#!/bin/bash

# Script to set the hostname in the k3os config.yaml file.
# It handles the read-only filesystem constraint of a running k3OS system.

# Define the path to the config file and the mount point
CONFIG_FILE="/k3os/system/config.yaml"
CONFIG_DIR="/k3os/system"

# --- Function to get user input ---
get_hostname_input() {
    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: **$NEW_HOSTNAME**"
    echo "Config file location: **$CONFIG_FILE**"
    
    # 1. Remount the filesystem as read/write (rw)
    echo "Attempting to remount $CONFIG_DIR as read/write..."
    if ! mount -o remount,rw "$CONFIG_DIR"; then
        echo "Error: Failed to remount $CONFIG_DIR as read/write. Aborting."
        exit 1
    fi
    echo "Filesystem successfully remounted as read/write."

    # 2. Modify the config file (same logic as before)
    if ! grep -q "^k3os:" "$CONFIG_FILE"; then
        echo "'k3os:' block not found. Appending the block and hostname."
        echo -e "\nk3os:\n$HOSTNAME_ENTRY" >> "$CONFIG_FILE"
    
    elif grep -q "^k3os:" "$CONFIG_FILE" && grep -q "^\s\+hostname:" "$CONFIG_FILE"; then
        echo "Existing hostname found. Replacing the entry."
        sed -i "/^\s*hostname:/c\\$HOSTNAME_ENTRY" "$CONFIG_FILE"
        
    else
        echo "'k3os:' block found, but no hostname entry. Appending the entry."
        sed -i "/^k3os:/a\\$HOSTNAME_ENTRY" "$CONFIG_FILE"
    fi

    local MODIFICATION_STATUS=$?

    # 3. Remount the filesystem back to read-only (ro)
    echo "Remounting $CONFIG_DIR back to read-only..."
    if ! mount -o remount,ro "$CONFIG_DIR"; then
        echo "Warning: Failed to remount $CONFIG_DIR back to read-only. Proceeding..."
    fi

    echo -e "$HOSTNAME_ENTRY" > /var/lib/rancher/k3os/hostname

    # 4. Report status
    if [ $MODIFICATION_STATUS -eq 0 ]; then
        echo ""
        echo "Successfully updated the hostname in $CONFIG_FILE."
        echo "The change will take effect after a **reboot**."
        echo ""
        echo "--- Verification (Hostname line only) ---"
        grep -E "^\s*hostname:" "$CONFIG_FILE"
    else
        echo "Error: Failed to modify $CONFIG_FILE during step 2."
        exit 1
    fi
}

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