"""Development-only file backend for Audit Core.

Writes hourly JSONL files under ``/tmp/audit-core`` by default. See
``docs/audit-backend-contract.md`` for retention guarantees and the migration
path to durable archive backends.
"""

from __future__ import annotations

import json
import os
from datetime import datetime, timedelta, timezone
from pathlib import Path

from audit_core.interface import AuditEvent, EventValidationError, RetentionPolicy, validate_event


class MockFileAuditBackend:
    """Append audit events to hourly JSONL files and clean up old files.

    Implements :class:`~audit_core.interface.AuditBackend` with
    ``custody_class=development``. Not suitable for production audit custody.
    """

    def __init__(
        self,
        base_dir: str | Path | None = None,
        retention_days: int | None = None,
        now: datetime | None = None,
    ) -> None:
        self.base_dir = Path(base_dir or os.environ.get("AUDIT_CORE_MOCK_DIR", "/tmp/audit-core"))
        self.retention_days = int(
            retention_days
            if retention_days is not None
            else os.environ.get("AUDIT_CORE_MOCK_RETENTION_DAYS", "7")
        )
        self._now = now

    @property
    def retention_policy(self) -> RetentionPolicy:
        days = self.retention_days if self.retention_days >= 0 else None
        return RetentionPolicy(
            custody_class="development",
            retention_days=days,
            immutable=False,
            tamper_evidence=False,
            durable=False,
        )

    def emit(self, event: AuditEvent) -> str:
        try:
            validate_event(event)
        except EventValidationError as exc:
            raise ValueError(str(exc)) from exc

        self.base_dir.mkdir(parents=True, exist_ok=True)
        self.cleanup_old_files()
        path = self.current_path()
        record = event.as_record()
        with path.open("a", encoding="utf-8") as handle:
            handle.write(json.dumps(record, sort_keys=True, separators=(",", ":")) + "\n")
        return str(path)

    def cleanup_old_files(self) -> list[str]:
        if self.retention_days < 0 or not self.base_dir.exists():
            return []

        cutoff = self.now() - timedelta(days=self.retention_days)
        removed: list[str] = []
        for path in self.base_dir.glob("audit-*.jsonl"):
            try:
                modified = datetime.fromtimestamp(path.stat().st_mtime, tz=timezone.utc)
            except FileNotFoundError:
                continue
            if modified < cutoff:
                path.unlink(missing_ok=True)
                removed.append(str(path))
        return removed

    def current_path(self) -> Path:
        stamp = self.now().strftime("%Y%m%dT%H")
        return self.base_dir / f"audit-{stamp}.jsonl"

    def now(self) -> datetime:
        return self._now or datetime.now(timezone.utc)