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

usage() {
  cat <<'EOF'
Usage: review-checkout-pr <owner/repo|github-url> <pr-number> [checkout-dir]

Examples:
  review-checkout-pr paperclipai/paperclip 432
  review-checkout-pr https://github.com/paperclipai/paperclip.git 432
EOF
}

if [[ $# -lt 2 || $# -gt 3 ]]; then
  usage >&2
  exit 1
fi

normalize_repo_slug() {
  local raw="$1"
  raw="${raw#git@github.com:}"
  raw="${raw#ssh://git@github.com/}"
  raw="${raw#https://github.com/}"
  raw="${raw#http://github.com/}"
  raw="${raw%.git}"
  printf '%s\n' "${raw#/}"
}

repo_slug="$(normalize_repo_slug "$1")"
pr_number="$2"

if [[ ! "$repo_slug" =~ ^[^/]+/[^/]+$ ]]; then
  echo "Expected GitHub repo slug like owner/repo or a GitHub repo URL, got: $1" >&2
  exit 1
fi

if [[ ! "$pr_number" =~ ^[0-9]+$ ]]; then
  echo "PR number must be numeric, got: $pr_number" >&2
  exit 1
fi

repo_key="${repo_slug//\//-}"
mirror_dir="/work/repos/${repo_key}"
checkout_dir="${3:-/work/checkouts/${repo_key}/pr-${pr_number}}"
pr_ref="refs/remotes/origin/pr/${pr_number}"

mkdir -p "$(dirname "$mirror_dir")" "$(dirname "$checkout_dir")"

if [[ ! -d "$mirror_dir/.git" ]]; then
  if command -v gh >/dev/null 2>&1; then
    gh repo clone "$repo_slug" "$mirror_dir" -- --filter=blob:none
  else
    git clone --filter=blob:none "https://github.com/${repo_slug}.git" "$mirror_dir"
  fi
fi

git -C "$mirror_dir" fetch --force origin "pull/${pr_number}/head:${pr_ref}"

if [[ -e "$checkout_dir" ]]; then
  printf '%s\n' "$checkout_dir"
  exit 0
fi

git -C "$mirror_dir" worktree add --detach "$checkout_dir" "$pr_ref" >/dev/null
printf '%s\n' "$checkout_dir"