"""
journal.py — SQLite-backed certified-mail journal.

Implements the DispatchHook protocol with SQLite persistence.
Provides write-ahead logging for message dispatch, enabling
crash recovery via replay of unacknowledged entries.

Lifecycle:
    1. on_intent        → INSERT journal entry  [PENDING]
    2. on_dispatched    → UPDATE status          [DISPATCHED]
    3. on_acknowledged  → UPDATE status          [ACKED]
    4. on_failed        → UPDATE status + error  [FAILED]
    5. on_thread_complete → compact acked entries
    6. startup          → scan DISPATCHED → re-inject [recovery]

Example:
    from xml_pipeline.message_bus.journal import MessageJournal

    journal = MessageJournal(db_path="~/.xml-pipeline/journal.db")
    await journal.initialize()

    pump.register_dispatch_hook(journal)

    # On restart, replay unacknowledged entries
    entries = await journal.get_unacknowledged()
    for entry in entries:
        await pump.inject(entry["payload_bytes"], entry["thread_id"], entry["from_id"])
"""

from __future__ import annotations

import logging
import uuid
from dataclasses import dataclass
from datetime import datetime, timezone
from enum import Enum
from typing import Any, Dict, List, Optional

from xml_pipeline.message_bus.journal_store import JournalStore

logger = logging.getLogger(__name__)


class JournalEntryStatus(Enum):
    """Status of a journal entry through its lifecycle."""
    PENDING = "pending"
    DISPATCHED = "dispatched"
    ACKNOWLEDGED = "acked"
    FAILED = "failed"


@dataclass(frozen=True)
class JournalEntry:
    """Immutable snapshot of a journal entry."""
    id: str
    thread_id: str
    from_id: str
    to_id: str
    payload_type: str
    payload_bytes: bytes
    status: JournalEntryStatus
    created_at: str
    dispatched_at: Optional[str] = None
    acked_at: Optional[str] = None
    retry_count: int = 0
    error: Optional[str] = None


class MessageJournal:
    """
    SQLite-backed certified-mail journal.

    Implements DispatchHook to track message dispatch lifecycle.
    Provides crash recovery via replay of unacknowledged entries.
    """

    def __init__(
        self,
        db_path: Optional[str] = None,
        *,
        compact_after_hours: int = 24,
        retry_after_seconds: float = 30.0,
        max_retries: int = 3,
    ) -> None:
        self._store = JournalStore(db_path)
        self._compact_after_hours = compact_after_hours
        self._retry_after_seconds = retry_after_seconds
        self._max_retries = max_retries

    async def initialize(self) -> None:
        """Initialize the underlying store."""
        await self._store.initialize()

    # ------------------------------------------------------------------
    # DispatchHook implementation
    # ------------------------------------------------------------------

    async def on_intent(
        self,
        thread_id: str,
        from_id: str,
        to_id: str,
        payload_type: str,
        payload_bytes: bytes,
    ) -> str:
        """Record intent to dispatch. Returns entry_id for correlation."""
        entry_id = str(uuid.uuid4())
        now = datetime.now(timezone.utc).isoformat()

        await self._store.insert(
            entry_id=entry_id,
            thread_id=thread_id,
            from_id=from_id,
            to_id=to_id,
            payload_type=payload_type,
            payload_bytes=payload_bytes,
            status=JournalEntryStatus.PENDING.value,
            created_at=now,
        )

        logger.debug(f"Journal: intent {entry_id[:8]}... {from_id}->{to_id}")
        return entry_id

    async def on_dispatched(self, entry_id: str) -> None:
        """Mark entry as dispatched (handler invocation started)."""
        if not entry_id:
            return
        now = datetime.now(timezone.utc).isoformat()
        await self._store.update_status(
            entry_id,
            JournalEntryStatus.DISPATCHED.value,
            timestamp_field="dispatched_at",
            timestamp_value=now,
        )
        logger.debug(f"Journal: dispatched {entry_id[:8]}...")

    async def on_acknowledged(self, entry_id: str) -> None:
        """Mark entry as acknowledged (handler returned successfully)."""
        if not entry_id:
            return
        now = datetime.now(timezone.utc).isoformat()
        await self._store.update_status(
            entry_id,
            JournalEntryStatus.ACKNOWLEDGED.value,
            timestamp_field="acked_at",
            timestamp_value=now,
        )
        logger.debug(f"Journal: acked {entry_id[:8]}...")

    async def on_failed(self, entry_id: str, error: str) -> None:
        """Mark entry as failed with error details."""
        if not entry_id:
            return
        now = datetime.now(timezone.utc).isoformat()
        await self._store.update_status(
            entry_id,
            JournalEntryStatus.FAILED.value,
            error=error,
            timestamp_value=now,
        )
        logger.warning(f"Journal: failed {entry_id[:8]}... — {error}")

    async def on_thread_complete(self, thread_id: str) -> None:
        """Compact acknowledged entries for the completed thread."""
        count = await self._store.compact_thread(thread_id)
        if count:
            logger.debug(
                f"Journal: compacted {count} entries for thread {thread_id[:8]}..."
            )

    # ------------------------------------------------------------------
    # Journal-specific methods (not part of DispatchHook protocol)
    # ------------------------------------------------------------------

    async def get_unacknowledged(
        self,
        older_than_seconds: Optional[float] = None,
    ) -> List[Dict[str, Any]]:
        """
        Get entries that need replay (pending or dispatched but never acked).

        Used for crash recovery on startup.

        Args:
            older_than_seconds: Override default retry delay

        Returns:
            List of entry dicts with payload_bytes for re-injection
        """
        delay = older_than_seconds or self._retry_after_seconds
        return await self._store.get_unacknowledged(
            older_than_seconds=delay,
            max_retries=self._max_retries,
        )

    async def compact_old(self, max_age_hours: Optional[int] = None) -> int:
        """
        Remove old acknowledged entries.

        Args:
            max_age_hours: Override default compaction age

        Returns:
            Number of entries removed
        """
        from datetime import timedelta

        hours = max_age_hours or self._compact_after_hours
        cutoff = (
            datetime.now(timezone.utc) - timedelta(hours=hours)
        ).isoformat()

        return await self._store.compact_old(cutoff)

    async def get_stats(self) -> Dict[str, int]:
        """Get entry counts by status."""
        return await self._store.get_stats()