package unit;

import java.util.*;

/**
 * haproxy-0004 — CWE-407: http_capture_headers O(H×C) per request
 *
 * Models http_ana.c http_capture_headers():
 *   Slow: for each of H request headers, walk C-entry cap_hdr linked list (O(C))
 *         → O(H × C) per request
 *   Fast: pre-build HashMap<name,cap_hdr> at config time → O(H) per request
 *
 * Hot path: called on every HTTP request and response when `capture request header`
 * directives are configured.
 */
public class HaproxyCaptureHeadersAlgorithmTest {

    // Simulates a cap_hdr linked-list entry (from include/haproxy/capture-t.h)
    static class CapHdr {
        final String name;
        final int index;
        CapHdr next;
        CapHdr(String name, int index) { this.name = name; this.index = index; }
    }

    // Simulates an HTTP header (name + value)
    static class HttpHeader {
        final String name;
        final String value;
        HttpHeader(String name, String value) { this.name = name; this.value = value; }
    }

    // --- SLOW: O(H × C) per request (defect) ---
    // Models: for each htx header → for each cap_hdr → strncasecmp
    static long captureHeadersSlow(List<HttpHeader> headers, CapHdr capHdrHead) {
        long ops = 0;
        String[] cap = new String[64];

        for (HttpHeader hdr : headers) {
            for (CapHdr h = capHdrHead; h != null; h = h.next) {
                ops++;  // strncasecmp call
                if (h.name.equalsIgnoreCase(hdr.name)) {
                    if (cap[h.index] == null)
                        cap[h.index] = hdr.value;
                }
            }
        }
        return ops;
    }

    // --- FAST: O(H) per request (fix) ---
    // Models: pre-built HashMap<lowercaseName, cap_hdr> at config time
    static long captureHeadersFast(List<HttpHeader> headers,
                                   Map<String, CapHdr> capHdrMap) {
        long ops = 0;
        String[] cap = new String[64];

        for (HttpHeader hdr : headers) {
            ops++;  // O(1) hash lookup
            CapHdr h = capHdrMap.get(hdr.name.toLowerCase());
            if (h != null && cap[h.index] == null)
                cap[h.index] = hdr.value;
        }
        return ops;
    }

    // Build cap_hdr linked list
    static CapHdr buildCapHdrList(int count) {
        CapHdr head = null;
        for (int i = count - 1; i >= 0; i--) {
            CapHdr h = new CapHdr("X-Custom-Header-" + i, i);
            h.next = head;
            head = h;
        }
        return head;
    }

    // Build pre-indexed cap_hdr map
    static Map<String, CapHdr> buildCapHdrMap(CapHdr head) {
        Map<String, CapHdr> map = new HashMap<>();
        for (CapHdr h = head; h != null; h = h.next)
            map.put(h.name.toLowerCase(), h);
        return map;
    }

    // Build HTTP request headers list
    static List<HttpHeader> buildHeaders(int count, int captureHits) {
        List<HttpHeader> headers = new ArrayList<>();
        for (int i = 0; i < count; i++) {
            String name;
            if (i < captureHits)
                name = "X-Custom-Header-" + i;  // will match cap_hdr
            else
                name = "Standard-Header-" + i;  // won't match cap_hdr
            headers.add(new HttpHeader(name, "value-" + i));
        }
        return headers;
    }

    public static void main(String[] args) {
        System.out.println("haproxy-0004 CWE-407: http_capture_headers O(H*C) vs O(H)");
        System.out.println("==========================================================");

        // Parameters: H request headers, C capture headers configured
        int[][] params = { {30, 10}, {50, 20}, {100, 50} };

        for (int[] p : params) {
            int H = p[0], C = p[1];
            CapHdr capHdrHead = buildCapHdrList(C);
            Map<String, CapHdr> capHdrMap = buildCapHdrMap(capHdrHead);
            List<HttpHeader> headers = buildHeaders(H, C / 2);

            long slowOps = captureHeadersSlow(headers, capHdrHead);
            long fastOps = captureHeadersFast(headers, capHdrMap);
            double ratio = (double) slowOps / fastOps;

            System.out.printf("  H=%3d headers, C=%2d captures: slow=%,5d ops  fast=%,3d ops  speedup=%.0fx%n",
                    H, C, slowOps, fastOps, ratio);

            assert ratio >= (double) C / 2 :
                "Expected speedup >= " + (C/2) + "x but got " + ratio;
        }

        System.out.println("\nPASS");
    }
}