#!/usr/bin/env ruby

require 'toml'
require 'net/ldap'
require 'English'

@configuration_file = '/etc/unipoly-mlmmj-ldap-sync.toml'
@configuration = nil

def read_configuration(path)
  begin
    TOML.load_file(path)
  rescue Errno::ENOENT => raised_error
    puts "Could not open configuration file: #{raised_error}"
    exit(1)
  end
end

def connect_ldap
  conn = Net::LDAP.new(
    host: @configuration['ldap']['host'],
    port: @configuration['ldap']['port'],
    auth: {
      method: :simple,
      username: @configuration['ldap']['auth']['username'],
      password: @configuration['ldap']['auth']['password']
    }
  )

  ldap_addr = @configuration['ldap']['host'] + ':' +
              @configuration['ldap']['port'].to_s
  begin
    if conn.bind
      conn
    else
      puts "Failed to authenticate against LDAP server: #{ldap_addr}"
      exit(1)
    end
  rescue LdapError => raised_error
    puts "Failed to contact LDAP server: #{ldap_addr}"
    puts raised_error
    exit(1)
  end
end

def get_mlmmj_subscribers(list)
  mlmmj_list_binary = @configuration['mlmmj']['list_binary']

  unless File.executable?(mlmmj_list_binary)
    puts "could not execute #{mlmmj_list_binary}"
    exit(1)
  end

  # Execute mlmmj-list and check whether it exited successfuly
  raw = `#{mlmmj_list_binary} -L #{list} -s`
  unless $CHILD_STATUS.exitstatus.zero?
    puts 'FAIL'
    exit(1)
  end

  # Return a list of mail addresses.
  raw.split("\n")
end

def add_subscriber_to(list_name, subscribers, list, addr)
  if subscribers.include?(addr)
    # The address is already subscribed to the list: we're done with it.
    subscribers.delete(addr)
  else
    # The address is not subscribed to the list yet.
    print "Adding #{addr}... "

    # Since the configuration file doesn't say we have to add new subscribers
    # to this list, we ignore this action.
    unless @configuration['lists_add'].include?(list_name)
      puts 'IGNORED'
      return
    end

    # Subscribe the address to the list.
    mlmmj_sub_binary = @configuration['mlmmj']['sub_binary']
    `#{mlmmj_sub_binary} -L #{list} -a #{addr} -q -f -s`
    if $CHILD_STATUS.exitstatus.zero?
      puts 'OK'
    else
      puts 'FAILED'
    end
  end
end

def remove_subscriber_from(list_name, list, addr)
  print "Removing #{addr}... "

  # We ignore this action if the configuration file doesn't say we are allowed
  # to remove addresses from this list.
  unless @configuration['lists_remove'].include?(list_name)
    puts 'IGNORED'
    return
  end

  # Unsubscribe the address from the list.
  mlmmj_unsub_binary = @configuration['mlmmj']['unsub_binary']
  `#{mlmmj_unsub_binary} -L #{list} -a #{addr} -q -s`
  if $CHILD_STATUS.exitstatus.zero?
    puts 'OK'
  else
    puts 'FAILED'
  end
end

def sync_list(list_name, ldap_group_entry)
  mlmmj_basepath = @configuration['mlmmj']['basepath']
  list = "#{mlmmj_basepath}/#{list_name}@#{@configuration['domain']}"

  # Members are formatted as
  # 'mail=user@domain.tld,ou=Users,dc=unipoly,dc=epfl,dc=ch': we extract the
  # mail address.
  ldap_members = ldap_group_entry.uniquemember.map do |dn|
    /mail=([^,]+),/.match(dn).values_at(1).first.downcase
  end
  puts "Found #{ldap_group_entry.dn} with #{ldap_members.size} members"

  # Extract mail addresses from Mlmmj
  print 'Searchin mlmmj... '
  mlmmj_subscribers = get_mlmmj_subscribers(list)
  puts 'OK'
  puts "Found #{list_name}@#{@configuration['domain']} with\
 #{mlmmj_subscribers.size} subscribers"

  # Add to the subscribers any missing entry
  # Remove successful matches
  ldap_members.each do |addr|
    add_subscriber_to(list_name, mlmmj_subscribers, list, addr)
  end

  # Remove remaining "subcribers" (= they did not match with LDAP members)
  mlmmj_subscribers.each do |addr|
    remove_subscriber_from(list_name, list, addr)
  end
  print "\n"
end

def main
  # Parse configuration, bind to LDAP server
  @configuration = read_configuration(@configuration_file)
  conn = connect_ldap

  domain = @configuration['domain']
  basetree = @configuration['ldap']['lists']['basetree']
  lists = (@configuration['lists_add'] + @configuration['lists_remove']).uniq

  # Sync Mlmmj lists with LDAP groups
  lists.each do |list_name|
    puts ">> Processing list #{list_name}@#{domain}"
    print 'Searching LDAP... '

    filter = Net::LDAP::Filter.eq('cn', list_name)
    matched_ldap_groups = conn.search(base: basetree, filter: filter)
    if matched_ldap_groups.nil? || matched_ldap_groups.empty?
      # Could not find matching LDAP group
      puts 'NOT FOUND'
    else
      puts 'OK'
      ldap_group_entry = matched_ldap_groups.first
      sync_list(list_name, ldap_group_entry)
    end
  end
end

###
# Execute script:
main