def fetch_decrypt_function(id = "CvFH_6DNRCY") document = YT_POOL.client &.get("/watch?v=#{id}&gl=US&hl=en&disable_polymer=1").body url = document.match(/src="(?\/yts\/jsbin\/player_ias-.{9}\/en_US\/base.js)"/).not_nil!["url"] player = YT_POOL.client &.get(url).body function_name = player.match(/^(?[^=]+)=function\(a\){a=a\.split\(""\)/m).not_nil!["name"] function_body = player.match(/^#{Regex.escape(function_name)}=function\(a\){(?[^}]+)}/m).not_nil!["body"] function_body = function_body.split(";")[1..-2] var_name = function_body[0][0, 2] var_body = player.delete("\n").match(/var #{Regex.escape(var_name)}={(?(.*?))};/).not_nil!["body"] operations = {} of String => String var_body.split("},").each do |operation| op_name = operation.match(/^[^:]+/).not_nil![0] op_body = operation.match(/\{[^}]+/).not_nil![0] case op_body when "{a.reverse()" operations[op_name] = "a" when "{a.splice(0,b)" operations[op_name] = "b" else operations[op_name] = "c" end end decrypt_function = [] of {name: String, value: Int32} function_body.each do |function| function = function.lchop(var_name).delete("[].") op_name = function.match(/[^\(]+/).not_nil![0] value = function.match(/\(a,(?[\d]+)\)/).not_nil!["value"].to_i decrypt_function << {name: operations[op_name], value: value} end return decrypt_function end def decrypt_signature(fmt, code) if !fmt["s"]? return "" end a = fmt["s"] a = a.split("") code.each do |item| case item[:name] when "a" a.reverse! when "b" a.delete_at(0..(item[:value] - 1)) when "c" a = splice(a, item[:value]) end end signature = a.join("") return "&#{fmt["sp"]?}=#{signature}" end def splice(a, b) c = a[0] a[0] = a[b % a.size] a[b % a.size] = c return a end