zsh/Functions/MIME/zsh-mime-handler

# Handler for MIME types using associative arrays
# zsh_mime_handlers and zsh_mime_flags set up by zsh-mime-setup.
#
# The only flags it handles are copiousoutput and needsterminal.
# copiousoutput is assumed to imply needsterminal.  Apart from
# those, it tries to be a bit cunning about quoting, which
# can be a nightmare in MIME handling.  If it sees something like
#   netscape %s
# and it only has one file to handle (the usual case then it will handle it
# internally just by appending a file.)
# 
# Anything else is handled by passing to sh -c, which is the only think
# with a high probability of working.  If it sees something with
# quotes, e.g.
#   /usr/bin/links "%s"
# it will assume someone else has tried to fix the quoting problem and not
# do that.  If it sees something with no quotes but other metacharacters,
# e.g.
#   cat %s | handler
# then it will do any quoting and pass the result to sh -c.
# So for example if the argument is "My File", the command executed
# is supposedly
#   sh -c 'cat My\ File | handler'
#
# This note is mostly here so you can work out what I tried to do when
# it goes horribly wrong.

emulate -L zsh
setopt extendedglob cbases

# We need zformat from zsh/zutil for %s replacement.
zmodload -i zsh/zutil

# Always called with a filename argument first.
# There might be other arguments; don't really know what to do
# with these, but if they came from e.g. `*.ps' then we might
# just as well pass them all down.  However, we just take the
# suffix from the first since that's what invoked us via suffix -s.

local suffix context
local -a match mbegin mend

[[ $1 = (#b)*.([^.]##) ]] || return 1
suffix=$match[1]
context=":mime:.${suffix}:"

local handler flags

zstyle -s $context handler handler ||
  handler="${zsh_mime_handlers[$suffix]}"
zstyle -s $context flags flags ||
  flags="${zsh_mime_flags[$suffix]}"

local -a files
local hasmeta stdin

# See if the handler has shell metacharacters in.
# Don't count whitespace since we can split that when it's unquoted.
if [[ $handler = *[\\\;\*\?\|\"\'\`\$]* ]]; then
    hasmeta=1
fi

local -a execargs

if [[ $handler = *%s* ]]; then
  # We need to replace %s with the file(s).
  local command
  if [[ -n $hasmeta || $# -gt 1 ]]; then
    # The handler is complicated, either due to special
    # characters or multiple files.  We are going to pass it
    # down to sh, since it's probably written for sh syntax.
    #
    # See if it's a good idea to quote the filename(s).
    # It isn't if there are already quotes in the handler, since
    # that means somebody already tried to take account of that.
    if [[ $handler = *[\'\"]* ]]; then
      # Probably we ought not even to handle multiple
      # arguments, but at least the error message ought
      # to make it obvious what's going on.
      zformat -f command $handler s:"$argv"
    else
      files=(${(q)argv})
      zformat -f command $handler s:"$files"
    fi
    execargs=(sh -c $command)
  else
    # Simple command, one filename.
    # Split and add the file without extra quoting,
    # since later we will just execute the array as is.
    for command in ${=handler}; do
	zformat -f command $command s:"$1"
	execargs+=($command)
    done
  fi
else
  # If there's no %s, the input is supposed to come from stdin.
  stdin=1
  if [[ -n $hasmeta ]]; then
    execargs=(sh -c "$handler")
  else
    execargs=(${=handler})
  fi
fi

# Now execute the command in the appropriate fashion.
if [[ $flags = *copiousoutput* ]]; then
  # We need to page the output.
  # Careful in case PAGER is a set of commands and arguments.
  local -a pager
  zstyle -a $context pager pager || pager=(${=PAGER:-more})
  if [[ -n $stdin ]]; then
    cat $argv | $execargs | $pager
  else
    $execargs | eval ${PAGER:-more}
  fi
elif [[ $flags = *needsterminal* || -z $DISPLAY ]]; then
  # Needs a terminal, so run synchronously.
  # Obviously, if $DISPLAY is empty but the handler needs a
  # GUI we are in trouble anyway.  However, it's possible for
  # the handler to be smart about this, like pick-web-browser,
  # and even if it just produces an error message it's better to
  # have it run synchronously.
  if [[ -n $stdin ]]; then
    cat $argv | $execargs
  else
    $execargs
  fi
else
  # Doesn't need a terminal and we have a $DISPLAY, so run
  # it in the background.  sh probably isn't smart enough to
  # exec the last command in the list, but it's not a big deal.
  #
  # The following Rococo construction is to try to make
  # the job output for the backgrounded command descriptive.
  # Otherwise it's equivalent to removing the eval and all the quotes,
  # including the (q) flags.
  if [[ -n $stdin ]]; then
    eval cat ${(q)argv} "|" ${(q)execargs} "&"
  else
    eval ${(q)execargs} "&"
  fi
fi