Class: MarkdownExpander::Expander

Inherits:
Object
  • Object
show all
Defined in:
lib/markdown-expander.rb

Defined Under Namespace

Classes: Expression, ExpressionDrillDownError, IfStart, LoopStart, MarkdownExpandError, Node

Constant Summary collapse

LOOP_START_MATCH = 
/{{\s*([a-zA-Z_]*)\s+in\s+([a-zA-Z_.]*)\s*}}/
END_MATCH = 
/{{\s*end\s*}}/
EXPRESSION_MATCH = 
/{{\s*([a-zA-Z_.]+)\s*}}/
IF_START_MATCH = 
/{{\s*if\s*([a-zA-Z_.]*)\s*(==|!=)\s*"(.*)"}}/

Instance Method Summary collapse

Constructor Details

#initialize(template) ⇒ Expander

Returns a new instance of Expander.



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# File 'lib/markdown-expander.rb', line 10

def initialize template
  @template = template
end

Instance Method Details

#drill_down_to_value(node, scope, expression) ⇒ Object 



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# File 'lib/markdown-expander.rb', line 88

def drill_down_to_value node, scope, expression
  expression_parts = expression.split(".").map(&:to_sym)
  expression_parts.each do |part|
    begin
      scope = scope[part]
    rescue NoMethodError
      raise ExpressionDrillDownError.new(node, expression)
    end
  end
  scope
end

#evaluate_nodes(root, scope) ⇒ Object 



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# File 'lib/markdown-expander.rb', line 100

def evaluate_nodes root, scope
  lines = []
  root.children.each_with_index do |child, index|
    if child.element.class == Expression
      lines << drill_down_to_value(child, scope, child.element.expression)
    elsif child.element.class == LoopStart
      name = child.element.name.to_sym
      scope = drill_down_to_value(child, scope, child.element.expression)
      scope.each do |item|
        lines << evaluate_nodes(child, {name => item})
      end
    elsif child.element.class == IfStart
      value = drill_down_to_value(child, scope, child.element.expression)
      expression_satisfied =
        (child.element.operator == "==" && value.to_s == child.element.value) ||
        (child.element.operator == "!=" && value.to_s != child.element.value)
      if expression_satisfied
        lines << evaluate_nodes(child, scope)
      end
    else
      lines << child.element
    end
  end
  lines.join("")
end

#render(scope) ⇒ Object 



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# File 'lib/markdown-expander.rb', line 14

def render scope
  root = Node.new(nil, nil, 1)
  node = root
  current_line = 1

  @template.each_line do |line|
    if line =~ LOOP_START_MATCH
      new_node = Node.new(node, LoopStart.new($1, $2), current_line)
      node.children << new_node
      node = new_node
    elsif line =~ IF_START_MATCH
      new_node = Node.new(node, IfStart.new($1, $2, $3), current_line)
      node.children << new_node
      node = new_node
    elsif line =~ END_MATCH
      node = node.parent
    else
      loop do
        if line =~ EXPRESSION_MATCH
          before_match = $`
          after_match = $'
          node.children << Node.new(node, before_match, current_line)
          node.children << Node.new(node, Expression.new($1), current_line)
          line = after_match
        else
          node.children << Node.new(node, line, current_line)
          break
        end
      end
    end
    current_line += 1
  end

  parse_error = if node != root
                  if node.element.class == IfStart
                    MarkdownExpandError.new(node.line_number, "if statement has no end")
                  elsif node.element.class == LoopStart
                    MarkdownExpandError.new(node.line_number, "loop has no end")
                  end
                end

  if parse_error.nil? == false
    raise parse_error
  end

  begin
    evaluate_nodes(root, scope)
  rescue ExpressionDrillDownError => e
    raise MarkdownExpandError.new(
      e.node.line_number,
      "expression '#{e.expression}' could not be evaluated",
    )
  end
end