youtube_scrape.rb

#!/usr/bin/env ruby

require 'faraday'
require 'faraday_middleware'

class ChannelResult
  attr_reader :channels, :next_page_token

  def initialize(channels, next_page_token)
    @channels = channels
    @next_page_token = next_page_token
  end
end

def fetch_channels(next_page_token = nil)
  url = "https://www.googleapis.com/youtube/v3/search?part=id&type=channel&maxResults=50&regionCode=JP&key=#{API_KEY}"
  conn = Faraday.new(url: url) { |faraday|
    faraday.adapter Faraday.default_adapter
    faraday.response :json
  }
  response = conn.get(nil, "pageToken" => next_page_token)
  pp response.body
  channels = response.body["items"].map { _1["id"]["channelId"] }
  next_page_token = response.body["nextPageToken"]

  ChannelResult.new(channels, next_page_token)
end

def channels
  t = nil
  (1..6).flat_map do
    resp = fetch_channels(t)
    t = resp.next_page_token
    resp
  end
end

class ChannelDetail
  attr_reader :id, :subscribers, :title

  def initialize(id, subscribers, title)
    @id = id
    @subscribers = subscribers
    @title = title
  end

  def format
    "#{title} #{subscribers}"
  end
end

def channel_details(list)
  ids = list.channels.join(",")
  url = "https://www.googleapis.com/youtube/v3/channels?part=statistics,snippet&id=#{ids}&key=#{API_KEY}"
  conn = Faraday.new(url: url) { |faraday|
    faraday.adapter Faraday.default_adapter
    faraday.response :json
  }
  response = conn.get
  response.body["items"].map do
    ChannelDetail.new(
      _1["id"],
      _1["statistics"]["subscriberCount"],
      _1["snippet"]["title"]
    )
  end
end

def ch(channel_lists)
  channel_lists.flat_map do |list|
    channel_details(list)
  end
end

details = ch(channels)
sorted = details.sort_by do
  _1.subscribers.to_i
end

sorted.each.with_index(1) do |c, i|
  puts "#{i} #{c.format}"
end