#!/bin/rc

rfork e

slashnhack=yes

smon='s/Jan/01/
	s/Feb/02/
	s/Mar/03/
	s/Apr/04/
	s/May/05/
	s/Jun/06/
	s/Jul/07/
	s/Aug/08/
	s/Sep/09/
	s/Oct/10/
	s/Nov/11/
	s/Dec/12/'

fn usage {
	echo 'usage: yesterday [-abcCdDN] [-[[[yy]yy]mm]dd] [-n daysago] file ...' >[1=2]
	exit 'usage'
}

fn Xcp {
	echo cp $1 $2
	cp $1 $2
}

fn Xdiff {
	echo diff $1 $2
	diff $1 $2
}
fn Xdiffn {
	echo diff -n $1 $2
	diff -n $1 $2
}
fn Xadiff {
	echo /acme/bin/adiff $1 $2
	/acme/bin/adiff $1 $2
}

fn Xcarefulcp {
	if(! cmp -s $1 $2) Xcp $1 $2
}

fn Xecho {
	echo $1
}

fn Xbind {
	echo bind $1 $2
	bind $1 $2
}

year=`{date|sed 's/.* //'}
copy=Xecho
last=()
while(! ~ $#* 0 && ~ $1 -* && ! ~ $1 --){
	switch($1){
	case -a
		copy=Xadiff
		shift
	case -b
		copy=Xbind
		shift
	case -c
		copy=Xcp
		shift
	case -d
		copy=Xdiff
		shift
	case -D
		copy=Xdiffn
		shift
	case -C
		copy=Xcarefulcp
		shift
# The slashnhack is always right.
#	case -N
#		slashnhack=no
#		shift
	case -n*
		if(~ $1 -n){
			if(~ $#* 1)
				usage
			shift
			days=$1
		}
		if not
			days=`{echo $1 | sed 's/^-.//'}
		last=`{date `{hoc -e `{date -n} ^ '-'$days'*60*60*24'} | \
				sed -e 's%... (...) (..) ..:..:.. ... (....)%\3/\1\2%' -e 'y/ /0/' -e $smon}
		shift
	case -?
		mon=`{date|sed -e 's/^....(...).*/\1/' -e $smon}
		last=$year/$mon ^`{echo $1|sed 's/^-/0/'}
		shift
	case -??
		mon=`{date|sed -e 's/^....(...).*/\1/' -e $smon}
		last=$year/$mon ^`{echo $1|sed 's/^-//'}
		shift
	case -????
		last=$year/ ^ `{echo $1|sed 's/^-//'}
		shift
	case -??????
		last=`{echo $year|sed 's/..$//'} ^ `{echo $1|sed 's/^-(..)/\1\//'}
		shift
	case -????????
		last=`{echo $1|sed 's/^-(....)/\1\//'}
		shift
	case *
		usage
	}
}
if(! ~ $#* 0 && ~ $1 --)
	shift

if(~ $#* 0)
	usage

dir=`{pwd}
if(! ~ $status ''){
	echo 'yesterday: can''t find directory' >[1=2]
	exit 'pwd failed'
}

for(i){
	xpath=`{cleanname -d $dir -- $i}
	xdump=dump
	dumppath=$xpath
	if(~ $slashnhack yes && ~ $xpath /n/*/*){
		xdump=`{echo $xpath | sed 's:/n/([^/]+)/.*:\1dump:'}
		dumppath=`{echo $xpath | sed 's:/n/[^/]+(/.*):\1:'}
	}
	if(! test -e /n/$xdump/$year)
		9fs $xdump

	if(~ $#last 0)
		xlast=`{ls -t /n/$xdump/$year|sed 1q}
	if not
		xlast=/n/$xdump/$last

	if(! test -e $xlast){
		echo 'yesterday:' \
			`{echo $xlast|sed 's/.n.dump.(....).(..)(..)/\1 \2 \3/'} \
			'is not a backup day for' $xdump >[1=2]
		exit 'bad date'
	}
	
	$copy $xlast^$dumppath $xpath
}
exit ''