require "http/client"
require "json" 

class RedditWrapper(T)
  JSON.mapping(
    kind: String,
    data: T)
end

class RedditChild
  JSON.mapping(
    url: String,
    name: String,
    title: String)
end

class RedditResponse
  JSON.mapping(
    modhash: String,
    dist: Int32,
    children: Array(RedditWrapper(RedditChild)))

  def self.from_subreddits(subreddits : Array(String))
    request_url = URI.new scheme: "https", host: "www.reddit.com", path: "/r/#{subreddits.join "+"}/hot.json", query: "limit=30"
    response = HTTP::Client.get(request_url, headers: HTTP::Headers {
      "User-agent" => "Joann-Pupper-Bot"
    })

    return nil unless body = response.body?

    begin
      RedditWrapper(RedditResponse).from_json body
    rescue e
      nil
    end
  end

  def self.from_subreddit(subreddit)
    from_subreddits [subreddit]
  end

  def posts_matching(&block)
    children
      .map(&.data)
      .select { |it| yield it }
  end
end