#!/usr/bin/env bash
set -e
[ -n "$RBENV_DEBUG" ] && set -x

# content from single commented line marked with a word such as "Usage" or "Summary"
extract_line() {
  grep "^# ${1}:" "$2" | head -1 | cut -d ' ' -f3-
}

# content of multiple consecutive commented lines starting with a word such as "Help"
extract_section() {
  sed -En "/^# ${1}: /,/^[^#]/s/^# ?//p" "$2" | sed "1s/${1}: //"
}

# print aligned command names with help summary
print_summary() {
  if [ ! -h "$1" ]; then
    local summary=$(extract_line Summary "$1")
    if [ -n "$summary" ]; then
      local name=$(basename "$1")
      echo "${name#rbenv-}" | awk '{ printf "   %-14s   ", $1 }'
      echo -n $summary
      echo
    else
      return 1
    fi
  fi
}

print_help() {
  local usage="$(extract_line Usage "$1")"
  local halp="$(extract_section Help "$1")"
  [ -z "$halp" ] && halp="$(extract_line Summary "$1")"

  if [ -n "$usage" ]; then
    echo usage: $usage
    [ -n "$halp" ] && echo && echo "$halp"
  else
    echo "Sorry, this command isn't documented yet." >&2
    return 1
  fi
}

print_summaries() {
  for command in $1; do
    print_summary "$(command -v rbenv-"$command")"
  done
}

print_set_version() {
  echo "<version> should be a string matching a Ruby version known by rbenv."

  local versions="$(rbenv-versions --bare)"
  if [ -z "$versions" ]; then
    echo "There are currently no Ruby versions installed for rbenv."
  else
    echo "The currently installed Ruby versions are:"
    echo "$versions" | sed 's/^/  /'
  fi

  echo
  echo "The special version string 'system' will use your default system Ruby."
}

case "$1" in
"") echo "usage: rbenv <command> [<args>]

Some useful rbenv commands are:
$(print_summaries "commands rehash global local shell version versions which whence")

See 'rbenv help <command>' for information on a specific command.
For full documentation, see: https://github.com/sstephenson/rbenv#readme"
;;
global) echo "usage: rbenv global <version>

Sets the global Ruby version. You can override the global version at
any time by setting a directory-specific version with \`rbenv local'
or by setting the RBENV_VERSION environment variable.

$(print_set_version)"
;;
local) echo "usage: rbenv local <version>
       rbenv local --unset

Sets the local directory-specific Ruby version by writing the version
name to a file named '.rbenv-version'.

When you run a Ruby command, rbenv will look for an '.rbenv-version'
file in the current directory and each parent directory. If no such
file is found in the tree, rbenv will use the global Ruby version
specified with \`rbenv global', or the version specified in the
RBENV_VERSION environment variable.

$(print_set_version)"
;;
shell) echo "usage: rbenv shell <version>
       rbenv shell --unset

Sets a shell-specific Ruby version by setting the 'RBENV_VERSION'
environment variable in your shell. This version overrides both
project-specific versions and the global version.

$(print_set_version)"
;;
*)
  command_path="$(command -v "rbenv-$1" || true)"
  if [ -n "$command_path" ]; then
    print_help "$command_path"
  else
    echo "rbenv: no such command \`$1'" >&2
    exit 1
  fi
esac