" Save user-defined completefunc so it can be restored after running this
" custom completion function
let s:old_completefunc = &completefunc
let s:old_completeopt = &completeopt

" Completion for Git SHAs in the current repository
function! gitcha#GitSHAComplete()
	" if a:findstart
		" locate the start of the word
		let line = getline('.')
		let start = col('.')
		while start > 0 && line[start - 2] =~ '[0-9a-f]'
			let start -= 1
		endwhile
		" return start
	" endif

	" Match Git SHAs in the current repository
	let matches = []
	let revs = system('git rev-list --all --pretty=oneline --no-abbrev-commit')
	let base = line[start - 1 : col('.') - 1]

	for m in s:BuildMatchDictionary(revs)
		if m['word'] =~ '^' . base
			call add(matches, m)
		endif
	endfor

	" echom start
	" echom string(matches)
	" let &completeopt = 'menu,pattern,menuone'
	set completeopt=menu,menuone,preview
	call complete(start, matches)
	" call complete(col('.'), matches)
	let &completeopt = s:old_completeopt
	return ''
endfunction

" Takes rev-list output from:
"   $ git rev-list --all --pretty=oneline --no-abbrev-commit
"
" Creates a dictionary to be used for matching that uses commit SHAs for the
" completion word and the commit subject as extra text.
function! s:BuildMatchDictionary(rev_list)
	let matches = []
	let commits = split(a:rev_list, '\n')

	for commit in commits
		let separator = stridx(commit, ' ')
		let sha = strpart(commit, 0, separator)
		let subject = strpart(commit, separator + 1)

		call add(matches, {
			\ 'word': sha,
			\ 'abbr': strpart(sha, 0, 10),
			\ 'menu': subject
		\ })
	endfor

	return matches
endfunction

" Allow mappings to initiate completion
function! gitcha#StartGitSHACompletion()
	" call gitcha#GitSHAComplete()
	" return ''
	" set completefunc=gitcha#GitSHAComplete
	" set completeopt=menu,menuone,preview
	" return "\<C-x>\<C-u>"
endfunction