#!/bin/bash
# DISCLAIMER: 
# This script is provided "AS IS" and is intended solely for illustrative or educational purposes. 
# Domotz makes no warranties, express or implied, including but not limited to warranties of merchantability, fitness for a particular purpose, or non-infringement. Use of this script is at your own risk. 
# By using this script, you acknowledge and agree that Domotz shall not be liable for any direct, indirect, incidental, or consequential damages or losses arising from its use.  
# You further agree to indemnify, defend, and hold harmless Domotz and its affiliates from and against any claims, liabilities, damages, or expenses resulting from your use or misuse of this script. 
#
# In the event of any conflict between this disclaimer and any other agreement between you and Domotz, this disclaimer shall prevail with respect to the use of this script. 
#
# This script provides an example configuration for setting up and configure the network on a Linux system.
# Prerequisites:
# - the system should use the netplan file for network configuration.
ver="1.1"

# !!!Please changhe the path of the netplan file according to your system setup.!!!

# Change this to your netplan file path
NETPLAN_FILE="/etc/netplan/00-installer-config.yaml"


# Check if the script is run as root
if [[ $EUID -ne 0 ]]; then
    echo "This script must be run as root"
    exit 1
fi

# Function to check if the IP address is valid
validate_ip() {
    local ip_with_mask=$1
    local ip=${ip_with_mask%%/*}
    local mask=${ip_with_mask##*/}

    # Validate IP format
    if [[ $ip =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}$ ]]; then
        IFS='.' read -r -a octets <<< "$ip"
        for octet in "${octets[@]}"; do
            if ((octet < 0 || octet > 255)); then
                return 1
            fi
        done
    else
        return 1
    fi

    # Validate subnet mask if present
    if [[ $ip_with_mask == */* ]]; then
        # Netplan typically expects CIDR prefix length (e.g., 24 for /24)
        # The original script's check ((mask < 16 || mask > 32)) is specific.
        if ! [[ $mask =~ ^[0-9]{1,2}$ ]] || ((mask < 16 || mask > 32)); then
            return 1
        fi
    fi

    return 0
}

# Function to add /24 subnet mask if not provided
add_subnet_mask() {
    local ip=$1
    if [[ ! $ip =~ /[0-9]{1,2}$ ]]; then
        ip="${ip}/24"
    fi
    echo "$ip"
}

# Function to check if the input is a number
is_number() {
    local num=$1
    [[ $num =~ ^[0-9]+$ ]]
}

# Show the interfaces currently configured
echo "Current interfaces configuration:"
echo ""
ip -o link show | awk -F': ' '{print $2}' | grep -v lo
echo ""
echo "========================"

# Function to check if an interface exists
validate_interface() {
    local iface=$1
    ip -o link show | awk -F': ' '{print $2}' | grep -v lo | grep -wq "$iface"
}

# Ask which interface to configure
while true; do
    read -p "Enter the interface name to configure: " IFACE
    if validate_interface "$IFACE"; then
        break
    else
        printf "Interface not found. Please enter a valid interface name.\n" >&2
    fi
done
echo "========================"

# Ask for DHCP or Static IP
while true; do
    read -p "Do you want to use DHCP for the interface? (yes/no): " dhcp
    if [[ $dhcp == "yes" || $dhcp == "no" ]]; then
        break
    else
        printf "Invalid input. Please enter 'yes' or 'no'.\n" >&2
    fi
done
echo "========================"

# If Static IP, get the details
if [[ $dhcp == "no" ]]; then
    while true; do
        read -p "Enter the static IP address (e.g., 192.168.1.10 or 192.168.1.10/24): " ip
        ip=$(add_subnet_mask "$ip")
        if validate_ip "$ip"; then
            break
        else
            printf "Invalid IP address or subnet mask not in range /16-/32. Please enter a valid IP address.\n" >&2
        fi
    done
    echo "========================"

    while true; do
        read -p "Enter the gateway IP address: " gateway
        if validate_ip "${gateway}"; then # Validate basic IP format for gateway
            break
        else
            printf "Invalid IP address. Please enter a valid gateway IP address.\n" >&2
        fi
    done
    echo "========================"

    while true; do
        read -p "Enter the first DNS server IP address: " dns1
        if validate_ip "${dns1}"; then # Validate basic IP format for DNS
            break
        else
            printf "Invalid IP address. Please enter a valid DNS server IP address.\n" >&2
        fi
    done
    echo "========================"

    while true; do
        read -p "Enter the second DNS server IP address: " dns2
        if validate_ip "${dns2}"; then # Validate basic IP format for DNS
            break
        else
            printf "Invalid IP address. Please enter a valid DNS server IP address.\n" >&2
        fi
    done
    echo "========================"
fi

# Define a function to make backup with incrementing names
make_backup() {
    local file=$1
    local backup_dir; backup_dir=$(dirname "$file")
    local backup_name; backup_name=$(basename "$file")
    local i=1

    # Check if the original file exists before trying to backup
    if [[ ! -f "$file" ]]; then
        echo "Original file $file does not exist. Skipping backup."
        return
    fi

    while [[ -f "$backup_dir/${backup_name}.bak$i" ]]; do
        let i++
    done
    cp "$file" "$backup_dir/${backup_name}.bak$i"
    echo "Backup made as ${backup_name}.bak$i"
}
echo "========================" # Separator after make_backup function definition

# ---- MODIFICATIONS ACCORDING TO USER REQUEST ----
# Initialize the temporary netplan file by writing the header.
# This effectively clears any previous content for NETPLAN_FILE.tmp
# and starts it with the required network configuration structure.
cat <<EOL > "${NETPLAN_FILE}.tmp"
network:
  version: 2
  ethernets:
EOL

# Append the new interface configuration to the initialized temporary file
# The indentation (4 spaces) ensures it's correctly placed under 'ethernets:'
cat <<EOL >> "${NETPLAN_FILE}.tmp"
    ${IFACE}:
      dhcp4: ${dhcp}
EOL

if [[ $dhcp == "no" ]]; then
    cat <<EOL >> "${NETPLAN_FILE}.tmp"
      addresses:
        - ${ip}
      routes:
        - to: default # Using "default" is more common in Netplan than 0.0.0.0/0
          via: ${gateway}
      nameservers:
        addresses:
          - ${dns1}
          - ${dns2}
EOL
fi
# ---- END OF MODIFICATIONS ----


# Preview the netplan file with new configurations:
echo "Preview of the netplan file with new configurations:"

# The old awk commands to read from NETPLAN_FILE and to append other configurations (like VLANs)
# have been removed as per the requirement to clear the file and start fresh with the specified header.

cat "${NETPLAN_FILE}.tmp"
echo "========================"

# Confirmation
read -p "Do you want to apply these settings? (yes/no): " confirm
if [[ $confirm == "yes" ]]; then
    make_backup "$NETPLAN_FILE"
    # Move the newly constructed temporary file to the actual netplan file path.
    # This overwrites the original file, effectively "clearing" it and applying the new content.
    if mv "${NETPLAN_FILE}.tmp" "$NETPLAN_FILE"; then
        echo "Configurations have been written to $NETPLAN_FILE. Please review and apply with 'sudo netplan apply'."
    else
        echo "Error: Failed to write configurations to $NETPLAN_FILE." >&2
        if [[ -f "${NETPLAN_FILE}.tmp" ]]; then
             echo "The new configuration is still available in ${NETPLAN_FILE}.tmp" >&2
        fi
        exit 1
    fi
else
    echo "Changes not applied."
    rm -f "${NETPLAN_FILE}.tmp" # Use -f to suppress error if file doesn't exist for rm
    exit 0
fi
echo "========================"