#!/usr/bin/env bash

echo "========================================="
echo " Keepalived HA Full Stack Generator"
echo " (Configs + Systemd + Diagram)"
echo "========================================="
echo ""

read -p "Service name (e.g. DNS / API / Nginx): " SERVICE
read -p "MASTER Router ID: " MASTER_ID
read -p "MASTER node IP: " MASTER_IP
echo ""

read -p "How many BACKUP nodes? " BACKUP_COUNT

declare -a BACKUP_IDS
declare -a BACKUP_IPS

for ((i=1; i<=BACKUP_COUNT; i++))
do
    echo "-----------------------------------"
    echo "Backup #$i"
    read -p "Router ID: " RID
    read -p "Node IP: " IP

    BACKUP_IDS[$i]=$RID
    BACKUP_IPS[$i]=$IP
done

echo ""
read -p "How many VIP instances? " INSTANCE_COUNT
echo ""

read -p "Use health check script? (y/n): " USE_SCRIPT

if [[ "$USE_SCRIPT" == "y" ]]; then
    read -p "Health check script path: " HEALTH_SCRIPT
else
    HEALTH_SCRIPT=""
fi

MASTER_CONF="keepalived-${SERVICE}-${MASTER_ID}.conf"
BACKUP_PREFIX="keepalived-${SERVICE}-backup"

SYSTEMD_DIR="systemd-${SERVICE}"
DIAGRAM_FILE="${SERVICE}-ha-diagram.md"

mkdir -p "$SYSTEMD_DIR"

# ---------------- SYSTEMD ----------------

cat > "$SYSTEMD_DIR/keepalived.service" <<EOF
[Unit]
Description=Keepalived High Availability Service ($SERVICE)
After=network-online.target
Wants=network-online.target

[Service]
Type=forking
ExecStart=/usr/sbin/keepalived --dont-fork
ExecReload=/bin/kill -HUP \$MAINPID
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target
EOF

# ---------------- DIAGRAM HEADER ----------------

cat > "$DIAGRAM_FILE" <<EOF
# $SERVICE High Availability Diagram

\`\`\`mermaid
flowchart LR

VIP[(Virtual IPs)]

MASTER[$MASTER_ID\\n$MASTER_IP]

VIP --> MASTER
EOF

for ((b=1; b<=BACKUP_COUNT; b++))
do
cat >> "$DIAGRAM_FILE" <<EOF
B$b[${BACKUP_IDS[$b]}\\n${BACKUP_IPS[$b]}]
VIP -. failover .-> B$b
EOF
done

cat >> "$DIAGRAM_FILE" <<EOF

style MASTER fill:#4caf50,stroke:#000,color:#fff
style VIP fill:#2196f3,stroke:#000,color:#fff
\`\`\`
EOF

# ---------------- CONFIG FILES ----------------

write_global() {
cat <<EOF
global_defs {
    router_id $1
    enable_script_security
    script_user root
}
EOF
}

write_script() {
if [[ -n "$HEALTH_SCRIPT" ]]; then
cat <<EOF

vrrp_script chk_service {
    script "$HEALTH_SCRIPT"
    interval 2
    timeout 2
    rise 2
    fall 2
    weight -50
}
EOF
fi
}

# MASTER base
write_global "$MASTER_ID" > "$MASTER_CONF"
write_script >> "$MASTER_CONF"

# BACKUP base files
for ((b=1; b<=BACKUP_COUNT; b++))
do
    write_global "${BACKUP_IDS[$b]}" > "$BACKUP_PREFIX$b.conf"
    write_script >> "$BACKUP_PREFIX$b.conf"
done

# ---------------- INSTANCES ----------------

for ((i=1; i<=INSTANCE_COUNT; i++))
do
    echo "-----------------------------------"
    echo "Instance #$i"
    read -p "Name (e.g. VLAN10 / APP1): " NAME
    read -p "Interface (e.g. eth0.10): " IFACE
    read -p "VIP (e.g. 192.168.10.3/24): " VIP
    read -p "VRID: " VRID
    read -p "Auth password: " PASS

    PEERS=""
    for ((b=1; b<=BACKUP_COUNT; b++))
    do
        PEERS="$PEERS ${BACKUP_IPS[$b]}"
    done

    # MASTER
    cat >> "$MASTER_CONF" <<EOF

vrrp_instance $NAME {
    state MASTER
    interface $IFACE
    virtual_router_id $VRID
    priority 200
    advert_int 1

    unicast_src_ip $MASTER_IP

    unicast_peer {
        $PEERS
    }

    authentication {
        auth_type PASS
        auth_pass $PASS
    }

    virtual_ipaddress {
        $VIP dev $IFACE
    }
EOF

if [[ -n "$HEALTH_SCRIPT" ]]; then
cat >> "$MASTER_CONF" <<EOF

    track_script {
        chk_service
    }
EOF
fi

cat >> "$MASTER_CONF" <<EOF
}
EOF

    # BACKUPS
    for ((b=1; b<=BACKUP_COUNT; b++))
do
    PRIORITY=$((200 - (b * 10)))
    [[ $PRIORITY -lt 50 ]] && PRIORITY=50

    cat >> "$BACKUP_PREFIX$b.conf" <<EOF

vrrp_instance $NAME {
    state BACKUP
    interface $IFACE
    virtual_router_id $VRID
    priority $PRIORITY
    advert_int 1
    nopreempt

    unicast_src_ip ${BACKUP_IPS[$b]}

    unicast_peer {
        $MASTER_IP
    }

    authentication {
        auth_type PASS
        auth_pass $PASS
    }

    virtual_ipaddress {
        $VIP dev $IFACE
    }
EOF

if [[ -n "$HEALTH_SCRIPT" ]]; then
cat >> "$BACKUP_PREFIX$b.conf" <<EOF

    track_script {
        chk_service
    }
EOF
fi

cat >> "$BACKUP_PREFIX$b.conf" <<EOF
}
EOF

done

done

echo ""
echo "========================================="
echo " DONE"
echo "========================================="
echo "Configs:"
echo " - $MASTER_CONF"
for ((b=1; b<=BACKUP_COUNT; b++))
do
    echo " - $BACKUP_PREFIX$b.conf"
done

echo ""
echo "Systemd:"
echo " - $SYSTEMD_DIR/keepalived.service"

echo ""
echo "Diagram:"
echo " - $DIAGRAM_FILE"
echo "========================================="