--[[
Copyright (c) 2016, Andrew Lewis <nerf@judo.za.org>
Copyright (c) 2016, Vsevolod Stakhov <vsevolod@highsecure.ru>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
]] --

local N = 'metric_exporter'
local logger = require "rspamd_logger"
local mempool = require "rspamd_mempool"
local util = require "rspamd_util"
local tcp = require "rspamd_tcp"

local pool = mempool.create()
local settings = {
  interval = 120,
  timeout = 15,
  statefile = string.format('%s/%s', rspamd_paths['DBDIR'], 'metric_exporter_last_push')
}

local VAR_NAME = 'metric_exporter_last_push'

local valid_metrics = {
  'actions.add header',
  'actions.greylist',
  'actions.no action',
  'actions.reject',
  'actions.rewrite subject',
  'actions.soft reject',
  'bytes_allocated',
  'chunks_allocated',
  'chunks_freed',
  'chunks_oversized',
  'connections',
  'control_connections',
  'ham_count',
  'learned',
  'pools_allocated',
  'pools_freed',
  'scanned',
  'shared_chunks_allocated',
  'spam_count',
}

local function validate_metrics(settings_metrics)
  if type(settings_metrics) ~= 'table' or #settings_metrics == 0 then
    logger.errx(rspamd_config, 'No metrics specified for collection')
    return false
  end
  for _, v in ipairs(settings_metrics) do
    local isvalid = false
    for _, vm in ipairs(valid_metrics) do
      if vm == v then
        isvalid = true
        break
      end
    end
    if not isvalid then
      logger.errx('Invalid metric: %s', v)
      return false
    end
    local split = rspamd_str_split(v, '.')
    if #split > 2 then
      logger.errx('Too many dots in metric name: %s', v)
      return false
    end
  end
  return true
end

local function load_defaults(defaults)
  for k, v in pairs(defaults) do
    if settings[k] == nil then
      settings[k] = v
    end
  end
end

local function graphite_config()
  load_defaults({
    host = 'localhost',
    port = 2003,
    metric_prefix = 'rspamd'
  })
  return validate_metrics(settings['metrics'])
end

local function graphite_push(kwargs)
  local stamp
  if kwargs['time'] then
    stamp = math.floor(kwargs['time'])
  else
    stamp = math.floor(util.get_time())
  end
  local metrics_str = ''
  for _, v in ipairs(settings['metrics']) do
    local mvalue
    local mname = string.format('%s.%s', settings['metric_prefix'], v:gsub(' ', '_'))
    local split = rspamd_str_split(v, '.')
    if #split == 1 then
      mvalue = kwargs['stats'][v]
    elseif #split == 2 then
      mvalue = kwargs['stats'][split[1]][split[2]]
    end
    metrics_str = metrics_str .. string.format('%s %s %s\n', mname, mvalue, stamp)
  end
  metrics_str = metrics_str .. '\n'
  tcp.request({
    ev_base = kwargs['ev_base'],
    pool = pool,
    host = settings['host'],
    port = settings['port'],
    timeout = settings['timeout'],
    read = false,
    data = {
      metrics_str,
    },
    callback = (function (err)
      if err then
        logger.errx('Push failed: %1', err)
        return
      end
      pool:set_variable(VAR_NAME, stamp)
    end)
  })
end

local backends = {
  graphite = {
    configure = graphite_config,
    push = graphite_push,
  },
}

local function configure_metric_exporter()
  local opts = rspamd_config:get_all_opt(N)
  local be = opts['backend']
  if not be then
    logger.debugm(N, rspamd_config, 'Backend is unspecified')
    return
  end
  if not backends[be] then
    logger.errx(rspamd_config, 'Backend is invalid: ' .. be)
    return false
  end
  for k, v in pairs(opts) do
    settings[k] = v
  end
  return backends[be]['configure']()
end

if not configure_metric_exporter() then return end

rspamd_config:add_on_load(function (_, ev_base, worker)
  -- Exit unless we're the first 'normal' worker
  if not (worker:get_name() == 'normal' and worker:get_index() == 0) then return end
  -- Persist mempool variable to statefile on shutdown
  rspamd_config:register_finish_script(function ()
    local stamp = pool:get_variable(VAR_NAME, 'double')
    if not stamp then
      logger.warn('No last metric exporter push to persist to disk')
      return
    end
    local f, err = io.open(settings['statefile'], 'w')
    if err then
      logger.errx('Unable to write statefile to disk: %s', err)
      return
    end
    if f then
      f:write(pool:get_variable(VAR_NAME, 'double'))
      f:close()
    end
  end)
  -- Push metrics to backend
  local function push_metrics(time)
    logger.infox('Pushing metrics to %s backend', settings['backend'])
    local args = {
      ev_base = ev_base,
      stats = worker:get_stat(),
    }
    if time then
      table.insert(args, time)
    end
    backends[settings['backend']]['push'](args)
  end
  -- Push metrics at regular intervals
  local function schedule_regular_push()
    rspamd_config:add_periodic(ev_base, settings['interval'], function ()
      push_metrics()
      return true
    end)
  end
  -- Push metrics to backend and reschedule check
  local function schedule_intermediate_push(when)
    rspamd_config:add_periodic(ev_base, when, function ()
      push_metrics()
      schedule_regular_push()
      return false
    end)
  end
  -- Try read statefile on startup
  local stamp
  local f, err = io.open(settings['statefile'], 'r')
  if err then
    logger.errx('Failed to open statefile: %s', err)
  end
  if f then
    io.input(f)
    stamp = tonumber(io.read())
    pool:set_variable(VAR_NAME, stamp)
  end
  if not stamp then
    logger.debugm(N, rspamd_config, 'No state found - pushing stats immediately')
    push_metrics()
    schedule_regular_push()
    return
  end
  local time = util.get_time()
  local delta = stamp - time + settings['interval']
  if delta <= 0 then
    logger.debugm(N, rspamd_config, 'Last push is too old - pushing stats immediately')
    push_metrics(time)
    schedule_regular_push()
    return
  end
  logger.debugm(N, rspamd_config, 'Scheduling next push in %s seconds', delta)
  schedule_intermediate_push(delta)
end)
