class Jekyll::PaginateV2::Generator::PaginationModel

def _debug_print_config_info(config, page_path)
  r = 20
  f = "Pagination: ".rjust(20)
  # Debug print the config

  if @debug
    puts f + "----------------------------"
    puts f + "Page: "+page_path.to_s
    puts f + " Active configuration"
    puts f + "  Enabled: ".ljust(r) + config['enabled'].to_s
    puts f + "  Items per page: ".ljust(r) + config['per_page'].to_s
    puts f + "  Permalink: ".ljust(r) + config['permalink'].to_s
    puts f + "  Title: ".ljust(r) + config['title'].to_s
    puts f + "  Limit: ".ljust(r) + config['limit'].to_s
    puts f + "  Sort by: ".ljust(r) + config['sort_field'].to_s
    puts f + "  Sort reverse: ".ljust(r) + config['sort_reverse'].to_s
    
    puts f + " Active Filters"
    puts f + "  Collection: ".ljust(r) + config['collection'].to_s
    puts f + "  Offset: ".ljust(r) + config['offset'].to_s
    puts f + "  Category: ".ljust(r) + (config['category'].nil? || config['category'] == "posts" ? "[Not set]" : config['category'].to_s)
    puts f + "  Tag: ".ljust(r) + (config['tag'].nil? ? "[Not set]" : config['tag'].to_s)
    puts f + "  Locale: ".ljust(r) + (config['locale'].nil? ? "[Not set]" : config['locale'].to_s)
    if config['legacy'] 
      puts f + " Legacy Paginate Code Enabled"
      puts f + "  Legacy Paginate: ".ljust(r) + config['per_page'].to_s
      puts f + "  Legacy Source: ".ljust(r) + config['legacy_source'].to_s
      puts f + "  Legacy Path: ".ljust(r) + config['paginate_path'].to_s
    end
  end
end

def _debug_print_filtering_info(filter_name, before_count, after_count)
  # Debug print the config

  if @debug
    puts "Pagination: ".rjust(20) + " Filtering by: "+filter_name.to_s.ljust(9) + " " + before_count.to_s.rjust(3) + " => " + after_count.to_s  
  end
end

def _fix_deprecated_config_features(config)
  keys_to_delete = []
  # As of v1.5.1 the title_suffix is deprecated and 'title' should be used 

  # but only if title has not been defined already!

  if( !config['title_suffix'].nil? )
    if( config['title'].nil? )
      config['title'] = ":title" + config['title_suffix'].to_s # Migrate the old key to title

    end
    keys_to_delete << "title_suffix" # Always remove the depricated key if found

  end
  # Delete the depricated keys

  config.delete_if{ |k,| keys_to_delete.include? k }
end

def discover_paginate_templates(site_pages)
  candidates = []
  site_pages.select do |page|
    # If the page has the enabled config set, supports any type of file name html or md

    if page.data['pagination'].is_a?(Hash) && page.data['pagination']['enabled']
      candidates << page
    end
  end
  return candidates
end # function discover_paginate_templates

def get_docs_in_collections(raw_collection_names)
  if raw_collection_names.is_a?(String)
    collection_names = raw_collection_names.split(/;|,|\s/)
  else
    collection_names = raw_collection_names
  end
  docs = []
  # Now for each of the collections get the docs

  collection_names.each do |coll_name|
    # Request all the documents for the collection in question, and join it with the total collection 

    docs += @collection_by_name_lambda.call(coll_name.downcase.strip)
  end
  # Hidden documents should not not be processed anywhere.

  docs = docs.reject { |doc| doc['hidden'] }
  return docs
end

def initialize(logging_lambda, page_add_lambda, page_remove_lambda, collection_by_name_lambda)
  @logging_lambda = logging_lambda
  @page_add_lambda = page_add_lambda
  @page_remove_lambda = page_remove_lambda
  @collection_by_name_lambda = collection_by_name_lambda
end

def paginate(template, config, site_title, all_posts, all_tags, all_categories, all_locales)
  # By default paginate on all posts in the site

  using_posts = all_posts
  
  # Now start filtering out any posts that the user doesn't want included in the pagination

  before = using_posts.size.to_i
  using_posts = PaginationIndexer.read_config_value_and_filter_posts(config, 'category', using_posts, all_categories)
  self._debug_print_filtering_info('Category', before, using_posts.size.to_i)
  before = using_posts.size.to_i
  using_posts = PaginationIndexer.read_config_value_and_filter_posts(config, 'tag', using_posts, all_tags)
  self._debug_print_filtering_info('Tag', before, using_posts.size.to_i)
  before = using_posts.size.to_i
  using_posts = PaginationIndexer.read_config_value_and_filter_posts(config, 'locale', using_posts, all_locales)
  self._debug_print_filtering_info('Locale', before, using_posts.size.to_i)
  
  # Apply sorting to the posts if configured, any field for the post is available for sorting

  if config['sort_field']
    sort_field = config['sort_field'].to_s
    # There is an issue in Jekyll related to lazy initialized member variables that causes iterators to 

    # break when accessing an uninitialized value during iteration. This happens for document.rb when the <=> compaison function 

    # is called (as this function calls the 'date' field which for drafts are not initialized.)

    # So to unblock this common issue for the date field I simply iterate once over every document and initialize the .date field explicitly

    if @debug
      puts "Pagination: ".rjust(20) + "Rolling through the date fields for all documents"
    end
    using_posts.each do |u_post|
      if u_post.respond_to?('date')
        tmp_date = u_post.date
        if( !tmp_date || tmp_date.nil? )
          if @debug
            puts "Pagination: ".rjust(20) + "Explicitly assigning date for doc: #{u_post.data['title']} | #{u_post.path}"
          end
          u_post.date = File.mtime(u_post.path)
        end
      end
    end
    using_posts.sort!{ |a,b| Utils.sort_values(Utils.sort_get_post_data(a.data, sort_field), Utils.sort_get_post_data(b.data, sort_field)) }
    # Remove the first x entries

    offset_post_count = [0, config['offset'].to_i].max
    using_posts.pop(offset_post_count)
    if config['sort_reverse']
      using_posts.reverse!
    end
  end
         
  # Calculate the max number of pagination-pages based on the configured per page value

  total_pages = Utils.calculate_number_of_pages(using_posts, config['per_page'])
  
  # If a upper limit is set on the number of total pagination pages then impose that now

  if config['limit'] && config['limit'].to_i > 0 && config['limit'].to_i < total_pages
    total_pages = config['limit'].to_i
  end
  #### BEFORE STARTING REMOVE THE TEMPLATE PAGE FROM THE SITE LIST!

  @page_remove_lambda.call( template )
  
  # list of all newly created pages

  newpages = []
  # Consider the default index page name and extension

  indexPageName = config['indexpage'].nil? ? '' : config['indexpage'].split('.')[0]
  indexPageExt =  config['extension'].nil? ? '' : Utils.ensure_leading_dot(config['extension'])
  indexPageWithExt = indexPageName + indexPageExt
  # In case there are no (visible) posts, generate the index file anyway

  total_pages = 1 if total_pages.zero?
  # Now for each pagination page create it and configure the ranges for the collection

  # This .pager member is a built in thing in Jekyll and defines the paginator implementation

  # Simpy override to use mine

  (1..total_pages).each do |cur_page_nr|
    # 1. Create the in-memory page

    #    External Proc call to create the actual page for us (this is passed in when the pagination is run)

    newpage = PaginationPage.new( template, cur_page_nr, total_pages, indexPageWithExt )
    # 2. Create the url for the in-memory page (calc permalink etc), construct the title, set all page.data values needed

    paginated_page_url = config['permalink']
    first_index_page_url = ""
    if template.data['permalink']
      first_index_page_url = Utils.ensure_trailing_slash(template.data['permalink'])
    else
      first_index_page_url = Utils.ensure_trailing_slash(template.dir)
    end
    paginated_page_url = File.join(first_index_page_url, paginated_page_url)
    
    # 3. Create the pager logic for this page, pass in the prev and next page numbers, assign pager to in-memory page

    newpage.pager = Paginator.new( config['per_page'], first_index_page_url, paginated_page_url, using_posts, cur_page_nr, total_pages, indexPageName, indexPageExt)
    # Create the url for the new page, make sure we prepend any permalinks that are defined in the template page before

    if newpage.pager.page_path.end_with? '/'
      newpage.set_url(File.join(newpage.pager.page_path, indexPageWithExt))
    elsif newpage.pager.page_path.end_with? indexPageExt
      # Support for direct .html files

      newpage.set_url(newpage.pager.page_path)
    else
      # Support for extensionless permalinks

      newpage.set_url(newpage.pager.page_path+indexPageExt)
    end
    if( template.data['permalink'] )
      newpage.data['permalink'] = newpage.pager.page_path
    end
    # Transfer the title across to the new page

    if( !template.data['title'] )
      tmp_title = site_title
    else
      tmp_title = template.data['title']
    end
    # If the user specified a title suffix to be added then let's add that to all the pages except the first

    if( cur_page_nr > 1 && config.has_key?('title') )
      newpage.data['title'] = "#{Utils.format_page_title(config['title'], tmp_title, cur_page_nr, total_pages)}"
    else
      newpage.data['title'] = tmp_title
    end
    # Signals that this page is automatically generated by the pagination logic

    # (we don't do this for the first page as it is there to mask the one we removed)

    if cur_page_nr > 1
      newpage.data['autogen'] = "jekyll-paginate-v2"
    end
    
    # Add the page to the site

    @page_add_lambda.call( newpage )
    # Store the page in an internal list for later referencing if we need to generate a pagination number path later on

    newpages << newpage
  end #each.do total_pages

  # Now generate the pagination number path, e.g. so that the users can have a prev 1 2 3 4 5 next structure on their page

  # simplest is to include all of the links to the pages preceeding the current one

  # (e.g for page 1 you get the list 2, 3, 4.... and for page 2 you get the list 3,4,5...)

  if( config['trail'] && !config['trail'].nil? && newpages.size.to_i > 1 )
    trail_before = [config['trail']['before'].to_i, 0].max
    trail_after = [config['trail']['after'].to_i, 0].max
    trail_length = trail_before + trail_after + 1
    if( trail_before > 0 || trail_after > 0 )
      newpages.select do | npage |
        idx_start = [ npage.pager.page - trail_before - 1, 0].max # Selecting the beginning of the trail

        idx_end = [idx_start + trail_length, newpages.size.to_i].min # Selecting the end of the trail

        # Always attempt to maintain the max total of <trail_length> pages in the trail (it will look better if the trail doesn't shrink)

        if( idx_end - idx_start < trail_length )
          # Attempt to pad the beginning if we have enough pages

          idx_start = [idx_start - ( trail_length - (idx_end - idx_start) ), 0].max # Never go beyond the zero index

        end              
        # Convert the newpages array into a two dimensional array that has [index, page_url] as items

        #puts( "Trail created for page #{npage.pager.page} (idx_start:#{idx_start} idx_end:#{idx_end})")

        npage.pager.page_trail = newpages[idx_start...idx_end].each_with_index.map {|ipage,idx| PageTrail.new(idx_start+idx+1, ipage.pager.page_path, ipage.data['title'])}
        #puts( npage.pager.page_trail )

      end #newpages.select

    end #if trail_before / trail_after

  end # if config['trail']

end # function paginate

def run(default_config, site_pages, site_title)
  # By default if pagination is enabled we attempt to find all index.html pages in the site

  templates = self.discover_paginate_templates(site_pages)
  if( templates.size.to_i <= 0 )
    @logging_lambda.call "Is enabled, but I couldn't find any pagination page. Skipping pagination. "+
    "Pages must have 'pagination: enabled: true' in their front-matter for pagination to work.", "warn"
    return
  end
  # Now for each template page generate the paginator for it

  templates.each do |template|
    # All pages that should be paginated need to include the pagination config element

    if template.data['pagination'].is_a?(Hash)
      template_config = Jekyll::Utils.deep_merge_hashes(default_config, template.data['pagination'] || {})
      # Handling deprecation of configuration values

      self._fix_deprecated_config_features(template_config)
      @debug = template_config['debug'] # Is debugging enabled on the page level

      self._debug_print_config_info(template_config, template.path)
      
      # Only paginate the template if it is explicitly enabled

      # requiring this makes the logic simpler as I don't need to determine which index pages 

      # were generated automatically and which weren't

      if( template_config['enabled'] )
        if !@debug
          @logging_lambda.call "found page: "+template.path, 'debug'
        end
        # Request all documents in all collections that the user has requested 

        all_posts = self.get_docs_in_collections(template_config['collection'])
        # Create the necessary indexes for the posts

        all_categories = PaginationIndexer.index_posts_by(all_posts, 'categories')
        all_categories['posts'] = all_posts; # Populate a category for all posts (this is here for backward compatibility, do not use this as it will be decommissioned 2018-01-01) 

                                            # (this is a default and must not be used in the category system)

        all_tags = PaginationIndexer.index_posts_by(all_posts, 'tags')
        all_locales = PaginationIndexer.index_posts_by(all_posts, 'locale')
        # TODO: NOTE!!! This whole request for posts and indexing results could be cached to improve performance, leaving like this for now during testing

        # Now construct the pagination data for this template page

        self.paginate(template, template_config, site_title, all_posts, all_tags, all_categories, all_locales)
      end
    end
  end #for

  # Return the total number of templates found

  return templates.size.to_i
end # function run

def run_compatability(legacy_config, site_pages, site_title, all_posts)
  # Decomissioning error

  if( date = Date.strptime("20180101","%Y%m%d") <= Date.today )
    raise ArgumentError.new("Legacy jekyll-paginate configuration compatibility mode has expired. Please upgrade to jekyll-paginate-v2 configuration.")
  end
  # Two month warning or general notification

  if( date = Date.strptime("20171101","%Y%m%d") <= Date.today )
    @logging_lambda.call "Legacy pagination logic will stop working on Jan 1st 2018, update your configs before that time.", "warn"
  else
    @logging_lambda.call "Detected legacy jekyll-paginate logic running. "+
    "Please update your configs to use the jekyll-paginate-v2 logic. This compatibility function "+
    "will stop working after Jan 1st 2018 and your site build will throw an error.", "warn"
  end
  if template = CompatibilityUtils.template_page(site_pages, legacy_config['legacy_source'], legacy_config['permalink'])
    CompatibilityUtils.paginate(legacy_config, all_posts, template, @page_add_lambda)
  else
    @logging_lambda.call "Legacy pagination is enabled, but I couldn't find " +
    "an index.html page to use as the pagination page. Skipping pagination.", "warn"
  end
end # function run_compatability (REMOVE AFTER 2018-01-01)