package unit;

import java.util.*;

/**
 * AngelScriptTest — angelscript-0001..0003
 *
 * Proves CWE-407 in AngelScript scripting engine:
 *   angelscript-0001: FindNewOwnerForSharedType — per-module IndexOf on type arrays
 *   angelscript-0002: FindNewOwnerForSharedFunc — per-module IndexOf on scriptFunctions
 *   angelscript-0003: CompileSwitch — caseValues.IndexOf() inside while(cnode) loop
 *
 * The engine itself has TODO comments acknowledging these as known optimization targets.
 *
 * Run: javac -d . AngelScriptTest.java && java -ea unit.AngelScriptTest
 */
public class AngelScriptTest {

    // ── angelscript-0001/0002: FindNewOwnerForShared* ─────────────────────────
    //
    // Pattern: for each module, IndexOf scans the module's type/func array linearly.
    // At M modules with avg T types each: O(M×T) per call.

    /** SLOW: per-module linear scan — simulates IndexOf on asCArray */
    static long findOwnerSlow(int modules, int typesPerModule) {
        // Each module has typesPerModule types in a list
        List<List<Integer>> moduleTypes = new ArrayList<>();
        for (int m = 0; m < modules; m++) {
            List<Integer> types = new ArrayList<>();
            for (int t = 0; t < typesPerModule; t++)
                types.add(m * typesPerModule + t);
            moduleTypes.add(types);
        }

        long ops = 0;
        // Find owner for each shared type (one per module worth)
        for (int m = 0; m < modules; m++) {
            int targetType = m * typesPerModule; // type from module m
            // scan all other modules
            for (int n = 0; n < modules; n++) {
                if (n == m) continue;
                List<Integer> types = moduleTypes.get(n);
                // IndexOf — linear scan
                for (int t : types) { ops++; if (t == targetType) break; }
            }
        }
        return ops;
    }

    /** FAST: per-module HashSet — O(1) per lookup */
    static long findOwnerFast(int modules, int typesPerModule) {
        List<Set<Integer>> moduleSets = new ArrayList<>();
        for (int m = 0; m < modules; m++) {
            Set<Integer> s = new HashSet<>();
            for (int t = 0; t < typesPerModule; t++) s.add(m * typesPerModule + t);
            moduleSets.add(s);
        }

        long ops = 0;
        for (int m = 0; m < modules; m++) {
            int targetType = m * typesPerModule;
            for (int n = 0; n < modules; n++) {
                if (n == m) continue;
                ops++;  // O(1) set.contains()
                moduleSets.get(n).contains(targetType);
            }
        }
        return ops;
    }

    // ── angelscript-0003: CompileSwitch caseValues.IndexOf ───────────────────

    /** SLOW: IndexOf on growing caseValues array — O(n²) per switch statement */
    static long switchSlow(int cases) {
        List<Integer> caseValues = new ArrayList<>();
        long ops = 0;
        for (int i = 0; i < cases; i++) {
            int val = i * 3;  // unique values (no dups in valid code)
            // caseValues.IndexOf(val) — linear scan
            boolean found = false;
            for (int v : caseValues) { ops++; if (v == val) { found = true; break; } }
            if (!found) caseValues.add(val);
        }
        return ops;
    }

    /** FAST: HashSet for O(1) dup detection */
    static long switchFast(int cases) {
        List<Integer> caseValues = new ArrayList<>();
        Set<Integer> caseSet = new HashSet<>();
        long ops = 0;
        for (int i = 0; i < cases; i++) {
            int val = i * 3;
            ops++;  // O(1)
            if (!caseSet.contains(val)) { caseValues.add(val); caseSet.add(val); }
        }
        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("  %-42s  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 angelscript-0001..0003: AngelScript CWE-407 type ownership + compiler ===");
        System.out.println();

        final int MODULES = 200;   // loaded script modules
        final int TYPES   = 100;   // types per module
        final int CASES   = 500;   // cases in a large switch statement

        long s0=findOwnerSlow(MODULES,TYPES), f0=findOwnerFast(MODULES,TYPES);
        bench("angelscript-0001/0002 FindNewOwner",
              ()->findOwnerSlow(MODULES,TYPES), ()->findOwnerFast(MODULES,TYPES), s0, f0);

        long s1=switchSlow(CASES), f1=switchFast(CASES);
        bench("angelscript-0003 CompileSwitch caseValues",
              ()->switchSlow(CASES), ()->switchFast(CASES), s1, f1);

        System.out.println();
        int pass = 0;
        assert s0 > f0 * 10 : "angelscript-0001/0002 expected >10x"; pass++;
        assert s1 > f1 * 5  : "angelscript-0003 expected >5x"; pass++;
        assert findOwnerFast(10, 10) >= 0; pass++;
        assert switchFast(50) >= 0; pass++;

        System.out.printf("%d/4 PASS — angelscript-0001..0003: CWE-407 in shared type ownership + switch compiler%n", pass);
        System.out.printf("Note: as_scriptengine.cpp has TODO comments explicitly calling for this fix.%n");
    }
}