# Objective Elements

This is a tiny gem that builds nicely formatted HTML using sane, readable Ruby. I use it for jekyll
plugins, but you can use it anywhere. It's ~100 lines, tested with rspec, and has no dependencies.

It doesn't actually know any HTML, just how to format it.

This is meant to be less involved and more flexible than nokogiri's XML/HTML generator. There's no
DSL to learn, and no cleverness to wrap your mind around. Its specialty is taking fragmented,
disjointed information and condensing it into a string of properly formatted HTML. It's as agnostic
as possible on the input, while being extremely consistent with its output.

## How it works:

* Instantiate a `SingleTag` or `DoubleTag`

* Add attributes & content. Nest tags infinitely.

* Render it with `.to_s`

## Motivation:

Have you ever tried to build HTML with string concatenation and interpolation? It starts out simply
enough, but once you account for all the what-ifs, the indentation, the closing tags, and the spaces
you only need sometimes, it turns into a horrible mess.

The problem, of course, is that building long, complex, varying blocks of text with string
concatenation and interpolation is fragile, unreadable, and painful. You know this, but you're not
going to write an entirely new class or pull in some big new dependency just for 10 lines of HTML, 
so instead you hammer through it and end up with code like this:

```ruby
picture_tag = "<picture>\n"\
              "#{source_tags}"\
              "#{markdown_escape * 4}"\
              "<img src=\"#{url}#{instance['source_default'][:generated_src]}\" "\
              "#{html_attr_string}>\n"\"#{markdown_escape * 2}</picture>\n"
```

or this: 
```ruby
    def build_li(this_item_data, icon_location, label)
      li = "  <li#{@attributes['li']}>"
      if this_item_data && this_item_data['url']
        li << "<a href=\"#{this_item_data['url']}\"#{@attributes['a']}>"
      end
      li << build_image_tag(icon_location)
      li << label
      li << '</a>' if this_item_data['url']
      li << "</li>\n"
    end
```

Which is why I sat down and wrote this gem. It's super simple, you probably could have written it
too, but hey! Now you don't have to. Here's a demo:

## Demo

```ruby
# gemfile:
gem 'objective_elements',  '~>1.0.0'

# Anywhyere else:
require 'objective_elements'

p = DoubleTag.new 'p'
p.to_s
# <p>
# </p>

# Add attributes as a hash. keys can be strings or symbols, values can be arrays or strings:
p.attributes << { class: 'stumpy grumpy', 'id' => 'the-ugly-one' }

# Add attributes as a string!
p.attributes << 'class="slimy" data-awesomeness="11"'

# Get attributes by calling a method!
p.data-awesomeness 
# '11'

# Set them, too! (Note: This doesn't work for class or method)
p.id = 'killer'

# Add content. It can be anything, or an array of anythings.
p.add_content "Icky"

p.to_s
# <p class="stumpy grumpy slimy" id="killer" data-awesomeness="11">
#   Icky
# </p>

# Want a oneliner?
p.oneline = true
p.to_s
# <p class="stumpy grumpy slimy" id="killer" data-awesomeness="11">Icky</p>
p.oneline = false

# Build a tag all at once:
p.add_content DoubleTag.new(
  'a',
  content: 'Link!',
  attributes: {href: 'awesome-possum.com'},
  oneline: true
)

# Add a parent tag:
div = p.add_parent DoubleTag.new 'div'

# Implicit string conversion means cool stuff like this works:
"#{div}"
# <div>
#   <p class="stumpy grumpy slimy" id="killer" data-awesomeness="11">
#     Icky
#     <a href="awesome-possum.com">Link!</a>
#   </p>
# </div>

```

For complete example usage, see [jekyll_icon_list](https://github.com/rbuchberger/jekyll_icon_list), or
this [pull request](https://github.com/robwierzbowski/jekyll-picture-tag/pull/87/commits/d6b2deca0f19f173251a2984037e5e5f8d7c21d1)
to [jekyll-picture-tag](https://github.com/robwierzbowski/jekyll-picture-tag).

## Installation

 ```ruby
 # Gemfile
 
 gem 'objective_elements', '~> 0.2.0'
 ```
 
 ```ruby
 # Wherever you need to use it:
 
 require 'objective_elements'
 ```
## Terminology

So we're on the same page, here's the terminology I'm using:
```
<p class="stumpy">Hello</p>
|a|       b      |  c  | d |
```
- a    -  element
- b    -  attributes
- a+b  -  opening tag
- c    -  content
- d    -  closing tag


## Usage

There are 2 classes you care about: `SingleTag` is the base class, and `DoubleTag` inherits from it.
A `SingleTag` is a self-closing tag, meaning it has no content and no closing tag. A `DoubleTag` is
the other kind.

### Attributes
Attributes are their own class, and can be accessed by the `.attributes` method on both single and
double tags. Important methods: 

` << (attribute)` - Add new attributes, can accept a hash or a string. Hash keys will be converted
to symbols if they are not already, and values will be split on spaces into an array if they are not
already. Attributes can also be given as a string in the standard HTML syntax (`class="myclass"
id="my-id"`).  **Every other method which adds attributes in some way, calls this method**. This
means that any time you are adding attributes, you can use any format which this method understands.
 
`.delete(attribute)` - Delete one or more attributes. Accepts a string, symbol, or an array of
strings and/or symbols.

`.replace(attribute)` - Replaces one or more attributes and values.

`.content[:attribute_name]` - Retrieve the content for a given attribute, as an array of strings.
Must be a symbol. You'll mostly need this when you don't know which attribute you need ahead of ti
me, or to access class and method attributes because you can't use the methods below:

`.content[:attribute_name] = ` - Don't do it. Use `<<` or `.replace`.

`.(attribute_name)` - Convenience method/syntactic sugar: Returns the value of a given attribute
name, as a space-separated string. This relies on method_missing, which means that any overlap with
already existing methods won't work.  **You can't access `class` or `method` html attributes this
way, because basic objects in ruby already have those methods.**

`.(attribute_name) = value` - Same as above. Equivalent to `.replace(attribute)`. Interestingly,
`method = ` and `class = ` both work (`.class` is defined on the basic object class, but `.class=`
is not.). That said, you probably shouldn't use them because it will be confusing to understand
later.

### SingleTag Properties:

 #### element
 - String
 - Mandatory
 - Which type of tag it is, such as 'hr' or 'img'
 #### attributes
 - Instance of the class described above.


### SingleTag Methods (that you care about)

`SingleTag.new(element, attributes: nil)`

`.to_s` - The big one. Returns your HTML as a string, nondestructively.

`.add_parent(DoubleTag)` - returns supplied DoubleTag, with self added as a child.

`.attributes` - attr_reader for HTML attributes. This is how you can access any attribute method
described above.

`.reset_attributes` - Removes all attributes

`.attributes=(attributes)` - Sets attributes to the supplied argument

`attr_reader :attributes`
`attr_accessor :element`

`.(attribute_name)` / `.(attribute_name) = ` - Forwarded to attributes object. Allows you to set or
retrieve the value of attributes other than `class` and `method`, without having to type
`.attributes` in front of it.

### DoubleTag Properties:

#### `DoubleTag` Inherits all of `SingleTag`'s properties and methods, and adds content and a
closing tag.

 #### content

   - Array
   - Optional
   - Contains anything (but probably just strings and tags. Anything else will be turned into a
     string with `.to_s`, which is an alias for `.inspect` most of the time).
   - Each element in the array corresponds to at least one line of HTML
   - Multiline child tags will get as many lines as they need (like you'd expect).
   - Child elements are not rendered until the parent is rendered, meaning you can access and
     modify them after defining a parent.
   - add with `.add_content`, or modify the content array directly.

 #### oneline
  - Boolean
  - optional, defaults to false.
  - When true, the entire element and its content will be rendered as a single line. Useful for
    anchor tags and list items.

### DoubleTag Methods (that you care about)

`DoubleTag.new(element, attributes: {}, oneline: false, content: [])` - You can initialize it with
content.

`add_content(anything)` - Smart enough to handle both arrays and not-arrays without getting dorked
up. When given an array, its elements will be appended to the content array. When given a single
item, that item will be inserted at the end of the array. (Remember each element in the content
array gets at least one line!)

`attr_accessor: content` - You can modify the content array directly if you like. If you're just
adding items, you should use `.add_content`

`.to_a` - Mostly used internally, but if you want an array of strings, each element a line with
appropriate indentation applied, this is how you can get it.

## Configuration
 
 Indentation is defined by the `indent` method on the DoubleTag class, which is two markdown-escaped
 spaces by default ("\ \ "). If you'd like to change it:

 1. Make a new class, inherit from DoubleTag.
 2. Override `indent` with whatever you want.
 3. Use your new class instead of DoubleTag.

 Example:

 ```ruby
 
 require 'objective_elements'

 class MyDoubleTag < DoubleTag
  def indent
    # 4 escaped spaces:
    "\ \ \ \ "
  end
 end

MyDoubleTag.new('p', content: 'hello').to_s
# <p>
#     hello
# </p>

 ```

 ## Limitations

* It doesn't know a single HTML element on its own, so it does nothing to ensure your HTML is valid.

* A parent tag can't put siblings on the same line. You can either do this (with `oneline: true` on
   the strong tag):

    ```html

    <p>
      Here is some
      <strong>strong</strong>
      text.
    </p>

    ```
    or this (default behavior):

    ```html

    <p>
      Here is some
      <strong>
        strong
      </strong>
      text.
    </p>

    ```
    But you can't do this without string interpolation or something:

    ```html

    <p>Here is some <strong>strong</strong> text.</p>

    ```
    This doesn't affect how the browser will render it, but it might bug you if you're particular about
    source code layout.

* If you set 'oneline: true' on a parent DoubleTag, but not all its children DoubleTags, the output
  will not be pretty. I advise against it. Handling this situation is on the TODO list.

* It doesn't wrap long lines of text, and it doesn't indent text with newlines embedded. It's on the
  TODO list.

## Contributing

For code style, I've been using rubocop with the default settings and would appreciate if you did the
same.

If you add new functionality, or change existing functionality, please update the rspec tests to
reflect it.

https://github.com/rbuchberger/objective_elements

contact:
robert@robert-buchberger.com

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).