#!/bin/bash

# Script to set the hostname in the k3os config.yaml file using only standard tools (sed, grep).

# Define the path to the config file
CONFIG_FILE="/k3os/system/config.yaml"

# --- Function to get user input ---
get_hostname_input() {
    # Loop until a non-empty hostname is provided
    while true; do
        read -r -p "Enter the desired new hostname: " NEW_HOSTNAME
        if [ -n "$NEW_HOSTNAME" ]; then
            break
        else
            echo "Error: Hostname cannot be empty. Please enter a valid name."
        fi
    done
}

# --- Function to modify the config file ---
set_hostname() {
    local NEW_HOSTNAME="$1"
    # Note the two spaces for YAML indentation under 'k3os:'
    local HOSTNAME_ENTRY="  hostname: $NEW_HOSTNAME" 

    echo "Attempting to set hostname to: **$NEW_HOSTNAME** in **$CONFIG_FILE**"

    # 1. Check if the 'k3os:' block exists
    if ! grep -q "^k3os:" "$CONFIG_FILE"; then
        echo "'k3os:' block not found. Appending the block and hostname."
        # Append the k3os block and the new hostname entry
        echo -e "\nk3os:\n$HOSTNAME_ENTRY" >> "$CONFIG_FILE"
    
    # 2. Check if a 'hostname' entry already exists under 'k3os:'
    # Checks for the 'k3os:' block AND an indented 'hostname:' line
    elif grep -q "^k3os:" "$CONFIG_FILE" && grep -q "^\s\+hostname:" "$CONFIG_FILE"; then
        echo "Existing hostname found. Replacing the entry."
        # Use sed to replace the existing hostname line under k3os
        # /^\s*hostname:/ matches any line starting with optional spaces followed by 'hostname:'
        sed -i "/^\s*hostname:/c\\$HOSTNAME_ENTRY" "$CONFIG_FILE"
        
    # 3. 'k3os:' exists but 'hostname:' does not.
    else
        echo "'k3os:' block found, but no hostname entry. Appending the entry."
        # Use sed to insert the new hostname entry immediately after the 'k3os:' line
        # The 'a\' command appends text after the matched line
        sed -i "/^k3os:/a\\$HOSTNAME_ENTRY" "$CONFIG_FILE"
    fi

    # Check the exit status of the previous command
    if [ $? -eq 0 ]; then
        echo "Successfully updated the hostname in $CONFIG_FILE."
        echo "The change will take effect after a reboot."
        echo ""
        echo "--- Verification (Hostname line only) ---"
        # Print the modified line for verification
        grep -E "^\s*hostname:" "$CONFIG_FILE"
    else
        echo "Failed to modify $CONFIG_FILE."
        exit 1
    fi
}

# --- Main execution ---
get_hostname_input
set_hostname "$NEW_HOSTNAME"