#!/usr/bin/env bash

CONFIG_FILE="/etc/update-manager.conf"
[[ -f "$CONFIG_FILE" ]] || CONFIG_FILE="./update-manager.conf"

if [[ -f "$CONFIG_FILE" ]]; then
    # shellcheck disable=SC1090
    source "$CONFIG_FILE"
fi

DEFAULT_HOSTS_FILE="${HOSTS_FILE:-/opt/update-manager/hosts.conf}"
SSH_OPTIONS="${SSH_OPTIONS:--o BatchMode=yes -o ConnectTimeout=5}"

########################################
# Ensure hosts file exists
########################################

ensure_hosts_file() {
    if [[ ! -f "$DEFAULT_HOSTS_FILE" ]]; then
        echo "Creating example hosts file: $DEFAULT_HOSTS_FILE"

        mkdir -p "$(dirname "$DEFAULT_HOSTS_FILE")"

        cat > "$DEFAULT_HOSTS_FILE" <<'EOF'
# Example hosts file
# Format:
# name          ip              user
#
# server1       192.168.1.10    user
# server2       192.168.1.20    user
# server3       10.0.0.5        root
EOF
    fi
}

########################################
# Helpers
########################################

get_hosts_file() {
    if [[ -n "$2" ]]; then
        echo "$2"
    else
        echo "$DEFAULT_HOSTS_FILE"
    fi
}

usage() {
    cat <<USAGE
Usage:
  $0 check [hosts_file]

Examples:
  $0 check
  $0 check /path/to/hosts.conf
  HOSTS_FILE=/path/to/hosts.conf $0 check
USAGE
}

########################################
# Check single host
########################################

check_host() {
    local name="$1"
    local ip="$2"
    local user="$3"
    local result
    local rc

    result=$(ssh -n $SSH_OPTIONS "${user}@${ip}" \
        "apt list --upgradable 2>/dev/null | sed '/^Listing/d'" 2>&1)
    rc=$?

    printf "===== %s (%s) =====\n" "$name" "$ip"

    if [[ $rc -ne 0 ]]; then
        echo "❌ connection failed"
        echo "$result"
        echo
        return
    fi

    if [[ -z "$result" ]]; then
        echo "Up-to-date"
    else
        echo "$result"
    fi

    echo
}

########################################
# Check all hosts
########################################

check_all() {
    local hosts_file="$1"

    ensure_hosts_file

    while IFS= read -r line; do
        [[ -z "$line" || "$line" =~ ^[[:space:]]*# ]] && continue

        local name ip user
        read -r name ip user <<< "$line"

        [[ -z "$name" || -z "$ip" || -z "$user" ]] && continue

        check_host "$name" "$ip" "$user"
    done < "$hosts_file"
}

########################################
# Main
########################################

case "${1:-}" in
    check)
        HOSTS_FILE_TO_USE="$(get_hosts_file "$@")"
        check_all "$HOSTS_FILE_TO_USE"
        ;;
    *)
        usage
        exit 1
        ;;
esac