#!/usr/bin/env ruby
# frozen_string_literal: true

# notify_backup — send a backup run result to the n8n backup monitor
#
# USAGE
#   notify_backup.rb [options]
#
# REQUIRED OPTIONS
#   --machine NAME        Identifier for this host (e.g. desktop, vps-ovh-prod-01)
#   --destination NAME    Backup destination (e.g. synology, backblaze-b2, local)
#   --status STATUS       Result: success | failure | skipped
#
# OPTIONAL OPTIONS
#   --bytes N             Bytes transferred (raw integer; formatted to human-readable before sending)
#   --snapshot ID         Restic snapshot ID or equivalent
#   --log-path PATH       Path to the backup log file for this run
#   --notes TEXT          Free-form output (restic tail, skip reason, error message, etc.)
#
# REQUIRED ENV VARS
#   N8N_SWANSONCLOUD_URL                Base URL of the n8n instance (no trailing slash)
#                                       e.g. https://n8n.swansoncloud.com
#   N8N_SWANSONCLOUD_BACKUP_AUTH_TOKEN  Bearer token for webhook authentication
#
# EXIT BEHAVIOR
#   Always exits 0. A notification failure is logged to stderr but never causes
#   the calling backup process to fail — the backup ran; the log is the source of truth.
#
# ADDING A NEW BACKUP SOURCE
#   1. Ensure the two ENV vars above are available on the new host
#   2. Call this script at the end of the backup process with --machine, --destination, --status
#   3. Add the {machine, destination} pair to the Set: Expected Sources node in n8n Workflow 2
#
# CLASSES
#   ByteFormatter    raw integer bytes → human-readable string (e.g. "4.50 GB")
#   PayloadBuilder   converts CLI option hash into a clean JSON-ready hash
#   WebhookClient    sends HTTP POST with auth header; knows nothing about backup data
#   BackupNotifier   orchestrates: build payload → send; the only public entry point

require 'net/http'
require 'json'
require 'optparse'

class ByteFormatter
  UNITS = [['GB', 1_073_741_824], ['MB', 1_048_576], ['KB', 1_024]].freeze

  def self.format(bytes)
    return nil if bytes.nil?

    bytes = bytes.to_i
    unit, divisor = UNITS.find { |_, d| bytes >= d }
    return "#{bytes} B" unless unit

    '%.2f %s' % [bytes.to_f / divisor, unit]
  end
end

class PayloadBuilder
  VALID_STATUSES = %w[success failure skipped].freeze

  def initialize(options)
    @options = options
  end

  def build
    validate!
    {
      timestamp:         Time.now.utc.strftime('%Y-%m-%dT%H:%M:%SZ'),
      machine:           @options[:machine],
      destination:       @options[:destination],
      status:            @options[:status],
      bytes_transferred: ByteFormatter.format(@options[:bytes]),
      snapshot_id:       @options[:snapshot],
      log_path:          @options[:log_path],
      notes:             @options[:notes]
    }.compact
  end

  private

  def validate!
    return if VALID_STATUSES.include?(@options[:status])

    raise ArgumentError, "status must be one of: #{VALID_STATUSES.join(', ')}"
  end
end

class WebhookClient
  def initialize(base_url:, auth_token:, http_adapter: Net::HTTP)
    @base_url     = base_url
    @auth_token   = auth_token
    @http_adapter = http_adapter
  end

  def post(payload)
    uri     = URI("#{@base_url}/webhook/backup-notify")
    request = build_request(uri, payload)

    response = @http_adapter.start(uri.hostname, uri.port, use_ssl: uri.scheme == 'https') do |http|
      http.request(request)
    end

    raise "HTTP #{response.code}: #{response.body}" unless response.is_a?(Net::HTTPSuccess)
  end

  private

  def build_request(uri, payload)
    req = Net::HTTP::Post.new(uri)
    req['Content-Type']  = 'application/json'
    req['Authorization'] = "Bearer #{@auth_token}"
    req.body             = JSON.generate(payload)
    req
  end
end

class BackupNotifier
end

if __FILE__ == $PROGRAM_NAME
  # CLI entry point — implemented in Task 5
end