package unit;

import support.ClosureAlgorithm;
import support.ClosureAlgorithm.Result;

import java.util.Set;

/**
 * Unit tests for DEFECT 0002b: InferenceGraph.Node.closure() uncached DFS.
 *
 * Proves:
 *   1. Both implementations produce identical closure sets (correctness).
 *   2. Defective version visits exactly K*V nodes for K calls on a V-node chain.
 *   3. Fixed version visits exactly V+(K-1) nodes for the same K calls.
 *   4. Doubling K doubles defective work; fixed is nearly constant.
 *
 * No build tool required. Compile and run:
 *
 *   cd tests
 *   java -m jdk.compiler/com.sun.tools.javac.Main -cp . \
 *        support/ClosureAlgorithm.java unit/ClosureComplexityTest.java
 *   java -cp . unit.ClosureComplexityTest
 */
public class ClosureComplexityTest {

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

    public static void main(String[] args) {
        System.out.println("=== ClosureComplexityTest (DEFECT 0002b) ===\n");

        System.out.println("-- Correctness: both versions return same closure set --");
        testCorrectnessSmall();
        testCorrectnessMedium();

        System.out.println("\n-- Complexity: defective visits K*V nodes --");
        testDefectiveExactCounts();

        System.out.println("\n-- Complexity: fixed visits V+(K-1) nodes --");
        testFixedExactCounts();

        System.out.println("\n-- Complexity: growth ratio proves linear vs constant in K --");
        testGrowthRatioInK();

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

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

    static void testCorrectnessSmall() {
        int v = 5, k = 3;
        ClosureAlgorithm.Node startDef = ClosureAlgorithm.buildLinearChain(v);
        ClosureAlgorithm.Node startFix = ClosureAlgorithm.buildLinearChain(v);

        Result def = ClosureAlgorithm.closureDefective(startDef, k);
        Result fix = ClosureAlgorithm.closureFixed(startFix, k);

        assertEqual("small: defective closure size", v, def.closure.size());
        assertEqual("small: fixed closure size",     v, fix.closure.size());
    }

    static void testCorrectnessMedium() {
        int v = 20, k = 5;
        ClosureAlgorithm.Node startDef = ClosureAlgorithm.buildLinearChain(v);
        ClosureAlgorithm.Node startFix = ClosureAlgorithm.buildLinearChain(v);

        Result def = ClosureAlgorithm.closureDefective(startDef, k);
        Result fix = ClosureAlgorithm.closureFixed(startFix, k);

        assertEqual("medium: defective closure size", v, def.closure.size());
        assertEqual("medium: fixed closure size",     v, fix.closure.size());
    }

    // ─── Exact node-visit counts ──────────────────────────────────────────────

    /**
     * PROVES DEFECT: K calls on a V-node chain visit exactly K*V nodes total.
     * Each call reruns the full DFS with no memory of previous calls.
     */
    static void testDefectiveExactCounts() {
        System.out.println("[defective] closureDefective(chain(V), K) — expected K*V:");
        int[][] cases = {{10, 5}, {20, 5}, {10, 10}, {20, 10}, {50, 20}};
        for (int[] c : cases) {
            int v = c[0], k = c[1];
            ClosureAlgorithm.Node start = ClosureAlgorithm.buildLinearChain(v);
            Result r = ClosureAlgorithm.closureDefective(start, k);
            long expected = (long) k * v;
            System.out.printf("  V=%-4d K=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    v, k, r.nodeVisits, expected,
                    r.nodeVisits == expected ? "PASS" : "FAIL expected=" + expected);
            assertEqual("defective V=" + v + " K=" + k, expected, r.nodeVisits);
        }
    }

    /**
     * PROVES FIX: K calls on a V-node chain visit exactly V+(K-1) nodes total.
     * First call runs the DFS (V visits), each of the K-1 subsequent calls
     * finds the cached result (1 visit each).
     */
    static void testFixedExactCounts() {
        System.out.println("[fixed] closureFixed(chain(V), K) — expected V+(K-1):");
        int[][] cases = {{10, 5}, {20, 5}, {10, 10}, {20, 10}, {50, 20}};
        for (int[] c : cases) {
            int v = c[0], k = c[1];
            ClosureAlgorithm.Node start = ClosureAlgorithm.buildLinearChain(v);
            Result r = ClosureAlgorithm.closureFixed(start, k);
            long expected = v + (k - 1);
            System.out.printf("  V=%-4d K=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    v, k, r.nodeVisits, expected,
                    r.nodeVisits == expected ? "PASS" : "FAIL expected=" + expected);
            assertEqual("fixed V=" + v + " K=" + k, expected, r.nodeVisits);
        }
    }

    // ─── Growth ratio (in K dimension) ────────────────────────────────────────

    /**
     * PROVES LINEAR GROWTH OF DEFECT IN K:
     * Doubling K → defective visits double (≈2x), fixed barely changes.
     *
     * Math (V=100 fixed):
     *   defective(K)   = K*V    → doubles when K doubles
     *   defective(2K)  = 2K*V   → ratio = 2.0 (exact)
     *
     *   fixed(K)   = V + (K-1)
     *   fixed(2K)  = V + (2K-1)
     *   ratio = (V+2K-1)/(V+K-1)  → 1 as V≫K (nearly constant)
     */
    static void testGrowthRatioInK() {
        int v = 100;
        int[][] kPairs = {{5, 10}, {10, 20}, {20, 40}};
        for (int[] pair : kPairs) {
            int k1 = pair[0], k2 = pair[1];

            ClosureAlgorithm.Node startDef1 = ClosureAlgorithm.buildLinearChain(v);
            ClosureAlgorithm.Node startDef2 = ClosureAlgorithm.buildLinearChain(v);
            ClosureAlgorithm.Node startFix1 = ClosureAlgorithm.buildLinearChain(v);
            ClosureAlgorithm.Node startFix2 = ClosureAlgorithm.buildLinearChain(v);

            long def1 = ClosureAlgorithm.closureDefective(startDef1, k1).nodeVisits;
            long def2 = ClosureAlgorithm.closureDefective(startDef2, k2).nodeVisits;
            long fix1 = ClosureAlgorithm.closureFixed(startFix1, k1).nodeVisits;
            long fix2 = ClosureAlgorithm.closureFixed(startFix2, k2).nodeVisits;

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

            System.out.printf("  V=%d K %d→%d:  defective ratio=%.2f (expect 2.0)  fixed ratio=%.2f (expect <1.2)%n",
                    v, k1, k2, defRatio, fixRatio);

            // Defective doubles exactly when K doubles (defective = K*V)
            assertTrue("defective K=" + k1 + "→" + k2 + " ratio = 2.0", defRatio == 2.0);
            // Fixed changes very little (V dominates K for V=100)
            assertTrue("fixed K=" + k1 + "→" + k2 + " ratio < 1.2",    fixRatio < 1.2);
        }
    }

    // ─── 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++;
        }
    }
}