TOOLS/lua/autoload: further optimize the natural sorting

Commits 257dbdf06f uses a algorithm of splitting strings
into a table of number and string values to achieve natural sorting.
This approach works well in most cases, but it does not work well
in some specific scenarios.
Now let's implement natural sorting with a stronger algorithm.

Also fixes indentation.

Ref: 3cf323f3c4
Closes https://github.com/mpv-player/mpv/issues/8969

TOOLS/lua/autoload.lua

@@ -94,35 +94,19 @@ table.filter = function(t, iter)
     end
 end
 
--- splitbynum and alnumcomp from alphanum.lua (C) Andre Bogus
+-- alphanum sorting for humans in Lua
--- Released under the MIT License
+-- http://notebook.kulchenko.com/algorithms/alphanumeric-natural-sorting-for-humans-in-lua
--- http://www.davekoelle.com/files/alphanum.lua
 
--- split a string into a table of number and string values
+function alphanumsort(o)
-function splitbynum(s)
+    local function padnum(d)
-    local result = {}
+        local dec, n = string.match(d, "(%.?)0*(.+)")
-    for x, y in (s or ""):gmatch("(%d*)(%D*)") do
+        return #dec > 0 and ("%.12f"):format(d) or ("%s%03d%s"):format(dec, #n, n)
-        if x ~= "" then table.insert(result, tonumber(x)) end
-        if y ~= "" then table.insert(result, y) end
     end
-    return result
+    table.sort(o, function(a,b)
-end
+        return tostring(a):lower():gsub("%.?%d+",padnum)..("%3d"):format(#b)
-
+             < tostring(b):lower():gsub("%.?%d+",padnum)..("%3d"):format(#a) 
-function clean_key(k)
+    end)
-    k = (' '..k..' '):gsub("%s+", " "):sub(2, -2):lower()
+    return o
-    return splitbynum(k)
-end
-
--- compare two strings
-function alnumcomp(x, y)
-    local xt, yt = clean_key(x), clean_key(y)
-    for i = 1, math.min(#xt, #yt) do
-        local xe, ye = xt[i], yt[i]
-        if type(xe) == "string" then ye = tostring(ye)
-        elseif type(ye) == "string" then xe = tostring(xe) end
-        if xe ~= ye then return xe < ye end
-    end
-    return #xt < #yt
 end
 
 local autoloaded = nil
@@ -181,7 +165,7 @@ function find_and_add_entries()
         end
         return EXTENSIONS[string.lower(ext)]
     end)
-    table.sort(files, alnumcomp)
+    alphanumsort(files)
 
     if dir == "." then
         dir = ""