template-bash-command/cmd

#!/bin/bash
# shellcheck disable=SC2016
set -e
# export PATH="/bin:/usr/bin:/usr/local/bin" # safer, if you can

(( BASH_VERSINFO[0] < 4 )) && echo "Bash 4+ required." && exit 1

: "${PAGER:=more}"
: "${EDITOR:=vi}"
: "${HELP_BROWSER:=}"
: "${EXE:="${0##*/}"}"

declare -A HELP
declare -A CONFIG

_initialize() {
  : # put initialization code here
}

HELP[main]='
# Bash Template Command

*This `README.md` is autogenerated.*

This is a GitHub template repo that will be copied instead of forked to
create a new Bash command with a command something like this:

```
gh repo create rwxrob/mycmd -p rwxrob/template-bash-command
```

This `cmd` inside can then be renamed and finished.

## Naming Conventions

* Name repos containing single bash commands with `cmd-`
* Name template repos beginning with `template-`
* Start command functions with `x_` to be completed
* Start command functions with `x__` to not be completed

Think of the `x` as in "executable" command.

If you want to keep a command but hide it from users just add another
underscore to the prefix which turns it into a hidden command, which
will not be included in help documentation and tab completion, but will
still be there. 

## Builtins and Utilities

A number of builtin and frequently used utility functions have been
included for convenience. These save developers from adding other
moronic things like `sed` and `awk` subprocesses. Obviously, not all of
this is needed for many Bash scripts. Just remove what you do not need
or want. 

### `_initialize`

The `_initialize` function is meant to contain initialization code and
be placed at the beginning of the script to be found easily even though
it is called at the bottom of the script (as bash requires).

### `_have`

Returns true (0) if the first argument exists as an executable in the
current `PATH`. Otherwise, return false (1).

### `_checkdep`

Checks that the first argument exists as an executable in the current
`PATH`. If so, returns true (0). If not, prints a generic error message
in English and returns false (1).  The "progressive enhancement" design
principle requires minimal functionality using what is available and
progressively upgrading based on what is detected.

### `_newest`

Uses `ls` to return the newest file or directory in the specified
directory.

### `_trim`

Removes all whitespace (`[:space:]`) from the beginning and ending
of a string without invoking a subprocess.

### `_filter`

Reads the first argument or each line of standard input passing
each individually as the first argument to the calling function one at
a time. The UNIX philosophy requires all commands be filters whenever possible.

### `_buffer`

Reads the first argument or all lines of standard input and then
passes them to the calling function as the first argument. The UNIX philosophy requires all command be filters whenever possible.

### `_reduce`

Takes the name of an array and a bash extended regular expression
and prints only the array entries that match, one to a line suitable for
converting back into an array with `IFS=$'"'\\\n'"'` or just as an in-memory
`grep` replacement.

### `_jsonstr`

Encodes first argument or all standard input into a single line of JSON text. This function depends on the `jq` command.

### `_urlencode`

Encodes the first argument or all standard input using standard URL
encoding suitable for passing to `curl` or whatever. This function has
no external dependencies.

## Dependencies

Required:

* Bash 4+

Optional:

* `pandoc` - for rich help docs
* `jq` - for `json` and anything that uses it

## Justification

Bash is the dominant shell scripting language and the official default
Linux interactive shell, which reduces cognitive overhead; every command
line *is* a line of code that could be put into script as is. Bash
scripts are at the core of cloud, containers, and Kubernetes. Bash 4+
with its associative array support, powerful regular expressions, and
multiple ways of feeding data to loops easily covers the needs
previously requiring Python and Perl scripts. Bash scripts are also much
more powerful, safer, flexible, and performant than POSIX shell or Zsh.

## Guidelines

* Write GitHub Flavored Markdown only
* Use present tense ("outputs" over "will output")
* Prefer term "output" and "display" over ~~print~~
* Follow the [naming conventions](#naming-conventions) 
* Use the official bash path: `#!/bin/bash`
* Use of `#!/usr/bin/bash` is outdated
* Using `#!/usr/bin/env bash` introduces unnecessary risk
* Explicitly export `PATH` in script when possible
* Always check script with [`shellcheck`] before releasing
* Always use `bc` for *any* floating point math

[`shellcheck`]: <https://www.shellcheck.net>

## Legal

Copyright 2021 Rob Muhlestein <rob@rwx.gg>  
Released under Apache-2.0 License  
Please mention rwxrob.tv'

HELP[foo]='Foos things.'

x_foo() {
  _filter "$@" && return $?
  echo "would foo: $*"
}

HELP[bar]='

```
'"$EXE"' bar
```

Bar the things.'

x_foo() {
  _buffer "$@" && return $?
  echo "would bar: $*"
}

HELP[some.config.setting]='Get and set `some.config.setting`.'

x_some.config.setting() {
  x_config some.config.setting "$@"
}

x__hidden() {
  _filter "$@" && return $?
  echo "would run _hidden: $*"
}

############################## BOILERPLATE ###########################
## Everything from here to the end of file can be snipped and updated
## with latest from https://github.com/rwxrob/template-bash-command.

# -------------------------- utility command -------------------------

HELP[usage]='Displays a summary of usage.'

x_usage() {
  local -a cmds
  for c in "${COMMANDS[@]}"; do
    [[ ${c:0:1} =~ _ ]] && continue
    cmds+=("$c")
  done
  local IFS='|'
  printf "usage: %s (%s)\n" "$EXE" "${cmds[*]}"
}

# --------------------------- help command ---------------------------

HELP[help]='

```
'"$EXE"' help [COMMAND]
```

Displays specific help information. If no argument is passed displays
general help information (main). Otherwise, the documentation for the
specific argument keyword is displayed, which usually corresponds to
a COMMAND name (but not necessarily). All documentation is written in
GitHub Flavored Markdown and will displayed as a web page if `pandoc`
and `$HELP_BROWSER` are detected, otherwise, just the Markdown is sent
to `$PAGER` (default: more).

Also see `readme` and `usage` commands.
'

x_help() { 
  local name="${1:-main}" title body
  title=$(_help_title "$name") || true
  if [[ -z "$title" ]]; then
    body="${HELP[$name]}"
    title="$EXE $name"
    [[ $name = main ]] && title="$EXE"
  else
    body="${HELP[$name]}"
    body=${body#*$title}
  fi
  local file="/tmp/help-$EXE-$name.html"
  if _have pandoc ; then
    if _have "$HELP_BROWSER" && [[ -t 1 ]] ;then
      pandoc -f gfm -s --metadata title="$title" \
        -o "$file" <<< "$body"
      [[ -z "$2" ]] && cd /tmp && exec "$HELP_BROWSER" "$file"
      return 0
    fi
    pandoc -f gfm -s --metadata title="$title" \
      -t plain <<< "$body" | "$PAGER"
    return 0
  fi
  echo -e "$title\n\n$body" | "$PAGER"
}

_help_title() {
  _filter "$@" && return $?;
  local name="$1"
  while IFS= read -r line; do
    [[ $line =~ ^[:space]*$ ]] && continue
    [[ $line =~ ^#\ (.+) ]] && echo "${BASH_REMATCH[1]}" && return 0
    return 1
  done <<< "${HELP[$name]}"
}

# -------------------------- readme command --------------------------

HELP[readme]='
## Generate `README.md` File

```
'"$EXE"' readme > README.md
```

The `readme` command will output the embedded help documentation in raw
GitHub Flavored Markdown suitable for use as a `README.md` file on
GitHub or similar hosting service.'

x_readme() {
  _trim "${HELP[main]}"
  echo
  while IFS= read -r name; do
    [[ $name = main ]] && continue
    body=$(_trim "${HELP[$name]}")
    [[ $body =~ ^\# ]] || body="## The \`$name\` Command"$'\n\n'$body
    printf "%s\n\n" "$body"
  done < <(printf "%s\n" "${!HELP[@]}" | LC_COLLATE=C sort)
  echo -e "----\n\n*Autogenerated $(date)*\n"
}

# x_json() { _jsonstr "$@"; }
# x_urlencode() { _urlencode "$@"; }

# -------------------------- config command --------------------------

HELP[config]='

```
'"$EXE"' config
'"$EXE"' config KEY
'"$EXE"' config KEY VALUE
'"$EXE"' config KEY ""
'"$EXE"' config keys
'"$EXE"' config val[ues]
'"$EXE"' config dir[ectory]
'"$EXE"' config path [file]
'"$EXE"' config edit [file]
'"$EXE"' config del[ete]
```

The `config` command is for reading, writing, and displaying standard
open desktop configuration properties. Pass an empty string to delete
a property.

### Arguments

With no arguments outputs all the currently cached configuration
settings.

With a single KEY argument fetches the value for that key and outputs
it unless it is one of the following special (reserved) key names:

* `dir*` full path to config directory
* `path` full path to specific config file (default: `values`) 
* `edit` opens config file in editor (default: `editor` or `$EDITOR)
* `keys` output the configuration keys, one per line
* `val*` output the configuration values, one per line
* `del*` if key argument then delete a specific key, otherwise prompt

With more than one argument the remaining arguments after the KEY will
be combined into the VALUE and written to a `values` file in the
configuration directory. 

### Configuration Directory

The configuration directory path relies on the following environment
variables:

* `EXE` - defaults to name of currently running command ('"$EXE"')
* `HOME` - checked for `$HOME/.config/$EXE/values`
* `XDG_CONFIG_HOME` - overrides `$HOME/.config`
* `CONFIG_DIR` - full path to directory containing `values` file

The `CONFIG_DIR` always takes priority over anything else if set, but is
never implied. If the directory does not exist it will be created the
first time a value is set.

### Configuration `values` File Format

The file (which is almost always located at
`~/.config/'"$EXE"'/values`) uses the simplest possible format to
facilitate standard UNIX parsing and filtering with any number of
existing tools (and no `jq` dependency).

* One KEY=VALUE per line
* KEYs may be anything but the equal sign (`=`)
* VALUEs may be anything but line returns must be escaped

Note that this is *not* the same as Java properties and other similar
format. It is designed for ultimate simplicity, efficiency, and
portability.'

x_config() {
  case $1 in 
    dir*) shift; _config_dir  "$@"; return $? ;;
    path) shift; _config_path "$@"; return $? ;;
    edit) shift; _config_edit "$@"; return $? ;;
    del*) shift; _config_del  "$@"; return $? ;;
    keys) shift; _config_keys "$@"; return $? ;;
    val*) shift; _config_vals "$@"; return $? ;;
  esac
  case $# in
    0) _config_dump ;; 
    1) _config_get "$@" ;;
    *) _config_set "$@" ;;
  esac
}

_config_edit() {
  : "${CONFIG[editor]:="${EDITOR:=vi}"}"
  exec "${CONFIG[editor]}" "$(_config_path "${1:-values}")"
}

_config_del() {
  if [[ -z "$1" ]];then
    select key in "${!CONFIG[@]}"; do
      _config_del "$key"
      return $? 
    done
  fi
  _config_set "$1" ''
}

_config_keys() { printf "%s\n" "${!CONFIG[@]}"; }

_config_vals() { printf "%s\n" "${CONFIG[@]}"; }

_config_dir() {
  local dir="$HOME/.config/$EXE"
  [[ -n "$XDG_CONFIG_HOME" ]] && dir="$XDG_CONFIG_HOME/$EXE" 
  [[ -n "$CONFIG_DIR" ]] && dir="$CONFIG_DIR"
  [[ -n "$1" ]] && echo "$dir/$1" && return 0
  printf "%s" "$dir"
  [[ -t 1 ]] && echo
}

_config_path() { 
  local file=${1:-values}
  printf "%s/%s" "$(_config_dir)" "$file"
  [[ -t 1 ]] && echo
}

_config_set() {
  local key="$1"; shift; local val="$*"
  val="${val//$'\n'/\\n}"
  CONFIG["$key"]="$val"
  _config_write
}

_config_get() { 
  printf "${CONFIG[$1]}"
  [[ -t 1 ]] && echo
}

_config_read() {
  local values="$(_config_path)"
  [[ -r "$values" ]] || return 0
  while IFS= read -r line; do
    [[ $line =~ ^([^=]+)=(.+)$ ]] || continue
    CONFIG["${BASH_REMATCH[1]}"]="${BASH_REMATCH[2]}"
  done < "$values"
}

_config_write() {
  local dir="$(_config_dir)"
  mkdir -p "$dir"
  _config_dump > "$dir/values"
}

_config_dump() {
  (( ${#CONFIG[@]} == 0 )) && return 0
  paste -d=\
    <(printf "%s\n" "${!CONFIG[@]}") \
    <(printf "%s\n" "${CONFIG[@]}")
}

# ----------------------------- utilities ----------------------------

_jsonstr() {
  _checkdep jq
  _buffer "$@" && return $?
  jq -MRsc <<< "$1"
}

_urlencode() {
  _buffer "$@" && return $?
  local string="$1"
  local strlen=${#string}
  local encoded=""
  local pos c o
  for ((pos = 0; pos < strlen; pos++)); do
    c=${string:$pos:1}
    case "$c" in
    [-_.~a-zA-Z0-9]) o="$c" ;;
    *) printf -v o '%%%02x' "'$c'" ;;
    esac
    encoded+="$o"
  done
  echo "$encoded"
}

_reduce() {
  local -n name="${1:?"name of array required"}"
  while IFS= read -r key; do
    [[ $key =~ $2 ]] && echo "$key"
  done < <(printf "%s\n" "${name[@]}")
}

_newest() {
  IFS=$'\n'
  local -a f=($(ls -1 --color=never -trd ${1:-.}/* 2>/dev/null))
  [[ ${#f} > 0 ]] && echo "${f[-1]}"
}

_trim() {
  local it="${1#"${1%%[![:space:]]*}"}"
  echo -e "${it%"${it##*[![:space:]]}"}"
}

_have(){ type "$1" &>/dev/null; }

_checkdep() {
  _have "$1" && return 0
  echo "'$EXE' depends on '$1' for this, but not found"
  return 1
}

_filter(){
  [[ -n "$1" ]] && return 1
  while IFS= read -ra args; do
    "${FUNCNAME[1]}" "${args[@]}"
  done
}

_buffer() {
  [[ -n "$1" ]] && return 1
  "${FUNCNAME[1]}" "$(</dev/stdin)"
}

# --------------------- completion and delegation --------------------
#      `complete -C foo foo` > `source <(foo bloated_completion)`

while IFS= read -r line; do
  [[ $line =~ ^declare\ -f\ x_ ]] || continue
  COMMANDS+=( "${line##declare -f x_}" )
done < <(declare -F)
mapfile -t COMMANDS < \
  <(LC_COLLATE=C sort < <(printf "%s\n" "${COMMANDS[@]}"))

if [[ -n $COMP_LINE ]]; then
  line=${COMP_LINE#* }
  for c in "${COMMANDS[@]}"; do
    [[ ${c:0:${#line}} == "${line,,}" && ${c:0:1} != _ ]] && echo "$c"
  done
  exit
fi

_config_read
_initialize

for c in "${COMMANDS[@]}"; do
  if [[ $c == "$EXE" ]]; then
    "x_$EXE" "$@"
    exit $?
  fi
done

if [[ -n "$1" ]]; then
  declare cmd="$1"; shift
  for c in "${COMMANDS[@]}"; do
    if [[ $c == "$cmd" ]]; then
      "x_$cmd" "$@"
      exit $?
    fi
  done
fi

x_usage "$@"