require 'mysql2'
require 'flydata/command_logger'
require 'flydata/util/mysql_util'

module Flydata

  class CompatibilityCheck
    include CommandLoggable

    class CompatibilityError < StandardError
    end

    def initialize(dp_hash, de_hash=nil, options={})
      @dp = dp_hash
      @errors=[]
    end

    def check
      self.methods.grep(/^check_/).each do |m|
        begin
          send(m)
        rescue ArgumentError => e
          # ignore
        rescue CompatibilityError => e
          @errors << e
        end
      end
      print_errors
    end

    def print_errors
      return if @errors.empty?
      log_error_stderr "There may be some compatibility issues with this current server : "
      @errors.each do |error|
        log_error_stderr "  * #{error.message}"
      end
      raise "Please correct these errors if you wish to run FlyData Agent"
    end

  end

  class AgentCompatibilityCheck < CompatibilityCheck
    class AgentCompatibilityError < StandardError
    end

    TCP_PORT=45326
    SSL_PORT=45327

    def check_outgoing_ports
      ports = [TCP_PORT]
      ports << SSL_PORT unless ENV['FLYDATA_ENV_KEY'] == 'development'

      url = @dp["servers"].first
      errors = {}
      ports.each do |port|
        begin
          e = TCPSocket.new(url, port)
          e.close
        rescue => e
          errors[port] = e
        end
      end

      unless errors.empty?
        message = "Cannot connect to outside ports. Please check to make sure you have these outgoing ports open."
        errors.each do |port, e|
          message += "  Port #{port}, Error #{e.class.name}: #{e.to_s}"
        end
        raise AgentCompatibilityError, message
      end
    end
  end

  class MysqlCompatibilityCheck < CompatibilityCheck

    class MysqlCompatibilityError < StandardError
    end

    SELECT_QUERY_TMPLT = "SELECT %s"
    BINLOG_RETENTION_HOURS = 24

    #def initialize(de_hash, dump_dir=nil)
    def initialize(dp_hash, de_hash, options={})
      super
      @db_opts = [:host, :port, :username, :password, :database].inject({}) {|h, sym| h[sym] = de_hash[sym.to_s]; h}
      @dump_dir = options[:dump_dir] || nil
      @backup_dir = options[:backup_dir] || nil
    end

    def print_errors
      return if @errors.empty?
      log_error_stderr "There may be some compatibility issues with your MySQL credentials: "
      @errors.each do |error|
        log_error_stderr "  * #{error.message}"
      end
      raise "Please correct these errors if you wish to run FlyData Sync"
    end

    def check_mysql_user_compat
      client = Mysql2::Client.new(@db_opts)
      grants_sql = "SHOW GRANTS"
      correct_db = ["ON (\\*|#{@db_opts[:database]})","TO '#{@db_opts[:username]}"]
      necessary_permission_fields= ["SELECT","RELOAD","LOCK TABLES","REPLICATION SLAVE","REPLICATION CLIENT"]
      all_privileges_field= ["ALL PRIVILEGES"]
      result = client.query(grants_sql)
      # Do not catch MySQL connection problem because check should stop if no MySQL connection can be made.
      client.close
      missing_priv = []
      result.each do |res|
        # SHOW GRANTS should only return one column
        res_value = res.values.first
        if correct_db.all? {|perm| res_value.match(perm)}
          necessary_permission_fields.each do |priv|
            missing_priv << priv unless res_value.match(priv)
          end
          return true if missing_priv.empty? or all_privileges_field.all? {|d| res_value.match(d)}
        end
      end
      raise MysqlCompatibilityError, "The user '#{@db_opts[:username]}' does not have the correct permissions to run FlyData Sync\n    * These privileges are missing: #{missing_priv.join(", ")}"
    end

    def check_mysql_protocol_tcp_compat
      query = Util::MysqlUtil.generate_mysql_show_grants_cmd(@db_opts)

      Open3.popen3(query) do |stdin, stdout, stderr|
        stdin.close
        while !stderr.eof?
          lines = []
          while line = stderr.gets; lines << line.strip; end
          err_reason = lines.join(" ")
          log_error("Error occured during access to mysql server.", {err: err_reason})

          unless /Warning: Using a password on the command line interface can be insecure/ === err_reason
            raise MysqlCompatibilityError, "Cannot connect to MySQL database. Please make sure you can connect with this command:\n      $ mysql -u #{@db_opts[:username]} -h #{@db_opts[:host]} -P #{@db_opts[:port]} #{@db_opts[:database]} --protocol=tcp -p"
          end
        end
      end
    end

    def check_mysql_parameters_compat
      sys_var_to_check = {'@@binlog_format'=>'ROW', '@@binlog_checksum'=>'NONE', '@@log_bin_use_v1_row_events'=>1, '@@log_slave_updates'=>1}
      errors={}

      client = Mysql2::Client.new(@db_opts)

      begin
        sys_var_to_check.each_key do |sys_var|
          sel_query = SELECT_QUERY_TMPLT % sys_var
          begin
            result = client.query(sel_query)
            unless result.first[sys_var] == sys_var_to_check[sys_var]
              errors[sys_var]=result.first[sys_var]
            end
          rescue Mysql2::Error => e
            if e.message =~ /Unknown system variable/
              unless e.message =~ /(binlog_checksum|log_bin_use_v1_row_events)/
                errors[sys_var] = false
              end
            else
              raise e
            end
          end
        end
      ensure
        client.close
      end
      unless errors.empty?
        error_explanation = ""
        errors.each_key do |err_key|
          error_explanation << "\n    * #{err_key} is #{errors[err_key]} but should be #{sys_var_to_check[err_key]}"
        end
        raise MysqlCompatibilityError, "These system variable(s) are not the correct value: #{error_explanation}\n   Please change these system variables for FlyData Sync to run correctly"
      end
    end

    def check_mysql_binlog_retention
      client = Mysql2::Client.new(@db_opts)
      begin
        if is_rds?(@db_opts[:host])
          run_rds_retention_check(client)
        else
          run_mysql_retention_check(client)
        end
      ensure
        client.close
      end
    end

    def check_writing_permissions
      write_errors = []
      paths_to_check = ["~/.flydata"]
      paths_to_check << @dump_dir unless @dump_dir.to_s.empty?
      paths_to_check << @backup_dir unless @backup_dir.to_s.empty?
      paths_to_check.each do |path|
        full_path = File.expand_path(path)
        full_path = File.dirname(full_path) unless File.directory?(full_path)
        write_errors << full_path unless File.writable?(full_path) and File.executable?(full_path)
      end
      unless write_errors.empty?
        error_dir = write_errors.join(", ")
        raise MysqlCompatibilityError, "We cannot access the directories: #{error_dir}"
      end
    end

    def run_mysql_retention_check(mysql_client)
      expire_logs_days_limit = BINLOG_RETENTION_HOURS / 24
      sel_query = SELECT_QUERY_TMPLT % '@@expire_logs_days'
      result = mysql_client.query(sel_query)
      if result.first["@@expire_logs_days"]!=0 and result.first["@@expire_logs_days"] <= expire_logs_days_limit
        raise MysqlCompatibilityError, "Binary log retention is too short\n " +
          "  We recommend the system variable '@@expire_logs_days' to be either set to 0 or at least #{expire_logs_days_limit} days"
      end
    end

    def run_rds_retention_check(mysql_client)
      sql_query =  "call mysql.rds_show_configuration;"

      begin
        result = mysql_client.query(sql_query)
        if result.first["name"]=="binlog retention hours"
          if result.first["value"].nil? or result.first["value"].to_i <= BINLOG_RETENTION_HOURS
            raise MysqlCompatibilityError, "Binary log retention is too short\n" +
                                           "  We recommend setting RDS binlog retention to be at least #{BINLOG_RETENTION_HOURS} hours. To do this, run this on your RDS MySQL database:\n" +
                                           "  $> call mysql.rds_set_configuration('binlog retention hours', 94);"
          end
        end
      rescue Mysql2::Error => e
        if e.message =~ /command denied to user/
          log_warn_stderr("[WARNING]Cannot verify RDS retention period on currend MySQL user account.\n" +
                          "To see retention period, please run this on your RDS:\n" +
                          "  $> call mysql.rds_show_configuration;\n" +
                          "Please verify that the hours is not nil and is at least #{BINLOG_RETENTION_HOURS} hours\n" +
                          "To set binlog retention hours, you can run this on your RDS:\n" +
                          "  $> call mysql.rds_set_configuration('binlog retention hours', #{BINLOG_RETENTION_HOURS});\n"
                         )
        else
          raise e
        end
      end

    end

    def is_rds?(hostname)
      hostname.match(/rds.amazonaws.com$/) != nil
    end
  end

end