require 'uri'
require_dependency "onebox/discourse_onebox_sanitize_config"
require_dependency 'final_destination'

Dir["#{Rails.root}/lib/onebox/engine/*_onebox.rb"].sort.each { |f| require f }

module Oneboxer
  # keep reloaders happy
  unless defined? Oneboxer::Result
    Result = Struct.new(:doc, :changed) do
      def to_html
        doc.to_html
      end

      def changed?
        changed
      end
    end
  end

  def self.ignore_redirects
    @ignore_redirects ||= ['http://www.dropbox.com', 'http://store.steampowered.com', Discourse.base_url]
  end

  def self.force_get_hosts
    @force_get_hosts ||= ['http://us.battle.net']
  end

  def self.preview(url, options = nil)
    options ||= {}
    invalidate(url) if options[:invalidate_oneboxes]
    onebox_raw(url, options)[:preview]
  end

  def self.onebox(url, options = nil)
    options ||= {}
    invalidate(url) if options[:invalidate_oneboxes]
    onebox_raw(url, options)[:onebox]
  end

  def self.cached_onebox(url)
    if c = Rails.cache.read(onebox_cache_key(url))
      c[:onebox]
    end
  rescue => e
    invalidate(url)
    Rails.logger.warn("invalid cached onebox for #{url} #{e}")
    ""
  end

  def self.cached_preview(url)
    if c = Rails.cache.read(onebox_cache_key(url))
      c[:preview]
    end
  rescue => e
    invalidate(url)
    Rails.logger.warn("invalid cached preview for #{url} #{e}")
    ""
  end

  def self.invalidate(url)
    Rails.cache.delete(onebox_cache_key(url))
  end

  # Parse URLs out of HTML, returning the document when finished.
  def self.each_onebox_link(string_or_doc)
    doc = string_or_doc
    doc = Nokogiri::HTML::fragment(doc) if doc.is_a?(String)

    onebox_links = doc.search("a.onebox")
    if onebox_links.present?
      onebox_links.each do |link|
        yield(link['href'], link) if link['href'].present?
      end
    end

    doc
  end

  HTML5_BLOCK_ELEMENTS ||= %w{address article aside blockquote canvas center dd div dl dt fieldset figcaption figure footer form h1 h2 h3 h4 h5 h6 header hgroup hr li main nav noscript ol output p pre section table tfoot ul video}

  def self.apply(string_or_doc, args = nil)
    doc = string_or_doc
    doc = Nokogiri::HTML::fragment(doc) if doc.is_a?(String)
    changed = false

    each_onebox_link(doc) do |url, element|
      onebox, _ = yield(url, element)
      if onebox
        parsed_onebox = Nokogiri::HTML::fragment(onebox)
        next unless parsed_onebox.children.count > 0

        if element&.parent&.node_name&.downcase == "p" &&
           element.parent.children.count == 1 &&
           HTML5_BLOCK_ELEMENTS.include?(parsed_onebox.children[0].node_name.downcase)
          element = element.parent
        end

        changed = true
        element.swap parsed_onebox.to_html
      end
    end

    # strip empty <p> elements
    doc.css("p").each { |p| p.remove if p.children.empty? }

    Result.new(doc, changed)
  end

  def self.is_previewing?(user_id)
    $redis.get(preview_key(user_id)) == "1"
  end

  def self.preview_onebox!(user_id)
    $redis.setex(preview_key(user_id), 1.minute, "1")
  end

  def self.onebox_previewed!(user_id)
    $redis.del(preview_key(user_id))
  end

  def self.engine(url)
    Onebox::Matcher.new(url).oneboxed
  end

  private

    def self.preview_key(user_id)
      "onebox:preview:#{user_id}"
    end

    def self.blank_onebox
      { preview: "", onebox: "" }
    end

    def self.onebox_cache_key(url)
      "onebox__#{url}"
    end

    def self.onebox_raw(url, opts = {})
      url = URI(url).to_s
      local_onebox(url, opts) || external_onebox(url)
    rescue => e
      # no point warning here, just cause we have an issue oneboxing a url
      # we can later hunt for failed oneboxes by searching logs if needed
      Rails.logger.info("Failed to onebox #{url} #{e} #{e.backtrace}")
      # return a blank hash, so rest of the code works
      blank_onebox
    end

    def self.local_onebox(url, opts = {})
      return unless route = Discourse.route_for(url)

      html =
        case route[:controller]
        when "uploads" then local_upload_html(url)
        when "topics"  then local_topic_html(url, route, opts)
        when "users"   then local_user_html(url, route)
        end

      html = html.presence || "<a href='#{url}'>#{url}</a>"
      { onebox: html, preview: html }
    end

    def self.local_upload_html(url)
      case File.extname(URI(url).path || "")
      when /^\.(mov|mp4|webm|ogv)$/i
        "<video width='100%' height='100%' controls><source src='#{url}'><a href='#{url}'>#{url}</a></video>"
      when /^\.(mp3|ogg|wav|m4a)$/i
        "<audio controls><source src='#{url}'><a href='#{url}'>#{url}</a></audio>"
      end
    end

    def self.local_topic_html(url, route, opts)
      return unless current_user = User.find_by(id: opts[:user_id])

      if current_category = Category.find_by(id: opts[:category_id])
        return unless Guardian.new(current_user).can_see_category?(current_category)
      end

      if current_topic = Topic.find_by(id: opts[:topic_id])
        return unless Guardian.new(current_user).can_see_topic?(current_topic)
      end

      topic = Topic.find_by(id: route[:topic_id])

      return unless topic
      return if topic.private_message?

      if current_category&.id != topic.category_id
        return unless Guardian.new.can_see_topic?(topic)
      end

      post_number = route[:post_number].to_i

      post = post_number > 1 ?
        topic.posts.where(post_number: post_number).first :
        topic.ordered_posts.first

      return if !post || post.hidden || post.post_type != Post.types[:regular]

      if post_number > 1 && current_topic&.id == topic.id
        excerpt = post.excerpt(SiteSetting.post_onebox_maxlength)
        excerpt.gsub!(/[\r\n]+/, " ")
        excerpt.gsub!("[/quote]", "[quote]") # don't break my quote

        quote = "[quote=\"#{post.user.username}, topic:#{topic.id}, post:#{post.post_number}\"]\n#{excerpt}\n[/quote]"

        PrettyText.cook(quote)
      else
        args = {
          topic_id: topic.id,
          post_number: post.post_number,
          avatar: PrettyText.avatar_img(post.user.avatar_template, "tiny"),
          original_url: url,
          title: PrettyText.unescape_emoji(CGI::escapeHTML(topic.title)),
          category_html: CategoryBadge.html_for(topic.category),
          quote: PrettyText.unescape_emoji(post.excerpt(SiteSetting.post_onebox_maxlength)),
        }

        template = File.read("#{Rails.root}/lib/onebox/templates/discourse_topic_onebox.hbs")
        Mustache.render(template, args)
      end
    end

    def self.local_user_html(url, route)
      username = route[:username] || ""

      if user = User.find_by(username_lower: username.downcase)
        args = {
          user_id: user.id,
          username: user.username,
          avatar: PrettyText.avatar_img(user.avatar_template, "extra_large"),
          name: user.name,
          bio: user.user_profile.bio_excerpt(230),
          location: user.user_profile.location,
          joined: I18n.t('joined'),
          created_at: user.created_at.strftime(I18n.t('datetime_formats.formats.date_only')),
          website: user.user_profile.website,
          website_name: UserSerializer.new(user).website_name,
          original_url: url
        }

        template = File.read("#{Rails.root}/lib/onebox/templates/discourse_user_onebox.hbs")
        Mustache.render(template, args)
      else
        nil
      end
    end

    def self.external_onebox(url)
      Rails.cache.fetch(onebox_cache_key(url), expires_in: 1.day) do
        fd = FinalDestination.new(url, ignore_redirects: ignore_redirects, force_get_hosts: force_get_hosts)
        uri = fd.resolve
        return blank_onebox if uri.blank? || SiteSetting.onebox_domains_blacklist.include?(uri.hostname)

        options = {
          cache: {},
          max_width: 695,
          sanitize_config: Sanitize::Config::DISCOURSE_ONEBOX
        }

        options[:cookie] = fd.cookie if fd.cookie

        if Rails.env.development? && SiteSetting.port.to_i > 0
          Onebox.options = { allowed_ports: [80, 443, SiteSetting.port.to_i] }
        end

        r = Onebox.preview(uri.to_s, options)

        { onebox: r.to_s, preview: r&.placeholder_html.to_s }
      end
    end

end