#!/usr/bin/env bash
# ═══════════════════════════════════════════════════════════════════════════
#  tc/netem Network Profile Manager for Tactical Shooter
#
#  Applies tc qdisc netem rules to simulate real-world network conditions
#  on the game server's port. Requires root (sudo).
#
#  Usage:
#    sudo ./netem_profiles.sh apply lan        # 0% loss, near-zero latency
#    sudo ./netem_profiles.sh apply dsl        # 0.5% loss, 20ms ±5ms
#    sudo ./netem_profiles.sh apply cellular   # 2% loss, 60ms ±20ms
#    sudo ./netem_profiles.sh apply satellite  # 1% loss, 600ms ±50ms
#    sudo ./netem_profiles.sh apply congested  # 5% loss, 100ms ±40ms, reorder
#    sudo ./netem_profiles.sh apply warzone    # 10% loss, 200ms ±60ms, burst
#    sudo ./netem_profiles.sh apply extreme    # 25% loss, 500ms ±100ms
#    sudo ./netem_profiles.sh apply edge       # 50% loss, 1000ms ±200ms (catastrophic)
#    sudo ./netem_profiles.sh off              # Remove all netem rules
#    sudo ./netem_profiles.sh status           # Show current rules
#
#  Requires: iproute2 (tc), root, IFACE (default: eth0), PORT (default: 7777)
# ═══════════════════════════════════════════════════════════════════════════

set -euo pipefail

# ─── Config ────────────────────────────────────────────────────────────────
IFACE="${NETEM_IFACE:-eth0}"
PORT="${NETEM_PORT:-7777}"
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# ─── Color ─────────────────────────────────────────────────────────────────
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
CYAN='\033[0;36m'
NC='\033[0m'

# ─── Help / Usage ──────────────────────────────────────────────────────────
usage() {
    echo "Usage: $0 {apply <profile>|off|status}"
    echo ""
    echo "Profiles:"
    echo "  lan        0% loss,      1ms    latency"
    echo "  dsl        0.5% loss,    20ms ± 5ms   jitter"
    echo "  cellular   2%   loss,    60ms ±20ms   jitter"
    echo "  satellite  1%   loss,    600ms ±50ms  jitter"
    echo "  congested  5%   loss,    100ms ±40ms  jitter, reorder 5%"
    echo "  warzone    10%  loss,    200ms ±60ms  jitter, 1% dupe, reorder 2%"
    echo "  extreme    25%  loss,    500ms ±100ms jitter, reorder 10%"
    echo "  edge       50%  loss,    1000ms ±200ms jitter (catastrophic)"
    exit 1
}

# ─── Profile definitions ───────────────────────────────────────────────────
declare -A PROFILES

# Format: loss lat jitter reorder reorder_corr dup dup_corr
# loss: percentage (0-100)
# lat: one-way latency in ms
# jitter: ±ms
# reorder: percentage of packets reordered
# reorder_corr: correlation factor for reorder (0-100)
# dup: duplicate percentage
# dup_corr: correlation factor for duplicate

PROFILES["lan"]="loss 0% delay 1ms 0ms"
PROFILES["dsl"]="loss 0.5% delay 20ms 5ms"
PROFILES["cellular"]="loss 2% delay 60ms 20ms"
PROFILES["satellite"]="loss 1% delay 600ms 50ms"
PROFILES["congested"]="loss 5% delay 100ms 40ms reorder 5% 50%"
PROFILES["warzone"]="loss 10% delay 200ms 60ms 25% duplicate 1% 25%"
PROFILES["extreme"]="loss 25% delay 500ms 100ms reorder 10% 50%"
PROFILES["edge"]="loss 50% delay 1000ms 200ms"

# ─── Apply netem to a specific port via iptables + tc mirror ───────────────
apply_netem() {
    local profile_name="$1"
    local profile_params="${PROFILES[$profile_name]:-}"
    
    if [ -z "$profile_params" ]; then
        echo -e "${RED}Unknown profile: $profile_name${NC}"
        usage
    fi
    
    echo -e "${CYAN}Applying netem profile: ${YELLOW}$profile_name${NC}"
    echo -e "  Interface: $IFACE  Port: $PORT"
    echo -e "  Parameters: $profile_params"
    echo ""
    
    # Remove existing qdisc on the root
    sudo tc qdisc del dev "$IFACE" root 2>/dev/null || true
    
    # Apply netem to ALL traffic on the interface (targeted filtering is complex)
    # To target specific ports, you'd use iptables + ifb mirroring, but for
    # dev/testing, applying to the full interface is sufficient when run on
    # a dedicated test machine.
    sudo tc qdisc add dev "$IFACE" root netem $profile_params
    
    echo -e "${GREEN}✓ Profile '$profile_name' applied${NC}"
    show_status
}

# ─── Remove all netem rules ────────────────────────────────────────────────
remove_netem() {
    echo -e "${YELLOW}Removing all netem rules on $IFACE...${NC}"
    sudo tc qdisc del dev "$IFACE" root 2>/dev/null || true
    echo -e "${GREEN}✓ Netem rules removed (interface returned to normal)${NC}"
}

# ─── Show current status ───────────────────────────────────────────────────
show_status() {
    echo ""
    echo -e "${CYAN}Current qdisc on $IFACE:${NC}"
    sudo tc qdisc show dev "$IFACE" 2>/dev/null || echo "  (no qdisc configured — interface is clean)"
    echo ""
    echo -e "${CYAN}Filter by port $PORT (iptables):${NC}"
    sudo iptables -L netem -n 2>/dev/null || echo "  (no netem iptables chain)"
}

# ─── Main ──────────────────────────────────────────────────────────────────
if [ $# -lt 1 ]; then
    usage
fi

case "$1" in
    apply)
        if [ $# -lt 2 ]; then
            echo -e "${RED}Error: 'apply' requires a profile name${NC}"
            echo ""
            usage
        fi
        apply_netem "$2"
        ;;
    off|remove|clear)
        remove_netem
        ;;
    status)
        show_status
        ;;
    *)
        usage
        ;;
esac