From 13d56da45a47f73b55aa5544aafe68d36774b51d Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Mon, 17 Jun 2019 00:47:52 +1200
Subject: Overhaul local Vim spellfile word list plugin

---
 vim/autoload/spellfile_local.vim | 79 +++++++++++++++++++++++++++++++++++-----
 vim/plugin/spellfile_local.vim   | 13 ++-----
 vim/vimrc                        | 16 ++++++++
 3 files changed, 89 insertions(+), 19 deletions(-)

diff --git a/vim/autoload/spellfile_local.vim b/vim/autoload/spellfile_local.vim
index aafe64ef..081b2970 100644
--- a/vim/autoload/spellfile_local.vim
+++ b/vim/autoload/spellfile_local.vim
@@ -1,11 +1,72 @@
+function! s:SplitOption(string) abort
+  return map(
+      \ split(a:string, '\\\@<!,[, ]*')
+      \,"substitute(v:val, '\\\\,', '', 'g')"
+      \)
+endfunction
+
+function! s:JoinOption(list) abort
+  return join(map(
+        \ a:list
+        \,"substitute(v:val, '\\\\\\@<!,', '\\\\,', 'g')"
+        \), ',')
+endfunction
+
+function! s:Establish(path) abort
+  return isdirectory(a:path)
+        \ || exists('*mkdir') && mkdir(a:path, 'p', 0700)
+endfunction
+
 function! spellfile_local#() abort
-  let spellfile = join([
-        \ substitute(expand('%:p'), '[^0-9A-Za-z_.-]', '%', 'g'),
-        \ substitute(v:lang, '_.*', '', ''),
-        \ &encoding
-        \ ], '.') . '.add'
-  Establish $MYVIM/cache/spell/local
-  execute 'setlocal spellfile+=$MYVIM/cache/spell/local/'.spellfile
-  nnoremap <buffer> zG 2zg
-  xnoremap <buffer> zG 2zg
+
+  set spellfile<
+
+  let spelllangs = s:SplitOption(&spelllang)
+  if !len(spelllangs) || &spelllang[0] ==# ''
+    echoerr 'Blank ''spelllang'''
+  endif
+  let spelllang = substitute(spelllangs[0], '_.*', '', '')
+
+  if !len(&encoding)
+    echoerr 'Blank ''encoding'''
+  endif
+
+  let spellfiles = s:SplitOption(&spellfile)
+  if len(spellfiles) != 1 || spellfiles[0] ==# ''
+    return
+  endif
+
+  let spelldir = fnamemodify(spellfiles[0], ':h')
+  if spelldir ==# ''
+    echoerr 'Blank directory'
+  endif
+
+  try
+    let path = substitute(expand('%:p'), '/', '%', 'g')
+    if path ==# ''
+      echoerr 'Blank path'
+    endif
+    call s:Establish(spelldir.'/path')
+    call add(spellfiles, spelldir.'/path/'.join([
+          \ path
+          \,spelllang
+          \,&encoding
+          \,'add'
+          \], '.'))
+
+    if &filetype ==# ''
+      echoerr 'Blank filetype'
+    endif
+    call s:Establish(spelldir.'/filetype')
+    call add(spellfiles, spelldir.'/filetype/'.join([
+          \ &filetype
+          \,spelllang
+          \,&encoding
+          \,'add'
+          \], '.'))
+  catch
+  endtry
+
+  let &l:spellfile = s:JoinOption(spellfiles)
+
 endfunction
diff --git a/vim/plugin/spellfile_local.vim b/vim/plugin/spellfile_local.vim
index c026d626..f6918bfb 100644
--- a/vim/plugin/spellfile_local.vim
+++ b/vim/plugin/spellfile_local.vim
@@ -1,19 +1,12 @@
-if exists('loaded_spellfile_local')
+if exists('loaded_spellfile_local') || &compatible
   finish
 endif
 let loaded_spellfile_local = 1
 
-let s:spellfile = join([
-      \ substitute(v:lang, '_.*', '', ''),
-      \ &encoding
-      \ ], '.') . '.add'
-Establish $MYVIM/cache/spell
-execute 'set spellfile=$MYVIM/cache/spell/'.s:spellfile
-
-command! -bar AddLocalSpellFile
+command! -bar SetLocalSpellFiles
       \ call spellfile_local#()
 
 augroup spellfile_local
   autocmd BufNew,BufRead *
-        \ AddLocalSpellFile
+        \ SetLocalSpellFiles
 augroup END
diff --git a/vim/vimrc b/vim/vimrc
index 7f2d9ae8..dc9430e1 100644
--- a/vim/vimrc
+++ b/vim/vimrc
@@ -398,6 +398,22 @@ if has('persistent_undo')
   set undodir^=$MYVIM/cache/undo//
 endif
 
+" For spelling, use New Zealand English by default, but later on we'll
+" configure a leader mapping to switch to United States English, since I so
+" often have to write for Yankees.  We'll set the 'spellfile' option too, to
+" place it in the cache directory into which we've been putting everything.
+" We'll follow Vim's standard naming convention for the file itself, though.
+" If available, my plugin spellfile_local.vim will extend this later to add
+" more spelling word lists per filetype and per file.
+"
+set spelllang=en_nz
+Establish $MYVIM/cache/spell
+let &spellfile = $MYVIM.'/cache/spell/'.join([
+      \ substitute(&spelllang, '_.*', '', '')
+      \,&encoding
+      \,'add'
+      \], '.')
+
 " For word completion in insert mode with CTRL-X CTRL-K, or if 'complete'
 " includes the 'k' flag, the 'dictionary' option specifies the path to the
 " system word list.  This makes the dictionary completion work consistently,
-- 
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