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

require 'optparse'
require 'csv'

opts = {}
OptionParser.new do |options|
  options.banner = "USAGE:
    #{$PROGRAM_NAME} [opts]
    EXAMPLE w/ Tenable Nessus Results:
    #{$PROGRAM_NAME} \\
      --csv-a vuln_scan1.csv \\
      --csv-b vuln_scan2.csv \\
      --csv-diff vuln_scan_diff.csv \\
      --exclude-column-names 'Synopsis,Description,Solution,See Also,Plugin Output,Asset UUID,Vulnerability State,IP Address,FQDN,NetBios,OS,MAC Address,Plugin Family,CVSS Base Score,CVSS Temporal Score,CVSS Temporal Vector,CVSS Vector,CVSS3 Base Score,CVSS3 Temporal Score,CVSS3 Temporal Vector,CVSS3 Vector,System Type,Host Start,Host End,Vulnerability Priority Rating (VPR),First Found,Last Found,Host Scan Schedule ID,Host Scan ID,Indexed At,Last Authenticated Results Date,Last Unauthenticated Results Date,Tracked,Risk Factor,Severity,Original Severity,Modification,Plugin Family ID,Plugin Type,Plugin Version,Service,Plugin Modification Date,Plugin Publication Date,Checks for Malware,Exploit Available,Exploited by Malware,Exploited by Nessus,CANVAS,D2 Elliot,Metasploit,Core Exploits,ExploitHub,Default Account,Patch Available,In The News,Unsupported By Vendor,Last Fixed'
  "

  options.on('-aCSV', '--csv-a=CSV', '<Required - First CSV to Compare)>') do |c1|
    opts[:c1_path] = c1
  end

  options.on('-bCSV', '--csv-b=CSV', '<Required - Second CSV to Compare)>') do |c2|
    opts[:c2_path] = c2
  end

  options.on('-dDIFF', '--csv-diff=DIFF', '<Required - Path of CSV Diff to Generate)>') do |d|
    opts[:diff_path] = d
  end

  options.on('-eNAMES', '--exclude-column-names=NAMES', '<Optional - Comma-Delimited List of Column Names to Exclude)>') do |n|
    opts[:column_names_to_exclude] = n
  end

  options.on('-n', '--no-headers', '<Optional - Redact CSV Headers in CSV Diff>') do |h|
    opts[:no_headers] = h
  end
end.parse!

if opts.empty?
  puts `#{$PROGRAM_NAME} --help`
  exit 1
end

def csv_diff(opts = {})
  larger_csv = opts[:larger_csv]
  smaller_csv = opts[:smaller_csv]
  diff_path = opts[:diff_path]
  include_csv_headers = opts[:include_csv_headers]
  column_names_to_exclude = opts[:column_names_to_exclude]

  columns_index_arr = []
  column_names_to_exclude&.each do |column_name|
    column_index = smaller_csv.first.find_index(column_name)
    columns_index_arr.push(column_index)
  end

  if columns_index_arr.any?
    larger_csv.each do |line_arr|
      line_arr.delete_if.with_index do |_, index|
        columns_index_arr.include?(index)
      end
    end

    smaller_csv.each do |line_arr|
      line_arr.delete_if.with_index do |_, index|
        columns_index_arr.include?(index)
      end
    end
  end

  csv_headers = larger_csv.first.join(',')
  File.open(diff_path, 'w') do |f|
    f.puts csv_headers if include_csv_headers
    larger_csv.each do |line_arr|
      line = line_arr.join(',')
      f.puts line unless smaller_csv.include?(line_arr)
    end
  end
end

c1_path = opts[:c1_path]
csv1 = CSV.read(c1_path)

c2_path = opts[:c2_path]
csv2 = CSV.read(c2_path)

diff_path = opts[:diff_path]

column_names_to_exclude = opts[:column_names_to_exclude].to_s.split(',')

include_csv_headers = false if opts[:no_headers]
include_csv_headers ||= true

# Compare which two is larger
if csv1.length >= csv2.length
  csv_diff(
    larger_csv: csv1,
    smaller_csv: csv2,
    diff_path: diff_path,
    include_csv_headers: include_csv_headers,
    column_names_to_exclude: column_names_to_exclude
  )
else
  csv_diff(
    larger_csv: csv2,
    smaller_csv: csv1,
    diff_path: diff_path,
    include_csv_headers: include_csv_headers,
    column_names_to_exclude: column_names_to_exclude
  )
end