Feat: Add LAN/WAN simulation to compare_rsync.sh

Added latency simulation support to compare_rsync.sh with:
- Direct latency value: ./compare_rsync.sh 100 1 20 (20ms RTT)
- Preset profiles: ./compare_rsync.sh 100 1 --lan (10ms) or --wan (100ms)
- tc netem integration for network delay simulation
- Clean display of network condition in output

This brings compare_rsync.sh in line with benchmark.sh and
benchmark_comprehensive.sh which already supported latency simulation.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

compare_rsync.sh

@@ -1,8 +1,85 @@
+# compare_rsync.sh — Compare fastSyncAI performance against rsync
+#
+# Usage:
+#   ./compare_rsync.sh [DATA_SIZE_MB] [RUN_COUNT]
+#
+# Examples:
+#   ./compare_rsync.sh          # 100 MB, 3 runs (default)
+#   ./compare_rsync.sh 500      # 500 MB, 3 runs
+#   ./compare_rsync.sh 100 5    # 100 MB, 5 runs
+#
+# Tests:
+#   - Small files (many files, 256KB each)
+#   - Medium files (fewer files, 1-5MB each)
+#   - Large single file
+#   - Mixed directory structure
+#
+# Compares: fastSyncAI (TCP, multi-connection) vs rsync vs rsync with compression
+# =============================================================================
+
+set -euo pipefail
+
+# ── Defaults ──────────────────────────────────────────────────────────────
+DATA_SIZE_MB=${1:-100}
+RUN_COUNT=${2:-3}
+PORT=19199
+HOST="127.0.0.1"
+=======
 #!/usr/bin/env bash
 # =============================================================================
 # compare_rsync.sh — Compare fastSyncAI performance against rsync
 #
 # Usage:
+#   ./compare_rsync.sh [DATA_SIZE_MB] [RUN_COUNT] [LATENCY_MS|--lan|--wan]
+#
+# Examples:
+#   ./compare_rsync.sh                          # 100 MB, 3 runs, no latency
+#   ./compare_rsync.sh 500                      # 500 MB, 3 runs, no latency
+#   ./compare_rsync.sh 100 5                    # 100 MB, 5 runs, no latency
+#   ./compare_rsync.sh 100 1 20                 # 100 MB, 1 run, 20ms RTT (LAN-like)
+#   ./compare_rsync.sh 100 1 100                # 100 MB, 1 run, 100ms RTT (WAN-like)
+#   ./compare_rsync.sh 100 1 --lan              # 100 MB, 1 run, 10ms RTT (LAN preset)
+#   ./compare_rsync.sh 100 1 --wan              # 100 MB, 1 run, 100ms RTT (WAN preset)
+#
+# Tests:
+#   - Small files (many files, 256KB each)
+#   - Medium files (fewer files, 1-5MB each)
+#   - Large single file
+#   - Mixed directory structure
+#
+# Compares: fastSyncAI (TCP, multi-connection) vs rsync vs rsync with compression
+#
+# Network Presets:
+#   --lan   : 10ms RTT (typical LAN)
+#   --wan   : 100ms RTT (typical WAN)
+# =============================================================================
+
+set -euo pipefail
+
+# ── Defaults ──────────────────────────────────────────────────────────────
+DATA_SIZE_MB=${1:-100}
+RUN_COUNT=${2:-3}
+
+# ── Parse latency argument ────────────────────────────────────────────────
+LATENCY_MS=0
+if [ $# -ge 3 ]; then
+    case "${3}" in
+        --lan)   LATENCY_MS=10  ;;
+        --wan)   LATENCY_MS=100 ;;
+        *)
+            # Check if it's a numeric value
+            if [[ "${3}" =~ ^[0-9]+$ ]]; then
+                LATENCY_MS="${3}"
+            fi
+            ;;
+    esac
+fi
+
+PORT=19199
+HOST="127.0.0.1"=============================================================================
+# compare_rsync.sh — Compare fastSyncAI performance against rsync
+#
+# Usage:
 #   ./compare_rsync.sh [DATA_SIZE_MB] [RUN_COUNT]
 #
 # Examples:
@@ -45,12 +122,35 @@ info() { echo -e "${CYAN}▶ $*${RESET}"; }
 ok()   { echo -e "${GREEN}✓ $*${RESET}"; }
 warn() { echo -e "${YELLOW}⚠ $*${RESET}"; }
 
+# ── Latency simulation (tc netem) ────────────────────────────────────────
+setup_latency() {
+    if [ "$LATENCY_MS" -gt 0 ]; then
+        info "Adding ${LATENCY_MS}ms RTT latency to lo via tc netem..."
+        if ! sudo -n true 2>/dev/null; then
+            echo -e "${YELLOW}⚠ sudo required for tc netem — enter password if prompted${RESET}"
+        fi
+        local half=$(( LATENCY_MS / 2 ))
+        sudo tc qdisc del dev lo root 2>/dev/null || true
+        sudo tc qdisc add dev lo root netem delay "${half}ms" || \
+            die "tc netem failed. Install iproute2 or run without latency argument."
+        ok "Latency applied (${half}ms one-way = ${LATENCY_MS}ms RTT)"
+    fi
+}
+
+cleanup_latency() {
+    if [ "$LATENCY_MS" -gt 0 ]; then
+        sudo tc qdisc del dev lo root 2>/dev/null || true
+        ok "Latency removed"
+    fi
+}
+
 # ── Sanity checks ──────────────────────────────────────────────────────────
 [ -x "$SERVER_BIN" ] || die "Server binary not found: $SERVER_BIN — run 'make' first."
 [ -x "$CLIENT_BIN" ] || die "Client binary not found: $CLIENT_BIN — run 'make' first."
 command -v rsync >/dev/null 2>&1 || die "rsync not found. Install rsync first."
 
 cleanup() {
+    cleanup_latency
     pkill -f "fastsync_server" 2>/dev/null || true
     pkill -f "fastsync_client" 2>/dev/null || true
     rm -rf "$TEST_DIR"
@@ -258,9 +358,23 @@ echo -e "${BOLD}╔════════════════════
 echo -e "${BOLD}║        fastSyncAI vs rsync — Performance Comparison             ║${RESET}"
 echo -e "${BOLD}╚══════════════════════════════════════════════════════════════╝${RESET}"
 echo ""
-echo -e "  Data size     : ${CYAN}${DATA_SIZE_MB} MB${RESET}"
+
-echo -e "  Runs per test : ${CYAN}${RUN_COUNT}${RESET}"
+# Display network condition
-echo -e "  Server port   : ${CYAN}${PORT}${RESET}"
+if [ "$LATENCY_MS" -gt 0 ]; then
+    echo -e "  Data size     : ${CYAN}${DATA_SIZE_MB} MB${RESET}"
+    echo -e "  Runs per test : ${CYAN}${RUN_COUNT}${RESET}"
+    echo -e "  Network       : ${CYAN}${LATENCY_MS}ms RTT${RESET}"
+    echo -e "  Server port   : ${CYAN}${PORT}${RESET}"
+else
+    echo -e "  Data size     : ${CYAN}${DATA_SIZE_MB} MB${RESET}"
+    echo -e "  Runs per test : ${CYAN}${RUN_COUNT}${RESET}"
+    echo -e "  Network       : ${GREEN}no latency (loopback)${RESET}"
+    echo -e "  Server port   : ${CYAN}${PORT}${RESET}"
+fi
+echo ""
+
+# Setup latency if configured
+setup_latency
 echo ""
 
 # Collect all results