"""Per-session pending queue overflow policy tests.

Covers configurable ``pending_overflow_policy`` with two
behaviours and per-channel override hook surfaced for noisy realtime
adapters.

- ``reject_newest`` (default): preserves legacy ``TaskQueueFullError`` raise.
- ``drop_oldest``: evicts the oldest QUEUED pending task on the same
  session and accepts the new turn. The evicted task is marked
  ``CANCELLED`` with ``terminal_reason="dropped_by_overflow"``.

Tests use ``max_concurrency=1`` plus a gating event so the running
task stays running while the queue fills, isolating overflow behaviour
from execution scheduling.
"""
from __future__ import annotations

import asyncio
from collections.abc import Awaitable, Callable
from typing import Any
from unittest.mock import MagicMock

import pytest

from opensquilla.gateway.routing import RouteEnvelope, SourceKind
from opensquilla.gateway.task_runtime import (
    PendingOverflowPolicy,
    TaskQueueFullError,
    TaskRuntime,
)
from opensquilla.session.models import AgentTaskRecord, AgentTaskStatus


def _make_envelope(session_key: str = "agent-1::sess-overflow") -> RouteEnvelope:
    return RouteEnvelope(
        source_kind=SourceKind.WEB,
        source_name="test",
        agent_id="agent-1",
        session_key=session_key,
        input_provenance={"kind": "test"},
    )


def _make_storage() -> Any:
    storage = MagicMock()
    task_db: dict[str, AgentTaskRecord] = {}

    async def create(record: AgentTaskRecord) -> None:
        task_db[record.task_id] = record

    async def update(task_id: str, **kwargs: Any) -> None:
        rec = task_db.get(task_id)
        if rec is None:
            return
        for key, value in kwargs.items():
            if hasattr(rec, key):
                object.__setattr__(rec, key, value)

    async def get(task_id: str) -> AgentTaskRecord | None:
        return task_db.get(task_id)

    async def list_tasks(**_: Any) -> list[AgentTaskRecord]:
        return list(task_db.values())

    storage.create_agent_task = create
    storage.update_agent_task = update
    storage.get_agent_task = get
    storage.list_agent_tasks = list_tasks
    return storage


def _make_runtime(
    *,
    turn_handler: Callable[..., Awaitable[Any]],
    max_pending_per_session: int = 2,
    pending_overflow_policy: PendingOverflowPolicy | str = (
        PendingOverflowPolicy.REJECT_NEWEST
    ),
) -> TaskRuntime:
    return TaskRuntime(
        storage=_make_storage(),
        turn_handler=turn_handler,
        max_concurrency=1,
        max_pending_per_session=max_pending_per_session,
        pending_overflow_policy=pending_overflow_policy,
    )


@pytest.mark.asyncio
async def test_reject_newest_raises_on_overflow() -> None:
    """Default policy preserves legacy TaskQueueFullError raise."""
    started = asyncio.Event()
    release = asyncio.Event()

    async def slow_handler(_run: Any) -> None:
        started.set()
        await release.wait()

    rt = _make_runtime(
        turn_handler=slow_handler,
        max_pending_per_session=2,
        pending_overflow_policy=PendingOverflowPolicy.REJECT_NEWEST,
    )

    env = _make_envelope("agent-1::sess-reject")
    first = await rt.enqueue(env, "first")
    await asyncio.wait_for(started.wait(), timeout=1.0)

    # Fill the pending queue: cap is 2 so two more enqueues occupy the queue.
    second = await rt.enqueue(env, "second")
    third = await rt.enqueue(env, "third")

    # Fourth enqueue exceeds the cap.
    with pytest.raises(TaskQueueFullError):
        await rt.enqueue(env, "fourth")

    release.set()
    await rt.wait(first.task_id, timeout=2.0)
    await rt.wait(second.task_id, timeout=2.0)
    await rt.wait(third.task_id, timeout=2.0)


@pytest.mark.asyncio
async def test_drop_oldest_evicts_oldest_pending_and_accepts_new() -> None:
    """drop_oldest evicts the oldest QUEUED pending task and admits the new turn."""
    started = asyncio.Event()
    release = asyncio.Event()
    seen_messages: list[str] = []

    async def slow_handler(run: Any) -> None:
        if not started.is_set():
            started.set()
            await release.wait()
        seen_messages.append(run.message)

    rt = _make_runtime(
        turn_handler=slow_handler,
        max_pending_per_session=2,
        pending_overflow_policy=PendingOverflowPolicy.DROP_OLDEST,
    )

    env = _make_envelope("agent-1::sess-drop")
    first = await rt.enqueue(env, "first")  # becomes RUNNING immediately
    await asyncio.wait_for(started.wait(), timeout=1.0)

    second = await rt.enqueue(env, "second")  # PENDING
    third = await rt.enqueue(env, "third")  # PENDING — fills cap

    # Fourth enqueue triggers overflow under drop_oldest. Expect:
    # - "second" evicted (oldest pending)
    # - "fourth" admitted
    fourth = await rt.enqueue(env, "fourth")

    # Drain the runtime so terminal records settle.
    release.set()
    second_record = await rt.wait(second.task_id, timeout=2.0)
    third_record = await rt.wait(third.task_id, timeout=2.0)
    fourth_record = await rt.wait(fourth.task_id, timeout=2.0)
    first_record = await rt.wait(first.task_id, timeout=2.0)

    assert second_record.status == AgentTaskStatus.CANCELLED
    assert second_record.terminal_reason == "dropped_by_overflow"
    assert third_record.status == AgentTaskStatus.SUCCEEDED
    assert fourth_record.status == AgentTaskStatus.SUCCEEDED
    assert first_record.status == AgentTaskStatus.SUCCEEDED
    # "second" is the only one that never reaches the handler.
    assert "second" not in seen_messages
    assert seen_messages == ["first", "third", "fourth"]


@pytest.mark.asyncio
async def test_drop_oldest_does_not_evict_running_task() -> None:
    """Running tasks are protected — only QUEUED pending entries are eligible."""
    started = asyncio.Event()
    release = asyncio.Event()

    async def slow_handler(_run: Any) -> None:
        if not started.is_set():
            started.set()
            await release.wait()

    rt = _make_runtime(
        turn_handler=slow_handler,
        max_pending_per_session=1,
        pending_overflow_policy=PendingOverflowPolicy.DROP_OLDEST,
    )

    env = _make_envelope("agent-1::sess-running")
    first = await rt.enqueue(env, "first")  # RUNNING
    await asyncio.wait_for(started.wait(), timeout=1.0)

    second = await rt.enqueue(env, "second")  # PENDING (fills cap=1)

    # Third enqueue must drop "second" (the only QUEUED pending), not the
    # RUNNING "first".
    third = await rt.enqueue(env, "third")

    release.set()
    first_record = await rt.wait(first.task_id, timeout=2.0)
    second_record = await rt.wait(second.task_id, timeout=2.0)
    third_record = await rt.wait(third.task_id, timeout=2.0)

    assert first_record.status == AgentTaskStatus.SUCCEEDED
    assert second_record.status == AgentTaskStatus.CANCELLED
    assert second_record.terminal_reason == "dropped_by_overflow"
    assert third_record.status == AgentTaskStatus.SUCCEEDED


@pytest.mark.asyncio
async def test_per_call_overflow_policy_overrides_default() -> None:
    """The overflow_policy kwarg on enqueue overrides the runtime default."""
    started = asyncio.Event()
    release = asyncio.Event()

    async def slow_handler(_run: Any) -> None:
        if not started.is_set():
            started.set()
            await release.wait()

    rt = _make_runtime(
        turn_handler=slow_handler,
        max_pending_per_session=1,
        pending_overflow_policy=PendingOverflowPolicy.REJECT_NEWEST,
    )

    env = _make_envelope("agent-1::sess-override")
    first = await rt.enqueue(env, "first")
    await asyncio.wait_for(started.wait(), timeout=1.0)
    second = await rt.enqueue(env, "second")

    # Default policy would raise; per-call override switches to drop_oldest.
    third = await rt.enqueue(
        env,
        "third",
        overflow_policy=PendingOverflowPolicy.DROP_OLDEST,
    )

    release.set()
    second_record = await rt.wait(second.task_id, timeout=2.0)
    third_record = await rt.wait(third.task_id, timeout=2.0)
    first_record = await rt.wait(first.task_id, timeout=2.0)

    assert second_record.status == AgentTaskStatus.CANCELLED
    assert second_record.terminal_reason == "dropped_by_overflow"
    assert third_record.status == AgentTaskStatus.SUCCEEDED
    assert first_record.status == AgentTaskStatus.SUCCEEDED


@pytest.mark.asyncio
async def test_apply_overflow_policy_public_entry_point() -> None:
    """apply_overflow_policy enforces the cap without enqueueing a new turn."""
    started = asyncio.Event()
    release = asyncio.Event()

    async def slow_handler(_run: Any) -> None:
        if not started.is_set():
            started.set()
            await release.wait()

    rt = _make_runtime(
        turn_handler=slow_handler,
        max_pending_per_session=1,
        pending_overflow_policy=PendingOverflowPolicy.REJECT_NEWEST,
    )

    env = _make_envelope("agent-1::sess-apply")
    first = await rt.enqueue(env, "first")
    await asyncio.wait_for(started.wait(), timeout=1.0)
    second = await rt.enqueue(env, "second")

    # Public entry point with drop_oldest evicts "second"; the queue is now
    # empty so a follow-up enqueue under reject_newest succeeds.
    await rt.apply_overflow_policy(
        env.session_key, policy=PendingOverflowPolicy.DROP_OLDEST
    )
    third = await rt.enqueue(env, "third")

    release.set()
    second_record = await rt.wait(second.task_id, timeout=2.0)
    third_record = await rt.wait(third.task_id, timeout=2.0)
    first_record = await rt.wait(first.task_id, timeout=2.0)

    assert second_record.status == AgentTaskStatus.CANCELLED
    assert second_record.terminal_reason == "dropped_by_overflow"
    assert third_record.status == AgentTaskStatus.SUCCEEDED
    assert first_record.status == AgentTaskStatus.SUCCEEDED


def test_invalid_policy_string_rejected() -> None:
    """Bad policy strings are rejected at construction time."""

    async def noop(_run: Any) -> None:
        return None

    with pytest.raises(ValueError, match="pending_overflow_policy"):
        TaskRuntime(
            storage=_make_storage(),
            turn_handler=noop,
            pending_overflow_policy="not-a-policy",
        )


@pytest.mark.asyncio
async def test_invalid_per_call_policy_rejected() -> None:
    async def noop(_run: Any) -> None:
        return None

    rt = _make_runtime(
        turn_handler=noop,
        max_pending_per_session=2,
        pending_overflow_policy=PendingOverflowPolicy.REJECT_NEWEST,
    )

    env = _make_envelope("agent-1::sess-invalid")
    with pytest.raises(ValueError, match="overflow_policy"):
        await rt.enqueue(env, "x", overflow_policy="bogus")