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

MOSAIC_HOME="${MOSAIC_HOME:-$HOME/.mosaic}"
RUNTIME="claude"
APPLY=0

usage() {
  cat <<USAGE
Usage: $(basename "$0") [options]

Remove legacy runtime files that were preserved as *.mosaic-bak-* after Mosaic linking.
Only removes backups when the active file is a symlink to ~/.mosaic.

Options:
  --runtime <name>   Runtime to prune (default: claude)
  --apply            Perform deletions (default: dry-run)
  -h, --help         Show help
USAGE
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --runtime)
      [[ $# -lt 2 ]] && { echo "Missing value for --runtime" >&2; exit 1; }
      RUNTIME="$2"
      shift 2
      ;;
    --apply)
      APPLY=1
      shift
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "Unknown argument: $1" >&2
      usage >&2
      exit 1
      ;;
  esac
done

case "$RUNTIME" in
  claude)
    TARGET_ROOT="$HOME/.claude"
    ;;
  *)
    echo "Unsupported runtime: $RUNTIME" >&2
    exit 1
    ;;
esac

if [[ ! -d "$TARGET_ROOT" ]]; then
  echo "[mosaic-prune] Runtime directory not found: $TARGET_ROOT" >&2
  exit 1
fi

mosaic_real="$(readlink -f "$MOSAIC_HOME")"
count_candidates=0
count_deletable=0

while IFS= read -r -d '' bak; do
  count_candidates=$((count_candidates + 1))

  base="${bak%%.mosaic-bak-*}"
  if [[ ! -L "$base" ]]; then
    continue
  fi

  base_real="$(readlink -f "$base" 2>/dev/null || true)"
  if [[ -z "$base_real" ]]; then
    continue
  fi

  if [[ "$base_real" != "$mosaic_real"/* ]]; then
    continue
  fi

  count_deletable=$((count_deletable + 1))
  if [[ $APPLY -eq 1 ]]; then
    rm -rf "$bak"
    echo "[mosaic-prune] deleted: $bak"
  else
    echo "[mosaic-prune] would delete: $bak"
  fi
done < <(find "$TARGET_ROOT" \( -type f -o -type d \) -name '*.mosaic-bak-*' -print0)

if [[ $APPLY -eq 1 ]]; then
  echo "[mosaic-prune] complete: deleted=$count_deletable candidates=$count_candidates runtime=$RUNTIME"
else
  echo "[mosaic-prune] dry-run: deletable=$count_deletable candidates=$count_candidates runtime=$RUNTIME"
  echo "[mosaic-prune] re-run with --apply to delete"
fi