package unit;

import support.Moad0011Algorithm;
import support.Moad0011Algorithm.Result;

/**
 * Unit tests for MOAD-0011: CWE-1333 — A Catastrophic Inheritance.
 *
 * Proves from first principles:
 *   1. Structural: hasCatastrophicStructure() detects nested quantifiers in
 *      known-bad patterns and passes known-safe patterns.
 *   2. Behavioral (step counting): defective NFA for (a+)+b explores
 *      exponentially many states on adversarial input; fixed NFA is linear.
 *   3. Growth: doubling adversarial input length more than doubles defective
 *      steps (super-linear / exponential growth); fixed steps grow exactly linearly.
 *   4. Both produce identical match results on matching and non-matching inputs.
 *
 * The step-counting NFA proves the algorithmic complexity without relying on
 * wall-clock timing — suitable for deterministic unit testing.  Functional tests
 * use a timed match on a moderate adversarial input to prove behavioral impact.
 *
 * No build tool required. Compile and run:
 *
 *   cd tests
 *   java -m jdk.compiler/com.sun.tools.javac.Main -cp . \
 *        support/Moad0011Algorithm.java unit/Moad0011UnitTest.java
 *   java -cp . unit.Moad0011UnitTest
 */
public class Moad0011UnitTest {

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

    public static void main(String[] args) {
        System.out.println("=== Moad0011UnitTest (A Catastrophic Inheritance) ===\n");

        System.out.println("-- Structural detection: hasCatastrophicStructure() --");
        testDetectsKnownBadPatterns();
        testPassesKnownSafePatterns();

        System.out.println("\n-- Correctness: both produce identical match results --");
        testBothMatchMatchingInput();
        testBothRejectNonMatchingInput();
        testBothMatchSingleA();

        System.out.println("\n-- Defect: step count grows super-linearly on adversarial input --");
        testDefectiveStepCountExponentialGrowth();
        testDefectiveAdversarialN8IsLarge();

        System.out.println("\n-- Fix: step count grows linearly on adversarial input --");
        testFixedStepCountLinearGrowth();
        testFixedAdversarialN8IsSmall();

        System.out.println("\n-- Ratio: defective steps >> fixed steps on adversarial input --");
        testStepRatioAdvantageForFixed();

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

    // ── Structural detection ──────────────────────────────────────────────────

    static void testDetectsKnownBadPatterns() {
        String[] bad = {
            "(a+)+b",           // classic ReDoS — outer + wraps inner a+
            "(a+)+",            // same, no terminal
            "(a*)+",            // inner * outer +
            "(ab+c*)+",         // complex inner group with quantifiers
            Moad0011Algorithm.DEFECTIVE_PATTERN_BLEACH,
            Moad0011Algorithm.DEFECTIVE_PATTERN_CSS,
        };
        for (String p : bad) {
            assertTrue("detects bad pattern: " + p,
                Moad0011Algorithm.hasCatastrophicStructure(p),
                "expected catastrophic, got safe");
        }
    }

    static void testPassesKnownSafePatterns() {
        String[] safe = {
            "a+b",              // simple concatenation — no nesting
            "a+",               // single quantifier
            "(a|b)+",           // alternation with outer +, no inner quantifier
            "[a-z]+",           // character class, single quantifier
            "(abc)+",           // fixed group, no inner quantifier
            Moad0011Algorithm.FIXED_PATTERN_BLEACH,
            Moad0011Algorithm.FIXED_PATTERN_CSS,
        };
        for (String p : safe) {
            assertFalse("passes safe pattern: " + p,
                Moad0011Algorithm.hasCatastrophicStructure(p),
                "expected safe, got catastrophic");
        }
    }

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

    static void testBothMatchMatchingInput() {
        String input = Moad0011Algorithm.matchingInput(5); // "aaaaab"
        Result def = Moad0011Algorithm.matchDefective(input);
        Result fix = Moad0011Algorithm.matchFixed(input);
        assertTrue("defective: matches 'aaaaab'", def.matched, "expected match");
        assertTrue("fixed: matches 'aaaaab'",     fix.matched, "expected match");
    }

    static void testBothRejectNonMatchingInput() {
        String input = Moad0011Algorithm.adversarialInput(5); // "aaaaac" — no 'b'
        Result def = Moad0011Algorithm.matchDefective(input);
        Result fix = Moad0011Algorithm.matchFixed(input);
        assertFalse("defective: rejects 'aaaaac'", def.matched, "expected no match");
        assertFalse("fixed: rejects 'aaaaac'",     fix.matched, "expected no match");
    }

    static void testBothMatchSingleA() {
        String input = "ab";
        Result def = Moad0011Algorithm.matchDefective(input);
        Result fix = Moad0011Algorithm.matchFixed(input);
        assertTrue("defective: matches 'ab'", def.matched, "expected match");
        assertTrue("fixed: matches 'ab'",     fix.matched, "expected match");
    }

    // ── Defect ────────────────────────────────────────────────────────────────

    static void testDefectiveStepCountExponentialGrowth() {
        // Adversarial input: N a's + 'c' — non-matching, forces maximum backtracking
        long steps4  = Moad0011Algorithm.matchDefective(Moad0011Algorithm.adversarialInput(4)).steps;
        long steps6  = Moad0011Algorithm.matchDefective(Moad0011Algorithm.adversarialInput(6)).steps;
        long steps8  = Moad0011Algorithm.matchDefective(Moad0011Algorithm.adversarialInput(8)).steps;

        // Exponential growth: steps8 >> steps6 >> steps4
        // Ratio should be super-linear (greater than linear doubling)
        double ratio64 = (double) steps6 / steps4;
        double ratio86 = (double) steps8 / steps6;

        assertTrue("defective: steps grow super-linearly from N=4 to N=6 (ratio > 2.0)",
            ratio64 > 2.0, "ratio64=" + ratio64);
        assertTrue("defective: steps grow super-linearly from N=6 to N=8 (ratio > 2.0)",
            ratio86 > 2.0, "ratio86=" + ratio86);

        System.out.printf("    steps N=4: %d, N=6: %d, N=8: %d (ratios: %.1fx, %.1fx)%n",
            steps4, steps6, steps8, ratio64, ratio86);
    }

    static void testDefectiveAdversarialN8IsLarge() {
        long steps = Moad0011Algorithm.matchDefective(Moad0011Algorithm.adversarialInput(8)).steps;
        // N=8 adversarial input: expect hundreds or thousands of steps (super-linear)
        assertTrue("defective: N=8 adversarial input requires many steps (>50)",
            steps > 50, "steps=" + steps);
    }

    // ── Fix ───────────────────────────────────────────────────────────────────

    static void testFixedStepCountLinearGrowth() {
        long steps4  = Moad0011Algorithm.matchFixed(Moad0011Algorithm.adversarialInput(4)).steps;
        long steps8  = Moad0011Algorithm.matchFixed(Moad0011Algorithm.adversarialInput(8)).steps;
        long steps16 = Moad0011Algorithm.matchFixed(Moad0011Algorithm.adversarialInput(16)).steps;

        // Linear growth: doubling N should roughly double steps (ratio ~2x)
        double ratio84  = (double) steps8  / steps4;
        double ratio168 = (double) steps16 / steps8;

        // Allow ratio up to 3.0 to be generous with small constants, but it must not be exponential
        assertTrue("fixed: doubling N from 4 to 8 roughly doubles steps (ratio 1.0-3.0)",
            ratio84 >= 1.0 && ratio84 <= 3.0, "ratio84=" + ratio84);
        assertTrue("fixed: doubling N from 8 to 16 roughly doubles steps (ratio 1.0-3.0)",
            ratio168 >= 1.0 && ratio168 <= 3.0, "ratio168=" + ratio168);

        System.out.printf("    steps N=4: %d, N=8: %d, N=16: %d (ratios: %.1fx, %.1fx)%n",
            steps4, steps8, steps16, ratio84, ratio168);
    }

    static void testFixedAdversarialN8IsSmall() {
        long steps = Moad0011Algorithm.matchFixed(Moad0011Algorithm.adversarialInput(8)).steps;
        // Fixed NFA: O(N) steps — N=8 means steps should be a small multiple of 8
        assertTrue("fixed: N=8 adversarial requires <= 20 steps (linear)",
            steps <= 20, "steps=" + steps);
    }

    // ── Ratio ─────────────────────────────────────────────────────────────────

    static void testStepRatioAdvantageForFixed() {
        String adversarial = Moad0011Algorithm.adversarialInput(10);
        long defSteps = Moad0011Algorithm.matchDefective(adversarial).steps;
        long fixSteps = Moad0011Algorithm.matchFixed(adversarial).steps;

        // At N=10, defective explores exponentially many states vs fixed linear scan
        double ratio = (double) defSteps / fixSteps;
        assertTrue("defective steps >> fixed steps at N=10 adversarial (ratio > 10x)",
            ratio > 10.0, "defSteps=" + defSteps + " fixSteps=" + fixSteps + " ratio=" + ratio);

        System.out.printf("    N=10 adversarial: defective=%d steps, fixed=%d steps (%.0fx advantage)%n",
            defSteps, fixSteps, ratio);
    }

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

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

    static void assertFalse(String label, boolean condition, String detail) {
        assertTrue(label, !condition, detail);
    }
}