# postgresql_adaptor.rb
# author: Luke Holden <lholden@cablelan.net>
# notes: Currently this adaptor does not pass the test_zero_date_fields
#        and test_zero_datetime_fields unit tests in the BasicsTest test
#        group.
#
#        This is due to the fact that, in postgresql you can not have a
#        totally zero timestamp. Instead null/nil should be used to 
#        represent no value.
#

require 'active_record/connection_adapters/abstract_adapter'
require 'parsedate'

module ActiveRecord
  class Base
    # Establishes a connection to the database that's used by all Active Record objects
    def self.postgresql_connection(config) # :nodoc:
      require_library_or_gem 'postgres' unless self.class.const_defined?(:PGconn)
      symbolize_strings_in_hash(config)
      host     = config[:host]
      port     = config[:port]     || 5432 unless host.nil?
      username = config[:username].to_s
      password = config[:password].to_s

      if config.has_key?(:database)
        database = config[:database]
      else
        raise ArgumentError, "No database specified. Missing argument: database."
      end

      ConnectionAdapters::PostgreSQLAdapter.new(
        PGconn.connect(host, port, "", "", database, username, password), logger
      )
    end
  end

  module ConnectionAdapters
    class PostgreSQLAdapter < AbstractAdapter # :nodoc:
      def select_all(sql, name = nil)
        select(sql, name)
      end

      def select_one(sql, name = nil)
        result = select(sql, name)
        result.nil? ? nil : result.first
      end

      def columns(table_name, name = nil)
        table_structure(table_name).inject([]) do |columns, field|
          columns << Column.new(field[0], field[2], field[1])
          columns
        end
      end

      def insert(sql, name = nil, pk = nil, id_value = nil)
        execute(sql, name = nil)
        table = sql.split(" ", 4)[2]
        return id_value || last_insert_id(table, pk)
      end

      def execute(sql, name = nil)
        log(sql, name, @connection) { |connection| connection.query(sql) }
      end

      alias_method :update, :execute
      alias_method :delete, :execute

      def begin_db_transaction()    execute "BEGIN" end
      def commit_db_transaction()   execute "COMMIT" end
      def rollback_db_transaction() execute "ROLLBACK" end

      def quote_column_name(name)
        return "\"#{name}\""
      end

      private
        def last_insert_id(table, column = "id")
          sequence_name = "#{table}_#{column || 'id'}_seq"
          @connection.exec("SELECT currval('#{sequence_name}')")[0][0].to_i
        end

        def select(sql, name = nil)
          res = nil
          log(sql, name, @connection) { |connection| res = connection.exec(sql) }
  
          results = res.result           
          rows = []
          if results.length > 0
            fields = res.fields
            results.each do |row|
              hashed_row = {}
              row.each_index { |cel_index| hashed_row[fields[cel_index]] = row[cel_index] }
              rows << hashed_row
            end
          end
          return rows
        end

        def split_table_schema(table_name)
          schema_split = table_name.split('.')
          schema_name = "public"
          if schema_split.length > 1
            schema_name = schema_split.first.strip
            table_name = schema_split.last.strip
          end
          return [schema_name, table_name]
        end

        def table_structure(table_name)
          database_name = @connection.db
          schema_name, table_name = split_table_schema(table_name)
          
          # Grab a list of all the default values for the columns.
          sql =  "SELECT column_name, column_default, character_maximum_length, data_type "
          sql << "  FROM information_schema.columns "
          sql << " WHERE table_catalog = '#{database_name}' "
          sql << "   AND table_schema = '#{schema_name}' "
          sql << "   AND table_name = '#{table_name}';"

          column_defaults = nil
          log(sql, nil, @connection) { |connection| column_defaults = connection.query(sql) }
          column_defaults.collect do |row|
              field   = row[0]
              type    = type_as_string(row[3], row[2])
              default = default_value(row[1])
              length  = row[2]

              [field, type, default, length]
          end
        end

        def type_as_string(field_type, field_length)
          type = case field_type
            when 'numeric', 'real', 'money'      then 'float'
            when 'character varying', 'interval' then 'string'
            when 'timestamp without time zone'   then 'datetime'
            else field_type
          end

          size = field_length.nil? ? "" : "(#{field_length})"

          return type + size
        end

        def default_value(value)
          # Boolean types
          return "t" if value =~ /true/i
          return "f" if value =~ /false/i
          
          # Char/String type values
          return $1 if value =~ /^'(.*)'::(bpchar|text|character varying)$/
          
          # Numeric values
          return value if value =~ /^[0-9]+(\.[0-9]*)?/

          # Date / Time magic values
          return Time.now.to_s if value =~ /^\('now'::text\)::(date|timestamp)/

          # Fixed dates / times
          return $1 if value =~ /^'(.+)'::(date|timestamp)/
          
          # Anything else is blank, some user type, or some function
          # and we can't know the value of that, so return nil.
          return nil
        end
    end
  end
end