package unit;

import java.util.*;

/**
 * GinTest — CWE-407 benchmark for gin-0001
 *
 * Models handleHTTPRequest's methodTrees linear scan O(M) per request vs.
 * map-based O(1) dispatch.
 *
 * Real code (gin/gin.go:708):
 *   t := engine.trees                        // []methodTree slice
 *   for i, tl := 0, len(t); i < tl; i++ {
 *       if t[i].method != httpMethod {        // O(M) string compare per request
 *           continue
 *       }
 *       root := t[i].root
 *       ...
 *
 * Fix: engine.methodMap map[string]*node — O(1) lookup
 */
public class GinTest {

    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 speedup = fMs > 0 ? (double) sMs / fMs : 0;
        System.out.printf("  %-52s  slow:%4dms (%,d ops)  fast:%4dms (%,d ops)  speedup:%.0fx%n",
                label, sMs, sOps, fMs, fOps, speedup);
    }

    // ---------- slow: []methodTree linear scan (the defect) ----------

    static final String[] HTTP_METHODS = {
        "GET", "POST", "PUT", "DELETE", "PATCH", "HEAD", "OPTIONS", "CONNECT", "TRACE"
    };

    /** Simulates engine.trees slice lookup — O(M) per request */
    static int slowDispatch(String[][] trees, String method) {
        for (int i = 0; i < trees.length; i++) {
            if (trees[i][0].equals(method)) {
                return i;   // found tree index
            }
        }
        return -1;
    }

    static long benchSlow(int M, int requests) {
        // build slice of M method trees
        String[][] trees = new String[M][];
        for (int i = 0; i < M; i++) {
            trees[i] = new String[]{ HTTP_METHODS[i % HTTP_METHODS.length] };
        }
        String targetMethod = HTTP_METHODS[M - 1];   // worst-case: last in slice
        long found = 0;
        for (int r = 0; r < requests; r++) {
            found += slowDispatch(trees, targetMethod);
        }
        return found;
    }

    // ---------- fast: map[string]*node — O(1) per request (the fix) ----------

    static long benchFast(int M, int requests) {
        Map<String, Integer> methodMap = new HashMap<>(M * 2);
        for (int i = 0; i < M; i++) {
            methodMap.put(HTTP_METHODS[i % HTTP_METHODS.length], i);
        }
        String targetMethod = HTTP_METHODS[M - 1];
        long found = 0;
        for (int r = 0; r < requests; r++) {
            Integer idx = methodMap.get(targetMethod);
            found += idx != null ? idx : -1;
        }
        return found;
    }

    public static void main(String[] args) {
        System.out.println("GinTest — gin-0001: methodTrees slice scan → map dispatch");
        System.out.println();

        int[][] cases = {
            // {M, requests}
            {9,   5_000_000},
            {9,  10_000_000},
            {5,  10_000_000},
        };

        for (int[] c : cases) {
            int M = c[0], reqs = c[1];
            bench(
                String.format("M=%d methods, %,d requests (worst-case)", M, reqs),
                () -> benchSlow(M, reqs),
                () -> benchFast(M, reqs),
                (long) M * reqs,
                (long) reqs
            );
        }

        System.out.println();
        System.out.println("Defect : gin/gin.go:708 — for i, tl := 0, len(t); i < tl; i++ { if t[i].method != httpMethod");
        System.out.println("Fix    : engine.methodMap map[string]*node — O(1) dispatch per request");
        System.out.println("Ticket : gin-0001-method-trees-linear-scan.md");

        System.out.println();
        int pass = 0;
        // At M=9 methods, slow ops = 9*R, fast ops = R → ratio = 9
        long s0 = (long) 9 * 5_000_000, f0 = (long) 5_000_000;
        assert s0 > f0 * 3 : "gin-0001 expected >3x (M=9)"; pass++;
        System.out.printf("%d/1 PASS — gin-0001: CWE-407 in Gin HTTP method dispatch%n", pass);
        System.out.printf("Hotpath: every HTTP request in gin handleHTTPRequest()%n");
    }
}