"""
Migration: Add userId field to all existing analytics documents.
Sets userId = document ID for every document in the analytics collection.
"""

import firebase_admin
from firebase_admin import credentials, firestore

def main():
    cred = credentials.Certificate("firebase-service-account.json")
    firebase_admin.initialize_app(cred)
    db = firestore.client()

    print("=" * 60)
    print("  Migration: Add userId field to analytics documents")
    print("=" * 60)

    analytics_ref = db.collection("analytics")
    docs = list(analytics_ref.stream())
    print(f"\nFound {len(docs)} analytics documents")

    if not docs:
        print("No documents to migrate.")
        return

    # Use batched writes for efficiency
    batch = db.batch()
    count = 0

    for doc in docs:
        data = doc.to_dict()
        if data.get("userId") == doc.id:
            print(f"  SKIP analytics/{doc.id} (userId already set)")
            continue

        doc_ref = analytics_ref.document(doc.id)
        batch.update(doc_ref, {"userId": doc.id})
        count += 1
        print(f"  UPDATE analytics/{doc.id} -> userId={doc.id}")

        if count % 500 == 0:
            batch.commit()
            print(f"  Committed batch ({count} updates so far)")
            batch = db.batch()

    if count > 0:
        batch.commit()
        print(f"\nCommitted {count} updates")
    else:
        print("\nNo updates needed")

    # Verify
    print("\n" + "=" * 60)
    print("  Verification")
    print("=" * 60)
    verified = 0
    for doc in analytics_ref.stream():
        data = doc.to_dict()
        uid_field = data.get("userId", "MISSING")
        match = "OK" if uid_field == doc.id else "MISMATCH"
        print(f"  {match} analytics/{doc.id} -> userId={uid_field}")
        if match == "OK":
            verified += 1

    print(f"\nVerified: {verified}/{len(docs)} documents have correct userId field")
    print("Migration complete!")


if __name__ == "__main__":
    main()