require File.join(File.dirname(__FILE__), "service")

module Charrington
  class AlterTable
    # This service will add columns to an existing table dynamically based on finding new keys in the JSON structure.
    # This is potentially called from Insert when an insert fails.

    include Service
    attr_reader :connection, :event, :table_name, :columns
    attr_accessor :column_types

    Error = Class.new(StandardError)
    AlterFailed = Class.new(Error)

    def initialize(connection, event, table_name, columns)
      @connection = connection
      @event = event
      @table_name = table_name
      @columns = columns
      @column_types = []
    end

    def call
      set_column_types
      alter_table
      true
    rescue => e
      raise AlterFailed, e.message
    ensure
      @column_types.clear if @column_types.is_a? Array
    end

    private

    def alter_table
      execute("ALTER TABLE IF EXISTS #{table_name} #{columns_fragment}")
    end

    def columns_fragment
      column_types.map do |column|
        "ADD COLUMN IF NOT EXISTS #{column}"
      end.join(",")
    end

    def set_column_types
      (columns - current_table_columns).each_with_index do |key, idx|

        case event[key]
        when Time, LogStash::Timestamp
          column_types << "#{key} TIMESTAMP"
        when Date
          column_types << "#{key} DATE"
        when Integer
          column_types << "#{key} BIGINT"
        when BigDecimal
          column_types << "#{key} DECIMAL"
        when Float
          column_types << "#{key} DOUBLE PRECISION"
        when true, false
          column_types << "#{key} BOOLEAN"
        else
          column_types << "#{key} VARCHAR"
        end
      end
    end

    def current_table_columns
      sql = "SELECT * FROM #{table_name} LIMIT 1;"
      rs = executeQuery(sql)
      meta_data = rs.getMetaData()
      column_count = meta_data.getColumnCount()

      (1..column_count).map {|i| meta_data.getColumnName(i) }
    end

    def execute(sql)
      stmt = connection.prepareStatement(prep_sql(sql))
      stmt.execute()
    rescue Java::OrgPostgresqlUtil::PSQLException => e
      # @logger.error("#{e.message}")
    ensure
      stmt.close unless stmt.nil?
    end

    def executeQuery(sql)
      stmt = connection.createStatement()
      stmt.executeQuery(prep_sql(sql))
    rescue Java::OrgPostgresqlUtil::PSQLException => e
      # @logger.error("#{e.message}")
    ensure
      stmt.close unless stmt.nil?
    end

    def prep_sql(sql)
      sql.gsub(/\s+/, " ").strip
    end
  end
end