# frozen_string_literal: true
module Asciidoctor
# A {Converter} implementation that uses templates composed in template
# languages supported by {https://github.com/rtomayko/tilt Tilt} to convert
# {AbstractNode} objects from a parsed AsciiDoc document tree to the backend
# format.
#
# The converter scans the specified directories for template files that are
# supported by Tilt. If an engine name (e.g., "slim") is specified in the
# options Hash passed to the constructor, the scan is restricted to template
# files that have a matching extension (e.g., ".slim"). The scanner trims any
# extensions from the basename of the file and uses the resulting name as the
# key under which to store the template. When the {Converter#convert} method
# is invoked, the transform argument is used to select the template from this
# table and use it to convert the node.
#
# For example, the template file "path/to/templates/paragraph.html.slim" will
# be registered as the "paragraph" transform. The template is then used to
# convert a paragraph {Block} object from the parsed AsciiDoc tree to an HTML
# backend format (e.g., "html5").
#
# As an optimization, scan results and templates are cached for the lifetime
# of the Ruby process. If the {https://rubygems.org/gems/concurrent-ruby
# concurrent-ruby} gem is installed, these caches are guaranteed to be thread
# safe. If this gem is not present, there is no such guarantee and a warning
# will be issued.
class Converter::TemplateConverter < Converter::Base
  DEFAULT_ENGINE_OPTIONS = {
    erb: { trim: 0 },
    # TODO line 466 of haml/compiler.rb sorts the attributes; file an issue to make this configurable
    # NOTE AsciiDoc syntax expects HTML/XML output to use double quotes around attribute values
    haml: { format: :xhtml, attr_wrapper: '"', escape_attrs: false, ugly: true },
    slim: { disable_escape: true, sort_attrs: false, pretty: false },
  }

  begin
    require 'concurrent/hash' unless defined? ::Concurrent::Hash
    @caches = { scans: ::Concurrent::Hash.new, templates: ::Concurrent::Hash.new }
  rescue ::LoadError
    @caches = { scans: {}, templates: {} }
  end

  def self.caches
    @caches
  end

  def self.clear_caches
    @caches[:scans].clear if @caches[:scans]
    @caches[:templates].clear if @caches[:templates]
  end

  def initialize backend, template_dirs, opts = {}
    Helpers.require_library 'tilt' unless defined? ::Tilt.new
    @backend = backend
    @templates = {}
    @template_dirs = template_dirs
    @eruby = opts[:eruby]
    @safe = opts[:safe]
    @active_engines = {}
    @engine = opts[:template_engine]
    @engine_options = {}.tap {|accum| DEFAULT_ENGINE_OPTIONS.each {|engine, engine_opts| accum[engine] = engine_opts.merge } }
    if opts[:htmlsyntax] == 'html' # if not set, assume xml since this converter is also used for DocBook (which doesn't specify htmlsyntax)
      @engine_options[:haml][:format] = :html5
      @engine_options[:slim][:format] = :html
    end
    @engine_options[:slim][:include_dirs] = template_dirs.reverse.map {|dir| ::File.expand_path dir }
    if (overrides = opts[:template_engine_options])
      overrides.each do |engine, override_opts|
        (@engine_options[engine] ||= {}).update override_opts
      end
    end
    case opts[:template_cache]
    when true
      logger.warn 'optional gem \'concurrent-ruby\' is not available. This gem is recommended when using the default template cache.' unless defined? ::Concurrent::Hash
      @caches = self.class.caches
    when ::Hash
      @caches = opts[:template_cache]
    else
      @caches = {} # the empty Hash effectively disables caching
    end
    scan
  end

  # Public: Convert an {AbstractNode} to the backend format using the named template.
  #
  # Looks for a template that matches the value of the template name or, if the template name is not specified, the
  # value of the {AbstractNode#node_name} property.
  #
  # node          - the AbstractNode to convert
  # template_name - the String name of the template to use, or the value of
  #                 the node_name property on the node if a template name is
  #                 not specified. (optional, default: nil)
  # opts          - an optional Hash that is passed as local variables to the
  #                 template. (optional, default: nil)
  #
  # Returns the [String] result from rendering the template
  def convert node, template_name = nil, opts = nil
    unless (template = @templates[template_name ||= node.node_name])
      raise %(Could not find a custom template to handle transform: #{template_name})
    end

    # Slim doesn't include helpers in the template's execution scope (like HAML), so do it ourselves
    node.extend ::Slim::Helpers if (defined? ::Slim::Helpers) && (::Slim::Template === template)

    # NOTE opts become locals in the template
    if template_name == 'document'
      (template.render node, opts).strip
    else
      (template.render node, opts).rstrip
    end
  end

  # Public: Checks whether there is a Tilt template registered with the specified name.
  #
  # name - the String template name
  #
  # Returns a [Boolean] that indicates whether a Tilt template is registered for the
  # specified template name.
  def handles? name
    @templates.key? name
  end

  # Public: Retrieves the templates that this converter manages.
  #
  # Returns a [Hash] of Tilt template objects keyed by template name.
  def templates
    @templates.merge
  end

  # Public: Registers a Tilt template with this converter.
  #
  # name     - the String template name
  # template - the Tilt template object to register
  #
  # Returns the Tilt template object
  def register name, template
    @templates[name] = if (template_cache = @caches[:templates])
      template_cache[template.file] = template
    else
      template
    end
    #create_handler name, template
  end

  private

  # Internal: Scans the template directories specified in the constructor for Tilt-supported
  # templates, loads the templates and stores the in a Hash that is accessible via the
  # {TemplateConverter#templates} method.
  #
  # Returns nothing
  def scan
    path_resolver = PathResolver.new
    backend = @backend
    engine = @engine
    @template_dirs.each do |template_dir|
      # FIXME need to think about safe mode restrictions here
      next unless ::File.directory?(template_dir = (path_resolver.system_path template_dir))

      if engine
        file_pattern = %(*.#{engine})
        # example: templates/haml
        if ::File.directory?(engine_dir = %(#{template_dir}/#{engine}))
          template_dir = engine_dir
        end
      else
        # NOTE last matching template wins for template name if no engine is given
        file_pattern = '*'
      end

      # example: templates/html5 (engine not set) or templates/haml/html5 (engine set)
      if ::File.directory?(backend_dir = %(#{template_dir}/#{backend}))
        template_dir = backend_dir
      end

      pattern = %(#{template_dir}/#{file_pattern})

      if (scan_cache = @caches[:scans])
        template_cache = @caches[:templates]
        unless (templates = scan_cache[pattern])
          templates = scan_cache[pattern] = scan_dir template_dir, pattern, template_cache
        end
        templates.each do |name, template|
          @templates[name] = template_cache[template.file] = template
        end
      else
        @templates.update scan_dir(template_dir, pattern, @caches[:templates])
      end
      nil
    end
  end

  # Internal: Scan the specified directory for template files matching pattern and instantiate
  # a Tilt template for each matched file.
  #
  # Returns the scan result as a [Hash]
  def scan_dir template_dir, pattern, template_cache = nil
    result, helpers = {}, nil
    # Grab the files in the top level of the directory (do not recurse)
    ::Dir.glob(pattern).select {|match| ::File.file? match }.each do |file|
      if (basename = ::File.basename file) == 'helpers.rb'
        helpers = file
        next
      elsif (path_segments = basename.split '.').size < 2
        next
      end
      if (name = path_segments[0]) == 'block_ruler'
        name = 'thematic_break'
      elsif name.start_with? 'block_'
        name = name.slice 6, name.length
      end
      unless template_cache && (template = template_cache[file])
        template_class, extra_engine_options, extsym = ::Tilt, {}, path_segments[-1].to_sym
        case extsym
        when :slim
          unless @active_engines[extsym]
            # NOTE slim doesn't get automatically loaded by Tilt
            Helpers.require_library 'slim' unless defined? ::Slim::Engine
            require 'slim/include' unless defined? ::Slim::Include
            ::Slim::Engine.define_options asciidoc: {}
            # align safe mode of AsciiDoc embedded in Slim template with safe mode of current document
            # NOTE safe mode won't get updated if using template cache and changing safe mode
            (@engine_options[extsym][:asciidoc] ||= {})[:safe] ||= @safe if @safe
            @active_engines[extsym] = true
          end
        when :haml
          unless @active_engines[extsym]
            Helpers.require_library 'haml' unless defined? ::Haml::Engine
            # NOTE Haml 5 dropped support for pretty printing
            @engine_options[extsym].delete :ugly if defined? ::Haml::TempleEngine
            @active_engines[extsym] = true
          end
        when :erb
          template_class, extra_engine_options = (@active_engines[extsym] ||= (load_eruby @eruby))
        when :rb
          next
        else
          next unless ::Tilt.registered? extsym.to_s
        end
        template = template_class.new file, 1, (@engine_options[extsym] ||= {}).merge(extra_engine_options)
      end
      result[name] = template
    end
    if helpers || ::File.file?(helpers = %(#{template_dir}/helpers.rb))
      require helpers
    end
    result
  end

  # Internal: Load the eRuby implementation
  #
  # name - the String name of the eRuby implementation
  #
  # Returns an [Array] containing the Tilt template Class for the eRuby implementation
  # and a Hash of additional options to pass to the initializer
  def load_eruby name
    if !name || name == 'erb'
      require 'erb' unless defined? ::ERB.version
      [::Tilt::ERBTemplate, {}]
    elsif name == 'erubis'
      Helpers.require_library 'erubis' unless defined? ::Erubis::FastEruby
      [::Tilt::ErubisTemplate, { engine_class: ::Erubis::FastEruby }]
    else
      raise ::ArgumentError, %(Unknown ERB implementation: #{name})
    end
  end
end
end