from __future__ import annotations

import shutil
import stat
from datetime import datetime, timezone
from pathlib import Path
from typing import Any

from pobsync.errors import ConfigError
from pobsync.lock import acquire_host_lock
from pobsync.paths import PobsyncPaths
from pobsync.retention import Snapshot, apply_base_protection, build_retention_plan
from pobsync.util import sanitize_host

from .models import HostConfig, SnapshotRecord


def run_sql_retention_plan(*, host: str, kind: str, protect_bases: bool) -> dict[str, Any]:
    host = sanitize_host(host)
    if kind not in {"scheduled", "manual", "all"}:
        raise ConfigError("kind must be scheduled, manual, or all")

    host_config = _enabled_host_config(host)
    retention = _retention_for_host(host_config)
    snapshots = _snapshots_for_retention(host_config=host_config, kind=kind)
    incomplete_snapshots = _incomplete_snapshots_for_host(host_config)

    plan = build_retention_plan(
        snapshots=snapshots,
        retention=retention,
        now=datetime.now(timezone.utc),
    )

    keep = set(plan.keep)
    reasons = dict(plan.reasons)
    if protect_bases:
        keep, reasons = apply_base_protection(snapshots=snapshots, keep=keep, reasons=reasons)

    delete = [snapshot for snapshot in snapshots if snapshot.dirname not in keep]
    keep_items = [snapshot for snapshot in snapshots if snapshot.dirname in keep]

    return {
        "ok": True,
        "host": host,
        "kind": kind,
        "protect_bases": bool(protect_bases),
        "retention": retention,
        "source": "sql",
        "keep": sorted(keep),
        "keep_items": [_snapshot_to_item(snapshot, reasons=reasons.get(snapshot.dirname, [])) for snapshot in keep_items],
        "delete": [_snapshot_to_item(snapshot, reasons=["outside retention policy"]) for snapshot in delete],
        "incomplete": [
            _snapshot_to_item(snapshot, reasons=["incomplete snapshot; excluded from retention cleanup"])
            for snapshot in incomplete_snapshots
        ],
        "reasons": reasons,
    }


def run_sql_retention_apply(
    *,
    prefix: Path,
    host: str,
    kind: str,
    protect_bases: bool,
    yes: bool,
    max_delete: int,
    acquire_lock: bool = True,
) -> dict[str, Any]:
    host = sanitize_host(host)
    if not yes:
        raise ConfigError("Refusing to delete snapshots without --yes")
    if max_delete < 0:
        raise ConfigError("--max-delete must be >= 0")

    paths = PobsyncPaths(home=prefix)

    def _do_apply() -> dict[str, Any]:
        plan = run_sql_retention_plan(host=host, kind=kind, protect_bases=bool(protect_bases))
        delete_list = plan.get("delete") or []
        incomplete_list = plan.get("incomplete") or []
        if not isinstance(delete_list, list):
            raise ConfigError("Invalid retention plan output: delete is not a list")
        if not isinstance(incomplete_list, list):
            raise ConfigError("Invalid retention plan output: incomplete is not a list")
        if max_delete == 0 and len(delete_list) > 0:
            raise ConfigError("Deletion blocked by --max-delete=0")
        if len(delete_list) > max_delete:
            raise ConfigError(f"Refusing to delete {len(delete_list)} snapshots (exceeds --max-delete={max_delete})")

        actions: list[str] = []
        deleted: list[dict[str, Any]] = []

        for item in delete_list:
            dirname = item.get("dirname") if isinstance(item, dict) else None
            snap_kind = item.get("kind") if isinstance(item, dict) else None
            snap_path = item.get("path") if isinstance(item, dict) else None
            if not isinstance(dirname, str) or not isinstance(snap_kind, str) or not isinstance(snap_path, str):
                continue
            if snap_kind not in {"scheduled", "manual"}:
                raise ConfigError(f"Refusing to delete unsupported snapshot kind: {snap_kind!r}")

            path = _snapshot_delete_path(path=Path(snap_path), dirname=dirname)
            if not path.exists():
                actions.append(f"skip missing {snap_kind}/{dirname}")
                continue
            if not path.is_dir():
                raise ConfigError(f"Refusing to delete non-directory path: {path}")

            _remove_snapshot_tree(path)
            SnapshotRecord.objects.filter(host__host=host, kind=snap_kind, dirname=dirname).delete()
            actions.append(f"deleted {snap_kind} {dirname}")
            deleted.append({"dirname": dirname, "kind": snap_kind, "path": str(path)})

        return {
            "ok": True,
            "host": host,
            "kind": kind,
            "protect_bases": bool(protect_bases),
            "max_delete": max_delete,
            "source": "sql",
            "planned_delete_count": len(delete_list),
            "incomplete_ignored_count": len(incomplete_list),
            "deleted": deleted,
            "actions": actions,
        }

    if acquire_lock:
        with acquire_host_lock(paths.locks_dir, host, command="retention-apply"):
            return _do_apply()
    return _do_apply()


def run_incomplete_cleanup(
    *,
    prefix: Path,
    host: str,
    yes: bool,
    max_delete: int,
    acquire_lock: bool = True,
) -> dict[str, Any]:
    host = sanitize_host(host)
    if not yes:
        raise ConfigError("Refusing to delete incomplete snapshots without --yes")
    if max_delete < 0:
        raise ConfigError("--max-delete must be >= 0")

    paths = PobsyncPaths(home=prefix)

    def _do_cleanup() -> dict[str, Any]:
        host_config = _enabled_host_config(host)
        incomplete_list = [
            _snapshot_to_item(snapshot, reasons=["manual incomplete cleanup"])
            for snapshot in _incomplete_snapshots_for_host(host_config)
        ]
        if max_delete == 0 and len(incomplete_list) > 0:
            raise ConfigError("Incomplete cleanup blocked by --max-delete=0")
        if len(incomplete_list) > max_delete:
            raise ConfigError(
                f"Refusing to delete {len(incomplete_list)} incomplete snapshots (exceeds --max-delete={max_delete})"
            )

        actions: list[str] = []
        deleted: list[dict[str, Any]] = []

        for item in incomplete_list:
            dirname = item["dirname"]
            snap_path = Path(item["path"])
            path = _snapshot_delete_path(path=snap_path, dirname=dirname)
            _validate_incomplete_delete_path(host=host, path=path, dirname=dirname)

            if not path.exists():
                actions.append(f"skip missing incomplete/{dirname}")
            elif not path.is_dir():
                raise ConfigError(f"Refusing to delete non-directory path: {path}")
            else:
                _remove_snapshot_tree(path)
                actions.append(f"deleted incomplete {dirname}")

            SnapshotRecord.objects.filter(
                host__host=host,
                kind=SnapshotRecord.Kind.INCOMPLETE,
                dirname=dirname,
            ).delete()
            deleted.append({"dirname": dirname, "kind": SnapshotRecord.Kind.INCOMPLETE, "path": str(path)})

        return {
            "ok": True,
            "host": host,
            "kind": SnapshotRecord.Kind.INCOMPLETE,
            "max_delete": max_delete,
            "source": "sql",
            "planned_delete_count": len(incomplete_list),
            "deleted": deleted,
            "actions": actions,
        }

    if acquire_lock:
        with acquire_host_lock(paths.locks_dir, host, command="incomplete-cleanup"):
            return _do_cleanup()
    return _do_cleanup()


def _enabled_host_config(host: str) -> HostConfig:
    try:
        return HostConfig.objects.get(host=host, enabled=True)
    except HostConfig.DoesNotExist as exc:
        raise ConfigError(f"Missing enabled host {host!r}") from exc


def _retention_for_host(host_config: HostConfig) -> dict[str, int]:
    return {
        "daily": host_config.retention_daily,
        "weekly": host_config.retention_weekly,
        "monthly": host_config.retention_monthly,
        "yearly": host_config.retention_yearly,
    }


def _snapshots_for_retention(*, host_config: HostConfig, kind: str) -> list[Snapshot]:
    kinds = ["scheduled", "manual"] if kind == "all" else [kind]
    records = (
        SnapshotRecord.objects.filter(host=host_config, kind__in=kinds)
        .exclude(kind=SnapshotRecord.Kind.INCOMPLETE)
        .select_related("base")
        .order_by("-started_at", "dirname")
    )
    return [_snapshot_from_record(record) for record in records]


def _incomplete_snapshots_for_host(host_config: HostConfig) -> list[Snapshot]:
    records = (
        SnapshotRecord.objects.filter(host=host_config, kind=SnapshotRecord.Kind.INCOMPLETE)
        .select_related("base")
        .order_by("-started_at", "dirname")
    )
    return [_snapshot_from_record(record) for record in records]


def _snapshot_from_record(record: SnapshotRecord) -> Snapshot:
    return Snapshot(
        kind=record.kind,
        dirname=record.dirname,
        path=record.path,
        dt=record.started_at or datetime.fromtimestamp(0, tz=timezone.utc),
        status=record.status or None,
        base=_base_meta_from_record(record),
    )


def _base_meta_from_record(record: SnapshotRecord) -> dict[str, str] | None:
    if record.base is not None:
        return {
            "kind": record.base.kind,
            "dirname": record.base.dirname,
            "path": record.base.path,
        }
    if record.base_kind and record.base_dirname:
        return {
            "kind": record.base_kind,
            "dirname": record.base_dirname,
            "path": record.base_path,
        }
    return None


def _snapshot_to_item(snapshot: Snapshot, *, reasons: list[str]) -> dict[str, Any]:
    return {
        "dirname": snapshot.dirname,
        "kind": snapshot.kind,
        "path": snapshot.path,
        "dt": snapshot.dt.isoformat(),
        "status": snapshot.status,
        "reasons": reasons,
        "reason": ", ".join(reasons),
    }


def _snapshot_delete_path(*, path: Path, dirname: str) -> Path:
    if path.name == "data" and path.parent.name == dirname:
        return path.parent
    return path


def _validate_incomplete_delete_path(*, host: str, path: Path, dirname: str) -> None:
    path_parts = path.parts
    if path.name != dirname or ".incomplete" not in path_parts or host not in path_parts:
        raise ConfigError(f"Refusing to delete unexpected incomplete snapshot path: {path}")
    incomplete_index = path_parts.index(".incomplete")
    if incomplete_index == 0 or path_parts[incomplete_index - 1] != host:
        raise ConfigError(f"Refusing to delete incomplete snapshot outside host backup root: {path}")


def _remove_snapshot_tree(path: Path) -> None:
    _make_directories_user_writable(path)
    shutil.rmtree(path)


def _make_directories_user_writable(path: Path) -> None:
    for directory in [path, *[child for child in path.rglob("*") if child.is_dir() and not child.is_symlink()]]:
        mode = directory.stat().st_mode
        if mode & stat.S_IWUSR:
            continue
        directory.chmod(mode | stat.S_IWUSR)