#!/bin/bash

set -euo pipefail

# -------------------------------
# Prompt user for subnet base
# -------------------------------

read -rp "Enter the second octet for your Docker network (e.g., 100 for 10.100.0.0/16): " octet

# Validate that it's a number between 1 and 254
if ! [[ "$octet" =~ ^[0-9]{1,3}$ ]] || ((octet < 1 || octet > 254)); then
    echo "Invalid input. Must be a number between 1 and 254."
    exit 1
fi

# -------------------------------
# Define values
# -------------------------------

DOCKER_CONFIG_FILE="/etc/docker/daemon.json"
ADDRESS_POOL_BASE="10.${octet}.0.0/16"
ADDRESS_POOL_SIZE=24
NETWORK_NAME="bridge_default"
NETWORK_SUBNET="10.${octet}.1.0/24"

# -------------------------------
# Replace daemon.json
# -------------------------------

echo "Writing Docker daemon.json with base $ADDRESS_POOL_BASE..."

mkdir -p /etc/docker
cat > "$DOCKER_CONFIG_FILE" <<EOF
{
    "default-address-pools": [
        {
            "base": "10.${octet}.0.0/16",
            "size": 24
        }
    ]
}
EOF

echo "Docker config updated at $DOCKER_CONFIG_FILE"

# -------------------------------
# Delete and recreate network
# -------------------------------

if docker network inspect "$NETWORK_NAME" >/dev/null 2>&1; then
    echo "Network '$NETWORK_NAME' exists. Deleting it..."
    docker network rm "$NETWORK_NAME"
fi

echo "Creating network '$NETWORK_NAME' with subnet $NETWORK_SUBNET..."
docker network create \
    --driver=bridge \
    --subnet="$NETWORK_SUBNET" \
    "$NETWORK_NAME"

echo "✅ Done. You may need to restart Docker to apply default address pool changes:"
echo "   sudo systemctl restart docker"