Add documentation and type signatures

Author: devjoaov

README.md

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+# MustachioRuby
+
+A Ruby port of the powerful [Mustachio](https://github.com/ActiveCampaign/mustachio) templating engine for C# and .NET - a lightweight, fast, and safe templating engine with model inference capabilities.
+
+> **Note**: This is an unofficial Ruby port of the original [Mustachio](https://github.com/ActiveCampaign/mustachio) templating engine created by ActiveCampaign. All credit for the original design, concepts, and innovations goes to the ActiveCampaign team and the Mustachio contributors.
+
+#### What's this for?
+
+_MustachioRuby_ allows you to create simple text-based templates that are fast and safe to render. It's a Ruby implementation that brings the power of the templating engine behind [Postmark Templates](https://postmarkapp.com/blog/special-delivery-postmark-templates) to the Ruby ecosystem.
+
+#### How to use MustachioRuby:
+
+```ruby
+# Parse the template:
+source_template = "Dear {{name}}, this is definitely a personalized note to you. Very truly yours, {{sender}}"
+template = MustachioRuby.parse(source_template)
+
+# Create the values for the template model:
+model = {
+  "name" => "John",
+  "sender" => "Sally"
+}
+
+# Combine the model with the template to get content:
+content = template.call(model)
+# => "Dear John, this is definitely a personalized note to you. Very truly yours, Sally"
+```
+
+#### Extending MustachioRuby with Token Expanders:
+
+```ruby
+# You can add support for Partials via Token Expanders.
+# Token Expanders can be used to extend MustachioRuby for many other use cases,
+# such as: Date/Time formatters, Localization, etc., allowing also custom Token Render functions.
+
+source_template = "Welcome to our website! [[CONTENT]] Yours Truly, John Smith."
+string_data = "This is a partial. You can also add variables here {{ testVar }} or use other expanders. Watch out for infinite loops!"
+
+token_expander = MustachioRuby::TokenExpander.new
+token_expander.regex = /\[\[CONTENT\]\]/ # Custom syntax to avoid conflicts
+token_expander.expand_tokens = lambda do |s, base_options|
+  # Create new ParsingOptions to avoid infinite loops
+  new_options = MustachioRuby::ParsingOptions.new
+  MustachioRuby::Tokenizer.tokenize(string_data, new_options)
+end
+
+parsing_options = MustachioRuby::ParsingOptions.new
+parsing_options.token_expanders = [token_expander]
+template = MustachioRuby.parse(source_template, parsing_options)
+
+# Create the values for the template model:
+model = { "testVar" => "Test" }
+
+# Combine the model with the template to get content:
+content = template.call(model)
+```
+
+#### Installing MustachioRuby:
+
+MustachioRuby can be installed via [RubyGems](https://rubygems.org/):
+
+```bash
+gem install mustachio_ruby
+```
+
+Or add this line to your application's Gemfile:
+
+```ruby
+gem 'mustachio_ruby'
+```
+
+And then execute:
+
+    $ bundle install
+
+## Usage Examples
+
+### Working with Arrays using `each` blocks:
+
+```ruby
+template = "{{#each items}}Item: {{name}} - ${{price}}\n{{/each}}"
+renderer = MustachioRuby.parse(template)
+
+model = {
+  "items" => [
+    { "name" => "Apple", "price" => 1.50 },
+    { "name" => "Banana", "price" => 0.75 }
+  ]
+}
+
+content = renderer.call(model)
+# => "Item: Apple - $1.5\nItem: Banana - $0.75\n"
+```
+
+### Complex Paths for Nested Objects:
+
+```ruby
+template = "User: {{user.profile.name}} ({{user.profile.age}}) from {{user.location.city}}, {{user.location.country}}"
+renderer = MustachioRuby.parse(template)
+
+model = {
+  "user" => {
+    "profile" => { "name" => "Alice Smith", "age" => 30 },
+    "location" => { "city" => "New York", "country" => "USA" }
+  }
+}
+
+content = renderer.call(model)
+# => "User: Alice Smith (30) from New York, USA"
+```
+
+### Conditional Sections:
+
+```ruby
+template = "{{#showMessage}}Hello, {{name}}!{{/showMessage}}{{^showMessage}}Goodbye!{{/showMessage}}"
+renderer = MustachioRuby.parse(template)
+
+# When showMessage is true
+model = { "showMessage" => true, "name" => "World" }
+content = renderer.call(model)
+# => "Hello, World!"
+
+# When showMessage is false
+model = { "showMessage" => false, "name" => "World" }
+content = renderer.call(model)
+# => "Goodbye!"
+```
+
+### HTML Escaping (Safe by Default):
+
+```ruby
+# Escaped by default for safety
+template = "Content: {{html}}"
+renderer = MustachioRuby.parse(template)
+model = { "html" => "<script>alert('xss')</script>" }
+content = renderer.call(model)
+# => "Content: &lt;script&gt;alert('xss')&lt;/script&gt;"
+
+# Unescaped with triple braces
+template = "Content: {{{html}}}"
+renderer = MustachioRuby.parse(template)
+content = renderer.call(model)
+# => "Content: <script>alert('xss')</script>"
+```
+
+### Model Inference:
+
+```ruby
+template = "Hello {{name}}! You have {{#each orders}}{{total}}{{/each}} orders."
+result = MustachioRuby.parse_with_model_inference(template)
+
+# result.parsed_template is the compiled template function
+# result.inferred_model contains information about expected model structure
+model = { "name" => "Alice", "orders" => [{ "total" => 5 }, { "total" => 3 }] }
+content = result.parsed_template.call(model)
+# => "Hello Alice! You have 53 orders."
+```
+
+### Advanced: Parsing Options
+
+```ruby
+options = MustachioRuby::ParsingOptions.new
+options.disable_content_safety = true  # Disable HTML escaping
+options.source_name = "my_template"    # For error reporting
+
+template = "Unsafe content: {{html}}"
+renderer = MustachioRuby.parse(template, options)
+model = { "html" => "<b>Bold Text</b>" }
+content = renderer.call(model)
+# => "Unsafe content: <b>Bold Text</b>"
+```
+
+##### Key differences between Mustachio and [Mustache](https://mustache.github.io/)
+
+MustachioRuby contains a few modifications to the core Mustache language that are important:
+
+1. `each` blocks are recommended for handling arrays of values. (We have a good reason!)
+2. Complex paths are supported, for example `{{ this.is.a.valid.path }}` and `{{ ../this.goes.up.one.level }}`
+3. Template partials are supported via Token Expanders.
+
+###### A little more about the differences:
+
+One awesome feature of Mustachio is that with a minor alteration in the mustache syntax, we can infer what model will be required to completely fill out a template. By using the `each` keyword when iterating over an array, our parser can infer whether an array or object (or scalar) should be expected when the template is used. Normal mustache syntax would prevent us from determining this.
+
+We think the model inference feature is compelling, because it allows for error detection, and faster debugging iterations when developing templates, which justifies this minor change to 'vanilla' mustache syntax.
+
+## Development
+
+After checking out the repo, run:
+
+```bash
+bundle install
+bundle exec rspec
+```
+
+You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+
+## Acknowledgments
+
+This Ruby port would not be possible without the incredible work of the original [Mustachio](https://github.com/ActiveCampaign/mustachio) team at ActiveCampaign. Special thanks to:
+
+- **ActiveCampaign Team**: For creating and maintaining the original Mustachio templating engine
+- **All Mustachio Contributors**: For their valuable contributions to the original project
+- **Postmark Team**: For demonstrating the power of this templating approach in production
+
+MustachioRuby aims to faithfully port the original concepts and functionality while adapting them to Ruby's idioms and conventions.
+
+## License
+
+The gem is available as open source under the [MIT License](LICENSE).

sig/mustachio_ruby.rbs

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+module MustachioRuby
+  VERSION: String
+  # See the writing guide of rbs: https://github.com/ruby/rbs#guides
+end