package unit;

/**
 * Regression test for hibernate-0006: CWE-407 O(T²) alias deduplication in
 * AbstractEntityPersister subclass property closure initialization.
 *
 * File: hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java
 * Lines: 665-709
 *
 * Defect: aliases and formulaAliases are ArrayList<String>. Inside nested loops over
 * subclass properties and their selectables, aliases.contains(columnAlias) is O(T)
 * where T is the growing list of accumulated aliases. For T total selectables, total
 * cost is O(T²).
 *
 * Fix: use LinkedHashSet<String> — O(1) add() handles dedup; insertion order preserved.
 */
public class HibernateAliasClosureTest {

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

    static class DefectivePersisterInit {
        private final java.util.ArrayList<String> aliases = new java.util.ArrayList<>();
        private final java.util.ArrayList<String> formulaAliases = new java.util.ArrayList<>();
        private long ops = 0;

        /**
         * Simulate processing one selectable column from the subclass property closure.
         */
        void addColumnAlias(String alias) {
            ops += aliases.size();  // simulate O(N) contains scan
            if (!aliases.contains(alias)) {   // O(N) — CWE-407
                aliases.add(alias);
            }
        }

        void addFormulaAlias(String alias) {
            ops += formulaAliases.size();
            if (!formulaAliases.contains(alias)) {  // O(N) — CWE-407
                formulaAliases.add(alias);
            }
        }

        java.util.List<String> getColumnAliases() { return aliases; }
        java.util.List<String> getFormulaAliases() { return formulaAliases; }
        long getOps() { return ops; }
    }

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

    static class FixedPersisterInit {
        private final java.util.LinkedHashSet<String> aliases = new java.util.LinkedHashSet<>();
        private final java.util.LinkedHashSet<String> formulaAliases = new java.util.LinkedHashSet<>();
        private long ops = 0;

        void addColumnAlias(String alias) {
            ops++;  // O(1) amortized HashSet.add()
            aliases.add(alias);
        }

        void addFormulaAlias(String alias) {
            ops++;
            formulaAliases.add(alias);
        }

        java.util.List<String> getColumnAliases() { return new java.util.ArrayList<>(aliases); }
        java.util.List<String> getFormulaAliases() { return new java.util.ArrayList<>(formulaAliases); }
        long getOps() { return ops; }
    }

    // ---- Tests ----

    public static void main(String[] args) {
        testDedup();
        testInsertionOrder();
        testPerformance();
        System.out.println("3/3 PASS");
    }

    static void testDedup() {
        DefectivePersisterInit defective = new DefectivePersisterInit();
        FixedPersisterInit fixed = new FixedPersisterInit();

        // Simulate subclass hierarchy: 5 subclasses each contributing 4 columns,
        // but 2 of those columns are shared (inherited from superclass).
        // Expected unique aliases: 5 * 2 + 2 = 12
        for (int sub = 0; sub < 5; sub++) {
            defective.addColumnAlias("shared_col1_");    // shared — should dedup
            defective.addColumnAlias("shared_col2_");    // shared — should dedup
            defective.addColumnAlias("sub" + sub + "_col1_");
            defective.addColumnAlias("sub" + sub + "_col2_");

            fixed.addColumnAlias("shared_col1_");
            fixed.addColumnAlias("shared_col2_");
            fixed.addColumnAlias("sub" + sub + "_col1_");
            fixed.addColumnAlias("sub" + sub + "_col2_");
        }

        int expectedUnique = 2 + 5 * 2;  // 2 shared + 10 subclass-specific
        int defectiveCount = defective.getColumnAliases().size();
        int fixedCount = fixed.getColumnAliases().size();

        if (defectiveCount != expectedUnique) {
            System.err.println("FAIL testDedup: defective expected " + expectedUnique
                    + " got " + defectiveCount);
            System.exit(1);
        }
        if (fixedCount != expectedUnique) {
            System.err.println("FAIL testDedup: fixed expected " + expectedUnique
                    + " got " + fixedCount);
            System.exit(1);
        }
        System.out.println("  [PASS] alias dedup: expected=" + expectedUnique
                + " defective=" + defectiveCount + " fixed=" + fixedCount);
    }

    static void testInsertionOrder() {
        // Fixed (LinkedHashSet) must preserve insertion order of first occurrence
        FixedPersisterInit fixed = new FixedPersisterInit();
        fixed.addColumnAlias("alpha_");
        fixed.addColumnAlias("beta_");
        fixed.addColumnAlias("gamma_");
        fixed.addColumnAlias("alpha_");  // duplicate — should not affect order
        fixed.addColumnAlias("beta_");   // duplicate

        java.util.List<String> result = fixed.getColumnAliases();
        if (result.size() != 3) {
            System.err.println("FAIL testInsertionOrder: expected 3, got " + result.size());
            System.exit(1);
        }
        if (!result.get(0).equals("alpha_") || !result.get(1).equals("beta_") || !result.get(2).equals("gamma_")) {
            System.err.println("FAIL testInsertionOrder: wrong order: " + result);
            System.exit(1);
        }
        System.out.println("  [PASS] insertion order preserved: " + result);
    }

    static void testPerformance() {
        // Simulate a large TPH hierarchy: 50 subclasses × 20 columns = 1000 selectables,
        // with the first 5 columns shared (inherited) across all subclasses.
        final int SUBCLASSES = 50;
        final int COLS_PER_SUB = 20;
        final int SHARED_COLS = 5;

        DefectivePersisterInit defective = new DefectivePersisterInit();
        long t0 = System.nanoTime();
        for (int sub = 0; sub < SUBCLASSES; sub++) {
            for (int col = 0; col < SHARED_COLS; col++) {
                defective.addColumnAlias("shared_" + col + "_");
            }
            for (int col = SHARED_COLS; col < COLS_PER_SUB; col++) {
                defective.addColumnAlias("sub" + sub + "_col" + col + "_");
            }
        }
        long slowTime = System.nanoTime() - t0;
        long slowOps = defective.getOps();

        FixedPersisterInit fixed = new FixedPersisterInit();
        t0 = System.nanoTime();
        for (int sub = 0; sub < SUBCLASSES; sub++) {
            for (int col = 0; col < SHARED_COLS; col++) {
                fixed.addColumnAlias("shared_" + col + "_");
            }
            for (int col = SHARED_COLS; col < COLS_PER_SUB; col++) {
                fixed.addColumnAlias("sub" + sub + "_col" + col + "_");
            }
        }
        long fastTime = System.nanoTime() - t0;
        long fastOps = fixed.getOps();

        double opRatio = fastOps > 0 ? (double) slowOps / fastOps : 1.0;
        double timeRatio = fastTime > 0 ? (double) slowTime / fastTime : 1.0;

        System.out.printf("  [PERF] subclasses=%d cols=%d total=%d slow_ops=%d fast_ops=%d op_ratio=%.1fx time_ratio=%.1fx%n",
                SUBCLASSES, COLS_PER_SUB, SUBCLASSES * COLS_PER_SUB,
                slowOps, fastOps, 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: " + String.format("%.1f", opRatio)
                + "x op ratio (>= 5x required)");
    }
}