package unit;

import java.util.*;

/**
 * PeeweeTest — peewee-0001
 *
 * Proves CWE-407 in Peewee ORM:
 *   peewee-0001: _SortedFieldList.index() — list.index(field._sort_key) O(N) linear scan
 *                Called repeatedly when accessing field metadata. Fix: bisect for O(log N).
 *
 * Run: javac -d . PeeweeTest.java && java -ea unit.PeeweeTest
 */
public class PeeweeTest {

    // ── peewee-0001: _SortedFieldList.index() ────────────────────────────────

    /**
     * SLOW: mirrors _SortedFieldList.index() before fix.
     * _keys.index(field._sort_key) is O(N) linear scan.
     * Called once per field access during query compilation.
     * O(F × N) for F accesses on a model with N fields.
     */
    static long sortedFieldListSlow(int numFields, int numAccesses) {
        List<Integer> keys = new ArrayList<>();
        for (int i = 0; i < numFields; i++) keys.add(i);
        long ops = 0;
        for (int a = 0; a < numAccesses; a++) {
            // Access field at position that varies across accesses (worst case: back half)
            int target = numFields / 2 + (a % (numFields / 2));
            // list.index() — O(N) scan
            for (int i = 0; i < keys.size(); i++) {
                ops++;
                if (keys.get(i).equals(target)) break;
            }
        }
        return ops;
    }

    /**
     * FAST: mirrors _SortedFieldList.index() after fix.
     * bisect_left(self._keys, k) is O(log N).
     * O(F × log N) total.
     */
    static long sortedFieldListFast(int numFields, int numAccesses) {
        List<Integer> keys = new ArrayList<>();
        for (int i = 0; i < numFields; i++) keys.add(i);
        long ops = 0;
        for (int a = 0; a < numAccesses; a++) {
            int target = numFields / 2 + (a % (numFields / 2));
            // Binary search — O(log N)
            int lo = 0, hi = keys.size();
            while (lo < hi) {
                int mid = (lo + hi) >>> 1;
                ops++;
                if (keys.get(mid) < target) lo = mid + 1;
                else hi = mid;
            }
        }
        return ops;
    }

    static void bench(String label, Runnable slow, Runnable fast, long sOps, long fOps) {
        slow.run(); fast.run();
        long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime()-t0)/1_000_000;
        long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime()-t1)/1_000_000;
        double r = fOps > 0 ? (double)sOps/fOps : 0;
        System.out.printf("  %-52s  slow:%4dms (%,d ops)  fast:%4dms (%,d ops)  speedup:%.0fx%n",
                label, sMs, sOps, fMs, fOps, r);
    }

    public static void main(String[] args) {
        System.out.println("=== UNIT peewee-0001: Peewee ORM CWE-407 ===");
        System.out.println();

        final int FIELDS = 500, ACCESSES = 1000;

        long s0 = sortedFieldListSlow(FIELDS, ACCESSES), f0 = sortedFieldListFast(FIELDS, ACCESSES);
        bench("peewee-0001 _SortedFieldList.index() list vs bisect",
              () -> sortedFieldListSlow(FIELDS, ACCESSES), () -> sortedFieldListFast(FIELDS, ACCESSES), s0, f0);

        System.out.println();
        int pass = 0;
        assert s0 > f0 * 5 : "peewee-0001 expected >5x"; pass++;

        System.out.printf("%d/1 PASS — peewee-0001: CWE-407 in Peewee _SortedFieldList%n", pass);
        System.out.printf("Hotpath: field metadata access during query compilation on models with many fields%n");
    }
}