" vim: set sw=4 sts=4:
" Maintainer : Gergely Kontra <[email protected]>
" Revised on : 2002.02.18. 23:34:05
" Language : Prolog

" TODO:
" checking with respect to syntax highlighting
" ignoring multiline comments
" detecting multiline strings

" Only load this indent file when no other was loaded.
if exists("b:did_indent")
finish
endif

let b:did_indent = 1

setlocal indentexpr=GetPrologIndent()
setlocal indentkeys-=:,0#
setlocal indentkeys+=0%,-,0;,>,0)

" Only define the function once.
"if exists("*GetPrologIndent")
" finish
"endif

function! GetPrologIndent()
" Find a non-blank line above the current line.
let pnum = prevnonblank(v:lnum - 1)
" Hit the start of the file, use zero indent.
if pnum == 0
return 0
endif
let line = getline(v:lnum)
let pline = getline(pnum)

let ind = indent(pnum)
" Previous line was comment -> use previous line's indent
if pline =~ '^\s*%'
retu ind
endif
" Check for clause head on previous line
if pline =~ ':-\s*\(%.*\)\?$'
let ind = ind + &sw
" Check for end of clause on previous line
elseif pline =~ '\.\s*\(%.*\)\?$'
let ind = ind - &sw
endif
" Check for opening conditional on previous line
if pline =~ '^\s*\([(;]\|->\)'
let ind = ind + &sw
endif
" Check for closing an unclosed paren, or middle ; or ->
if line =~ '^\s*\([);]\|->\)'
let ind = ind - &sw
endif
return ind
endfunction