script to assist ASCII text

[Gary Kline]

People,

This had eluded me for years and it may not be possible, but here goes.
I write using vi or, less frequently vim.  Is there any sh script that
would make sure that there were exactly one space ('\040') between
words, and three spaces between sentences?  My definition of "a
sentence" is a string of words that ends in a period or question-mark,
exclamation-mark, or ellipse ("... . || ... ? || ... !)  Also, any dash
"--" could not have any whitespace around it.

Anything except these would print an error.

thanks for idea or input,

gary