require 'pg'

class MicroSql::PgAdapter < MicroSql
  def initialize(url)
    uri = URI.parse(url)
    
    @impl = PG.connect :host     => uri.host, 
                       :port     => uri.port || 5433, 
                       :user     => uri.user, 
                       :password => uri.password, 
                       :dbname   => uri.path[1..-1]
  end

  def tables
    exec("SELECT tablename FROM pg_tables WHERE tablename NOT LIKE 'pg_%' AND tablename NOT LIKE 'sql_%'").map(&:first)
  end
  
  def execute_batch(sql)
    sql.split(";").each { exec(part) }
  end
  
  private

  def execute(flag, sql, *args)
    statement = prepare(sql) if flag == :prepare
    result = if statement
      @impl.exec_prepared(statement, args)
    else
      @impl.exec(sql, args)
    end

    if sql =~ /^\s*(UPDATE|DELETE|INSERT)/i
      return result.cmd_tuples
    end

    types = (0 ... result.num_fields).map do |i| 
      # Get the type of the second column of the result 'res'
      @impl.exec( "SELECT format_type($1,$2)", [result.ftype(i), result.fmod(i)] ).getvalue( 0, 0 )
    end

    result.values.map do |rec|
      types.each_with_index do |type, idx|
        case type
        when "text", "name"           then :nop
        when "integer", "bigint"      then rec[idx] = rec[idx] && rec[idx].to_i
        else  raise "Unknown column type #{type}: #{rec[idx].inspect}"
        end
      end
      
      rec
    end
  end
  
  def prepare_query(key, sql)
    idx = 0
    query = sql.gsub("?") do 
      idx += 1
      "$#{idx}" 
    end

    return nil if idx == 0
    @impl.prepare(key, query)
    key
  end
end