db

#!/usr/bin/env bash

usage()
{
  printf "

  Usage:

    db database_file {{key}} {{value}} # set
    db database_file {{key}}           # get
    db database_file {{key}} unset     # unset

" >&2
}

if [[ -f "$1" ]] ; then

  database_file="$1" ; shift

  if [[ ! -f "$database_file" ]] ; then

    directory=$(dirname "$database_file")

    if [[ ! -d "$directory" ]] ; then
      mkdir -p "$directory"
    fi

    touch "$database_file"

  fi

else

  printf "\n\nDatabase file $1 does not exist.\n\n" >&2

  exit 1

fi

key="$1" ; shift

if [[ -z "$key" ]] ; then

  usage

  exit 1

else

  if [[ ${escape_flag:-0} -eq 1 ]]; then
    escaped_key="$(\printf "$key" | \sed -e 's#\\#\\#g' -e 's#/#\\/#g' -e 's#\.#\.#g')"
  else
    escaped_key="$key"
  fi

  value="$*"

  if [[ "unset" = "$value" || "delete" = "$value" ]] ; then

    \sed -e "s#^$escaped_key=.*\$##"  -e '/^$/d' "$database_file" \
      > "$database_file.new"

    mv "$database_file.new" "$database_file"

  else

    if [[ -z "$value" ]] ; then # get

      \awk -F= '/^'"$escaped_key"'=/' "$database_file" \
        | \sed -e "s#^$escaped_key=##" -e '/^$/d'

    else # set

      \sed -e "s#^$escaped_key=.*\$##" -e '/^$/d' "$database_file" > "$database_file.new"

      mv "$database_file.new" "$database_file"

      if [[ -z "$(awk -F= "/^'"$escaped_key"'=/{print $2}" "$database_file")" ]] ; then # append

        echo "$escaped_key=$value" >> "$database_file"

      else # overwrite

        \sed -i.tmp "s#^$escaped_key=.*\$#$escaped_key=$value#" "$database_file" > "$database_file.new"

        mv "$database_file.new" "$database_file"

      fi

    fi

  fi

fi