# encoding: utf-8
require 'net/http'
require 'uri'

class HealthCheckMonitor
  include Mongoid::Document
  include Mongoid::Timestamps

  # 視為失敗的狀態碼。0 代表連不上（逾時、DNS 失敗、憑證錯誤等）
  # 若只要 502 才算失敗，改成 [502]
  FAILURE_STATUSES = [0, 500, 502, 503, 504]

  # 告警視窗。只看這段時間內的檢查紀錄，同一網址在這段時間內也只寄一封
  ALERT_WINDOW = 4.hours

  # 跨 unicorn worker 的互斥鎖，存在 multithreads collection
  LOCK_KEY = 'health_check'

  field :name,                   type: String
  field :target_urls,            type: Array,   default: []
  field :notification_emails,    type: Array,   default: []
  field :check_interval_minutes, type: Integer, default: 5
  field :fail_threshold,         type: Integer, default: 3
  field :timeout,                type: Integer, default: 10
  field :enabled,                type: Boolean, default: true
  field :check_now,              type: Boolean, default: false
  field :last_checked_at,        type: DateTime
  field :create_user_id
  field :update_user_id

  validates :name, presence: true
  validates :check_interval_minutes, numericality: { greater_than_or_equal_to: 1, only_integer: true }

  scope :is_enabled, -> { where(enabled: true) }

  # ── 表單用的字串轉陣列 ──────────────────────────────

  def target_urls_text
    (target_urls || []).join("\n")
  end

  def target_urls_text=(value)
    self.target_urls = value.to_s.split(/\r?\n/).map(&:strip).reject(&:blank?).map do |u|
      u.match(/\Ahttps?:\/\//) ? u : "https://#{u}"
    end
  end

  def notification_emails_text
    (notification_emails || []).join(", ")
  end

  def notification_emails_text=(value)
    self.notification_emails = value.to_s.split(",").map(&:strip).reject(&:blank?)
  end

  # ── 參數 ────────────────────────────────────────

  def threshold
    fail_threshold.to_i > 0 ? fail_threshold.to_i : 3
  end

  def interval_minutes
    check_interval_minutes.to_i > 0 ? check_interval_minutes.to_i : 5
  end

  def due?
    return true if check_now
    return true if last_checked_at.nil?
    last_checked_at + interval_minutes.minutes <= Time.now
  end

  # ── 實際檢查 ─────────────────────────────────────

  def check_url(url)
    uri = URI.parse(url)
    started = Time.now
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = (uri.scheme == 'https')
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE
    http.open_timeout = self.timeout
    http.read_timeout = self.timeout
    response = http.request(Net::HTTP::Get.new(uri.request_uri))
    elapsed = ((Time.now - started) * 1000).round(2)
    { :status => response.code.to_i, :response_time => elapsed, :error => nil }
  rescue => e
    { :status => 0, :response_time => 0, :error => e.message }
  end

  def check_all
    results = {}
    (target_urls || []).each do |url|
      results[url] = check_url(url)
    end
    results
  end

  # 手動與自動共用的唯一入口：檢查 → 寫紀錄 → 判斷 → 寄信
  def run_check
    results = check_all
    alert_logs = []
    results.each do |url, result|
      HealthCheckLog.create(
        :health_check_monitor_id => self.id,
        :url => url,
        :status => result[:status],
        :response_time => result[:response_time],
        :error_message => result[:error]
      )
      target = alert_target(url)
      alert_logs << target if target
    end
    send_alert_email(alert_logs) if alert_logs.present?
    self.check_now = false
    self.last_checked_at = Time.now
    self.save
    results
  end

  # ── 告警判斷 ─────────────────────────────────────

  def failure?(status)
    FAILURE_STATUSES.include?(status.to_i)
  end

  # 條件：ALERT_WINDOW 內已檢查滿 threshold 次、最近 threshold 次全部失敗、
  #       且 ALERT_WINDOW 內還沒寄過這個網址
  def alert_target(url)
    n = threshold
    window_start = Time.now - ALERT_WINDOW
    logs = HealthCheckLog.where(:health_check_monitor_id => self.id,
                                :url => url,
                                :created_at.gte => window_start)
                         .desc(:created_at).limit(n).to_a
    return nil if logs.size < n
    return nil unless logs.all? { |log| failure?(log.status) }
    return nil if alerted_recently?(url)
    logs.first
  end

  def alerted_recently?(url)
    HealthCheckAlert.where(:health_check_monitor_id => self.id,
                           :url => url,
                           :created_at.gte => Time.now - ALERT_WINDOW).exists?
  end

  def mark_alerted(url)
    HealthCheckAlert.create(:health_check_monitor_id => self.id, :url => url)
  end

  # logs 是這次剛好達標的 HealthCheckLog 陣列，全部合併成一封
  def send_alert_email(logs)
    return false if notification_emails.blank? || logs.blank?
    rows = logs.map do |log|
      {
        'url'    => log.url.to_s,
        'status' => log.status.to_s,
        'error'  => log.error_message.to_s
      }
    end
    email = Email.new(
      :module_app_key => 'health_check',
      :mail_to        => notification_emails,
      :mail_subject   => "[網站監控] #{self.name} - #{logs.size} 個網址失敗",
      :template       => 'email/health_check_alert.html.erb',
      :template_data  => {
        'monitor_name' => self.name.to_s,
        'threshold'    => threshold,
        'rows'         => rows,
        'checked_at'   => logs.first.created_at.strftime('%Y-%m-%d %H:%M:%S')
      },
      :mail_sentdate  => Time.now - 1.minute
    )
    email.save
    begin
      email.deliver
      logs.each { |log| mark_alerted(log.url) }
      true
    rescue => e
      Rails.logger.error("[health_check] 寄信失敗: #{e}")
      false
    end
  end

  # ── 自動檢測進入點，由 CronWorker 每分鐘呼叫一次 ──────────

  def self.run_due_checks
    return unless claim_lock
    begin
      is_enabled.each do |monitor|
        begin
          monitor.run_check if monitor.due?
        rescue => e
          Rails.logger.error("[health_check] #{monitor.name} 檢查失敗: #{e}")
        end
      end
    ensure
      release_lock
    end
  end

  # 用 Mongo 的 findAndModify 做原子性搶鎖，只有搶到的 worker 會執行
  def self.claim_lock
    Multithread.create(:key => LOCK_KEY, :status => {}) if Multithread.where(:key => LOCK_KEY).count == 0
    Multithread.where(:key => LOCK_KEY).to_a[1..-1].to_a.each { |m| m.destroy }
    claimed = Multithread.where(:key => LOCK_KEY).any_of(
      { 'status.locked_until' => nil },
      { :'status.locked_until'.lt => Time.now }
    ).find_one_and_update({ '$set' => { 'status.locked_until' => Time.now + 10.minutes } })
    !claimed.nil?
  rescue => e
    Rails.logger.error("[health_check] 搶鎖失敗: #{e}")
    false
  end

  def self.release_lock
    Multithread.where(:key => LOCK_KEY).update_all('$set' => { 'status.locked_until' => nil })
  rescue => e
    Rails.logger.error("[health_check] 釋放鎖失敗: #{e}")
  end
end