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A Ruby DSL for sorting and delivering email to locations on the filesystem and elsewhere

branch: master
README.md

sortah

For sortin' your friggin' mail.


Build Status


Sortah sort's mail. It provides a ruby EDSL for manipulating email objects. The DSL allows the definition of three principle components:

  • Destinations

A destination takes in an Email object, and returns a system path. This is where the email object passed into it will be saved. Ex:

destination :spam, "spam/" 
destination :ham, "/"

These are -- in essence -- simple delcarations of the structure of your sorting system. They may take one of several forms. The examples above are relative to the mail directory, and will transparently manage organization south of that. They can also be absolute paths, eg:

destination :devnull, :abs => "/dev/null"

which is regarded as an absolutely qualified path. It may also alias another path:

destination :tldr, :devnull 
  • Lenses

Lenses are functions which produce a value given an input email. This value is interpreted as metadata to be used by the routers. Ex:

lens :spam_value do
  x = 0
  email.text.each_line do |line|
    x += (line =~ /extension/) ? 1 : 0
  end
  x
end

lens :word_count do
  email.text.split.size
end

lenses can also depend on other lenses.

lens :spam_ratio :lenses => [:spam_value, :word_count] do
  email.spam_value / email.word_count 
end

You may specify the pass_through option to cause the lens to not set any metadata. This is useful in two cases, updating old metadata, and interaction (typically creational) with other services. Eg:

lens :example_update, :pass_through => true do
  email.spam_value = 1000000 if email.sender == "annoying_guy0022493@hotmail.com"
end

lens :example_interaction, :pass_through => true, lenses => [:spam_value] do
  return unless email.spam_value >= 1000000
  HTTParty.post "http://spamblacklist.net/spammer/new", :body => email.sender
end
  • Routers

This is the core of the language, a router is an object which produce either a router object, or a destination. If it produces a destination, then the email is delivered to that destination. If it produces another router, then the email is passed along to the router produced. A router also 'depends' on lenses. These lenses get applied when the router is called. There is one router which is special, the "root" router, this is the first router which gets called. To declare it, simply declare a router without a name. Ex:

router :spam_filter, :lenses => [:spam_value] do
  send_to :ham if email.spam_value < 10
  send_to :spam 
end

router :root, :lenses => [:word_count] do
  send_to :tldr if email.word_count > 100 
  send_to :spam_filter 
end

send_to will first search for a destination with the given name, if it cannot find one, it will send it search for the corresponding router. It also acts as return -- halting execution of the block when it is called. This is implemented via an exception, which means it may cause performance issues on things like the JVM, YMMV.

when defining a root router with lenses, you must specify ":root" as the title.

Common problems, and how to solve them:

Problem: Adding a mail to an external service, and then saving it.

As a user of sortah, you want to set up filters to save all email from the address "searchable@somewhere.net" to the folder "foobar/", as well as register it with the external service "RubberBandSearch".

Solution

destination :foobar, "foobar/"

lens :search_index , :pass_through => true do
  #code to register the email in RubberBandSearch
  email.indexed? = true
end

router :index_in_rubberband, :lenses => [:search_index] do
  send_to :foobar
end

router :lenses => [:spam?] do
  send_to :devnull if email.spam? 
  send_to :index_in_rubberband 
end

Here we've used a pass_through lens to do the actual indexing, and the router is left as more of a proxy to call the lens.

Problem

As a user of sortah, you want to maintain a whitelist of people who should have their own folders, and you want those people to be subsorted in some arbitrarily deep parent folders, eg:

family/ 
  mom/
  dad/
  uncle_timmy/ 
coworkers/
  pointy_hair/
  dilbert/
  old_coworkers/
    jim/
personal/
  wife/
  friends/
    bob/
    mike/
    jack/

etc. Further, you'd like to only maintain the above file (or something like it), and not have to write new sortah code every time you move jobs or make new friends.[1]

[1] Ideally, this code would maintain a directory structure for you. But as of right now, sortah has no aspirations to do such a thing. Each edition which moves files in the yaml definition file will simply create new folders, it is up to the author of that yaml file to keep the directory coherent with the yaml file.

Solution

First, define a yaml file like the following:

personal: 
  - name: wife
    sender:
      - pretty-lady-who-feeds-me@scary.com
family: 
  - name: mom
    sender:
      - mom@hotmail.com
      - mom@gmail.com
  - name: dad
    sender:
      - dad@work.org
nested:
  - name: example
    reply-to: some_list@place.com
  - deeper-nesting:
    - name: deeper-nested-example
    - reply-to: somewhere_else@overtherainbow.biz.co.uk
#...

This yaml file will represent the directory structure, as well as provide information about how to determine whether the email is from that person or not.

Next, you could define a class Contact, which could be built with the following methods:

class Contact
  # ... contains a definition for 'path' -- which is built from the yaml file.

  def destination 
    destination name, path
  end

  def wants?(email)
    search_fields.any? { |f,v| email[f] =~ /#{v}/ }
  end

  def search_fields
    #these are the key/value pairs from the YAML file which are of the form:
    #  email-field: content_string
    #eg:
    #  sender: 'me@place.net'
    #  reply-to: 'mailing-list@majordomo.com'
    #etc
  end
  # ...
end

All of this code could be bound up in a router, eg:

router :contacts do
  contacts = Contact.load_from_file('contacts.yml') 
  contacts.select { |c| c.wants?(email) }.first.destination
end

Much of this is left to pseudocode, but you can see how being able to use pure-ruby allows for complex routes to be expressed simply.

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