#!/bin/bash
# nas-system-update — Check available system updates (apt)
# Usage: nas-system-update
# Output: JSON (non-interactive mode) or colored text (terminal mode)

set -euo pipefail

if [ -t 1 ]; then INTERACTIVE=true; else INTERACTIVE=false; fi

# Colors (terminal mode only)
if $INTERACTIVE; then
    RED='\033[0;31m'
    GREEN='\033[0;32m'
    YELLOW='\033[1;33m'
    CYAN='\033[0;36m'
    BOLD='\033[1m'
    RESET='\033[0m'
else
    RED='' GREEN='' YELLOW='' CYAN='' BOLD='' RESET=''
fi

if $INTERACTIVE; then
    echo -e "${BOLD}--- Refreshing package list ---${RESET}"
fi

apt-get update -qq 2>/dev/null

# Parse apt-get --simulate full-upgrade
# Format:
#   Inst name (available_version ...) → new package
#   Inst name [current_version] (available_version ...) → upgrade
packages_json=""
count=0

while IFS= read -r line; do
    # Extract package name (2nd field)
    name=$(echo "$line" | awk '{print $2}' | tr -d '[:space:]')
    [ -z "$name" ] && continue

    # Current version: inside [...] if present, else N/A
    current=$(echo "$line" | grep -oP '(?<=\[)[^\]]+' | tr -d '[:space:]' || echo "")
    [ -z "$current" ] && current="N/A"

    # Available version: first word inside first (...)
    available=$(echo "$line" | grep -oP '(?<=\()[^ ]+' | head -1 | tr -d '[:space:]')
    [ -z "$available" ] && continue

    if $INTERACTIVE; then
        echo -e "  ${CYAN}${name}${RESET} : ${YELLOW}${current}${RESET} → ${GREEN}${available}${RESET}"
    fi

    # Build JSON entry
    entry="{\"name\":\"${name}\",\"current\":\"${current}\",\"available\":\"${available}\"}"
    if [ $count -eq 0 ]; then
        packages_json="${entry}"
    else
        packages_json="${packages_json},${entry}"
    fi
    count=$((count + 1))

done < <(apt-get --simulate full-upgrade 2>/dev/null | grep "^Inst")

# Check if reboot is required
reboot_required=false
if [ -f /var/run/reboot-required ]; then
    reboot_required=true
fi

if $INTERACTIVE; then
    echo ""
    echo -e "${BOLD}--- Summary ---${RESET}"
    if [ $count -eq 0 ]; then
        echo -e "${GREEN}✅ System is up to date.${RESET}"
    else
        echo -e "${YELLOW}📦 ${count} package(s) available for upgrade.${RESET}"
    fi
    if $reboot_required; then
        echo -e "${RED}⚠️  Reboot required.${RESET}"
    fi
else
    printf '{"count":%d,"reboot_required":%s,"packages":[%s]}\n' \
        "$count" "$reboot_required" "$packages_json"
fi