sd.bash-completion

#!/bin/bash
#
# sd Bash Completion
# =======================
#
# The script is inspired by the BZR/Bazaar bash completion script
# available at https://launchpad.net/bzr-bash-completion
#
# Installation
# ------------
#
# 1. Place it in a `bash-completion.d` folder:
#
#   * /etc/bash-completion.d
#   * /usr/local/etc/bash-completion.d
#   * ~/bash-completion.d
#
# 2. Open new bash, and type `sd [TAB][TAB]`
#
# Documentation
# -------------
# The script is called by bash whenever [TAB] or [TAB][TAB] is pressed after
# 'sd (..)'. By reading entered command line parameters, it determines possible
# bash completions and writes them to the COMPREPLY variable. Bash then
# completes the user input if only one entry is listed in the variable or
# shows the options if more than one is listed in COMPREPLY.
#
# The script first determines the current parameter ($cur), the first word ($firstword).
# Using the $firstword variable (= the command) and a giant switch/case,
# completions are written to $complete_words and $complete_options.
#
# If the current user input ($cur) starts with '-', only $command_options are
# displayed/completed, otherwise only $command_words.
#
# References
# ----------
# [1] http://stackoverflow.com/a/12495480/1440785
# [2] http://tiswww.case.edu/php/chet/bash/FAQ
#

shopt -s progcomp

_sd() {

  local cur firstword complete_words complete_options

  COMP_WORDBREAKS=${COMP_WORDBREAKS//[:=]}

  cur=${COMP_WORDS[COMP_CWORD]}
  firstword=$(_sd_get_firstword)

  GLOBAL_COMMANDS="\
    save\
    delete\
    get\
    export\
    list\
    help"

  GLOBAL_OPTIONS="\
    -h --help"

  LIST_OPTIONS="\
    -l"

  GET_OPTIONS="\
    -key\
    -val"

  DELETE_OPTIONS="\
    -key"

  SAVE_OPTIONS="\
    -key\
    -val"

  EXPORT_OPTIONS="\
    -id\
    -ssh\
    -ip\
    -user\
    -to-alias"

  case "${firstword}" in
  save)
    complete_options="$SAVE_OPTIONS"
    ;;
  delete)
    complete_words=$( sd get -key )
    complete_options="$DELETE_OPTIONS"
    ;;
  export)
    complete_options="$EXPORT_OPTIONS"
    ;;
  get)
    complete_options="$GET_OPTIONS"
    ;;
  list)
    complete_options="$LIST_OPTIONS"
    ;;
  *)
    complete_words="$GLOBAL_COMMANDS "
    complete_words+=$( sd get -key )
    complete_options="$GLOBAL_OPTIONS"
    ;;
  esac

  # Either display words or options, depending on the user input
  if [[ $cur == -* ]]; then
    COMPREPLY=( $( compgen -W "$complete_options" -- $cur ))
  else
    COMPREPLY=( $( compgen -W "$complete_words" -- $cur ))
  fi

  return 0
}


# Determines the first non-option word of the command line. This is usually the command
_sd_get_firstword() {
  local firstword i

  firstword=
  for ((i = 1; i < ${#COMP_WORDS[@]}; ++i)); do
    if [[ ${COMP_WORDS[i]} != -* ]]; then
      firstword=${COMP_WORDS[i]}
      break
    fi
  done

  echo $firstword
}

## Define bash completions ###

complete -F _sd sd