#!/usr/bin/env bash
# Roll an env BACK to a prior release: re-point releases/latest/ at a chosen release
# and re-fire the deploy. Run by rollback.yml after aws creds are configured.
#
#   ENV         dev | prod                          (required)
#   BUCKET      open-swe-<env>-assets               (required)
#   DEPLOY_DOC  open-swe-<env>-deploy               (required)
#   TARGET_SHA  release sha to restore; blank => releases/last-good/  (optional)
#
# releases/latest/ is moved TRANSACTIONALLY (same as the forward deploy): pointed at
# the target, the box rolled, and on a failed roll latest is reverted to whatever it
# was before the rollback attempt — so a failed rollback never leaves latest at a
# release the box could not bring up. releases/last-good/ is left untouched; advance
# it by running a forward deploy.
#
# Reuses the app deploy role's existing releases/* write + tag-scoped ssm:SendCommand
# — no new IAM. The fire/wait/gate is the SAME roll-box.sh the forward deploy uses.
set -euo pipefail
: "${ENV:?}" "${BUCKET:?}" "${DEPLOY_DOC:?}"
HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# Copy a release prefix into releases/latest/ AND record the resolved sha, so
# releases/latest/sha.txt is always a real commit a later revert can resolve.
point_latest() {  # $1 = source prefix (releases/<sha>|releases/last-good); $2 = sha to record
  local src="$1" sha="$2" f
  for f in app.tar.gz spa.tar.gz; do
    aws s3 cp "s3://${BUCKET}/${src}/${f}" "s3://${BUCKET}/releases/latest/${f}"
  done
  printf '%s\n' "${sha}" | aws s3 cp - "s3://${BUCKET}/releases/latest/sha.txt"
}

if [ -n "${TARGET_SHA:-}" ]; then
  SRC="releases/${TARGET_SHA}"
  LABEL="${TARGET_SHA}"
  RESOLVED_SHA="${TARGET_SHA}"
else
  SRC="releases/last-good"
  LABEL="last-good"
  # resolve last-good's real sha so latest/sha.txt records a commit, not a label.
  RESOLVED_SHA="$(aws s3 cp "s3://${BUCKET}/releases/last-good/sha.txt" - 2>/dev/null | tr -d '[:space:]' || true)"
  RESOLVED_SHA="${RESOLVED_SHA:-last-good}"
fi
echo "==> rollback ${ENV} to ${LABEL}  (s3://${BUCKET}/${SRC}/, sha=${RESOLVED_SHA})"

# Refuse to roll back to a release that is not fully present.
for f in app.tar.gz spa.tar.gz; do
  aws s3 ls "s3://${BUCKET}/${SRC}/${f}" >/dev/null 2>&1 \
    || { echo "ERROR: ${SRC}/${f} not found in s3://${BUCKET} — cannot roll back to ${LABEL}" >&2; exit 1; }
done

# Capture what latest points at now, so a failed rollback can be reverted.
PREV_SHA="$(aws s3 cp "s3://${BUCKET}/releases/latest/sha.txt" - 2>/dev/null | tr -d '[:space:]' || true)"

echo "==> point releases/latest/ -> ${SRC} (was ${PREV_SHA:-<none>})"
point_latest "${SRC}" "${RESOLVED_SHA}"

if ! ROLL_COMMENT="rollback ${ENV} to ${LABEL}" bash "${HERE}/roll-box.sh"; then
  if [ -n "${PREV_SHA}" ]; then
    echo "!! rollback deploy failed — reverting releases/latest/ -> ${PREV_SHA}" >&2
    point_latest "releases/${PREV_SHA}" "${PREV_SHA}"
  fi
  exit 1
fi

echo "==> ${ENV} rolled back to ${LABEL}"
echo "NOTE: releases/last-good/ is left unchanged; re-run a forward deploy to advance it."