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

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

    # Creates a new instace of Haml::Engine that will compile the given
    # template string when <tt>render</tt> is called.
    # See README for available options.
    #
    #--
    # When adding options, remember to add information about them
    # to README!
    #++
    #
    def initialize(template, options = {})
      @options = {
        :suppress_eval => false,
        :attr_wrapper => "'",
        :autoclose => ['meta', 'img', 'link', 'br', 'hr', 'input', 'area'],
        :filters => {
          'sass' => Sass::Engine,
          'plain' => Haml::Filters::Plain,
          'preserve' => Haml::Filters::Preserve,
          'redcloth' => Haml::Filters::RedCloth,
          'textile' => Haml::Filters::Textile,
          'markdown' => Haml::Filters::Markdown }
      }
      @options.rec_merge! options

      unless @options[:suppress_eval]
        @options[:filters].merge!({
          'erb' => ERB,
          'ruby' => Haml::Filters::Ruby
        })
      end
      @options[:filters].rec_merge! options[:filters] if options[:filters]

      if @options[:locals]
        warn <<END
DEPRECATION WARNING:
The Haml :locals option is deprecated and will be removed in version 2.0.
Use the locals option for Haml::Engine#render instead.
END
      end

      @template = template.strip #String
      @to_close_stack = []
      @output_tabs = 0
      @template_tabs = 0
      @index = 0
      @flat_spaces = -1

      precompile
    rescue Haml::Error => e
      e.add_backtrace_entry(@index, @options[:filename])
      raise e
    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)
      locals = (@options[:locals] || {}).merge(locals)
      buffer = Haml::Buffer.new(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_stack ||= Array.new
        @haml_stack.push(buffer)
        @haml_is_haml = true
      end

      begin
        eval(@precompiled, scope, '(haml-eval)')
      rescue Exception => e
        raise Engine.add_exception_info(e, @precompiled, @options[:filename])
      end

      # Get rid of the current buffer
      scope_object.instance_eval do
        @haml_stack.pop
        @haml_is_haml = false
      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

      begin
        eval("Proc.new { |*_haml_locals| _haml_locals = _haml_locals[0] || {};" +
             precompiled_with_ambles(local_names) + "}\n", scope, '(haml-eval)')
      rescue Exception => e
        raise Haml::Engine.add_exception_info(e, @precompiled, @options[:filename])
      end
    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

      begin
        object.send(method, "def #{name}(_haml_locals = {}); #{precompiled_with_ambles(local_names)}; end", '(haml-eval)')
      rescue Exception => e
        raise Haml::Engine.add_exception_info(e, @precompiled, @options[:filename])
      end
    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

    def self.add_exception_info(e, precompiled, filename)
      metaclass = class << e; self; end
      metaclass.send(:include, Haml::Error)

      eval_line = e.backtrace[0].scan(/:([0-9]*)/)[0][0].to_i
      line_marker = precompiled.split("\n")[0...eval_line].grep(/#haml_lineno: [0-9]+/)[-1]
      e.add_backtrace_entry(line_marker ? line_marker.scan(/[0-9]+/)[0].to_i : -1, filename)

      # Format Ruby compiler errors nicely
      message = e.message.scan(/compile error\n\(haml-eval\):[0-9]*: (.*)/)[0]
      metaclass.send(:define_method, :message) { "compile error: #{message}" } if message

      return e
    end

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