set -euo pipefail

dir="${1:?directory holding the shard records}"

total="${2:?number of shards}"

fail() { echo "SHARD COVERAGE FAILED: $*" >&2; exit 1; }

sorted() { LC_ALL=C sort -u "$1"; }

for ((i = 1; i <= total; i++)); do

[ -s "$dir/shard-$i/all.txt" ] || fail "shard $i recorded no enumeration; either it did not get far enough to have one, or its report did not reach here"

sorted "$dir/shard-$i/all.txt" > "$dir/all.$i.sorted"

if [ "$i" != 1 ] && ! cmp -s "$dir/all.1.sorted" "$dir/all.$i.sorted"; then

fail "shard $i enumerated a different set of tests than shard 1, so the shards did not all see the same repository"

fi

for ((i = 1; i <= total; i++)); do

[ -s "$dir/shard-$i/shard.$i.txt" ] || fail "shard $i was assigned no tests"

for ((j = i + 1; j <= total; j++)); do

overlap=$(LC_ALL=C comm -12 <(sorted "$dir/shard-$i/shard.$i.txt") <(sorted "$dir/shard-$j/shard.$j.txt"))

[ -z "$overlap" ] || fail "shards $i and $j were both assigned $(echo "$overlap" | wc -l) test(s), e.g. $(echo "$overlap" | head -1)"

done

cat "$dir"/shard-*/shard.*.txt | LC_ALL=C sort -u > "$dir/union.txt"

cp "$dir/all.1.sorted" "$dir/expected.txt"

missing=$(LC_ALL=C comm -23 "$dir/expected.txt" "$dir/union.txt")

[ -z "$missing" ] || fail "$(echo "$missing" | wc -l) test(s) were in no shard and so did not run, e.g. $(echo "$missing" | head -1)"

extra=$(LC_ALL=C comm -13 "$dir/expected.txt" "$dir/union.txt")

[ -z "$extra" ] || fail "$(echo "$extra" | wc -l) test(s) were assigned that the repository does not have, e.g. $(echo "$extra" | head -1)"

echo "shard coverage OK: $(wc -l < "$dir/expected.txt") tests across $total shards, disjoint and complete"