const AWS = require('aws-sdk');
var SSM;
var CW;

exports.handler = (event, context, callback) => {
  if(SSM===undefined){
    SSM = new AWS.SSM({region: 'ap-northeast-1'});
  }
  if(CW===undefined){
    CW = new AWS.CloudWatch({region: 'ap-northeast-1'});
  }

  Promise.resolve()
  .then(()=>{
    return new Promise((resolve)=>{
      let ssm_params = {
        Name: "/monitor/certificate/domains"
      };
      let ssm_parameter = SSM.getParameter(ssm_params).promise();
      ssm_parameter.then((data)=>{
        resolve(JSON.parse(data.Parameter.Value));
      });
    });
  })
  .then((domains)=>{
    return new Promise((resolve)=>{
      let check_expire_list = [];
      domains.forEach((domain)=>{
        check_expire_list.push(checkExpire(domain));
      });
      Promise.all(check_expire_list)
      .then((result_valid)=>{
        resolve(result_valid);
      });
    });
  })
  .then((valid_list)=>{
    return new Promise((resolve)=>{
      let metric_list = [];
      valid_list.forEach((result)=>{
        var params = {
          MetricData: [
            {
              MetricName: 'valid_days',
              Dimensions: [
                {
                  Name: 'domain',
                  Value: result.domain
                }
              ],
              Unit: 'None',
              Value: result.valid_days
            }
          ],
          Namespace: 'SSLCertificate'
        };
        metric_list.push(CW.putMetricData(params).promise());
      });
      Promise.all(metric_list)
      .then((data)=>{
        resolve();
      });
    });
  })
  .then(()=>{
    callback();
  });
};

var checkExpire = (domain)=>{
  return new Promise((resolve)=>{
    let exec = require('child-process-promise').exec;
    let cmd = "openssl s_client -connect " + domain + ":443 -servername " + domain + " < /dev/null 2> /dev/null | openssl x509 -text | grep Not | sed -e 's/^  *//g' | sed -e 's/Not.*:\ //g'";
    let now = new Date();
    exec(cmd)
    .then((result)=>{
      let not = result.stdout.split("\n");
      let expire_date = new Date(not[1]);
      let valid_days = Math.floor((expire_date - now) / 1000 / 3600 / 24);
      console.log(domain+" の残り日数は "+valid_days + " です");
      resolve({'domain': domain,'valid_days': valid_days});
    });
  });
};

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: SSL certificate monitoring function.
Resources:
  monitorCertExpire:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: monitorCertExpire/index.handler
      Runtime: nodejs6.10
      Description: ''
      MemorySize: 256
      Timeout: 300
      Events:
        CheckExpire:
          Type: Schedule
          Properties:
            Schedule: rate(1 day)
            Input: "{}"