#!/bin/sh
# Flags Co-Authored-By trailers with Claude/Anthropic attribution in PR commits.
# The hive convention in /knowledge/hive-rules.md forbids these trailers.
#
# Pattern is anchored to an actual git trailer line — `^[[:space:]]*co-authored-by:`
# — not any mention of the phrase, then requires the value name `claude`,
# `anthropic`, or `noreply@anthropic.com`. Matching is case-insensitive and
# per-line (git trailers are one `Key: value` per line) to cover variants like
# `Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>` while letting a
# commit subject/body that merely *discusses* the trailer (e.g. this script's
# own "add CI lint for Co-Authored-By/Claude/Anthropic trailers") pass.
#
# Scope is the PR's commits (BASE..HEAD), not entire history — old commits
# must not fail the build.
set -eu

trailer_re='^[[:space:]]*co-authored-by:.*(claude|anthropic|noreply@anthropic\.com)'

if [ -n "${GITHUB_BASE_REF:-}" ]; then
  base="origin/${GITHUB_BASE_REF}"
else
  base="origin/main"
fi

# actions/checkout@v3 fetches the PR head but may not fetch the base branch
if ! git rev-parse --verify "$base" >/dev/null 2>&1; then
  branch="${base#origin/}"
  git fetch origin "$branch" 2>/dev/null || true
  if ! git rev-parse --verify "$base" >/dev/null 2>&1; then
    base="origin/main"
    if ! git fetch origin main 2>/dev/null || ! git rev-parse --verify "$base" >/dev/null 2>&1; then
      echo 'check-attribution-trailers: base ref unresolvable — cannot fetch origin/main to diff against, refusing to guess a commit range' >&2
      exit 1
    fi
  fi
fi

# `|| true` here used to erase git log's own exit status, so a genuine
# failure (bad range, corrupt ref) and a merely-empty range read the same:
# both fell through to `-z "$commits"` and exited 0 "clean". Capture the
# status via the `if` guard instead — that's exempt from `set -e` on
# purpose — so a failure exits loudly and an empty-but-successful range
# still means "no commits, nothing to check".
if ! commits="$(git log --reverse --format='%H' "${base}..HEAD")"; then
  echo "check-attribution-trailers: git log failed for range ${base}..HEAD — see error above" >&2
  exit 1
fi

if [ -z "$commits" ]; then
  exit 0
fi

hits=""
for sha in $commits; do
  msg="$(git log -1 --format='%B' "$sha")"
  if printf '%s\n' "$msg" | grep -qiE "$trailer_re"; then
    subject="$(git log -1 --format='%s' "$sha")"
    hits="${hits}${sha}|${subject}
"
  fi
done

if [ -n "$hits" ]; then
  printf '%s' "$hits" | while IFS='|' read -r sha subject; do
    [ -z "$sha" ] && continue
    short_sha="$(printf '%s' "$sha" | cut -c1-8)"
    printf '::error title=Attribution trailer found in %s::%s — commit carries a Co-Authored-By trailer with Claude/Anthropic attribution, forbidden by /knowledge/hive-rules.md\n' \
      "$short_sha" "$subject"
  done
  count="$(printf '%s' "$hits" | grep -c '|' || true)"
  printf 'check-attribution-trailers: %s commit(s) with prohibited trailers found\n' "$count" >&2
  exit 1
fi

exit 0