#!/bin/sh
# Roll back ~/bin/forge to ~/bin/forge.prev after a unit failed.
# Usage: forge-rollback <unit-name>. Output goes to the journal.
set -eu

unit="${1:?usage: forge-rollback <unit-name>}"
bin="$HOME/bin/forge"
prev="$bin.prev"
bad="$bin.bad"

if [ ! -e "$prev" ]; then
    echo "forge-rollback: $unit failed and $prev does not exist, nothing to roll back"
    exit 0
fi

sha=$(sha256sum "$bin" | cut -d' ' -f1)
# Keep one hash per line, even if the file was edited by hand without a final newline.
if [ -s "$bad" ] && [ -n "$(tail -c 1 "$bad")" ]; then
    echo >> "$bad"
fi
echo "$sha" >> "$bad"
mv -f "$prev" "$bin"
echo "forge-rollback: $unit failed, marked $sha bad, restored $prev"

systemctl --user reset-failed "$unit"
systemctl --user start "$unit"
echo "forge-rollback: started $unit on the previous binary"