Teer - Template Engingeering Rebourn

Picture the scene. You have a lot of data and you want to present the results of that data on a chart or a web page. How would you go about turning variable data into a human readable format - let's say you wanted to summarise a chart?

This small library aims to solve that problem.

Add this line to your application's Gemfile:

gem 'teer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install teer

Given a table and the dream of translating it into human readable format:

You can pass it in with a template yaml/hash with the format:

names: # only run if names is a variable in the template scope
  worst_name: "names.sort[-1].key"
  worst_value: "names.sort[-1].value"
  text:
    GB_en: "{{ worst_name }} has the least apples, having only {{ worst_value }}"
    FR: "{{ worst_name }} a le moins de pommes, n'en ayant que {{ worst_value }}"

(under the hood the yaml gets converted into a hash anyway)

and by running:

teer = Teer::Template.create([
  { 'name' => 'Bob', 'count' => 4 },
  { 'name' => 'Alan', 'count' => 14 },
  { 'name' => 'Jeff', 'count' => 2 }
], 'count', template).finding

It parses the template and substitutes the values into the text:

=> "Jeff has the least apples, having only 2"

As the teer parses the data, it takes a mandatory argument "name", in this case count which is what the data is indexed against. The teer takes each index (there could be many) and defines new variables by pluralising the index. In this example, names becomes a variable (as it's one of the indexes) that we can apply methods to.

The template passed in has a first key (names) which checks for the presence of that variable (it's actually optional to do that check).

Variables can also be defined in the template itself, and substituted into the output text. In the example above, worst_name is defined as variable, defined by: names.sort[-1].key which means take each row, and sort (ascending is false) the names by count and take the last row and the key is the row member of name and the value is the count associated with that name.

As well as this, as count is a column, it can be accessed like counts and simple arithmetic operations can be applied to it, such as counts.mean or counts.sum to get the required value if filtering is not required. If filtering is required then the correct approach is to filter using the indexes.

We can inspect the names variable, as it elucidates how these methods interact with it:

teer.data.names # teer is defined above
=> <DataStore:0x007f83bd3e1398 @data=[["Bob", 4], ["Alan", 14], ["Jeff", 2]], @locale=:GB_en>
# it's useful to try methods here before adding them to the template:
teer.data.names.keys
=> <Teer::VectorStore:0x00007fbaa7373200 @data=["Bob", "Alan", "Jeff"], @locale=:GB_en>

teer.data.names.values
=> <Teer::VectorStore:0x00007fbaa739a378 @data=[4, 14, 2], @locale=:GB_en>

teer.data.names.max.key
=> "Alan"

teer.data.names.min.value
=> 2

teer.data.names.slice("Jeff")
=> <Teer::DataStore:0x00007fbaa8a02188 @data=[["Jeff", 2]], @locale=:GB_en>

Here each index row is associated with the value of the data and methods can be applied to that (defined in lib/teer/data_store.rb) such as min, count, [], sort and also conditionals (such as gt, lt, ne, eq) which are able to create rich verbatims from the underlying data.

If you notice, the key inside text is GB_en this is the default. However, other languages and keys are supported and can be used like:

teer = Teer::Template.create([
  { 'name' => 'Bob', 'count' => 4 },
  { 'name' => 'Alan', 'count' => 14 },
  { 'name' => 'Jeff', 'count' => 2 }
], 'count', template, {}, :FR).finding

=> "Jeff a le moins de pommes, n'en ayant que 2"

To expand on the previous example:

names:
  best_name: names.max.key
  best_value: names.max.value
  text:
    GB_en: "{{ best_name }} has the most apples."

  second_best_value: "names.sort.second.value"
  much_larger: best_value > second_best_value + 5
  much_larger:
    second_best_name: names.sort.second.key
    text:
      GB_en: "It's a lot more than {{ second_best_name }} who came in second place."
  not much_larger:
    text:
      GB_en: "However, {{ second_best_name }}'s {{ second_best_value }} was close behind."

With this template, the results concatenate (in a top down fashion) and it results in:

=> "Alan has the most apples. It's a lot more than Bob who came in second place."

You can also collect them all separately (using the method findings) so as to join them anyway you like:

Teer::Template.create([
  { 'name' => 'Bob', 'count' => 4 },
  { 'name' => 'Alan', 'count' => 14 },
  { 'name' => 'Jeff', 'count' => 2 }
], 'count', template).findings.join("\n")

=> "Alan has the most apples.\nIt's a lot more than Bob who came in second place."

teer = Teer::Template.create([
  { 'name' => 'Bob', 'count' => 4 },
  { 'name' => 'Alan', 'count' => 14 },
  { 'name' => 'Jeff', 'count' => 2 }
], 'count', template, {'some_other_var' => 'my special variable'}).finding

{{ some_other_var }} will yield 'my special variable' when placed inside the template

Note: This library is not turing complete, which means it's not for programming inside of the template. For instance, filtering the indexes less than or greater than a value is not appropriate to do inside of the template - you can filter the data before passing it in, using your favourite library.

Having said that, there is a helper method, which translates as "only select the rows from this index that match these other index keys":

kpis.slice_from(names, 'Bob') # translates as select only Bob's KPIs

Also see teer_spec.rb. Markdown can be written, returning a result such as:

Behaviour change was worst for respondents who selected:

• West for regUS
• Female for gender

for Would you change your response to Apple?

Our use-case internally was to pull in 'rules' from Google Sheets and alongside the data, display key findings. Using this library you can easily achieve this. Let's say you have wide data with many columns and you don't care about the indexes:

data = [
  {'person_id' => 'a', 'banana' => 0.3, 'apple' => 0.5, 'pear' => 1, 'orange' => 0.45},
  {'person_id' => 'b', 'banana' => 0.5, 'apple' => 0.1, 'pear' => 2, 'orange' => 0.1},
  {'person_id' => 'c', 'banana' => 0.8, 'apple' => 0.7, 'pear' => 5, 'orange' => 0.6},
  {'person_id' => 'd', 'banana' => 0.9, 'apple' => 0.7, 'pear' => 9, 'orange' => 10}
]

Google Sheets rules in 2d array format [[condition, text], ...]:

rules = [
  ['bananas.mean > 2', 'Lots of bananas'],
  ['bananas.mean > 1 && bananas.mean < 2', 'Not that many bananas'],
  ['bananas.mean < 1', 'No bananas'],
  .
  .
  .
]

• N.B. because there are multiple columns, the variables are accessed as the column name with an s on the end (plural columns will return an error) and to access the index data now, you have to access it by the column name e.g. banana.person_ids.slice("a").value # = 0.3

The results of which can be calculated by doing

template = Teer::Template.create(data, data.first.keys - ['person_id'], rules)
template.findings # = ['No bananas'...]

To format variables as the template is interpolated, helpers are used to do things such as round numbers of format time. They take the form of {{METHOD VARIABLE}}

Examples below:

horrible_floats_and_time = [
  { 'time' => Time.new(1993, 02, 24, 12, 0, 0, "+09:00"), 'name' => 'Bob', 'count' => 4.213432 },
  { 'time' => Time.new(1993, 02, 24, 12, 0, 0, "+09:00"), 'name' => 'Alan', 'count' => 14.35 },
  { 'time' => Time.new(1993, 02, 24, 12, 0, 0, "+09:00"), 'name' => 'Jeff', 'count' => 2.1 }
]

text = '{{round best_value }}'
template = { 'best_value' => 'names.sort[0].value', 'text' => { 'GB_en' => text } }
Teer::Template.create(horrible_floats_and_time, 'count', template).finding
=> "14.4"

text = '{{month month_key }}'
template = { 'month_key' => 'times.sort[0].key', 'text' => { 'GB_en' => text } }
Teer::Template.create(horrible_floats_and_time, 'count', template).finding
=> "February"

Although only those two currently come out of the box, it's easy to add more when your app initialises:

Teer::Template.handlebars.register_helper(:year) do |_context, condition, _block|
  Time.at(condition).strftime('%Y')
end

See here for more advanced usage. If you feel the helper will benefit all, please submit a PR!

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/Rambatino/teer. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Teer project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.