Class: Joggle::Pablotron::Cache

Inherits:
Object
  • Object
show all
Includes:
Observable
Defined in:
lib/joggle/pablotron/cache.rb

Constant Summary collapse

DEFAULTS = 
{
  'user-agent' => "Pablotron-Cacher/0.0.0",
}
HEADER_DELIM =

delimiter for appending header string to url (chosen because it won’t appear in a valid url)

'://?&#'

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Observable

#fire, #on, #un

Constructor Details

#initialize(cache_store, extra_headers = nil) ⇒ Cache 



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# File 'lib/joggle/pablotron/cache.rb', line 15

def initialize(cache_store, extra_headers = nil)
  @extras = extra_headers
  @store = cache_store
end

Class Method Details

.urlify(base, args = nil, hash = nil) ⇒ Object 



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# File 'lib/joggle/pablotron/cache.rb', line 20

def self.urlify(base, args = nil, hash = nil)
  ret = base

  if args && args.size > 0
    ret = base + '?' + args.map { |k, v| 
      [k, v].map { |s| CGI.escape(s.to_s) }.join('=') 
    }.join('&')
  end

  if hash
    ret << '#' + hash
  end
  
  # return result
  ret
end

Instance Method Details

#delete(url, headers = nil) ⇒ Object 



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# File 'lib/joggle/pablotron/cache.rb', line 111

def delete(url, headers = nil)
  key = url_key(url, headers)
  @store.delete_cached(key)
end

#get(url, headers = nil) ⇒ Object 



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# File 'lib/joggle/pablotron/cache.rb', line 58

def get(url, headers = nil)
  ret = nil

  # create store key
  key = url_key(url, headers)

  # build headers
  opt = expand_headers(headers)

  # if we have an existing cache entry for this url,
  # then use the last-modified and etag headers
  if entry = @store.get_cached(key)
    opt.update({
      'if-modified-since' => entry['last'].to_s,
      'if-none-match'     => entry['etag'],
    })
  end

  # fetch url and handle result
  begin 
    open(url, opt) do |fh|
      ret  = fh.read

      # update store
      @store.add_cached(key, {
        'last'  => fh.last_modified.to_s || fh.meta['date'],
        'etag'  => fh.meta['etag'],
        'data'  => ret.to_s.dup,
      })

      fire('cache_updated', url, ret)
    end
  rescue OpenURI::HTTPError => err
    case err.io.status.first
    when  /^304/
      # not modified
      ret = entry['data'] 
      fire('cache_not_modified', url)
    else
      # unknown status code
      fire('cache_http_error', url, err.io.status.first, err.io.status.last)
    end
  end

  # return result
  ret
end

#has?(url, headers = nil) ⇒ Boolean 



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# File 'lib/joggle/pablotron/cache.rb', line 106

def has?(url, headers = nil)
  key = url_key(url, headers)
  @store.has_cached?(key)
end

#url_key(url, headers = nil) ⇒ Object 



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# File 'lib/joggle/pablotron/cache.rb', line 41

def url_key(url, headers = nil)
  ret = url

  # append header fragment
  if headers && headers.size > 0
    # sort, concatenate, and append headers to url
    ret += HEADER_DELIM + headers.keys.map { |key| 
      key.downcase 
    }.sort.map { |k| 
      "#{k}:#{headers[k]}" 
    }.join(',')
  end

  # return results
  ret
end