class SqlEventAnalyzer

# File lib/sql_event_analyzer.rb, line 38
def initialize(name:)
  @name = name
  @root = Rails.root.to_s
  @stats = {}
end

# File lib/sql_event_analyzer.rb, line 12
def self.start(name: Time.current)
  instance = SqlEventAnalyzer.new(name: name)

  subscription_name = ActiveSupport::Notifications.subscribe('sql.active_record') do |*args|
    event = ActiveSupport::Notifications::Event.new(*args)
    instance.process_event(event)
  end

  if block_given?
    begin
      yield
    ensure
      ActiveSupport::Notifications.unsubscribe(subscription_name)
    end
    write_html(instance)
  end
end

# File lib/sql_event_analyzer.rb, line 30
def self.write_html(instance)
  output_dir = 'tmp/sql_event_analyzer'
  output_path = File.join(output_dir, "#{instance.name}.html")
  FileUtils.mkdir_p(output_dir)
  html = instance.render_as_html
  File.open(output_path, 'w') {|f| f << html}
end

# File lib/sql_event_analyzer.rb, line 45
def process_event(event)
  # Callers from Rails root and not the subscriber itself
  backtrace = caller.select{|line| relevent_caller?(line) }

  # Initialize a uniq SQL use.
  # `:payload` will always be the first instance of the call.
  stat = @stats[backtrace] ||= {
    order: @stats.size,
    count: 0,
    duration: 0,
    payload: event.payload
  }

  # increment stats
  stat[:count] += 1
  stat[:duration] += event.duration
end

# File lib/sql_event_analyzer.rb, line 63
def render_as_html
  ERB.new(erb_template).result(binding)
end

# File lib/sql_event_analyzer.rb, line 91
  def debug_rb(c)
    return unless c
    first = trim_caller(c)
    file, line = if first =~ /(.*\.rb):(\d+)/
                   [$1, $2]
                 end
    rb_src = File.readlines(file)[line.to_i - 1].strip
    <<-EOF.strip_heredoc
    -- #{first}
    --     #{rb_src}
    EOF
  end

# File lib/sql_event_analyzer.rb, line 83
def erb_template
  File.read(File.join(__dir__, 'sql_event_analyzer.erb'))
end

# File lib/sql_event_analyzer.rb, line 79
def explain(payload)
  ActiveRecord::Base.connection.explain(payload[:sql], payload[:binds])
end

# File lib/sql_event_analyzer.rb, line 73
def pretty_sql(sql)
  sql
    .delete('"')
    .gsub(/\b+(SELECT|FROM|WHERE|GROUP|HAVING|LEFT JOIN|LEFT OUTER JOIN|INNER JOIN|JOIN|RIGHT|ORDER|WINDOW)\b+/, "\n\\1")
end

# File lib/sql_event_analyzer.rb, line 69
def relevent_caller?(c)
  c.start_with?(@root) && !c.start_with?(__FILE__)
end

# File lib/sql_event_analyzer.rb, line 87
def trim_caller(c)
  c.gsub(@root, '.')
end