#!/usr/bin/env bash
set -euo pipefail

ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
cd "$ROOT"
REMOTE="upstream-oxi"
COMMIT="${1:-}"

if [ -z "$COMMIT" ]; then
  echo "usage: $0 <oxi-commit>" >&2
  exit 2
fi
if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
  echo "error: not a Git checkout" >&2
  exit 1
fi
if ! git diff --quiet || ! git diff --cached --quiet; then
  echo "error: working tree must be clean before porting an Oxi commit" >&2
  exit 1
fi
if ! git remote get-url "$REMOTE" >/dev/null 2>&1; then
  echo "error: Oxi remote is not configured; run ./scripts/setup-upstream.sh" >&2
  exit 1
fi

git fetch "$REMOTE" --tags >/dev/null
SHA="$(git rev-parse "$COMMIT^{commit}")"
PARENT="$(git rev-parse "$SHA^1")"
branch="port/oxi-${SHA:0:12}"
git switch -c "$branch"

tmp_raw="$(mktemp)"
tmp_mapped="$(mktemp)"
cleanup() { rm -f "$tmp_raw" "$tmp_mapped"; }
trap cleanup EXIT

git diff --binary --find-renames "$PARENT..$SHA" -- backend/ > "$tmp_raw"
sed \
  -e 's#^diff --git a/backend/#diff --git a/#' \
  -e 's# b/backend/# b/#' \
  -e 's#^--- a/backend/#--- a/#' \
  -e 's#^+++ b/backend/#+++ b/#' \
  -e 's#^rename from backend/#rename from #' \
  -e 's#^rename to backend/#rename to #' \
  -e 's#^copy from backend/#copy from #' \
  -e 's#^copy to backend/#copy to #' \
  -e 's#^Binary files a/backend/#Binary files a/#' \
  -e 's# and b/backend/# and b/#' \
  "$tmp_raw" > "$tmp_mapped"

if [ ! -s "$tmp_mapped" ]; then
  echo "Oxi commit $SHA has no backend/ changes to map."
else
  git apply --3way --index "$tmp_mapped"
fi

printf 'Ported backend portion of Oxi commit %s onto branch %s.\n' "$SHA" "$branch"
printf 'UPSTREAM_BASE was intentionally NOT changed.\n'
printf 'Review the original commit, especially frontend changes: git show %s -- frontend/\n' "$SHA"