require 'haml/helpers'
require 'haml/buffer'
require 'haml/precompiler'
require 'haml/filters'
require 'haml/error'

module Haml
  # This is the class where all the parsing and processing of the Haml
  # template is done. It can be directly used by the user by creating a
  # new instance and calling <tt>to_html</tt> to render the template. For example:
  #
  #   template = File.read('templates/really_cool_template.haml')
  #   haml_engine = Haml::Engine.new(template)
  #   output = haml_engine.to_html
  #   puts output
  class Engine
    include Precompiler

    # Allow reading and writing of the options hash
    attr :options, true

    # This string contains the source code that is evaluated
    # to produce the Haml document.
    attr :precompiled, true

    # A string containing the indentation used for the Haml document.
    # nil if the indentation is ambiguous
    # (for example, for a single-level document).
    attr :indentation, true

    # True if the format is XHTML
    def xhtml?
      not html?
    end

    # True if the format is any flavor of HTML
    def html?
      html4? or html5?
    end

    # True if the format is HTML4
    def html4?
      @options[:format] == :html4
    end

    # True if the format is HTML5
    def html5?
      @options[:format] == :html5
    end

    # Creates a new instace of Haml::Engine that will compile the given
    # template string when <tt>render</tt> is called.
    # See the Haml module documentation for available options.
    #
    #--
    # When adding options, remember to add information about them
    # to lib/haml.rb!
    #++
    #
    def initialize(template, options = {})
      @options = {
        :suppress_eval => false,
        :attr_wrapper => "'",

        # Don't forget to update the docs in lib/haml.rb if you update these
        :autoclose => %w[meta img link br hr input area param col base],
        :preserve => %w[textarea pre],

        :filename => '(haml)',
        :line => 1,
        :ugly => false,
        :format => :xhtml,
        :escape_html => false
      }
      @options.merge! options
      @index = 0

      unless [:xhtml, :html4, :html5].include?(@options[:format])
        raise Haml::Error, "Invalid format #{@options[:format].inspect}"
      end

      @template = (template.rstrip + "\n-#\n-#").split(/\r\n|\r|\n/)
      @template_index = 0
      @to_close_stack = []
      @output_tabs = 0
      @template_tabs = 0
      @flat = false
      @newlines = 0
      @precompiled = ''
      @merged_text = ''
      @tab_change  = 0

      if @options[:filters]
        warn <<END
DEPRECATION WARNING:
The Haml :filters option is deprecated and will be removed in version 2.1.
Filters are now automatically registered.
END
      end

      precompile
    rescue Haml::Error => e
      e.backtrace.unshift "#{@options[:filename]}:#{(e.line ? e.line + 1 : @index) + @options[:line] - 1}" if @index
      raise
    end

    # Processes the template and returns the result as a string.
    #
    # +scope+ is the context in which the template is evaluated.
    # If it's a Binding or Proc object,
    # Haml uses it as the second argument to Kernel#eval;
    # otherwise, Haml just uses its #instance_eval context.
    #
    # Note that Haml modifies the evaluation context
    # (either the scope object or the "self" object of the scope binding).
    # It extends Haml::Helpers, and various instance variables are set
    # (all prefixed with "haml").
    # For example:
    #
    #   s = "foobar"
    #   Haml::Engine.new("%p= upcase").render(s) #=> "<p>FOOBAR</p>"
    #
    #   # s now extends Haml::Helpers
    #   s.responds_to?(:html_attrs) #=> true
    #
    # +locals+ is a hash of local variables to make available to the template.
    # For example:
    #
    #   Haml::Engine.new("%p= foo").render(Object.new, :foo => "Hello, world!") #=> "<p>Hello, world!</p>"
    #
    # If a block is passed to render,
    # that block is run when +yield+ is called
    # within the template.
    #
    # Due to some Ruby quirks,
    # if scope is a Binding or Proc object and a block is given,
    # the evaluation context may not be quite what the user expects.
    # In particular, it's equivalent to passing <tt>eval("self", scope)</tt> as scope.
    # This won't have an effect in most cases,
    # but if you're relying on local variables defined in the context of scope,
    # they won't work.
    def render(scope = Object.new, locals = {}, &block)
      buffer = Haml::Buffer.new(scope.instance_variable_get('@haml_buffer'), options_for_buffer)

      if scope.is_a?(Binding) || scope.is_a?(Proc)
        scope_object = eval("self", scope)
        scope = scope_object.instance_eval{binding} if block_given?
      else
        scope_object = scope
        scope = scope_object.instance_eval{binding}
      end

      set_locals(locals.merge(:_hamlout => buffer, :_erbout => buffer.buffer), scope, scope_object)

      scope_object.instance_eval do
        extend Haml::Helpers
        @haml_buffer = buffer
      end

      eval(@precompiled, scope, @options[:filename], @options[:line])

      # Get rid of the current buffer
      scope_object.instance_eval do
        @haml_buffer = buffer.upper
      end

      buffer.buffer
    end
    alias_method :to_html, :render

    # Returns a proc that, when called,
    # renders the template and returns the result as a string.
    #
    # +scope+ works the same as it does for render.
    #
    # The first argument of the returned proc is a hash of local variable names to values.
    # However, due to an unfortunate Ruby quirk,
    # the local variables which can be assigned must be pre-declared.
    # This is done with the +local_names+ argument.
    # For example:
    #
    #   # This works
    #   Haml::Engine.new("%p= foo").render_proc(Object.new, :foo).call :foo => "Hello!"
    #     #=> "<p>Hello!</p>"
    #
    #   # This doesn't
    #   Haml::Engine.new("%p= foo").render_proc.call :foo => "Hello!"
    #     #=> NameError: undefined local variable or method `foo'
    #
    # The proc doesn't take a block;
    # any yields in the template will fail.
    def render_proc(scope = Object.new, *local_names)
      if scope.is_a?(Binding) || scope.is_a?(Proc)
        scope_object = eval("self", scope)
      else
        scope_object = scope
        scope = scope_object.instance_eval{binding}
      end

      eval("Proc.new { |*_haml_locals| _haml_locals = _haml_locals[0] || {};" +
           precompiled_with_ambles(local_names) + "}\n", scope, @options[:filename], @options[:line])
    end

    # Defines a method on +object+
    # with the given name
    # that renders the template and returns the result as a string.
    #
    # If +object+ is a class or module,
    # the method will instead by defined as an instance method.
    # For example:
    #
    #   t = Time.now
    #   Haml::Engine.new("%p\n  Today's date is\n  .date= self.to_s").def_method(t, :render)
    #   t.render #=> "<p>\n  Today's date is\n  <div class='date'>Fri Nov 23 18:28:29 -0800 2007</div>\n</p>\n"
    #
    #   Haml::Engine.new(".upcased= upcase").def_method(String, :upcased_div)
    #   "foobar".upcased_div #=> "<div class='upcased'>FOOBAR</div>\n"
    #
    # The first argument of the defined method is a hash of local variable names to values.
    # However, due to an unfortunate Ruby quirk,
    # the local variables which can be assigned must be pre-declared.
    # This is done with the +local_names+ argument.
    # For example:
    #
    #   # This works
    #   obj = Object.new
    #   Haml::Engine.new("%p= foo").def_method(obj, :render, :foo)
    #   obj.render(:foo => "Hello!") #=> "<p>Hello!</p>"
    #
    #   # This doesn't
    #   obj = Object.new
    #   Haml::Engine.new("%p= foo").def_method(obj, :render)
    #   obj.render(:foo => "Hello!") #=> NameError: undefined local variable or method `foo'
    #
    # Note that Haml modifies the evaluation context
    # (either the scope object or the "self" object of the scope binding).
    # It extends Haml::Helpers, and various instance variables are set
    # (all prefixed with "haml").
    def def_method(object, name, *local_names)
      method = object.is_a?(Module) ? :module_eval : :instance_eval

      object.send(method, "def #{name}(_haml_locals = {}); #{precompiled_with_ambles(local_names)}; end",
                  @options[:filename], @options[:line])
    end

    private

    def set_locals(locals, scope, scope_object)
      scope_object.send(:instance_variable_set, '@_haml_locals', locals)
      set_locals = locals.keys.map { |k| "#{k} = @_haml_locals[#{k.inspect}]" }.join("\n")
      eval(set_locals, scope)
    end

    # Returns a hash of options that Haml::Buffer cares about.
    # This should remain loadable from #inspect.
    def options_for_buffer
      {
        :autoclose => @options[:autoclose],
        :preserve => @options[:preserve],
        :attr_wrapper => @options[:attr_wrapper],
        :ugly => @options[:ugly],
        :format => @options[:format]
      }
    end
  end
end