require 'pg'

class Instructor

  # These are my database credentials. You'll need to replace them with yours.
  CONN = PG::Connection.new({
                                host: 'localhost',
                                user: 'postgres',
                                password: 'postgres',
                                dbname: 'ormlecture'
                            })

  attr_accessor :name, :coolness
  attr_reader :id

  def initialize(name, coolness, id=nil)
    @name = name
    @coolness = coolness
    @id = id
  end

  def is_new?
    @id.nil?
  end

  def valid?
    @coolness > 9000
  end

  def save
    raise 'Invalid Instructor!' unless valid?
    if is_new?
      result = CONN.exec_params('INSERT INTO instructors (name, coolness) VALUES ($1, $2) returning id', [@name, @coolness])
      @id = result[0]['id']
    else
      CONN.exec_params('UPDATE instructors SET name = $1, coolness = $2 WHERE id = $3', [@name, @coolness, @id])
    end
  end

  def destroy
    CONN.exec_params('DELETE FROM instructors WHERE id = $1', [@id])
  end

  ## DANGER Below is wet wet code. It's up to you to DRY it out and make it more succinct.
  
  def self.find(id)
    result = nil
    CONN.exec_params('SELECT id, name, coolness FROM instructors WHERE id = $1 LIMIT 1', [id]) do |rows|
      rows.each do |row|
        result = Instructor.new(
            row['name'],
            row['coolness'],
            row['id']
        )
      end
    end
    result
  end

  def self.all
    results = []
    CONN.exec_params('SELECT id, name, coolness FROM instructors') do |rows|
      rows.each do |row|
        results << Instructor.new(
            row['name'],
            row['coolness'],
            row['id']
        )
      end
    end
    results
  end

  def self.where_coolness_above(coolness)
    results = []
    CONN.exec_params('SELECT id, name, coolness FROM instructors WHERE coolness > $1', [coolness]) do |rows|
      rows.each do |row|
        results << Instructor.new(
            row['name'],
            row['coolness'],
            row['id']
        )
      end
    end
    results
  end

end