"""
One-time migration: convert plain .bak backup blobs to AES-256 encrypted .zip files.

Usage: python migrate_to_zip.py

Walks BACKUP_PATH, finds all .bak files, creates encrypted .zip for each,
then deletes the original .bak. Resumable: skips files where .zip already exists.
"""

import os
import sys
import time
import pyzipper
from indexer.config import BACKUP_PATH, BACKUP_PASSWORD


def collect_bak_files(backup_root: str) -> list:
    """Walk backup dir and collect all .bak file paths."""
    bak_files = []
    for dirpath, _dirnames, filenames in os.walk(backup_root):
        for fn in filenames:
            if fn.endswith(".bak"):
                bak_files.append(os.path.join(dirpath, fn))
    return bak_files


def migrate(backup_root: str, password: str):
    print(f"Backup dir: {backup_root}")
    print("Scanning for .bak files...")
    bak_files = collect_bak_files(backup_root)
    total = len(bak_files)
    print(f"Found {total} .bak files to migrate.\n")

    if total == 0:
        print("Nothing to migrate.")
        return

    password_bytes = password.encode("utf-8")
    converted = 0
    skipped = 0
    errors = 0
    start_time = time.time()

    try:
        for i, bak_path in enumerate(bak_files, 1):
            # Derive the .zip path from the .bak path
            # e.g., ab/cd/abcdef...64hex.bak -> ab/cd/abcdef...64hex.zip
            base = bak_path[:-4]  # strip ".bak"
            zip_path = base + ".zip"
            hex_hash = os.path.basename(base)  # the 64-char hex name

            # Resume support: skip if .zip already exists
            if os.path.exists(zip_path):
                skipped += 1
                if i % 500 == 0 or i == total:
                    elapsed = time.time() - start_time
                    print(f"  [{i}/{total}] ({100*i//total}%) "
                          f"converted={converted} skipped={skipped} errors={errors} "
                          f"elapsed={elapsed:.0f}s")
                continue

            try:
                # Create encrypted zip in a temp file, then rename
                tmp_path = zip_path + ".tmp"
                with pyzipper.AESZipFile(
                    tmp_path, "w",
                    compression=pyzipper.ZIP_DEFLATED,
                    encryption=pyzipper.WZ_AES,
                ) as zf:
                    zf.setpassword(password_bytes)
                    zf.write(bak_path, arcname=hex_hash + ".blob")

                os.replace(tmp_path, zip_path)

                # Verify the zip is valid before deleting original
                with pyzipper.AESZipFile(zip_path, "r") as zf:
                    zf.setpassword(password_bytes)
                    names = zf.namelist()
                    if not names:
                        raise ValueError("ZIP is empty after creation")

                # Delete original .bak
                os.remove(bak_path)
                converted += 1

            except Exception as e:
                print(f"  ERROR: {bak_path}: {e}")
                errors += 1
                # Clean up temp file if it exists
                if os.path.exists(zip_path + ".tmp"):
                    try:
                        os.remove(zip_path + ".tmp")
                    except OSError:
                        pass
                continue

            # Progress every 500 files
            if i % 500 == 0 or i == total:
                elapsed = time.time() - start_time
                rate = converted / elapsed if elapsed > 0 else 0
                eta = (total - i) / rate if rate > 0 else 0
                print(f"  [{i}/{total}] ({100*i//total}%) "
                      f"converted={converted} skipped={skipped} errors={errors} "
                      f"elapsed={elapsed:.0f}s  ETA={eta:.0f}s")

    except KeyboardInterrupt:
        print(f"\n\nInterrupted by user at file {i}/{total}.")
        print("Migration is resumable — run again to continue.")

    elapsed = time.time() - start_time
    print(f"\n{'='*60}")
    print(f"Migration complete.")
    print(f"  Total .bak files : {total}")
    print(f"  Converted        : {converted}")
    print(f"  Skipped (exists) : {skipped}")
    print(f"  Errors           : {errors}")
    print(f"  Time             : {elapsed:.0f}s")
    print(f"{'='*60}")


if __name__ == "__main__":
    if not BACKUP_PATH or not os.path.isdir(BACKUP_PATH):
        print(f"ERROR: BACKUP_PATH is not a valid directory: {BACKUP_PATH}")
        sys.exit(1)
    if not BACKUP_PASSWORD:
        print("ERROR: BACKUP_PASSWORD not set in .env")
        sys.exit(1)

    print("=" * 60)
    print("MIGRATION: .bak -> encrypted .zip")
    print(f"Backup dir: {BACKUP_PATH}")
    print("=" * 60)

    migrate(BACKUP_PATH, BACKUP_PASSWORD)