" Vim indent file
" Language:	Fortran90 (and Fortran95, Fortran77, F and elf90)
" Version:	0.33
" Last Change:	2001 Sep 17
" Maintainer:	Ajit J. Thakkar <ajit@unb.ca>; <http://www.unb.ca/chem/ajit/>
" For the latest version of this file, see <http://www.unb.ca/chem/ajit/vim.htm>

" Only load this indent file when no other was loaded.
if exists("b:did_indent")
  finish
endif
let b:did_indent = 1

setlocal indentkeys+==~end,=~case,=~if,=~else,=~do,=~where,=~elsewhere,=~select

" Determine whether this is a fixed or free format source file
" if this hasn't been done yet
if !exists("b:fortran_fixed_source")
  if exists("fortran_free_source")
    let b:fortran_fixed_source = 0
  else
    " f90 and f95 allow both fixed and free source form
    " assume fixed source form unless signs of free source form
    " are detected in the first five columns of the first 25 lines
    " Detection becomes more accurate and time-consuming if more lines
    " are checked. Increase the limit below if you keep lots of comments at
    " the very top of each file and you have a fast computer
    let s:lmax = 25
    if ( s:lmax > line("$") )
      let s:lmax = line("$")
    endif
    let b:fortran_fixed_source = 1
    let s:ln=1
    while s:ln <= s:lmax
      let s:test = strpart(getline(s:ln),0,5)
      if s:test[0] !~ '[Cc*!#]' && s:test !~ '^ \+[!#]' && s:test =~ '[^ 0-9\t]'
	let b:fortran_fixed_source = 0
	break
      endif
      let s:ln = s:ln + 1
    endwhile
  endif
endif

" Define the appropriate indent function but only once
if (b:fortran_fixed_source == 1)
  setlocal indentexpr=FortranGetFixedIndent()
  if exists("*FortranGetFixedIndent")
    finish
  endif
else
  setlocal indentexpr=FortranGetFreeIndent()
  if exists("*FortranGetFreeIndent")
    finish
  endif
endif

function FortranGetIndent(lnum)
  let ind = indent(a:lnum)
  let prevline=getline(a:lnum)
  " Strip tail comment
  let prevstat=substitute(prevline, '!.*$', '', '')

  "Indent do loops only if they are all guaranteed to be of do/end do type
  if exists("b:fortran_do_enddo") || exists("fortran_do_enddo")
    if prevstat =~? '^\s*\(\d\+\s\)\=\s*\(\a\w*\s*:\)\=\s*do\>'
      let ind = ind + &sw
    endif
    if getline(v:lnum) =~? '^\s*\(\d\+\s\)\=\s*end\s*do\>'
      let ind = ind - &sw
    endif
  endif

  "Add a shiftwidth to statements following if, else, case,
  "where and elsewhere statements
  if prevstat =~? '^\s*\(\d\+\s\)\=\s*\(else\|case\|where\|elsewhere\)\>' || prevstat =~? '^\s*\(\d\+\s\)\=\s*\(\a\w*\s*:\)\=\s*if\>'
     let ind = ind + &sw
    " Remove unwanted indent after logical and arithmetic ifs
    if prevstat =~? '\<if\>' && prevstat !~? '\<then\>'
      let ind = ind - &sw
    endif
  endif

  "Subtract a shiftwidth from else, elsewhere, case, end if,
  " end where and end select statements
  if getline(v:lnum) =~? '^\s*\(\d\+\s\)\=\s*\(else\|elsewhere\|case\|end\s*\(if\|where\|select\)\)\>'
    let ind = ind - &sw
    " Fix indent for case statement immediately after select
    if prevstat =~? '\<select\>'
      let ind = ind + &sw
    endif
  endif

  return ind
endfunction

function FortranGetFreeIndent()
  "Find the previous non-blank line
  let lnum = prevnonblank(v:lnum - 1)

  "Use zero indent at the top of the file
  if lnum == 0
    return 0
  endif

  let ind=FortranGetIndent(lnum)
  return ind
endfunction

function FortranGetFixedIndent()
  let currline=getline(v:lnum)
  "Don't indent comments, continuation lines and labelled lines
  if strpart(currline,0,6) =~ '[^ \t]'
    let ind = indent(v:lnum)
    return ind
  endif

  "Find the previous line which is not blank, not a comment,
  "not a continuation line, and does not have a label
  let lnum = v:lnum - 1
  while lnum > 0
    let prevline=getline(lnum)
    if (prevline =~ "^[C*!]") || (prevline =~ "^\s*$") || (strpart(prevline,5,1) !~ "[ 0]")
      " Skip comments, blank lines and continuation lines
      let lnum = lnum - 1
    else
      let test=strpart(prevline,0,5)
      if test =~ "[0-9]"
	" Skip lines with statement numbers
	let lnum = lnum - 1
      else
	break
      endif
    endif
  endwhile

  "First line must begin at column 7
  if lnum == 0
    return 6
  endif

  let ind=FortranGetIndent(lnum)
  return ind
endfunction

" vim:sw=2 tw=130
