[tex-hyphen] Hyphenation algorithm in Lua

[Keno Wehr]

LuaTeX provides a “hyphenate” callback allowing to replace TeX's 
hyphenation routine (LuaTeX manual, p. 175).
This callback is used by the luatexko and luavlna packages, which 
however do not use it for real hyphenation.
I would like to get an idea how this callback can be used for hyphenation.
Is there any known Lua implementation of TeX's or any other hyphenation 
algorithm?
What is the preferred way to access the hyphenation patterns within Lua?
Keno