plumb

#!/bin/sh

# Documentation ────────────────────────────────────────────────────────────────

if test $# -eq 0; then
  cat <<'EOF' > /dev/stderr
Description
‾‾‾‾‾‾‾‾‾‾‾
Plumber from Plan 9.
Use (wl-clipboard|xclip|pb{copy,paste}) (or $CLIPBOARD_COPY and $CLIPBOARD_PASTE if set) to access the clipboard and jq for JSON.
dmenu (or $DMENU if set) is used for validating execution.

Dependencies
‾‾‾‾‾‾‾‾‾‾‾‾
– Clipboard
  – Wayland: wl-clipboard (https://github.com/bugaevc/wl-clipboard)
  – X11: xclip (https://github.com/astrand/xclip)
– jq (https://stedolan.github.io/jq/)
– dmenu (https://tools.suckless.org/dmenu/)

Usage
‾‾‾‾‾
$ plumb [commands]

Allowed commands are passed through the command-line, and a validation step
(with a dmenu filter program) is required before proceeding.

Primary selection (JSON) format:
❯ [<command>, <arguments>]
❯ ["input", <input>, <command>, <arguments>]

The primary selection is used as input for the command (in a JSON array of strings)
and will be escaped suitable (list of single-quoted strings, separated by spaces)
for use in a command-line for a POSIX shell.  The output of the command will be
copied to the clipboard.

Examples
‾‾‾‾‾‾‾‾
$ plumb mpv pandoc xdg-open

Primary selection contents:
❯ ["mpv", "https://youtu.be/dP1xVpMPn8M"]
❯ ["input", "<p>Tchou</p>", "pandoc", "--from", "html", "--to", "markdown"]

A Tour of the Acme Editor: https://research.swtch.com/acme

Configuration
‾‾‾‾‾‾‾‾‾‾‾‾‾
Change the dmenu command:
$ export DMENU=dmenu

Change the clipboard copy and paste commands:
$ export CLIPBOARD_COPY=wl-copy
$ export CLIPBOARD_PASTE=wl-paste
EOF
  exit 1
fi

# Environment variables ────────────────────────────────────────────────────────

OS=$(uname -s)

# Options ──────────────────────────────────────────────────────────────────────

# Validate input with a dmenu filter program.
if test -z "$DMENU"; then
  DMENU=dmenu
fi

# Copy content to the clipboard.
if test -z "$CLIPBOARD_COPY"; then
  case "$OS" in
    Darwin) CLIPBOARD_COPY='pbcopy' ;;
    Linux|FreeBSD|OpenBSD)
      case "$XDG_SESSION_TYPE" in
        wayland) CLIPBOARD_COPY='wl-copy' ;;
        x11) CLIPBOARD_COPY='xclip -filter -selection clipboard | xclip' ;;
      esac
      ;;
  esac
fi

# Paste content from the clipboard.
if test -z "$CLIPBOARD_PASTE"; then
  case "$OS" in
    Darwin) CLIPBOARD_PASTE='pbpaste' ;;
    Linux|FreeBSD|OpenBSD)
      case "$XDG_SESSION_TYPE" in
        wayland) CLIPBOARD_PASTE='wl-paste' ;;
        x11) CLIPBOARD_PASTE='xclip -out' ;;
      esac
      ;;
  esac
fi

# Main ─────────────────────────────────────────────────────────────────────────

main() {

  # List of allowed commands
  PLUMBERS=$@

  # Get message from the primary selection
  script=$(
    sh -c "$CLIPBOARD_PASTE" |
    jq --raw-output '
      @sh "
        set -- \(.)
      "
    '
  )

  # Abort if invalid JSON
  if test $? != 0; then
    notify-send --urgency critical 'Plumb' 'Invalid JSON'
    exit 1
  fi

  # Get the argument list – now it is safe to proceed.
  eval "$script"
  # Input handler
  if test "$1" = 'input'; then
    exec <<EOF
$2
EOF
    shift 2
  fi

  # Use `xdg_open` wrapper function
  if test "$1" = xdg-open; then
    for plumber in $PLUMBERS; do
      if test "$plumber" = xdg-open; then
        PLUMBERS=xdg_open
        shift
        set -- xdg_open "$@"
        break
      fi
    done
  fi

  plumb "$@"

}

# Functions ────────────────────────────────────────────────────────────────────

plumb() {
  command=$1
  plumbed=no
  # Iterate allowed commands
  for plumber in $PLUMBERS; do
    if test "$plumber" = "$command"; then
      # Validate command:
      if ! validate_command "$@"; then
        exit 1
      fi
      # Execute the command and copy its output to the clipboard
      "$@" | sh -c "$CLIPBOARD_COPY"
      notify-send 'Plumb' "Command finished: $command"
      plumbed=yes
      break
    fi
  done
  # Reject other commands
  if test "$plumbed" = no; then
    notify-send --urgency critical 'Plumb' "Command not allowed: $command"
    exit 1
  fi
}

# Requires validation before proceeding commands.
validate_command() {
  # Display one item per argument.
  # Separator for dmenu: '\0'
  # Newline display: '\t'
  # Note: '␤' could be nice, but `tr` only supports ASCII characters.
  printf '%s\0' "$@" |
  tr '\n\0' '\t\n' |
  sh -c "$DMENU" > /dev/null 2>&1
}

# Wrapper function to open multiple URLs.
xdg_open() {
  for url do
    xdg-open "$url" < /dev/null > /dev/null 2>&1 &
  done
}

main "$@"