Brush

Brush is a compiler for the Braai templating language written in Go. Braai allows development teams to supply a limited vocabulary of transformation functions to be used by editorial organizations. This allows for some flexibility of the presentation of the template while avoiding having a Turing complete language exposed to CMS users.

Parsing a Braai template is easy. Just include brush and instantiate a new Braai parser. Next, provide a responder for each identifier that you would like to support.

package main

import "github.com/reviewed/brush"

const temp = "This is an amazing product: {{product.name}}"

func main() {
  parser, err := brush.New(temp).Parse()
  handlerStack := brush.NewHandleMux()
  handlerStack.Handle("product", func(scope brush.Scope) (string, error) {
    if scope.Env["path"] == ".name" {
      return "Acme Lazer", nil
    } else {
      return nil, fmt.Errorf("I only work in conjunction with a dot handler")
    }
  })
  handlerStack.HandleDot("name", func(scope brush.Scope) brush.Scope {
    scope.Env["path"] = ".name"
    return scope
  })

  result := parser.Exec(handlerStack)
  fmt.Println(result) // This is an amazing product: Acme Lazer
}

Each Braai handler has an environment available to it in the form of a brush.Scope. Dot Commands are statements in Braai which transform the environment in a right-to-left fashion. Environments are scoped lexically to a braai tag. The command handler is responsible for outputting the final response, regardless of previous alterations to the environment. For example, in this template:

Here is an attachment that can be viewed in a modal {{article.attachments(12345).popup}}

The DotHandlers for attachments and popup could set the environment to look something like this: attachment_id="12345", mode="popup". It would be the responsibility of the article CommandHandler to derive what those arguments mean, and whether they are valid. Environments can also be set on the right-most side of a Braai tag, but are overrideable by dot commands. Consequently, this Braai tag would be equivalent of the previous example, given the previously stated facts about the dot commands:

Here is an attachment that can be viewed in a modal {{article attachment_id="12345", mode="popup"}}

Block Tags

Tags can also be specified to the Parser to be block-mode tags. These tags are able to access the global scope only, and receive their contents as a Braai AST argument. This is useful for creating tags for floating certain pieces of content, for example. It is the responsibility of the Block tag for compiling its contents. This also permits block tags to have a different set of handlers for its contents, as well as altering the global scope for its subtree.