youtube.lua: use alternative API URL

It seems that the normal URLs included in the web page miss a
"signature" field and return 403 errors now. This approach has a number
of issues, it requires an extra HTTP request, still seems to fail due
to lack of signatures, and have different access restrictions than the
the web pages.

This shall meet the popular demand for now.

Closes #7471

share/lua/playlist/youtube.lua

 --[[
  $Id$
 
- Copyright © 2007-2011 the VideoLAN team
+ Copyright © 2007-2012 the VideoLAN team
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@@ -47,6 +47,50 @@ function get_prefres()
     return prefres
 end
 
+function get_fmt( fmt_list )
+    local prefres = get_prefres()
+    if prefres < 0 then
+        return nil
+    end
+
+    local fmt = nil
+    for itag,height in string.gmatch( fmt_list, "(%d+)/%d+x(%d+)/[^,]+" ) do
+        -- Apparently formats are listed in quality
+        -- order, so we take the first one that works,
+        -- or fallback to the lowest quality
+        fmt = itag
+        if tonumber(height) <= prefres then
+            break
+        end
+    end
+    return fmt
+end
+
+function pick_url( url_map, fmt )
+    local path = nil
+    -- Handle both orderings, as unfortunately both may appear
+    if string.match( url_map, "^url" ) then
+        for url,itag in string.gmatch( url_map, "url=([^&,]+)[^,]*&itag=(%d+)" ) do
+            -- Apparently formats are listed in quality order,
+            -- so we can afford to simply take the first one
+            if not fmt or tonumber( itag ) == tonumber( fmt ) then
+                url = vlc.strings.decode_uri( url )
+                path = url
+                break
+            end
+        end
+    else
+        for itag,url in string.gmatch( url_map, "itag=(%d+)&[^,]*url=([^&,]+)" ) do
+            if not fmt or tonumber( itag ) == tonumber( fmt ) then
+                url = vlc.strings.decode_uri( url )
+                path = url
+                break
+            end
+        end
+    end
+    return path
+end
+
 -- Probe function.
 function probe()
     if vlc.access ~= "http" and vlc.access ~= "https" then
@@ -62,6 +106,7 @@ function probe()
         end
     end
     return (  string.match( vlc.path, "/watch%?" ) -- the html page
+            or string.match( vlc.path, "/get_video_info%?" ) -- info API
             or string.match( vlc.path, "/v/" ) -- video in swf player
             or string.match( vlc.path, "/player2.swf" ) ) -- another player url
 end
@@ -73,6 +118,9 @@ function parse()
         -- fmt is the format of the video
         -- (cf. http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs)
         fmt = get_url_param( vlc.path, "fmt" )
+        -- URLs in the web page are no good since
+        -- they miss the "signature" parameter :/
+--[[
         while true do
             -- Try to find the video's title
             line = vlc.readline()
@@ -98,20 +146,10 @@ function parse()
             -- "SWF_ARGS", "swfArgs", "PLAYER_CONFIG" ...
             if string.match( line, "playerConfig" ) then
                 if not fmt then
-                    prefres = get_prefres()
-                    if prefres >= 0 then
                     fmt_list = string.match( line, "\"fmt_list\": \"(.-)\"" )
                     if fmt_list then
-                            for itag,height in string.gmatch( fmt_list, "(%d+)\\/%d+x(%d+)\\/[^,]+" ) do
-                                -- Apparently formats are listed in quality
-                                -- order, so we take the first one that works,
-                                -- or fallback to the lowest quality
-                                fmt = itag
-                                if tonumber(height) <= prefres then
-                                    break
-                                end
-                            end
-                        end
+                        fmt_list = string.gsub( fmt_list, "\\/", "/" )
+                        fmt = get_fmt( fmt_list )
                     end
                 end
 
@@ -119,21 +157,24 @@ function parse()
                 if url_map then
                     -- FIXME: do this properly
                     url_map = string.gsub( url_map, "\\u0026", "&" )
-                    for url,itag in string.gmatch( url_map, "url=([^&,]+)[^,]*&itag=(%d+)" ) do
-                        -- Apparently formats are listed in quality order,
-                        -- so we can afford to simply take the first one
-                        if not fmt or tonumber( itag ) == tonumber( fmt ) then
-                            url = vlc.strings.decode_uri( url )
-                            path = url
-                            break
-                        end
-                    end
+                    path = pick_url( url_map, fmt )
                 end
             -- There is also another version of the parameters, encoded
             -- differently, as an HTML attribute of an <object> or <embed>
             -- tag; but we don't need it now
             end
         end
+--]]
+
+        local video_id = get_url_param( vlc.path, "v" )
+        if video_id then
+            if fmt then
+                format = "&fmt=" .. fmt
+            else
+                format = ""
+            end
+            path = "http://www.youtube.com/get_video_info?video_id="..video_id..format.."&el=detailpage"
+        end
 
         if not path then
             vlc.msg.err( "Couldn't extract youtube video URL, please check for updates to this script" )
@@ -145,6 +186,43 @@ function parse()
         end
 
         return { { path = path; name = name; description = description; artist = artist; arturl = arturl } }
+
+    elseif string.match( vlc.path, "/get_video_info%?" ) then
+        local line = vlc.readline() -- data is on one line only
+
+        local fmt = get_url_param( vlc.path, "fmt" )
+        if not fmt then
+            local fmt_list = string.match( line, "&fmt_list=([^&]*)" )
+            if fmt_list then
+                fmt_list = vlc.strings.decode_uri( fmt_list )
+                fmt = get_fmt( fmt_list )
+            end
+        end
+
+        local url_map = string.match( line, "&url_encoded_fmt_stream_map=([^&]*)" )
+        if url_map then
+            url_map = vlc.strings.decode_uri( url_map )
+            path = pick_url( url_map, fmt )
+        end
+
+        if not path then
+            vlc.msg.err( "Couldn't extract youtube video URL, please check for updates to this script" )
+            return { }
+        end
+
+        local title = string.match( line, "&title=([^&]*)" )
+        if title then
+            title = string.gsub( title, "+", " " )
+            title = vlc.strings.decode_uri( title )
+        end
+        local artist = string.match( line, "&author=([^&]*)" )
+        local arturl = string.match( line, "&thumbnail_url=([^&]*)" )
+        if arturl then
+            arturl = vlc.strings.decode_uri( arturl )
+        end
+
+        return { { path = path, title = title, artist = artist, arturl = arturl } }
+
     else -- This is the flash player's URL
         video_id = get_url_param( vlc.path, "video_id" )
         if not video_id then