Folding completed tasks

Todo.txt

@@ -1,13 +1,13 @@
-(A) 2011-06-03 Accept variable space length between fields @syntax
-(A) 2011-06-03 Implement foldings @ftplugin
+(A) 2011-06-06 Easier date input @ftplugin
 (B) 2011-05-31 Start documentation @doc
 (C) 2011-05-30 Create README.markdown to be published in github @doc
 (C) 2011-06-01 Improve syntax file @syntax
 2011-05-30 Contact main project for reference
 2011-05-30 Map commands to add, rm, ls, pri, depri etc @ftplugin
+2011-06-06 Check file syntax @syntax
 X 2011-05-30 Implement colorized priorities @syntax
 X 2011-05-30 Implement filetype detection @ftdetect
 X 2011-05-30 Sort lines per priority @ftplugin
 X 2011-05-31 Highlight date, project and context of tasks with no priority @syntax
 X 2011-05-31 Stop breaking lines automatically @ftplugin
-X 2011-05-31 Stop breaking lines automatically @ftplugin
+X 2011-06-06 Implement foldings @ftplugin

ftplugin/todo.vim

@@ -3,7 +3,7 @@
 " Author:      Leandro Freitas <freitass@gmail.com>
 " Licence:     Vim licence
 " Website:     http://github.com/freitass/todo.txt.vim
-" Version:     0.2
+" Version:     0.3
 
 if exists("g:loaded_todo")
     finish
@@ -16,4 +16,28 @@ set cpo&vim
 setlocal textwidth=0
 setlocal wrapmargin=0
 
+setlocal foldmethod=expr
+setlocal foldexpr=TodoFoldLevel(v:lnum)
+setlocal foldtext=TodoFoldText()
+
+function! TodoFoldLevel(lnum)
+    " The match function returns the index of the matching pattern or -1 if
+    " the pattern doesn't match. In this case, we always try to match a
+    " completed task from the beginning of the line so that the matching
+    " function will always return -1 if the pattern doesn't match or 0 if the
+    " pattern matches. Incrementing by one the value returned by the matching
+    " function we will return 1 for the completed tasks (they will be at the
+    " first folding level) while for the other lines 0 will be returned,
+    " indicating that they do not fold.
+    return match(getline(a:lnum),'^[xX]\s.\+$') + 1
+endfunction
+
+function! TodoFoldText()
+    " The text displayed at the fold is formatted as '+- N Completed tasks'
+    " where N is the number of lines folded.
+    return '+' . v:folddashes . ' '
+                \ . (v:foldend - v:foldstart + 1)
+                \ . ' Completed tasks'
+endfunction
+
 let &cpo = s:save_cpo