package unit;

import support.BoundSetAlgorithm;
import support.BoundSetAlgorithm.Result;

import java.util.List;

/**
 * Unit tests for DEFECT 0005: InferenceContext.isEquiv() List.containsAll().
 *
 * Proves:
 *   1. Both implementations correctly identify equivalent and non-equivalent sets.
 *   2. Defective version makes exactly B*(B+1) comparisons for equal sets of size B.
 *   3. Fixed version makes exactly B comparisons for the same check.
 *   4. Doubling B quadruples defective work; doubling B doubles fixed work.
 *
 * No build tool required. Compile and run:
 *
 *   cd tests
 *   java -m jdk.compiler/com.sun.tools.javac.Main -cp . \
 *        support/BoundSetAlgorithm.java unit/BoundSetComplexityTest.java
 *   java -cp . unit.BoundSetComplexityTest
 */
public class BoundSetComplexityTest {

    private static int passed = 0;
    private static int failed = 0;

    public static void main(String[] args) {
        System.out.println("=== BoundSetComplexityTest (DEFECT 0005) ===\n");

        System.out.println("-- Correctness: equivalent and non-equivalent sets --");
        testCorrectnessEquivalent();
        testCorrectnessNotEquivalent();
        testCorrectnessEmpty();
        testCorrectnessSingleElement();

        System.out.println("\n-- Complexity: defective comparison counts B*(B+1) --");
        testDefectiveExactCounts();

        System.out.println("\n-- Complexity: fixed comparison counts B --");
        testFixedExactCounts();

        System.out.println("\n-- Complexity: growth ratio proves quadratic vs linear --");
        testGrowthRatio();

        System.out.printf("\n%d passed, %d failed%n", passed, failed);
        if (failed > 0) System.exit(1);
    }

    // ─── Correctness ─────────────────────────────────────────────────────────

    static void testCorrectnessEquivalent() {
        // Forward vs reversed — same elements, different order → equivalent
        List<Integer> b1 = BoundSetAlgorithm.buildForwardList(5);
        List<Integer> b2 = BoundSetAlgorithm.buildReversedList(5);

        Result def = BoundSetAlgorithm.isEquivDefective(b1, b2);
        Result fix = BoundSetAlgorithm.isEquivFixed(b1, b2);

        assertTrue("equiv-5: defective returns true", def.equivalent);
        assertTrue("equiv-5: fixed returns true",     fix.equivalent);
    }

    static void testCorrectnessNotEquivalent() {
        // [0,1,2] vs [0,1,3] — differ in one element
        List<Integer> b1 = java.util.List.of(0, 1, 2);
        List<Integer> b2 = java.util.List.of(0, 1, 3);

        Result def = BoundSetAlgorithm.isEquivDefective(new java.util.ArrayList<>(b1),
                                                         new java.util.ArrayList<>(b2));
        Result fix = BoundSetAlgorithm.isEquivFixed(new java.util.ArrayList<>(b1),
                                                     new java.util.ArrayList<>(b2));

        assertTrue("not-equiv: defective returns false", !def.equivalent);
        assertTrue("not-equiv: fixed returns false",     !fix.equivalent);
    }

    static void testCorrectnessEmpty() {
        List<Integer> b1 = new java.util.ArrayList<>();
        List<Integer> b2 = new java.util.ArrayList<>();

        Result def = BoundSetAlgorithm.isEquivDefective(b1, b2);
        Result fix = BoundSetAlgorithm.isEquivFixed(b1, b2);

        assertTrue("empty: defective returns true", def.equivalent);
        assertTrue("empty: fixed returns true",     fix.equivalent);
        assertEqual("empty: defective comparisons", 0L, def.comparisons);
        assertEqual("empty: fixed comparisons",     0L, fix.comparisons);
    }

    static void testCorrectnessSingleElement() {
        List<Integer> b1 = java.util.List.of(42);
        List<Integer> b2 = java.util.List.of(42);

        Result def = BoundSetAlgorithm.isEquivDefective(new java.util.ArrayList<>(b1),
                                                         new java.util.ArrayList<>(b2));
        Result fix = BoundSetAlgorithm.isEquivFixed(new java.util.ArrayList<>(b1),
                                                     new java.util.ArrayList<>(b2));

        assertTrue("single-42: defective returns true", def.equivalent);
        assertTrue("single-42: fixed returns true",     fix.equivalent);
        // defective: b1.containsAll(b2) = 1 comparison, b2.containsAll(b1) = 1 → total 2 = B*(B+1)=1*2
        assertEqual("single-42: defective comparisons", 2L, def.comparisons);
        // fixed: 1 element in set1 → 1 comparison
        assertEqual("single-42: fixed comparisons",     1L, fix.comparisons);
    }

    // ─── Exact comparison counts ──────────────────────────────────────────────

    /**
     * PROVES DEFECT: checking two equal B-element sets (forward vs reversed)
     * forces exactly B*(B+1) comparisons.
     *
     * Derivation (b1=[0..B-1], b2=[B-1..0]):
     *   b1.containsAll(b2): b2[0]=B-1 found at b1[B-1] → B comparisons;
     *                        b2[1]=B-2 found at b1[B-2] → B-1 comparisons; ...
     *                        Total = B + (B-1) + ... + 1 = B*(B+1)/2.
     *   b2.containsAll(b1): symmetric = B*(B+1)/2.
     *   Both execute because sets are equal (|| short-circuits only on false).
     *   Grand total: B*(B+1).
     */
    static void testDefectiveExactCounts() {
        System.out.println("[defective] isEquiv(forward, reversed, B) — expected B*(B+1):");
        int[] sizes = {5, 10, 20, 50, 100};
        for (int b : sizes) {
            List<Integer> b1 = BoundSetAlgorithm.buildForwardList(b);
            List<Integer> b2 = BoundSetAlgorithm.buildReversedList(b);
            Result r = BoundSetAlgorithm.isEquivDefective(b1, b2);
            long expected = (long) b * (b + 1);
            System.out.printf("  B=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    b, r.comparisons, expected,
                    r.comparisons == expected ? "PASS" : "FAIL expected=" + expected);
            assertEqual("defective B=" + b, expected, r.comparisons);
        }
    }

    /**
     * PROVES FIX: checking two equal B-element sets via Set.equals() requires
     * exactly B comparisons — one per element in the iteration.
     */
    static void testFixedExactCounts() {
        System.out.println("[fixed] isEquiv(forward, reversed, B) — expected B:");
        int[] sizes = {5, 10, 20, 50, 100};
        for (int b : sizes) {
            List<Integer> b1 = BoundSetAlgorithm.buildForwardList(b);
            List<Integer> b2 = BoundSetAlgorithm.buildReversedList(b);
            Result r = BoundSetAlgorithm.isEquivFixed(b1, b2);
            long expected = b;
            System.out.printf("  B=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    b, r.comparisons, expected,
                    r.comparisons == expected ? "PASS" : "FAIL");
            assertEqual("fixed B=" + b, expected, r.comparisons);
        }
    }

    // ─── Growth ratio ─────────────────────────────────────────────────────────

    /**
     * PROVES QUADRATIC GROWTH:
     * Doubling B → defective comparisons quadruple (≈4x), fixed double (≈2x).
     *
     * Math:
     *   defective(B)   = B*(B+1) ≈ B²
     *   defective(2B)  = 2B*(2B+1) ≈ 4B²  → ratio ≈ 4
     *   fixed(B)  = B,  fixed(2B) = 2B     → ratio = 2 (exact)
     */
    static void testGrowthRatio() {
        int[][] pairs = {{10, 20}, {20, 40}, {50, 100}, {100, 200}};
        for (int[] pair : pairs) {
            int b1 = pair[0], b2 = pair[1];

            long def1 = BoundSetAlgorithm.isEquivDefective(
                    BoundSetAlgorithm.buildForwardList(b1),
                    BoundSetAlgorithm.buildReversedList(b1)).comparisons;
            long def2 = BoundSetAlgorithm.isEquivDefective(
                    BoundSetAlgorithm.buildForwardList(b2),
                    BoundSetAlgorithm.buildReversedList(b2)).comparisons;
            long fix1 = BoundSetAlgorithm.isEquivFixed(
                    BoundSetAlgorithm.buildForwardList(b1),
                    BoundSetAlgorithm.buildReversedList(b1)).comparisons;
            long fix2 = BoundSetAlgorithm.isEquivFixed(
                    BoundSetAlgorithm.buildForwardList(b2),
                    BoundSetAlgorithm.buildReversedList(b2)).comparisons;

            double defRatio = (double) def2 / def1;
            double fixRatio = (double) fix2 / fix1;

            System.out.printf("  B %d→%d:  defective ratio=%.2f (expect ~4.0)  fixed ratio=%.2f (expect 2.0)%n",
                    b1, b2, defRatio, fixRatio);

            assertTrue("defective B=" + b1 + "→" + b2 + " ratio ≥ 3.8", defRatio >= 3.8);
            assertTrue("defective B=" + b1 + "→" + b2 + " ratio ≤ 4.2", defRatio <= 4.2);
            assertTrue("fixed B=" + b1 + "→" + b2 + " ratio = 2.0",     fixRatio == 2.0);
        }
    }

    // ─── Helpers ─────────────────────────────────────────────────────────────

    static void assertEqual(String name, long expected, long actual) {
        if (expected == actual) {
            System.out.printf("  PASS  %s%n", name);
            passed++;
        } else {
            System.out.printf("  FAIL  %s  expected=%d  actual=%d%n", name, expected, actual);
            failed++;
        }
    }

    static void assertTrue(String name, boolean condition) {
        if (condition) {
            System.out.printf("  PASS  %s%n", name);
            passed++;
        } else {
            System.out.printf("  FAIL  %s%n", name);
            failed++;
        }
    }
}