From 4b364f096f9c5ad06daa99f5d302e0b07424f0bf Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Sat, 30 May 2020 19:21:03 +1200
Subject: First version, spun out from dotfiles v9.10.0

---
 autoload/detect_indent.vim | 108 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 autoload/detect_indent.vim

(limited to 'autoload/detect_indent.vim')

diff --git a/autoload/detect_indent.vim b/autoload/detect_indent.vim
new file mode 100644
index 0000000..71a43e8
--- /dev/null
+++ b/autoload/detect_indent.vim
@@ -0,0 +1,108 @@
+" Numeric comparison function to sort in a Vim v7.0 compatible way
+function! s:CompareNumeric(a, b) abort
+  return a:a > a:b ? 1 : -1
+endfunction
+
+" Entry point for plugin
+function! detect_indent#() abort
+
+  " For spaces, we count both the total space-indented lines, and also the
+  " count of lines indexed by space count, so that if we need to, we can
+  " figure out a good 'shiftwidth' setting; for tabs, we just count the
+  " indented lines, since we won't need to set 'shiftwidth' for that.
+  "
+  let tabs = 0
+  let spaces = {
+        \ 'hist': {},
+        \ 'total': 0,
+        \}
+
+  " Figure out how many lines we'll check; cap this to 1,024, or whatever the
+  " user configured
+  let total = max([line('$'), get(g:, 'detect_indent_limit', 1024)])
+
+  " Iterate through the lines
+  for line in getline(1, total)
+
+    " If there are leading tabs, we'll call this a tab-indented line; bump the
+    " appropriate count, and skip the rest of the loop.
+    "
+    if matchstr(line, '^\t*') !=# ''
+      let tabs += 1
+      continue
+    endif
+
+    " Figure out count of space indenting; skip to the next line if it's zero
+    let indent = strlen(matchstr(line, '^ *'))
+    if indent == 0
+      continue
+    endif
+
+    " Increment the count of space-indented lines
+    let spaces['total'] += 1
+
+    " Create a dictionary entry in the histogram for this indent if necessary,
+    " and increment that counter
+    "
+    if !has_key(spaces['hist'], indent)
+      let spaces['hist'][indent] = 0
+    endif
+    let spaces['hist'][indent] += 1
+
+  endfor
+
+  " If the value for 'expandtab' as determined by the user's configuration
+  " matches the expected dominance of space-indented lines over tab-indented
+  " lines, we're already using the right setting, and we stop here
+  "
+  if &expandtab == (spaces['total'] >= tabs)
+    return
+  endif
+
+  " If 'expandtab' is set, we need to unset it and switch to pure tab
+  " indenting; that's straightforward, we just need to make sure 'shiftwidth'
+  " matches 'tabstop', and that 'softtabstop' is off.
+  "
+  if &expandtab
+    setlocal noexpandtab softtabstop=0
+    let &l:shiftwidth = &tabstop
+
+  " If 'expandtab' is not set, we need to set it, and guess an appropriate
+  " 'shiftwidth'.
+  else
+    setlocal expandtab
+
+    " Iterate through the keys of the histogram from smallest to largest.
+    " We'll accept as our 'shiftwidth' the smallest indent level that
+    " constitutes more than 5% of the total lines, configurable by the user.
+    " This is just an heuristic, but it seems to work pretty well.
+    "
+    let shiftwidth = 0
+    let indents = keys(spaces['hist'])
+    call map(indents, 'str2nr(v:val)')  " Coerce the string keys to numeric
+    call sort(indents, 's:CompareNumeric')  " Force numeric sort
+    for shiftwidth in indents
+      if spaces['hist'][shiftwidth] * 100 / spaces['total']
+            \ >= get(g:, 'detect_indent_confidence', 5)
+        break
+      endif
+    endfor
+
+    " We have our 'shiftwidth'; set it, with 'softtabstop' set to match
+    let &l:shiftwidth = shiftwidth
+    let &l:softtabstop = shiftwidth
+
+  endif
+
+  " Since we just messed with indent settings, stack up a command to revert
+  " the changes when the indent plugin is unloaded, as if we ourselves were
+  " a single filetype indent plugin.
+  "
+  let undo_indent = 'setlocal expandtab< shiftwidth< softtabstop<'
+  if exists('b:undo_indent')
+    let b:undo_indent .= '|' . undo_indent
+  else
+    let b:undo_indent = undo_indent
+  endif
+
+endfunction
-- 
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