options.subscribe = true
options.keepalive = 10
options.expunge = true
options.info = false
options.certificates = false

-- Global variables
accounts = {}
accounts_fetched = 0
fetch_accounts_every = 3600
filter_every = 30

MONTHS={Jan=1,Feb=2,Mar=3,Apr=4,May=5,Jun=6,Jul=7,Aug=8,Sep=9,Oct=10,Nov=11,Dec=12}
DATE_FORMAT = "(%d+)-(%a+)-(%d+) (%d+):(%d+):(%d+)"

-- Split string
function split(str, delim)
    local result,pat,lastPos = {},"(.-)" .. delim .. "()",1
    for part, pos in string.gmatch(str, pat) do
        table.insert(result, part); lastPos = pos
    end
    table.insert(result, string.sub(str, lastPos))
    return result
end

-- Table size
function size(tbl)
  tbl_length = 0
  for k, v in ipairs(tbl) do
    tbl_length = tbl_length + 1
  end
  return tbl_length
end

-- Move to Gmail Trash with logging
function move_to_trash(imap, messages)
  for _, msg in ipairs(messages) do
    mbox, uid = table.unpack(msg)
    print('IMAPFilter ' .. mbox[uid]:fetch_field('From') .. ' ' .. mbox[uid]:fetch_field('To') ..
          ' ' .. mbox[uid]:fetch_field('Subject') .. ' ' .. mbox[uid]:fetch_date())
  end
  messages:move_messages(imap['[Gmail]/Trash'])
end

-- IMAP Date string to seconds before now
function seconds_old(date_string)
  local day, mon, year, hour, min, sec = date_string:match(DATE_FORMAT)
  local time_stamp = os.time({day=day,month=MONTHS[mon],year=year,hour=hour,min=min,sec=sec})
  return os.difftime(os.time(), time_stamp)
end

function fetch_accounts()
  mysql_command = 'mysql -BNe "select SERVERNAME, smtp_port, mailusername, mailpassword from mailserver where protocol like \'imap%\'"'
  status, output = pipe_from(mysql_command)
  accounts = {}

  for _, account in ipairs(split(output, "\n")) do
    local _, _, server, port, username, password = string.find(account, '([^%s]+)[%s]+([^%s]+)[%s]+([^%s]+)[%s]+([^%s]+)')
    if server and port and username and password then
      local imap = IMAP {
          server = server,
        port = tonumber(port),
          username = username,
          password = password,
          ssl = 'tls1.2'
      }
      -- Get a list of the available mailboxes and folders
      local mailboxes, folders = imap:list_all()

      table.insert(accounts, imap)
    end
  end
end

-- Filters
function filter(imap)
        imap.INBOX:check_status()

        results = imap.INBOX:select_all()

  -- * for AND, + for OR, - for NOT, () to group
                -- Google Calendar Invites
    calendar_notifications = ( results:contain_from("calendar-notification@google.com") +
                               results:contain_field("Sender", "calendar-notification@google.com") )
    if size(calendar_notifications) > 0 then
      print('IMAPFilter Deleting Google Calendar Invites')
      move_to_trash(imap, calendar_notifications)
    end

                -- Too Old
    too_old = ( results:is_older(5) )
    if size(too_old) > 0 then
      print('IMAPFilter Deleting Too Old')
      move_to_trash(imap, too_old)
    end

                -- Mailer Daemon
    mailer_daemon = ( results:contain_from("mailer-daemon@.*") +
                      results:contain_field("Sender", "mailer-daemon@.*") )
    if size(mailer_daemon) > 0 then
      print('IMAPFilter Deleting Mailer Daemon Emails')
      move_to_trash(imap, mailer_daemon)
    end

    -- JIRA Trouble Parsing
    seen_msgs = ( results:is_seen() )
    jira_unable_to_parse = Set {}
    if size(seen_msgs) > 0 then
      for _, msg in ipairs(seen_msgs) do
        mbox, uid = table.unpack(msg)
        if seconds_old(mbox[uid]:fetch_date()) > 900 then
          table.insert(jira_unable_to_parse, msg)
        end
      end
    end
    if size(jira_unable_to_parse) > 0 then
      print('IMAPFilter Deleting Mail JIRA Cannot Parse')
      move_to_trash(imap, jira_unable_to_parse)
    end
  -- done
end

function main()
  print("IMAPFilter Running at " .. os.date("%Y-%m-%d %H:%M:%S"))

  -- Fetch accounts once per hour from MySQL
  if os.time() - accounts_fetched > fetch_accounts_every then
    fetch_accounts()
  end

  -- Loop through all accounts and run filtering on them
  for _, imap in ipairs(accounts) do
    filter(imap)
  end

  -- print('---------')
end

-- Two methods for running in loop
-- Only uncomment one at a time

-- become_daemon forks into background and calls a function every x seconds
-- become_daemon(filter_every, main)

-- While true loop runs in forground
-- while true do
  -- main()
  -- Lua has no built in sleep function
  -- os.execute('sleep ' .. filter_every)
-- end

-- Run once and exit
main()