module Templater
  class Template
  
    attr_accessor :context, :name, :source, :destination, :options
  
    # Builds a new template, given the context (e.g. binding) in which the template will be rendered
    # (usually a generator), the name of the template and its source and destination.
    #
    # === Parameters
    # context<Object>:: Context for rendering
    # name<Symbol>:: The name of this template
    # source<String>:: Full path to the source of this template
    # destination<String>:: Full path to the destination of this template
    # render<Boolean>:: If set to false, will do a copy instead of rendering.
    def initialize(context, name, source, destination)
      @context = context
      @name = name
      @source = source
      @destination = destination
    end
    
    # Returns the destination path relative to Dir.pwd. This is useful for prettier output in interfaces
    # where the destination root is Dir.pwd.
    #
    # === Returns
    # String:: The destination relative to Dir.pwd
    def relative_destination
      @destination.sub(::Dir.pwd + ::File::SEPARATOR, '')
    end
  
    # Renders the template using ERB and returns the result as a String.
    #
    # === Returns
    # String:: The rendered template.
    def render
      ERB.new(::File.read(source), nil, '-').result(context.send(:binding))
    end

    # Checks if the destination file already exists.
    #
    # === Returns
    # Boolean:: true if the file exists, false otherwise.
    def exists?
      ::File.exists?(destination)
    end
  
    # Checks if the content of the file at the destination is identical to the rendered result.
    # 
    # === Returns
    # Boolean:: true if it is identical, false otherwise.
    def identical?
      ::File.read(destination) == render if ::File.exists?(destination)
    end
  
    # Renders the template and copies it to the destination.
    def invoke!
      ::FileUtils.mkdir_p(::File.dirname(destination))
      ::File.open(destination, 'w') {|f| f.write render }
    end
    
    # removes the destination file
    def revoke!
      ::FileUtils.rm(destination)
    end
      
  end
end