Funky zsh prompts

[Adam Spiers <adam@thelonious.new.ox.ac.uk>]

C. v. Stuckrad (stucki@math.fu-berlin.de) wrote:
> On Wed, 25 Mar 1998, Andrew Main wrote:
> 
> > >Benbar came up with the amusing idea of making the smiley prompt change
> > >randomly every time I hit return (or even change to something that
> > >reflects the load of the machine).
> > 
> > Cool idea.

Very cool!  I think it's about time I posted my BPFH :-)

Any suggestions for improving it welcome.

-------- 8< -------- 8< --------

reset_colour="$(echo -n '\e[0m')"
bold_colour="$(echo -n '\e[1m')"

# Foreground

grey="$(echo -n '\e[30m')"
red="$(echo -n '\e[31m')"
green="$(echo -n '\e[32m')"
yellow="$(echo -n '\e[33m')"
blue="$(echo -n '\e[34m')"
magenta="$(echo -n '\e[35m')"
cyan="$(echo -n '\e[36m')"
white="$(echo -n '\e[37m')"

# Background

bg_grey="$(echo -n '\e[40m')"
bg_red="$(echo -n '\e[41m')"
bg_green="$(echo -n '\e[42m')"
bg_yellow="$(echo -n '\e[43m')"
bg_blue="$(echo -n '\e[44m')"
bg_magenta="$(echo -n '\e[45m')"
bg_cyan="$(echo -n '\e[46m')"
bg_white="$(echo -n '\e[47m')"

BASE_PROMPT="%{$bg_blue%}%m:%n%{$reset_colour%} "
POST_PROMPT="%{$reset_colour%}"

BASE_PROMPT_NO_COLOUR=$(echo "$BASE_PROMPT" | perl -pe "s/%{.*?%}//g")
POST_PROMPT_NO_COLOUR=$(echo "$POST_PROMPT" | perl -pe "s/%{.*?%}//g")

# Define prompts

PROMPT_NEWLINE=$(echo -ne "\n%{\r%}")

function precmd {
	setopt noxtrace localoptions
	local base_prompt base_prompt_etc prompt_length space_left

	base_prompt=$(print -P "$BASE_PROMPT_NO_COLOUR")
	base_prompt_etc=$(print -P "$base_prompt%(4~|...|)%3.")
	prompt_length=${#base_prompt_etc}
#	echo "Prompt length is $prompt_length"
#	echo "Base prompt length is $#base_prompt"
	if [[ $prompt_length -lt 40 ]]; then
		PATH_PROMPT="%{$bold_colour$cyan%}%(4~|...|)%3.%{$white%}"
	else
		space_left=$(( $COLUMNS - $#base_prompt - 2 ))
#		echo "Space left is $space_left"
		PATH_PROMPT="%{$bold_colour$green%}%${space_left}<...<%~$PROMPT_NEWLINE%{$white%}"
	fi
	PS1="$BASE_PROMPT$PATH_PROMPT %# $POST_PROMPT"
	PS2="$BASE_PROMPT$PATH_PROMPT %_> $POST_PROMPT"
	PS3="$BASE_PROMPT$PATH_PROMPT ?# $POST_PROMPT"
}