"""Cursor reads for the durable project-scoped workbench event log."""
from __future__ import annotations

from psycopg import AsyncConnection, Connection


EVENT_ORDER_LOCK = "tjwater-workbench:event-order"


async def lock_event_transaction(connection: AsyncConnection) -> None:
    """Serialize v2 event-producing transactions before business locks/writes.

    PostgreSQL sequence allocation is not commit order. All producers must use
    this same transaction lock so a committed higher cursor cannot hide an
    earlier, still-uncommitted event. The lock is local to the connected BizDB
    and creates no schema or data in projects without an event log.
    """
    await connection.execute(
        "SELECT pg_advisory_xact_lock(hashtextextended(%s,0))", (EVENT_ORDER_LOCK,)
    )


def lock_event_transaction_sync(connection: Connection) -> None:
    """Synchronous counterpart using the identical PostgreSQL lock key."""
    connection.execute(
        "SELECT pg_advisory_xact_lock(hashtextextended(%s,0))", (EVENT_ORDER_LOCK,)
    )


class WorkbenchEventRepository:
    def __init__(self, connection: AsyncConnection, project_id):
        self.connection = connection
        self.project_id = str(project_id)

    async def current_cursor(self) -> int:
        cursor = await self.connection.execute(
            "SELECT COALESCE(max(event_seq),0) AS cursor FROM workbench.domain_event_log WHERE project_id=%s",
            (self.project_id,),
        )
        row = await cursor.fetchone()
        return int(row["cursor"])

    async def oldest_cursor(self) -> int | None:
        cursor = await self.connection.execute(
            "SELECT min(event_seq) AS cursor FROM workbench.domain_event_log WHERE project_id=%s",
            (self.project_id,),
        )
        row = await cursor.fetchone()
        return int(row["cursor"]) if row and row["cursor"] is not None else None

    async def read_after(self, after: int, limit: int = 200) -> list[dict]:
        cursor = await self.connection.execute(
            """SELECT event_seq,event_id,project_id,topic,aggregate_type,aggregate_id,
                      aggregate_revision,occurred_at,metadata
               FROM workbench.domain_event_log
               WHERE project_id=%s AND event_seq>%s
               ORDER BY event_seq LIMIT %s""",
            (self.project_id, after, limit),
        )
        return [dict(row) for row in await cursor.fetchall()]