# Author::    Eric Crane  (mailto:eric.crane@mac.com)
# Copyright:: Copyright (c) 2023 Eric Crane.  All rights reserved.
#
# A Postgres database connection.
#
#   https://rubygems.org/gems/pg/versions/0.18.4
#   https://github.com/ged/ruby-pg
#   
require 'pg'

module Gloo
  module Objs
    class Pg < Gloo::Core::Obj

      KEYWORD = 'postgres'.freeze
      KEYWORD_SHORT = 'pg'.freeze

      HOST = 'host'.freeze
      DB = 'database'.freeze
      USER = 'username'.freeze
      PASSWD = 'password'.freeze

      #
      # The name of the object type.
      #
      def self.typename
        return KEYWORD
      end

      #
      # The short name of the object type.
      #
      def self.short_typename
        return KEYWORD_SHORT
      end

      # ---------------------------------------------------------------------
      #    Children
      # ---------------------------------------------------------------------

      #
      # Does this object have children to add when an object
      # is created in interactive mode?
      # This does not apply during obj load, etc.
      #
      def add_children_on_create?
        return true
      end

      #
      # Add children to this object.
      # This is used by containers to add children needed
      # for default configurations.
      #
      def add_default_children
        fac = @engine.factory
        fac.create_string HOST, nil, self
        fac.create_string DB, nil, self
        fac.create_string USER, nil, self
        fac.create_string PASSWD, nil, self
      end

      # ---------------------------------------------------------------------
      #    Messages
      # ---------------------------------------------------------------------

      #
      # Get a list of message names that this object receives.
      #
      def self.messages
        return super + [ 'verify' ]
      end

      #
      # SSH to the host and execute the command, then update result.
      #
      def msg_verify
        return unless connects?

        @engine.heap.it.set_to true
      end

      # ---------------------------------------------------------------------
      #    DB functions (all database connections)
      # ---------------------------------------------------------------------

      #
      # Open a connection and execute the SQL statement.
      # Return the resulting data.
      #
      def query( sql, params = nil )
        heads = []
        data = []
        client = pg_conn

        if params
          param_arr =  []
          params.each do |p|
            param_arr << { :value => p, :type => 0, :format => 0 }
          end
          rs = client.exec_params( sql, params )
        else
          rs = client.exec( sql )
        end

        if rs && ( rs.count > 0 )
          rs[0].each do |name, val|
            heads << name
          end
          rs.each_with_index do |row, index|
            arr = []
            row.each do |name, val|
              arr << val
            end
            data << arr
          end
        end

        return [ heads, data ]
      end

      # 
      # Based on the result set, build a QueryResult object.
      # 
      def get_query_result( result )
        return QueryResult.new result[0], result[1], @engine
      end


      # ---------------------------------------------------------------------
      #    Private functions
      # ---------------------------------------------------------------------

      private

      #
      # Get the host from the child object.
      # Returns nil if there is none.
      #
      def host_value
        o = find_child HOST
        return nil unless o

        o = Gloo::Objs::Alias.resolve_alias( @engine, o )
        return o.value
      end

      #
      # Get the Database name from the child object.
      # Returns nil if there is none.
      #
      def db_value
        o = find_child DB
        return nil unless o

        o = Gloo::Objs::Alias.resolve_alias( @engine, o )
        return o.value
      end

      #
      # Get the Username from the child object.
      # Returns nil if there is none.
      #
      def user_value
        o = find_child USER
        return nil unless o

        o = Gloo::Objs::Alias.resolve_alias( @engine, o )
        return o.value
      end

      #
      # Get the Password name from the child object.
      # Returns nil if there is none.
      #
      def passwd_value
        o = find_child PASSWD
        return nil unless o

        o = Gloo::Objs::Alias.resolve_alias( @engine, o )
        return o.value
      end

      #
      # Try the connection and make sure it works.
      # Returns true if we can establish a connection.
      #
      def connects?
        begin
          result = pg_conn.exec( "SELECT NOW()" )
        rescue => e
          @engine.err e.message
          @engine.heap.it.set_to false
          return false
        end
        return true
      end

      # 
      # Get the PG connection.
      # 
      def pg_conn
        if host_value
          conn = PG.connect(
            host_value, 5432, '', '', 
            db_value, 
            user_value, 
            passwd_value )
        else
          conn = PG.connect( dbname: db_value )
        end
      end

    end
  end
end