Class: Diffux::Snapshotter

Inherits:
Object
  • Object
show all
Defined in:
lib/diffux_core/snapshotter.rb

Overview

Snapshotter is responsible for delegating to PhantomJS to take the snapshot for a given URL and viewoprt, and then saving that snapshot to a file and storing any metadata on the Snapshot object.

Constant Summary collapse

SCRIPT_PATH = 
File.join(File.dirname(__FILE__), 'script/take-snapshot.js').to_s

Instance Method Summary collapse

Constructor Details

#initialize(url: raise, viewport_width: raise, outfile: raise, user_agent: nil) ⇒ Snapshotter

Returns a new instance of Snapshotter.

Parameters:

  • url (String) (defaults to: raise) —

    the URL to snapshot

  • viewport_width (Integer) (defaults to: raise) —

    the width of the screen used when snapshotting

  • outfile (File) (defaults to: raise) —

    where to store the snapshot PNG.

  • user_agent (String) (defaults to: nil) —

    an optional useragent string to used when requesting the page.



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# File 'lib/diffux_core/snapshotter.rb', line 19

def initialize(url:     raise, viewport_width: raise,
               outfile: raise, user_agent: nil)
  @viewport_width = viewport_width
  @user_agent     = user_agent
  @outfile        = outfile
  @url            = url
end

Instance Method Details

#take_snapshot! ⇒ Hash

Takes a snapshot of the URL and saves it in the out_file as a PNG image.

Returns:

  • (Hash) —

    a hash containing the following keys: title [String] the <title> of the page being snapshotted log [String] a log of events happened during the snapshotting process



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# File 'lib/diffux_core/snapshotter.rb', line 32

def take_snapshot!
  result = {}
  opts = {
    address: @url,
    outfile: @outfile,
    viewportSize: {
      width:  @viewport_width,
      height: @viewport_width,
    },
  }
  opts[:userAgent] = @user_agent if @user_agent

  run_phantomjs(opts) do |line|
    begin
      result = JSON.parse line, symbolize_names: true
    rescue JSON::ParserError
      # We only expect a single line of JSON to be output by our snapshot
      # script. If something else is happening, it is likely a JavaScript
      # error on the page and we should just forget about it and move on
      # with our lives.
    end
  end
  result
end