#!/usr/bin/env python3

import argparse
import os
import subprocess


def get_service_dataset_paths(data_root):
    return { d: os.path.join(data_root, d) for d in os.listdir(data_root) }

def get_last_daily_snapshot_name(dataset_path):
    dataset = ''.join(["rpool", dataset_path])
    snapshots = subprocess.getoutput(
        f"zfs list -t snapshot -H -r {dataset} -o name -s creation"
    )
    daily_snapshots = filter(lambda s: s.endswith("_daily"), snapshots.split('\n'))
    return list(daily_snapshots)[-1]

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Backup service data using restic")
    parser.add_argument("--data-root", type=str, required=True,
                        help="Service data root")
    parser.add_argument("--bucket-endpoint", type=str, required=True,
                        help="S3 bucket endpoint")
    args = parser.parse_args()

    snapshots_for_backup = {
        service: {
            "dataset_path": service_dataset_path,
            "snapshot": get_last_daily_snapshot_name(service_dataset_path),
        } for service, service_dataset_path in get_service_dataset_paths(args.data_root).items()
    }

    for service, info in snapshots_for_backup.items():
        backup_path = os.path.normpath(
            os.path.join("/", "mnt", os.path.relpath(info["dataset_path"], "/"))
        )
        snapshot = info["snapshot"]
        restic_cmd_base = "restic " \
            f"--repo s3:https://{args.bucket_endpoint}/the-nine-worlds---{service} " \
            "--option s3.storage-class=ONEZONE_IA"

        print(f"Backing up {service} : {snapshot}")

        subprocess.run(f"zfs clone -o mountpoint={backup_path} {snapshot} rpool/restic",
                       shell=True, check=True)
        try:
            subprocess.run(f"{restic_cmd_base} snapshots || {restic_cmd_base} init",
                           shell=True, check=True)
            subprocess.run(f"{restic_cmd_base} backup .", shell=True, cwd=backup_path, check=True)
            subprocess.run(f"{restic_cmd_base} forget --prune --keep-daily 90 --keep-monthly 12",
                           shell=True, check=True)
            subprocess.run(f"{restic_cmd_base} check", shell=True, check=True)

        finally:
            subprocess.run("zfs destroy rpool/restic", shell=True, check=True)