#!/usr/bin/env ruby

require 'sqlite3'
require 'syslog'

DB_FILE = "metrics.db"

# Syslog と DB の準備
facility= if STDERR.tty? then Syslog::LOG_USER else Syslog::LOG_NEWS end
Syslog.open('iwg_watch', Syslog::LOG_PID, facility)
db = SQLite3::Database.new(DB_FILE)

# メッセージカウンタ
$nalert=0

# DB最新更新時刻の取得。取得できなければDBがカラなので終了
now_ts =
  db.get_first_value(
    "select max(ts) from metrics"
  )
unless now_ts
  Syslog.error("metrics table empty") 
  abort("metrics table empty") 
end

# syslog用英語メッセージを日本語訳する
def translate msg
  msg.gsub!(/ALERT/, "【注意】")
  msg.gsub!(/INFO/, "〔参考〕")
  msg.gsub!(/RECOVER/, "〖解除〗")
  msg.gsub!(/CLEAR/, "〔終了〕")
  msg.gsub!(/low(\d+)/, "\\1h減少")
  msg.gsub!(/high(\d+)/, "\\1h増加")
  msg.gsub!(/\.not_stored/, ".電文数（不保存）")
  msg.gsub!(/\.stored/, ".電文数（保存）")
  msg.gsub!(/\.bulletins/, ".全電文数")
  msg.gsub!(/\.files_received/, ".受信ファイル数")
  msg.gsub!(/\.errors/, ".エラーファイル数")
  msg.gsub!(/\.invalid/, ".不正ファイル数")
  msg.gsub!(/current=/, "現状=")
  msg.gsub!(/threshold=/, "閾値=")
  msg.gsub!(/\(null\)/, "記録なし")
  msg.gsub!(/last_nonzero=/, "直近非ゼロ=")
  msg.gsub!(/last_zero=/, "直近ゼロ=")
  msg.gsub!(/hours_since_(\S+)/, "\\1時間前")
  msg.gsub!(/days_since_(\S+)/, "\\1日前")
  msg.gsub!(/duration_hours=(\S+)/, "継続=\\1時間")
end

# メッセージをSyslogと標準出力に出す
$nolog=true
def sys_notice msg
  $nolog=false
  case msg
  when /^(ALERT|RECOVER)/ then
    Syslog.warning(msg)
  else
    Syslog.notice(msg)
  end
  translate(msg)
  puts msg
end

# 時刻表示用フォーマット：スペースを含まないのが特徴
class Time
  def show
    self.utc.strftime('%Y-%m-%dT%H:%M:%SZ')
  end
end

# アラート発報状態表
db.execute <<~SQL
  CREATE TABLE IF NOT EXISTS alert_state (
    center_id TEXT,
    metric TEXT,

    since_low1   INTEGER,
    since_low3   INTEGER,
    since_low24  INTEGER,

    since_high1  INTEGER,
    since_high3  INTEGER,

    PRIMARY KEY(center_id, metric)
  );
SQL

db.execute <<~SQL
INSERT OR IGNORE INTO alert_state
(center_id,metric)
SELECT center_id,metric
FROM thresholds;
SQL

# センター・メトリックに対して閾値、最新ゼロ経緯、発報状態を取得
thresholds = db.execute(
  <<~SQL
    SELECT
      t.center_id,
      t.metric,

      t.low1,
      t.low3,
      t.low24,

      t.high1,
      t.high3,

      s.last_zero_time,
      s.last_nonzero_time,

      a.since_low1,
      a.since_low3,
      a.since_low24,

      a.since_high1,
      a.since_high3

    FROM thresholds t

    LEFT JOIN last_state s
      USING(center_id, metric)

    LEFT JOIN alert_state a
      USING(center_id, metric)
  SQL
)

def alert_begin(db, center_id, metric, kind, now_ts)
  db.execute(
    <<~SQL, [now_ts, center_id, metric]
      UPDATE alert_state
      SET #{kind} = ?
      WHERE center_id=? AND metric=? ;
    SQL
  )
  $nalert+=1
end

def alert_end(db, center_id, metric, kind)
  db.execute(
    <<~SQL, [center_id, metric]
      UPDATE alert_state
      SET #{kind} = NULL
      WHERE center_id=? AND metric=? ;
    SQL
  )
  $nalert+=1
end

def add_history(msg, last_ts, label, now_ts)
  if last_ts then
    unit='days'
    age=((now_ts-last_ts)/86400.0).round(2)
    if age < 1.0 then
      unit='hours'
      age=((now_ts-last_ts)/3600.0).round(2)
    end
    msg << " last_#{label}=#{Time.at(last_ts).show}"\
      " #{unit}_since_last_#{label}=#{age}"
  else
    msg << " last_#{label}=(null)"
  end
end

thresholds.each do |row|

  center_id,
  metric,
  low1,
  low3,
  low24,
  high1,
  high3,
  last_zero_time,
  last_nonzero_time,
  since_low1,
  since_low3,
  since_low24,
  since_high1,
  since_high3 = row
  
  #
  # 最新24時間分取得
  #

  data =
    db.execute(
      <<~SQL, [center_id, metric, now_ts - 24 * 3600]
        select
          ts,
          value
        from metrics
        where center_id = ?
          and metric = ?
          and ts >= ?
        order by ts
      SQL
    )

  # max(ts) が取れても、新規追加のセンターなどで空になるかもしれない
  next if data.empty?

  values =
    data.map { |_, value| value.to_f }

  #
  # v1
  #

  next if values.size < 2

  curr_v1 = values[-1]

  #
  # v3
  #

  curr_v3 = nil

  if values.size >= 3
    curr_v3 = values.last(3).sum
  end

  #
  # v24
  #

  curr_v24 = values.sum

  #
  # low1
  #

  # 閾値未満の異常値かつ未発報状態なら発報する
  if curr_v1 < low1 and not since_low1 then
    msg="ALERT low1 #{center_id}.#{metric} "\
      "current=#{curr_v1} threshold=#{low1.round(2)}"
    # 現在値がゼロになって発報するときは履歴情報を追加
    if curr_v1==0 then
      add_history(msg, last_zero_time, 'zero', now_ts)
    end
    msg.sub!(/^ALERT/, 'INFO') if /stored/===metric
    sys_notice(msg)
    alert_begin(db, center_id, metric, 'since_low1', now_ts)
  # 正常値かつ既発報状態なら解除報
  elsif curr_v1 >= low1 and since_low1
    hours = ((now_ts - since_low1) / 3600.0).round(2)
    msg="RECOVER low1 #{center_id}.#{metric} "\
      "current=#{curr_v1} threshold=#{low1.round(2)}"\
      " duration_hours=#{hours}"
    add_history(msg, last_nonzero_time, 'nonzero', now_ts)
    msg.sub!(/^RECOVER/, 'CLEAR') if /stored/===metric
    sys_notice(msg)
    alert_end(db, center_id, metric, 'since_low1')
  end

  #
  # high1
  #

  if curr_v1 > high1 and not since_high1 then
    msg=
      "ALERT high1 "\
      "#{center_id}.#{metric} "\
      "current=#{curr_v1} threshold=#{high1.round(2)}"
    if high1==0.0 then
      add_history(msg, last_nonzero_time, 'nonzero', now_ts)
    end
    msg.sub!(/^ALERT/, 'INFO') if /stored/===metric
    sys_notice(msg)
    alert_begin(db, center_id, metric, 'since_high1', now_ts)
  end
  if curr_v1 <= high1 and since_high1 then
    msg=
      "RECOVER high1 "\
      "#{center_id}.#{metric} "\
      "current=#{curr_v1} threshold=#{high1.round(2)}"
    add_history(msg, last_zero_time, 'zero', now_ts)
    msg.sub!(/^RECOVER/, 'CLEAR') if /stored/===metric
    sys_notice(msg)
    alert_end(db, center_id, metric, 'since_high1')
  end

  #
  # low3
  #

  if curr_v3 < low3 and not since_low3 then
    msg =
      "ALERT low3 #{center_id}.#{metric} "\
      "current=#{curr_v3} threshold=#{low3.round(2)}"
    if curr_v3==0 then
      add_history(msg, last_zero_time, 'zero', now_ts)
    end
    msg.sub!(/^ALERT/, 'INFO') if /stored/===metric
    sys_notice(msg)
    alert_begin(db, center_id, metric, 'since_low3', now_ts)
  elsif curr_v3 >= low3 and since_low3 then
    hours = ((now_ts - since_low3) / 3600.0).round(2)
    msg =
      "RECOVER low3 #{center_id}.#{metric} "\
      "current=#{curr_v3} threshold=#{low3.round(2)}"\
      " duration_hours=#{hours}"
    msg.sub!(/^RECOVER/, 'CLEAR') if /stored/===metric
    sys_notice(msg)
    alert_end(db, center_id, metric, 'since_low3')
  end

  #
  # high3
  #

  if curr_v3 > high3 and not since_high3 then
    msg=
      "ALERT high3 "\
      "#{center_id}.#{metric} "\
      "current=#{curr_v3} threshold=#{high3.round(2)}"
    if high3==0.0 then
      add_history(msg, last_nonzero_time, 'nonzero', now_ts)
    end
    msg.sub!(/^ALERT/, 'INFO') if /stored/===metric
    sys_notice(msg)
    alert_begin(db, center_id, metric, 'since_high3', now_ts)
  end
  if curr_v3 <= high3 and since_high3 then
    msg=
      "RECOVER high3 "\
      "#{center_id}.#{metric} "\
      "current=#{curr_v3} threshold=#{high3.round(2)}"
    add_history(msg, last_zero_time, 'zero', now_ts)
    msg.sub!(/^RECOVER/, 'CLEAR') if /stored/===metric
    sys_notice(msg)
    alert_end(db, center_id, metric, 'since_high3')
  end


  #
  # low24
  #

  if curr_v24 < low24 and not since_low24 then
    msg="ALERT low24 #{center_id}.#{metric} "\
      "current=#{curr_v24} threshold=#{low24.round(2)}"
    if curr_v24==0 then
      add_history(msg, last_nonzero_time, 'nonzero', now_ts)
    end
    msg.sub!(/^ALERT/, 'INFO') if /stored/===metric # tested
    sys_notice(msg)
    alert_begin(db, center_id, metric, 'since_low24', now_ts)
  elsif curr_v24 >= low24 and since_low24
    hours = ((now_ts - since_low24) / 3600.0).round(2)
    msg="RECOVER low24 #{center_id}.#{metric} "\
      "current=#{curr_v24} threshold=#{low24.round(2)}"\
      " duration_hours=#{hours}"
    add_history(msg, last_nonzero_time, 'nonzero', now_ts)
    msg.sub!(/^RECOVER/, 'CLEAR') if /stored/===metric
    sys_notice(msg)
    alert_end(db, center_id, metric, 'since_low24')
  end

end

if $nalert>0 then
  puts ""
  puts "monitor: https://toyoda-eizi.net/rrd/wis.html"
  puts "source: https://www.wis-jma.go.jp/iwgmonitor/iwgmonitor.jsp"
end

Syslog.info('okay no alert this time') if $nolog

db.close
Syslog.close