# Autoload this function, run `zle -N <func-name>' and bind <func-name>
# to a key.


# This allows incremental completion of a word.  After starting this
# command, a list of completion choices can be shown after every character
# you type, which you can delete with ^h or DEL.  RET will accept the
# completion so far.  You can hit TAB to do normal completion, ^g to
# abort back to the state when you started, and ^d to list the matches.
#
# This works best with the new function based completion system.
#
# Configuration keys:
#
#  incremental_prompt
#    Prompt to show in status line during icompletion. The sequence `%u'
#    is replaced by the unambiguous part of all matches if there is any
#    and it is different from the word on the line. A `%s' is replaced
#    with `-no match-', `-no prefix-', or an empty string if there is
#    no completion matching the word on the line, if the matches have 
#    no common prefix different from the word on the line or if there is
#    such a common prefix, respectively. The sequence `%c' is replaced
#    by the name of the completer function that generated the matches
#    (without the leading underscore). Finally, `%n' is replaced by the
#    number of matches generated, `%a' is replaced by an empty string
#    if the matches are in the normal set (i.e. the one without file names
#    with one of the suffixes from `fignore') and with ` -alt-' if the
#    matches are in the alternate set, and if the `incremental_list' key
#    (see below) is set, `%l' is replaced by `...' if the list of matches
#    is too long to fit on the screen and with an empty string otherwise.
#
#  incremental_stop
#    Pattern matching keys which will cause icompletion to stop and the
#    key to be re-executed.
#
#  incremental_break
#    Pattern matching keys which will cause icompletion to stop and the
#    key to be discarded.
#
#  incremental_completer
#    Set of completers, like the `completer' key for normal completion.
#
#  incremental_list
#    If set to a non-empty string, the matches will be listed on every
#    key-press.


# The main widget function.

incremental-complete-word() {
  emulate -L zsh
  unsetopt autolist menucomplete automenu # doesn't work well

  local key lbuf="$LBUFFER" rbuf="$RBUFFER" pmpt word
  local lastl lastr wid twid num alt post toolong

  [[ -n "$compconfig[incremental_completer]" ]] &&
      set ${(s.:.)compconfig[incremental_completer]}
  pmpt="${compconfig[incremental_prompt]-incremental (%c): %u%s  %l}"

  if [[ -n "$compconfig[incremental_list]" ]]; then
    wid=list-choices
    post=( icw-list-helper )
  else
    wid=complete-word
    post=()
  fi

  comppostfuncs=( "$post[@]" )
  zle $wid "$@"
  LBUFFER="$lbuf"
  RBUFFER="$rbuf"
  num=$_lastcomp[nmatches]
  if (( ! num )); then
    num="${_lastcomp[alternate_nmatches]}"
    alt=' -alt-'
  fi
  if (( ! num )); then
    word=''
    state='-no match-'
  elif [[ "${LBUFFER}${RBUFFER}" = *${_lastcomp[unambiguous]}* ]]; then
    word=''
    state='-no prefix-'
  else
    word="${_lastcomp[unambiguous]}"
    state=''
  fi
  zle -R "${${${${${${pmpt//\\%u/$word}//\\%s/$state}//\\%c/${_lastcomp[completer][2,-1]}}//\\%n/$num}//\\%a/$alt}//\\%l/$toolong}"
  read -k key

  while [[ '#key' -ne '#\\r' && '#key' -ne '#\\n' &&
           '#key' -ne '#\\C-g' ]]; do
    twid=$wid
    if [[ "$key" = ${~compconfig[incremental_stop]} ]]; then
      zle -U "$key"
      return
    elif [[ "$key" = ${~compconfig[incremental_break]} ]]; then
      return
    elif [[ '#key' -eq '#\\C-h' || '#key' -eq '#\\C-?' ]]; then
      [[ $#LBUFFER -gt $#l ]] && LBUFFER="$LBUFFER[1,-2]"
    elif [[ '#key' -eq '#\\t' ]]; then
      zle complete-word "$@"
      lbuf="$LBUFFER"
      rbuf="$RBUFFER"
    elif [[ '#key' -eq '#\\C-d' ]]; then
      twid=list-choices
    else
      LBUFFER="$LBUFFER$key"
    fi
    lastl="$LBUFFER"
    lastr="$RBUFFER"
    [[ "$twid" = "$wid" ]] && comppostfuncs=( "$post[@]" )
    toolong=''
    zle $twid "$@"
    LBUFFER="$lastl"
    RBUFFER="$lastr"
    num=$_lastcomp[nmatches]
    if (( ! num )); then
      num="${_lastcomp[alternate_nmatches]}"
      alt=' -alt-'
    else
      alt=''
    fi
    if (( ! num )); then
      word=''
      state='-no match-'
    elif [[ "${LBUFFER}${RBUFFER}" = *${_lastcomp[unambiguous]}* ]]; then
      word=''
      state='-no prefix-'
    else
      word="${_lastcomp[unambiguous]}"
      state=''
    fi
    zle -R "${${${${${${pmpt//\\%u/$word}//\\%s/$state}//\\%c/${_lastcomp[completer][2,-1]}}//\\%n/$num}//\\%a/$alt}//\\%l/$toolong}"
    read -k key
  done

  if [[ '#key' -eq '#\\C-g' ]]; then
    LBUFFER="$lbuf"
    RBUFFER="$rbuf"
  fi
  zle -Rc
}

# Helper function used as a completion post-function used to make sure that
# the list of matches in only shown if it fits on the screen.

icw-list-helper() {

  # +1 for the status line we will add...

  if [[ compstate[list_lines]+BUFFERLINES+1 -gt LINES ]]; then
    compstate[list]='list explanations'
    if [[ compstate[list_lines]+BUFFERLINES+1 -gt LINES ]]; then
      compstate[list]=''
      compstate[force_list]=yes
    fi
    toolong='...'
  fi
}

incremental-complete-word "$@"