asyncomplete-muttgoobook.vim/autoload/asyncomplete/sources/muttgoobook.vim

function! s:get_fields()
    if exists('g:muttgoobook_address_fields')
        "echomsg "Found g:muttgoobook_address_fields:  " . g:muttgoobook_address_fields
        let fields = g:muttgoobook_address_fields
    else
        "echomsg "Using default fields..."
        let fields = '^\s*\(from\|to\|b\?cc\):\s*'
    endif
    return fields
endfunction

function! s:is_address_field(section)
    "echomsg "Checking whether we're in an address field..."

    let fields = s:get_fields()

    "echomsg "Section:  " . a:section
    "echomsg "Fields:  " . l:fields

    if a:section =~? l:fields
        "echomsg "In an address field!"
        return 1
    else
        "echomsg "Not in an address field..."
        return 0
    endif
endfunction

function! s:get_section()
    let cur = getline('.')
    if cur !~ '^\w\+:'
        return getline(search('^\w\+:', 'b'))
    else
        return getline('.')
    endif
endfunction

function! s:search_mutt_aliases(query)
    let aliases = {}
    if filereadable(expand('~/.mutt/aliases'))
        for myline in readfile(expand('~/.mutt/aliases'))
            if myline =~ '^alias'
                let mylist = split(myline)
                let myname = mylist[1]
                if l:myname =~ a:query
                    let addresses = join(mylist[2:])
                    let aliases[l:myname] = l:addresses
                endif
            else
                continue
            endif
        endfor
    endif
    return aliases
endfunction

function! s:query_goobook(query)
    let addresses = {}
    for myline in systemlist('goobook query ' . a:query . ' | sed "/^$/d"')
        ""echomsg 'myline:  ' . myline
        let entry = split(myline, '\t')
        let addr = entry[0]
        let name = entry[1]
        let addresses[l:name] = l:addr
    endfor
    return addresses
endfunction

function! s:address_map(name, address)
    return {
                \ 'menu':  '[muttgoobook]',
                \ 'abbr':  a:name,
                \ 'word':  a:address
                \}
endfunction

function! asyncomplete#sources#muttgoobook#completor(opt, ctx) abort
    "echomsg 'Calling completor...'
    let l:matches = {}
    if !s:is_address_field(s:get_section())
        "echomsg 'Not in an address field.  Exiting...'
        call asyncomplete#complete(a:opt['name'], a:ctx, l:startcol, l:matches, 1)
        return
    endif

    "echomsg "a:ctx['col'] = " . a:ctx['col']
    "echomsg "a:ctx['typed'] = " . a:ctx['typed']

    let l:col       = a:ctx['col']
    let l:typed     = a:ctx['typed']

    "echomsg "Getting keyword..."
    let l:kw        = substitute(l:typed, '\c' . s:get_fields() . '\(.*\)$', '\2', '')
    let l:kwlen     = len(l:kw)
    let l:startcol  = l:col - l:kwlen

    "echomsg "l:startcol:  " . l:startcol
    "echomsg "keyword:  " . l:kw . ", len(l:kw) " . l:kwlen

    if l:kwlen < 3
        "echomsg "a:opt['name']:  " . a:opt['name']
        "echomsg "a:ctx:  " . a:ctx
        "echomsg "l:startcol:  " . l:startcol
        "echomsg "l:matches:  " . l:matches
        call asyncomplete#complete(a:opt['name'], a:ctx, l:startcol, l:matches, 1)
        return
    endif

    "echomsg "Generating address dictionary..."
    let l:address_dict  = extend(s:search_mutt_aliases(l:kw), s:query_goobook(l:kw))

    "for [k, v] in items(l:address_dict)
    "    "echomsg "Key:  " . k
    "    "echomsg "Value:  " . v
    "endfor

    "echomsg "Getting matches..."
    let l:matches = values(map(l:address_dict, {key, val -> s:address_map(key, val)}))
    "echomsg l:matches

    "let i = 0
    "for k in keys(l:matches)
    "    let l:matches[i] = l:matches[k]
    "    call remove(l:matches, k)
    "    let i+=1
    "endfor

    call asyncomplete#complete(a:opt['name'], a:ctx, l:startcol, l:matches)
endfunction