.bash_completion

#!/bin/bash

# USAGE: _alias_complete_reuse REF CMD
# use the same completion function as REF for CMD
_alias_complete_reuse() {
  (($# == 2)) || return
  complete -p "$1" &>/dev/null || __load_completion "$1"
  $(complete -p "$1" 2>/dev/null || echo false) "$2"
}

# USAGE: _alias_complete_decompose STRING ARRAY
# decompose STRING into ARRAY of single character or quoted string
_alias_complete_decompose() {
  local c q=
  local -i i
  local -a chars
  for ((i=0; i<${#1}; i++)); do
    c=${1:i:1}
    if [[ $c == [\\] ]]; then
      c=${1:i:2}
      let i++ && :
    fi
    if [[ $q ]]; then
      [[ $c == $q ]] && q=
      chars[-1]+=$c
    else
      [[ $c == [\"\'] ]] && q=$c
      chars+=("$c")
    fi
  done
  local "$2" && _upvars -a${#chars[@]} "$2" "${chars[@]}"
}
# USAGE: _alias_complete_split STRING ARRAY
# split STRING into ARRAY in the same way as COMP_LINE into COMP_WORDS
_alias_complete_split() {
  local w prev= next
  local -a chars words=()
  _alias_complete_decompose "$1" chars
  for w in "${chars[@]}"; do
    case $w in
      ["$IFS"]) prev=; continue;;
      [\"\']) next=normal;;
      [';|&(']) prev=; words=(); continue;;
      ["$COMP_WORDBREAKS"]) next=break;;
      *) next=normal;;
    esac
    [[ $prev == $next ]] || words+=('')
    words[-1]+=$w
    prev=$next
  done
  local "$2" && _upvars -a${#words[@]} "$2" "${words[@]}"
}
# USAGE: _alias_complete_expand
# expand alias and reset COMP_{POINT,CWORD,LINE,WORDS} variables
_alias_complete_expand() {
  local cmd=${COMP_WORDS[0]} alias line
  local -a words args
  local -i point cword
  [[ -v BASH_ALIASES[$cmd] ]] || return 0
  alias=${BASH_ALIASES[$cmd]}
  _alias_complete_split "$alias" words
  let point=$COMP_POINT+${#alias}-${#cmd} && :
  let cword=$COMP_CWORD+${#words[@]}-1 && :
  line=${COMP_LINE/#$cmd/$alias}
  words+=("${COMP_WORDS[@]:1}")
  args+=(-v COMP_POINT $point)
  args+=(-v COMP_CWORD $cword)
  args+=(-v COMP_LINE "$line")
  args+=(-a${#words[@]} COMP_WORDS "${words[@]}")
  local COMP_{POINT,CWORD,LINE,WORDS} && _upvars "${args[@]}"
}
# USAGE: _alias_complete_emulate CMD
# invoke completion function for CMD
_alias_complete_emulate() {
  local cmd=$1 comp func comm
  local -a reply compopt=(compopt) generate=(compgen) filter=(compgen)
  if ! comp=$(complete -p "$cmd" 2>/dev/null); then
    cmd=${cmd%%*/}
    comp=$(complete -p "$cmd" 2>/dev/null) || return
  fi
  set -- $comp
  [[ ${1-} == complete && ${@: -1} == $cmd ]] || return
  shift
  while (($# > 1)); do
    case $1 in
      -[abcdefgjksuv]) generate+=($1); shift 1;;
      -o) compopt+=($1 "$2"); shift 2;;
      -[AGW]) generate+=($1 "$2"); shift 2;;
      -F) func=$2; shift 2;;
      -C) comm=$(eval echo "$2"); shift 2;;
      -[XPS]) filter+=($1 "$2"); shift 2;;
      *) echo "ERROR: invalid complete: $comp" >&2; return 1;;
    esac
  done
  local cur prev words cword
  _init_completion || return
  readarray -t reply < <("${generate[@]}" -- "$cur")
  set -- "$cmd" "$cur" "$prev"
  COMPREPLY=()
  [[ -v func ]] && "$func" "$@"
  reply+=("${COMPREPLY[@]}")
  [[ -v comm ]] && readarray -O ${#reply[@]} -t reply < <("$comm" "$@")
  readarray -t COMPREPLY < <(IFS=$'\n'; "${filter[@]}" -W "${reply[*]}")
  ((${#compopt[@]} > 1)) && "${compopt[@]}"
  return 0
}
# USAGE: complete -F _alias_complete -- CMD
# perform completion after expanding alias
_alias_complete() {
  local cmd comp
  _alias_complete_expand
  cmd=${COMP_WORDS[0]}
  comp=$(complete -p "$cmd" 2>/dev/null) || _alias_complete_loader "$cmd"
  [[ $comp == *' -F _alias_complete '* ]] && complete -F _minimal -- "$cmd"
  _alias_complete_emulate "$cmd"
}
# USAGE: complete -D -F _alias_complete_loader
# completion loader for _alias_complete
_alias_complete_loader() {
  local cmd=${1:-_EmptycmD_}
  __load_completion "$cmd" && return 124
  complete -F _alias_complete -- "$cmd" && return 124
} && complete -D -F _alias_complete_loader