# encoding: utf-8

require 'github_api/utils/url'

module Github
  class PageIterator
    include Github::Constants
    include Github::Utils::Url
    include Github::PagedRequest

    # Setup attribute accesor for all the link types
    ATTRIBUTES = [ META_FIRST, META_NEXT, META_PREV, META_LAST ]

    ATTRIBUTES.each do |attr|
      attr_accessor :"#{attr}_page_uri", :"#{attr}_page"
    end

    def initialize(env)
      @links = Github::PageLinks.new(env[:response_headers])
      update_page_links @links
    end

    def has_next?
      next_page == 0 || !next_page_uri.nil?
    end

    def first
      return nil unless first_page_uri

      response = if next_page < 1
        parsed_query = parse_query(first_page_uri.split(QUERY_STR_SEP).last)
        params = {}
        if parsed_query.keys.include?('sha')
          params['sha'] = 'master'
        end
        params['per_page'] = parse_per_page_number(first_page_uri)

        page_request first_page_uri.split(QUERY_STR_SEP).first, params
      else
        page_request first_page_uri.split(QUERY_STR_SEP).first,
                           'per_page' => parse_per_page_number(first_page_uri)
      end

      update_page_links response.links
      response
    end

    def next
      return nil unless has_next?

      response = if next_page < 1
        parsed_query = parse_query(next_page_uri.split(QUERY_STR_SEP).last)
        params = {}
        if parsed_query.keys.include?('last_sha')
          params['sha'] = parsed_query['last_sha']
        end
        params['per_page'] = parse_per_page_number(next_page_uri)

        page_request next_page_uri.split(QUERY_STR_SEP).first, params
      else
        params = parse_query next_page_uri.split(QUERY_STR_SEP).last
        params['page'] = parse_page_number(next_page_uri)
        params['per_page'] = parse_per_page_number(next_page_uri)
        page_request next_page_uri.split(QUERY_STR_SEP).first, params
      end
      update_page_links response.links
      response
    end

    def prev
      return nil unless prev_page_uri
      params   = parse_query prev_page_uri.split(QUERY_STR_SEP).last
      params['page'] = parse_page_number(prev_page_uri)
      params['per_page'] = parse_per_page_number(prev_page_uri)
      response = page_request prev_page_uri.split(QUERY_STR_SEP).first, params

      update_page_links response.links
      response
    end

    def last
      return nil unless last_page_uri
      params   = parse_query last_page_uri.split(QUERY_STR_SEP).last
      params['page'] = parse_page_number(last_page_uri)
      params['per_page'] = parse_per_page_number(last_page_uri)
      response = page_request last_page_uri.split(QUERY_STR_SEP).first, params

      update_page_links response.links
      response
    end

    # Returns the result for a specific page.
    def get_page(page_number)
      # Find URI that we can work with, if we cannot get the first or the
      # last page URI then there is only one page.
      page_uri = first_page_uri || last_page_uri
      return nil unless page_uri
      params   = parse_query page_uri.split(QUERY_STR_SEP).last
      params['page'] = page_number
      params['per_page'] = parse_per_page_number(page_uri)
      response = page_request page_uri.split(QUERY_STR_SEP).first, params

      update_page_links response.links
      response
    end

  private

    def parse_per_page_number(uri) # :nodoc:
      parse_page_params(uri, PARAM_PER_PAGE)
    end

    def parse_page_number(uri) # :nodoc:
      parse_page_params(uri, PARAM_PAGE)
    end

    # Extracts query string parameter for given name
    def parse_page_params(uri, attr) # :nodoc:
      return -1 if uri.nil? || uri.empty?
      parsed = nil
      begin
        parsed = URI.parse(uri)
      rescue URI::Error => e
        return -1
      end
      param = parse_query_for_param(parsed.query, attr)
      return -1 if param.nil? || param.empty?
      begin
        return param.to_i
      rescue ArgumentError => err
        return -1
      end
    end

    # Wholesale update of all link attributes
    def update_page_links(links) # :nodoc:
      ATTRIBUTES.each do |attr|
        self.send(:"#{attr}_page_uri=", links.send(:"#{attr}"))
        self.send(:"#{attr}_page=", parse_page_number(links.send(:"#{attr}")))
      end
    end

  end # PageIterator
end # Github