#!/hint/bash

if [[ $TERM == eterm* ]]; then
	## Primatives for interacting with Emacs ###############################

	# _emacs_run LISP
	_emacs_run() {
		emacsclient -a false -e "$*" 2>/dev/null
	}
	# _emacs_quote UNQUOTED_STRING
	_emacs_quote() {
		local str="$*"
		str="${str//\\/\\\\}" # \ -> \\
		str="${str//\"/\\\"}" # " -> \"
		str="\"${str}\""      # wrap it in quotes
		printf '%s' "$str"
	}
	# _emacs_unquote QUOTED_STRING
	_emacs_unquote() {
		local str="$*"
		if [[ $str =~ ^\"(.*)\"$ ]]; then
			str=${BASH_REMATCH[1]} # un-quote it
			str="${str//\\\\/\\}" # \\ -> \
			str="${str//\\\"/\"}" # \" -> "
		fi
		printf '%s' "$str"
	}

	## High-level tasks ####################################################

	# Set the TRAMP directory for remote hosts (shell -> emacs)
	_emacs_set_remote_dir() {
		# Because (term-handle-ansi-terminal-messages) is run
		# after each item is set, the user should be set
		# before the hostname is set, otherwise it will set
		# (default-directory) to an invalid TRAMP string.
		#
		# The hostname is compared to (system-name) to check
		# if it is localhost.  In Emacs 25, (system-name) is
		# just gethostname(2), and in Bash 4.2, $HOSTNAME is
		# also just gethostname(2).
		#
		# As an aside, Emacs and Bash deal with hostnames >
		# 255 bytes differently.  They both use 255 bytes for
		# the initial call, but Bash won't retry with a bigger
		# limit, but Emacs will.  I don't care, because
		# besides such long hostnames being uncommon, Linux's
		# HOST_NAME_MAX on i686 and x86_64 is only 64, so it's
		# actually impossible.  IDK about other kernels or
		# architectures.
		printf '\eAnSiT%s %s\n' \
		       u "$USER" \
		       c "$PWD" \
		       h "$HOSTNAME"
	}
	# Set the shell's X11 display (emacs -> shell)
	_emacs_set_shell_DISPLAY() {
		export DISPLAY=$(_emacs_unquote "$(_emacs_run "(cdr (assoc 'display (frame-parameters)))")")
		[[ $DISPLAY != nil ]] || unset DISPLAY
	}

	## Install the hooks ###################################################

	export SELECTED_EDITOR='emacsclient'
	export EDITOR=$SELECTED_EDITOR
	export VISUAL=$SELECTED_EDITOR
	export PAGER=cat
	if _emacs_run '()' >/dev/null; then
		PROMPT_COMMAND+='_emacs_set_shell_DISPLAY;'
	fi
	# Remember, the $() strips the trailing newline, so add it back in
	PS1_EXTRA+='\[$(_emacs_set_remote_dir)'$'\n\\]'
fi