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

usage() {
  echo "Usage: $0 --uri <uri> --db <dbname> --input <file> [--dry-run]"
  echo ""
  echo "  --uri      MongoDB connection URI (e.g. mongodb://user:pass@host:27017/admin)"
  echo "  --db       Database name"
  echo "  --input    Path to input JSON file"
  echo "  --dry-run  Show planned actions without executing them"
  exit 1
}

URI=""
DB=""
INPUT=""
DRY_RUN="false"

while [[ $# -gt 0 ]]; do
  case "$1" in
    --uri)     URI="$2";   shift 2 ;;
    --db)      DB="$2";    shift 2 ;;
    --input)   INPUT="$2"; shift 2 ;;
    --dry-run) DRY_RUN="true"; shift ;;
    *) echo "Unknown argument: $1"; usage ;;
  esac
done

[[ -z "$URI" ]]   && echo "Error: --uri is required"   && usage
[[ -z "$DB" ]]    && echo "Error: --db is required"    && usage
[[ -z "$INPUT" ]] && echo "Error: --input is required" && usage

[[ ! -f "$INPUT" ]] && echo "Error: input file not found: $INPUT" && exit 1

TMP_JS=$(mktemp /tmp/mongo-import-XXXXXX.js)
trap 'rm -f "$TMP_JS"' EXIT

cat > "$TMP_JS" <<'EOF'
const dbName = process.env.MONGO_DB;
const dryRun = process.env.DRY_RUN === "true";
const data = JSON.parse(process.env.INDEXES_JSON);

const targetDb = db.getSiblingDB(dbName);
const existingCollections = new Set(targetDb.getCollectionNames());

function normalizeKey(key) {
  return JSON.stringify(key, Object.keys(key).sort());
}

function normalizeIndex(idx) {
  const { v, ns, background, ...rest } = idx;
  return JSON.stringify(rest, Object.keys(rest).sort());
}

function indexesEqual(a, b) {
  return normalizeIndex(a) === normalizeIndex(b);
}

if (dryRun) {
  print("[dry-run] No changes will be made.\n");
}

for (const [collName, indexes] of Object.entries(data)) {
  print(`Collection: ${collName}`);

  const coll = targetDb.getCollection(collName);

  if (!existingCollections.has(collName)) {
    if (dryRun) {
      print(`  [dry-run] Would create collection: ${collName}`);
    } else {
      targetDb.createCollection(collName);
      print(`  Created collection`);
    }
  }

  const existingByName = {};
  const existingByKey = {};
  if (existingCollections.has(collName)) {
    for (const idx of coll.getIndexes()) {
      if (idx.name !== "_id_") {
        existingByName[idx.name] = idx;
        existingByKey[normalizeKey(idx.key)] = idx;
      }
    }
  }

  const consumedExistingNames = new Set();

  for (const idx of indexes) {
    if (idx.name === "_id_") continue;

    const { key, name, ...rest } = idx;
    const options = { name, ...rest };

    if (existingByName[name]) {
      consumedExistingNames.add(name);
      if (indexesEqual(existingByName[name], idx)) {
        print(`  Index "${name}" is up to date, skipping`);
      } else {
        if (dryRun) {
          print(`  [dry-run] Would drop and recreate index "${name}" (definition changed)`);
        } else {
          coll.dropIndex(name);
          coll.createIndex(key, options);
          print(`  Dropped and recreated index "${name}" (definition changed)`);
        }
      }
    } else {
      const conflicting = existingByKey[normalizeKey(key)];
      if (conflicting) {
        consumedExistingNames.add(conflicting.name);
        if (dryRun) {
          print(`  [dry-run] Would drop index "${conflicting.name}" and create "${name}" (same key, name changed)`);
        } else {
          coll.dropIndex(conflicting.name);
          coll.createIndex(key, options);
          print(`  Dropped "${conflicting.name}" and created "${name}" (same key, name changed)`);
        }
      } else {
        if (dryRun) {
          print(`  [dry-run] Would create index "${name}"`);
        } else {
          coll.createIndex(key, options);
          print(`  Created index "${name}"`);
        }
      }
    }
  }

  for (const name of Object.keys(existingByName)) {
    if (!consumedExistingNames.has(name)) {
      if (dryRun) {
        print(`  [dry-run] Would drop obsolete index "${name}"`);
      } else {
        coll.dropIndex(name);
        print(`  Dropped obsolete index "${name}"`);
      }
    }
  }
}

if (!dryRun) {
  print("\nImport complete.");
}
EOF

MONGO_DB="$DB" \
DRY_RUN="$DRY_RUN" \
INDEXES_JSON="$(cat "$INPUT")" \
  mongosh --quiet "$URI" --file "$TMP_JS"