#!/usr/bin/env bash
# Follow a new upstream sync: re-pin upstream.rev, replay patches/ on top of it,
# and write the forward-ported result back out.
#
#   usage: update-upstream.sh [--dry-run] [--to <rev>]

source "$(dirname "${BASH_SOURCE[0]}")/lib.sh"

DRY_RUN=0
TARGET=""
while [[ $# -gt 0 ]]; do
  case "$1" in
    -n|--dry-run) DRY_RUN=1; shift ;;
    --to) TARGET="${2:?--to needs a revision}"; shift 2 ;;
    *) die "unknown argument: $1" ;;
  esac
done

ensure_upstream

OLD="$(read_rev)"
if [[ -n "$TARGET" ]]; then
  NEW="$(git -C "$UPSTREAM_DIR" rev-parse --verify "${TARGET}^{commit}")" \
    || die "revision '$TARGET' not found in upstream"
else
  NEW="$(git -C "$UPSTREAM_DIR" rev-parse --verify "origin/$UPSTREAM_BRANCH")"
fi

if [[ "$OLD" == "$NEW" ]]; then
  info "Already pinned to the newest upstream commit ($(git -C "$UPSTREAM_DIR" rev-parse --short "$NEW")). Nothing to do."
  exit 0
fi

count="$(git -C "$UPSTREAM_DIR" rev-list --count "$OLD..$NEW" 2>/dev/null || echo '?')"
info "Upstream moved: $(git -C "$UPSTREAM_DIR" rev-parse --short "$OLD") -> $(git -C "$UPSTREAM_DIR" rev-parse --short "$NEW") ($count new commit(s))"
git -C "$UPSTREAM_DIR" log --oneline --no-decorate "$OLD..$NEW" | sed 's/^/     /'

# Each upstream commit is a squashed monorepo drop; SOURCE_REV names the
# internal commit it came from, which is the only human-meaningful version here.
old_src="$(git -C "$UPSTREAM_DIR" show "$OLD:SOURCE_REV" 2>/dev/null | tr -d '[:space:]' || true)"
new_src="$(git -C "$UPSTREAM_DIR" show "$NEW:SOURCE_REV" 2>/dev/null | tr -d '[:space:]' || true)"
[[ -n "$old_src$new_src" ]] && info "SOURCE_REV: ${old_src:-?} -> ${new_src:-?}"

changed="$(git -C "$UPSTREAM_DIR" diff --name-only "$OLD" "$NEW" | wc -l | tr -d ' ')"
info "$changed file(s) changed upstream"

if [[ "$DRY_RUN" == "1" ]]; then
  info "--dry-run: upstream.rev left at $OLD"
  exit 0
fi

info "Pinning upstream.rev -> $NEW"
write_rev "$NEW"

info "Replaying patches on the new base"
if ! "$ROOT/scripts/apply-patches.sh" --force; then
  cat >&2 <<EOF

${C_YELLOW}${C_BOLD}==> upstream.rev has been bumped, but patches did not apply cleanly.${C_RESET}

  Finish the 'git am' in work/ (instructions above), then run:

    make rebuild

  To abandon this update entirely and go back:

    cd work && git am --abort
    printf '%s\\n' "$OLD" > upstream.rev   # or: git checkout upstream.rev
    make apply

EOF
  exit 1
fi

info "Patches replayed cleanly -- regenerating patches/ against the new base"
"$ROOT/scripts/rebuild-patches.sh"

cat <<EOF

${C_GREEN}${C_BOLD}==> Update complete.${C_RESET}
  Review and commit the result:
    git diff --stat upstream.rev patches/
    make build
    git add upstream.rev patches/ && git commit -m 'Update upstream to $(git -C "$UPSTREAM_DIR" rev-parse --short "$NEW")'
EOF