"""Push/pull stack backups to remote destinations (SFTP or S3-compatible).

All operations are synchronous (paramiko / boto3); async callers should wrap
them with ``asyncio.to_thread``. Destination config is a plain dict parsed from
the ``BackupDestination.config`` JSON column.
"""
from __future__ import annotations

import io
import json
import logging
import os
import posixpath
import stat
from typing import Any

from models.backup_destination import BackupDestination

logger = logging.getLogger("stackpilot.backup_dest")


class DestinationError(Exception):
    pass


def parse_config(dest: BackupDestination) -> dict:
    try:
        return json.loads(dest.config or "{}")
    except json.JSONDecodeError:
        return {}


# --------------------------------------------------------------------------- #
# SFTP (paramiko)
# --------------------------------------------------------------------------- #


def _sftp_connect(cfg: dict):
    import paramiko

    host = cfg.get("host")
    if not host:
        raise DestinationError("SFTP host is required")
    port = int(cfg.get("port") or 22)
    username = cfg.get("username")
    transport = paramiko.Transport((host, port))
    try:
        pkey = None
        if cfg.get("private_key"):
            pkey = _load_key(cfg["private_key"])
        transport.connect(username=username, password=cfg.get("password") or None, pkey=pkey)
    except Exception as exc:  # noqa: BLE001
        transport.close()
        raise DestinationError(f"SFTP connection failed: {exc}") from exc
    return paramiko.SFTPClient.from_transport(transport), transport


def _load_key(key_str: str):
    import paramiko

    for cls in (paramiko.Ed25519Key, paramiko.ECDSAKey, paramiko.RSAKey):
        try:
            return cls.from_private_key(io.StringIO(key_str))
        except Exception:  # noqa: BLE001
            continue
    raise DestinationError("Could not parse SFTP private key")


def _sftp_makedirs(sftp, path: str) -> None:
    if not path or path in (".", "/"):
        return
    parts = path.strip("/").split("/")
    cur = "/" if path.startswith("/") else ""
    for p in parts:
        cur = posixpath.join(cur, p) if cur else p
        try:
            sftp.stat(cur)
        except IOError:
            sftp.mkdir(cur)


def _sftp_upload(cfg: dict, local_path: str, filename: str) -> str:
    sftp, transport = _sftp_connect(cfg)
    try:
        base = cfg.get("path") or "."
        if base not in (".", ""):
            _sftp_makedirs(sftp, base)
        remote = posixpath.join(base, filename) if base not in (".", "") else filename
        sftp.put(local_path, remote)
        return remote
    finally:
        sftp.close()
        transport.close()


def _sftp_list(cfg: dict) -> list[dict]:
    sftp, transport = _sftp_connect(cfg)
    try:
        base = cfg.get("path") or "."
        out = []
        try:
            entries = sftp.listdir_attr(base)
        except IOError:
            return []
        for e in entries:
            if stat.S_ISDIR(e.st_mode):
                continue
            if not e.filename.endswith(".tar.gz"):
                continue
            out.append({"name": e.filename, "size": e.st_size, "modified": e.st_mtime})
        return sorted(out, key=lambda x: x["modified"] or 0, reverse=True)
    finally:
        sftp.close()
        transport.close()


def _sftp_download(cfg: dict, name: str, local_path: str) -> None:
    sftp, transport = _sftp_connect(cfg)
    try:
        base = cfg.get("path") or "."
        remote = posixpath.join(base, name) if base not in (".", "") else name
        sftp.get(remote, local_path)
    finally:
        sftp.close()
        transport.close()


def _sftp_delete(cfg: dict, name: str) -> None:
    sftp, transport = _sftp_connect(cfg)
    try:
        base = cfg.get("path") or "."
        remote = posixpath.join(base, name) if base not in (".", "") else name
        sftp.remove(remote)
    finally:
        sftp.close()
        transport.close()


# --------------------------------------------------------------------------- #
# S3-compatible (boto3)
# --------------------------------------------------------------------------- #


def _s3_client(cfg: dict):
    import boto3

    bucket = cfg.get("bucket")
    if not bucket:
        raise DestinationError("S3 bucket is required")
    return boto3.client(
        "s3",
        endpoint_url=cfg.get("endpoint_url") or None,
        region_name=cfg.get("region") or None,
        aws_access_key_id=cfg.get("access_key") or None,
        aws_secret_access_key=cfg.get("secret_key") or None,
    )


def _s3_key(cfg: dict, filename: str) -> str:
    prefix = (cfg.get("prefix") or "").strip("/")
    return f"{prefix}/{filename}" if prefix else filename


def _s3_upload(cfg: dict, local_path: str, filename: str) -> str:
    client = _s3_client(cfg)
    key = _s3_key(cfg, filename)
    try:
        client.upload_file(local_path, cfg["bucket"], key)
    except Exception as exc:  # noqa: BLE001
        raise DestinationError(f"S3 upload failed: {exc}") from exc
    return key


def _s3_list(cfg: dict) -> list[dict]:
    client = _s3_client(cfg)
    prefix = (cfg.get("prefix") or "").strip("/")
    kwargs: dict[str, Any] = {"Bucket": cfg["bucket"]}
    if prefix:
        kwargs["Prefix"] = prefix + "/"
    try:
        resp = client.list_objects_v2(**kwargs)
    except Exception as exc:  # noqa: BLE001
        raise DestinationError(f"S3 list failed: {exc}") from exc
    out = []
    for obj in resp.get("Contents", []):
        name = obj["Key"].split("/")[-1]
        if not name.endswith(".tar.gz"):
            continue
        out.append(
            {
                "name": name,
                "size": obj.get("Size", 0),
                "modified": obj["LastModified"].timestamp() if obj.get("LastModified") else None,
            }
        )
    return sorted(out, key=lambda x: x["modified"] or 0, reverse=True)


def _s3_download(cfg: dict, name: str, local_path: str) -> None:
    client = _s3_client(cfg)
    try:
        client.download_file(cfg["bucket"], _s3_key(cfg, name), local_path)
    except Exception as exc:  # noqa: BLE001
        raise DestinationError(f"S3 download failed: {exc}") from exc


def _s3_delete(cfg: dict, name: str) -> None:
    client = _s3_client(cfg)
    client.delete_object(Bucket=cfg["bucket"], Key=_s3_key(cfg, name))


# --------------------------------------------------------------------------- #
# Dispatch
# --------------------------------------------------------------------------- #


def upload(dest: BackupDestination, local_path: str, filename: str) -> str:
    cfg = parse_config(dest)
    if dest.type == "sftp":
        return _sftp_upload(cfg, local_path, filename)
    if dest.type == "s3":
        return _s3_upload(cfg, local_path, filename)
    raise DestinationError(f"Unknown destination type '{dest.type}'")


def list_backups(dest: BackupDestination) -> list[dict]:
    cfg = parse_config(dest)
    if dest.type == "sftp":
        return _sftp_list(cfg)
    if dest.type == "s3":
        return _s3_list(cfg)
    raise DestinationError(f"Unknown destination type '{dest.type}'")


def download(dest: BackupDestination, name: str, local_path: str) -> None:
    cfg = parse_config(dest)
    if dest.type == "sftp":
        _sftp_download(cfg, name, local_path)
    elif dest.type == "s3":
        _s3_download(cfg, name, local_path)
    else:
        raise DestinationError(f"Unknown destination type '{dest.type}'")


def delete(dest: BackupDestination, name: str) -> None:
    cfg = parse_config(dest)
    if dest.type == "sftp":
        _sftp_delete(cfg, name)
    elif dest.type == "s3":
        _s3_delete(cfg, name)
    else:
        raise DestinationError(f"Unknown destination type '{dest.type}'")


def test(dest: BackupDestination) -> bool:
    """Connectivity check — lists the target (cheap, validates auth + path)."""
    list_backups(dest)
    return True