#!/bin/bash
#
# To start tracking a file,
#   cp ~/.screenrc dot/screenrc
#
# To sort out symlinks when things are clean
#   infra/makelinks install

set -e -o posix -o pipefail

badusage () {
    echo >&2 "usage: $0 [-n|-v] list|setup|dirimport|dirmove|clean"
    exit 18
}

real_act=''

while true; do
    if [ $# = 0 ]; then break; fi
    case "$1" in
    -n) real_act=log_only ;;
    -v) real_act=with_log ;;
    -*) badusage ;;
    *) break ;;
    esac
    shift
done

case "$#.$1" in
1.list|1.setup|1.import|1.dirimport|1.clean) ;;
*)  badusage ;;
esac

mode=$1; shift

basepath=$(pwd)
basepath=${basepath#$HOME/}

estatus=0

show () {
    printf "%s\n" "$1"
}

good () {
    if [ $mode = list ]; then
	show "good: $prhome: $1"
    fi
}

bad () {
    estatus=16
    show "bad: $prhome: $1" >&2
}

needs () {
    if [ $mode = $1 ]; then
	act=$real_act
	show "DOING $1: $prhome ($2)"
    else
	show "needs $1: $prhome: $2"
	act=:
    fi
}

log_only () {
    echo "x $*"
}

with_log () {
    log_only "$@"
    "$@"
}

process_object () {
    inhome="$HOME/$underhome"
    prhome="~/$underhome"
    linktarget="$basepath/$ours"
    chompy="$underhome"
    while true; do
	case "$chompy" in
        *?/?*)
	    linktarget="../$linktarget"
	    chompy="${chompy%/*}"
	    ;;
	*)
	    break
	    ;;
	esac
    done
    if [ "$inhome" -ef "$ours" ]; then
	good "already symlinked here"
    elif [ -h "$inhome" ]; then
        bad "wrong symlink target"
    elif ! [ -e "$inhome" ]; then
	needs setup "absent here"
	$act ln -s "$linktarget" "$inhome"
    elif [ -f "$inhome" ] && [ -f "$ours" ]; then
	if cmp -s "$ours" "$inhome"; then
	    needs setup "identical in this ~ but not yet symlinked"
	    $act rm -f "$inhome"~
	    $act ln -s "$linktarget" "$inhome"~
	    $act mv -f "$inhome"~ "$inhome"
	else
	    needs import "modified here"
	    $act rm -f "$ours"~
	    $act cp "$inhome" "$ours"~
	    $act mv -f "$ours"~ "$ours"
	fi
    elif [ -d "$inhome" ] && [ -d "$ours" ]; then
	needs dirimport "directory in this ~, not yet symlinked"
	$act mv "$ours" "$ours~"
	$act ln -s "$linktarget" "$inhome"~
	$act mv "$inhome" "$ours"
	$act mv "$inhome~" "$inhome"
	$act rm -rf "$ours~"
    else
	bad "mismatched file types"
    fi
}

dots=$( find dot -mindepth 1 -maxdepth 1 -name '[0-9a-zA-Z]*[0-9a-zA-Z]' )

for ours in $dots; do
    underhome=".${ours#dot/}"
    process_object
done

nondots=$( find home -mindepth 1 -maxdepth 1 -name '[0-9a-zA-Z]*[0-9a-zA-Z]' )

for ours in $nondots; do
    underhome="${ours#home/}"
    process_object
done

exec 3<correspondences
while read <&3 ours underhome; do
    case "$ours" in
    ''|'#'*) ;;
    *)
	case "$underhome" in
	*/*)
	    parent=${underhome%/*}
	    punderhome="$HOME/$parent"
	    prhome="~/${underhome%/*}"
	    if [ -d "$punderhome" ]; then
		good "directory exists"
	    elif ! [ -e "$punderhome" ]; then
		needs setup "directory does not exist"
		$act mkdir -p "$punderhome"
	    else
		bad "ought to be director but isn't"
	    fi
	    ;;
	esac
	process_object
	;;
    esac
done

brokens=$(
    cd $HOME
    find -L .[0-9a-zA-Z]* -maxdepth 0 -xdev -type l \
	 \( -lname "$basepath/dot/*" -o -lname "$basepath/home/*" \)
)
for underhome in $brokens; do
    inhome="$HOME/$underhome"
    prhome="~/$underhome"
    needs clean "symlink to removed file in dot/"
    $act rm -f "$inhome"
done