[TxMt] autocomplete

Hello,

Can someone please give me hint how to implement the following simple auto-complete scheme in TextMate:

1. We have three commands: \hi, \hello, \world

2. They can be used as:

a) \hi[mum] or \hi[mum,dad,grandpa] or \hi[mummy,daddy] ... where we are allowed to put only one of the words mum, mummy, dad, daddy, grandma, grandpa into brackets (can be a list)

b) \hello[mum,grandpa] ... the same way as \hi is used

c) \world[shape=sphere,color=blue] or \world[color=brown] where one can use only "shape=sphere/geoid/cube" and "color=blue/black/gray/brown"

I'm confident with writing ruby code, but I need some basic hints for the TextMate part of it.

Thanks a lot, Mojca