require 'cgi'
require 'net/http'
require 'octokit'

Net::OpenTimeout = Class.new(RuntimeError) unless Net.const_defined?(:OpenTimeout)
Net::ReadTimeout = Class.new(RuntimeError) unless Net.const_defined?(:ReadTimeout)

module Jekyll
  module Gist
    class GistTag < Liquid::Tag

      def render(context)
        @encoding = context.registers[:site].config['encoding'] || 'utf-8'
        @settings = context.registers[:site].config['gist']
        if tag_contents = determine_arguments(@markup.strip)
          gist_id, filename = tag_contents[0], tag_contents[1]
          if context_contains_key?(context, gist_id)
            gist_id = context[gist_id]
          end
          if context_contains_key?(context, filename)
            filename = context[filename]
          end
          noscript_tag = gist_noscript_tag(gist_id, filename)
          script_tag = gist_script_tag(gist_id, filename)
          "#{noscript_tag}#{script_tag}"
        else
          raise ArgumentError.new <<-eos
  Syntax error in tag 'gist' while parsing the following markup:

    #{@markup}

  Valid syntax:
    {% gist user/1234567 %}
    {% gist user/1234567 foo.js %}
    {% gist 28949e1d5ee2273f9fd3 %}
    {% gist 28949e1d5ee2273f9fd3 best.md %}
  eos
        end
      end

      private

      def determine_arguments(input)
        matched = input.match(/\A([\S]+|.*(?=\/).+)\s?(\S*)\Z/)
        [matched[1].strip, matched[2].strip] if matched && matched.length >= 3
      end

      private

      def context_contains_key?(context, key)
        if context.respond_to?(:has_key?)
          context.has_key?(key)
        else
          context.key?(key)
        end
      end

      def gist_script_tag(gist_id, filename = nil)
        url = "https://gist.github.com/#{gist_id}.js"
        url = "#{url}?file=#{filename}" unless filename.to_s.empty?
        "<script src=\"#{url}\"> </script>"
      end

      def gist_noscript_tag(gist_id, filename = nil)
        return if @settings && @settings["noscript"] == false
        code = fetch_raw_code(gist_id, filename)
        if !code.nil?
          code = code.force_encoding(@encoding)
          code = CGI.escapeHTML(code)

          # CGI.escapeHTML behavior differs in Ruby < 2.0
          # See https://github.com/jekyll/jekyll-gist/pull/28
          code = code.gsub("'", "&#39;") if RUBY_VERSION < "2.0"

          "<noscript><pre>#{code}</pre></noscript>"
        else
          Jekyll.logger.warn "Warning:", "The <noscript> tag for your gist #{gist_id} could not"
          Jekyll.logger.warn "", "be generated. This will affect users who do not have"
          Jekyll.logger.warn "", "JavaScript available or enabled in their browsers."
        end
      end

      def fetch_raw_code(gist_id, filename = nil)
        return code_from_api(gist_id, filename) if ENV["JEKYLL_GITHUB_TOKEN"]

        url = "https://gist.githubusercontent.com/#{gist_id}/raw"
        url = "#{url}/#{filename}" unless filename.to_s.empty?
        uri = URI(url)
        Net::HTTP.start(uri.host, uri.port,
          use_ssl: uri.scheme == 'https',
          read_timeout: 3, open_timeout: 3) do |http|
          request = Net::HTTP::Get.new uri.to_s
          response = http.request(request)
          response.body
        end
      rescue SocketError, Net::HTTPError, Net::OpenTimeout, Net::ReadTimeout, TimeoutError
        nil
      end

      private

      def code_from_api(gist_id, filename = nil)
        gist = GistTag.client.gist gist_id

        file = if filename.to_s.empty?
          # No file specified, return the value of the first key/value pair
          gist.files.first[1]
        else
          # .files is a hash of :"filename.extension" => data pairs
          # Rather than using to_sym on arbitrary user input,
          # Find our file by calling to_s on the keys
          match = gist.files.find { |name, data| name.to_s == filename }
          match[1] if match
        end

        file[:content] if file
      end

      def self.client
        @client ||= Octokit::Client.new :access_token => ENV["JEKYLL_GITHUB_TOKEN"]
      end
    end
  end
end

Liquid::Template.register_tag('gist', Jekyll::Gist::GistTag)