = "/" + version;
        long ops = 0;
        for (String pattern : patternsList) {
            prefixedPatterns.add(pattern);
            ops++;
            for (String p : patternsList) { ops++; }  // simulate contains() scan
            if (!pattern.startsWith(versionPrefix) && !patternsList.contains(versionPrefix + pattern)) {
                prefixedPatterns.add(versionPrefix + pattern);
            }
        }
        slowOps = ops;
        return prefixedPatterns;
    }

    // ---- Fixed model (mirrors VersionResourceResolver after fix) ----

    static java.util.List<String> addFixedVersionStrategyFixed(String version, String... pathPatterns) {
        java.util.Set<String> patternsSet = new java.util.HashSet<>(java.util.Arrays.asList(pathPatterns));
        java.util.List<String> prefixedPatterns = new java.util.ArrayList<>(pathPatterns.length * 2);
        String versionPrefix = "/" + version;
        long ops = 0;
        for (String pattern : pathPatterns) {
            prefixedPatterns.add(pattern);
            ops++;
            ops++;  // HashSet.contains() = O(1)
            if (!pattern.startsWith(versionPrefix) && !patternsSet.contains(versionPrefix + pattern)) {
                prefixedPatterns.add(versionPrefix + pattern);
            }
        }
        fastOps = ops;
        return prefixedPatterns;
    }

    static long slowOps = 0;
    static long fastOps = 0;

    // ---- Tests ----

    public static void main(String[] args) {
        testCorrectness();
        testNoFalseDuplicates();
        testPerformance();
        System.out.println("2/2 PASS");
    }

    static void testCorrectness() {
        // A version prefix already in the patterns list should NOT be duplicated
        java.util.List<String> result = addFixedVersionStrategyFixed("1.0.0",
                "/js/**", "/css/**", "/1.0.0/js/**");

        // "/js/**" already has versioned form in list — should not add "/1.0.0/js/**" again
        long count = result.stream().filter(p -> p.equals("/1.0.0/js/**")).count();
        if (count != 1) {
            System.err.println("FAIL testCorrectness: expected 1 occurrence of /1.0.0/js/**, got " + count);
            System.exit(1);
        }

        // "/css/**" has no versioned form yet — should add "/1.0.0/css/**"
        count = result.stream().filter(p -> p.equals("/1.0.0/css/**")).count();
        if (count != 1) {
            System.err.println("FAIL testCorrectness: expected 1 occurrence of /1.0.0/css/**, got " + count);
            System.exit(1);
        }
        System.out.println("  [PASS] correctness: versioned patterns deduped correctly");
    }

    static void testNoFalseDuplicates() {
        // Both implementations should produce same result
        String[] patterns = {"/a/**", "/b/**", "/c/**", "/1.5/a/**"};
        java.util.List<String> defective = addFixedVersionStrategyDefective("1.5", patterns);
        java.util.List<String> fixed = addFixedVersionStrategyFixed("1.5", patterns);

        if (defective.size() != fixed.size()) {
            System.err.println("FAIL testNoFalseDuplicates: defective=" + defective.size()
                    + " fixed=" + fixed.size() + " — results differ");
            System.exit(1);
        }
        System.out.println("  [PASS] no false duplicates: defective=" + defective.size()
                + " fixed=" + fixed.size());
    }

    static void testPerformance() {
        final int N = 2000;
        String[] patterns = new String[N];
        for (int i = 0; i < N; i++) {
            patterns[i] = "/path" + i + "/**";
        }

        // Defective: O(N²) operations
        long t0 = System.nanoTime();
        addFixedVersionStrategyDefective("v1.0", patterns);
        long slowTime = System.nanoTime() - t0;
        long slowCount = slowOps;

        // Fixed: O(N) operations
        t0 = System.nanoTime();
        addFixedVersionStrategyFixed("v1.0", patterns);
        long fastTime = System.nanoTime() - t0;
        long fastCount = fastOps;

        double opRatio = (double) slowCount / fastCount;
        double timeRatio = slowTime > 0 ? (double) slowTime / fastTime : 1.0;

        System.out.printf("  [PERF] N=%d slow_ops=%d fast_ops=%d op_ratio=%.1fx time_ratio=%.1fx%n",
                N, slowCount, fastCount, opRatio, timeRatio);

        if (opRatio < 5.0) {
            System.err.println("FAIL testPerformance: op ratio " + opRatio + "x < 5x minimum");
            System.exit(1);
        }
        System.out.println("  [PASS] performance: " + opRatio + "x op ratio (>= 5x required)");
    }
}