#!/usr/local/bin/lua
-- $OpenBSD: yt.lua,v 1.12 2008/06/02 17:43:10 martynas Exp $
-- Fetch videos from YouTube.com and convert them to MPEG.
-- Written by Pedro Martelletto in August 2006. Public domain.
-- Example: lua yt.lua http://www.youtube.com/watch?v=c5uoo1Kl_uA

http = require("socket.http")

-- Make sure a URL was given.
url = assert(arg[1], "Wrong usage, no URL given")

-- Set this to a command capable of talking HTTP and following 3XX requests.
fetch = "ftp -o <file> <url>"

-- Set this to a command capable of converting from FLV to MPEG.
convert = "ffmpeg -y -i <flv> -b 1000k -f mp4 -vcodec mpeg4 -acodec libfaac -ab 128k <mp4> 1>/dev/null 2>&1"

-- Set this to the base location where to fetch YouTube videos from.
base_url = "http://www.youtube.com/get_video"

-- Fetch the page holding the embedded video.
print(string.format("Getting %s ...", url))
body = assert(http.request(url))

-- Look for the video title.
pattern = "<title>(.-)</title>"
title = assert(string.match(body, pattern))

-- Build a name for the files the video will be stored in.
file = string.gsub(title, "[^%w-]", "_")
file = string.lower(file)
flv = file .. ".flv"
mp4 = file .. ".mp4"

-- Escape the file names.
e_flv = string.format("%q", flv)
e_mp4 = string.format("%q", mp4)

-- Look for the video ID.
pattern = "/watch_fullscreen%?.*video_id=(.-)&"
video_id = string.match(body, pattern)

if video_id then
	--- Look for the additional video ID.
	pattern = "/watch_fullscreen%?.*&t=(.-)&"
	t = assert(string.match(body, pattern))
	url = string.format("%q", base_url .. "?video_id=" .. video_id
		.. "&t=" .. t)
else
	-- We assume it's Google Video URL.
	pattern = "'/googleplayer.swf%?videoUrl(.-)'"
	url = assert(string.match(body, pattern))
	url = string.gsub (url, "\\x", "%%")
	url = string.gsub (url, "%%(%x%x)", function(h)
		return string.char(tonumber(h,16)) end)
	url = string.gsub (url, "^=", "")
	url = string.format("%q", url)
end

-- Fetch the video.
cmd = string.gsub(fetch, "<(%w+)>", { url = url, file = e_flv })
assert(os.execute(cmd) == 0, "Failed")

-- Convert it to MPEG.
cmd = string.gsub(convert, "<(%w+)>", { flv = e_flv, mp4 = e_mp4 })
print("Converting ...")
assert(os.execute(cmd) == 0, "Failed")

os.remove(flv)
print("Done. Video saved in " .. mp4 .. ".")