"""Manual thread-context compaction helpers."""

from __future__ import annotations

import asyncio
import logging
from collections.abc import Mapping
from dataclasses import dataclass
from types import SimpleNamespace

from langgraph.types import Overwrite

from deerflow.agents.middlewares.summarization_middleware import DeerFlowSummarizationMiddleware, SummaryGenerationError, create_summarization_middleware
from deerflow.config.agents_config import validate_agent_name
from deerflow.config.app_config import AppConfig, get_app_config
from deerflow.runtime.checkpoint_state import CheckpointStateAccessor
from deerflow.runtime.context_keys import CHECKPOINT_AGENT_NAME_METADATA_KEY, DEFAULT_AGENT_NAME_METADATA_VALUE

logger = logging.getLogger(__name__)
_AGENT_CONFIG_NOT_LOADED = object()


def _checkpoint_agent_binding(metadata: object) -> tuple[bool, str | None]:
    """Resolve the server-authored agent binding carried by a checkpoint."""
    if not isinstance(metadata, Mapping) or CHECKPOINT_AGENT_NAME_METADATA_KEY not in metadata:
        logger.warning("Skipping memory flush: checkpoint carries no agent binding (pre-binding state)")
        return False, None
    value = metadata[CHECKPOINT_AGENT_NAME_METADATA_KEY]
    if value == DEFAULT_AGENT_NAME_METADATA_VALUE:
        return True, None
    if not isinstance(value, str):
        logger.warning("Ignoring non-string checkpoint agent binding; memory flush will be skipped")
        return False, None
    try:
        return True, validate_agent_name(value)
    except ValueError:
        logger.warning("Ignoring invalid checkpoint agent binding; memory flush will be skipped")
        return False, None


class ContextCompactionDisabled(RuntimeError):
    """Raised when manual compaction is requested while summarization is disabled."""


class ContextCompactionFailed(RuntimeError):
    """Raised when a compressible thread cannot be summarized."""


@dataclass(frozen=True)
class ThreadCompactionResult:
    """Result returned after a manual context-compaction attempt."""

    thread_id: str
    compacted: bool
    reason: str | None = None
    removed_message_count: int = 0
    preserved_message_count: int = 0
    summary_updated: bool = False
    checkpoint_id: str | None = None
    total_tokens: int = 0


def _create_compaction_middleware(
    *,
    app_config: AppConfig,
    keep: tuple[str, int | float] | None,
    run_model_name: str | None = None,
    skip_memory_flush: bool = False,
) -> DeerFlowSummarizationMiddleware:
    middleware = create_summarization_middleware(
        app_config=app_config,
        keep=keep,
        run_model_name=run_model_name,
        skip_memory_flush=skip_memory_flush,
    )
    if middleware is None:
        raise ContextCompactionDisabled("Context compaction is disabled.")
    return middleware


def _safe_load_agent_config(agent_name: str, user_id: str | None):
    """Load a custom agent's config, returning ``None`` on any failure.

    A missing / unparseable agent config must not fail compaction. Model resolution
    falls back to the default, while the optional memory flush fails closed because
    an unreadable policy cannot authorize a durable write. The caller runs this off
    the event loop via ``asyncio.to_thread``, so the strict blocking-IO detector does
    not flag the filesystem read and the broad ``except`` here cannot mask a
    ``BlockingError`` raised on the loop.
    """
    from deerflow.config.agents_config import load_agent_config

    try:
        return load_agent_config(agent_name, user_id=user_id)
    except Exception:
        logger.warning("Could not load agent config for %r; using the default model and skipping memory flush", agent_name, exc_info=True)
        return None


async def _aresolve_thread_model_name(
    model_name: str | None,
    agent_name: str | None,
    user_id: str | None,
    app_config: AppConfig,
    *,
    agent_config: object = _AGENT_CONFIG_NOT_LOADED,
) -> str | None:
    """Resolve the model a thread should summarize with, mirroring lead resolution.

    Precedence matches ``lead_agent._resolve_model_name``: an explicit request model
    override (validated against configured models) wins, else the thread's custom-agent
    configured model, else ``config.models[0]``. Manual ``/compact`` does not execute
    the agent, so there is no live runtime carrying the selected model — the caller
    (route / client) supplies it as ``model_name`` the same way a normal run submits
    ``context.model_name``. The custom-agent config read happens only when no request
    model was supplied, runs off the event loop, and passes the owning ``user_id`` so
    the per-user agent directory resolves.
    """
    default = app_config.models[0].name if getattr(app_config, "models", None) else None
    candidate = model_name
    if not candidate and agent_name:
        if agent_config is _AGENT_CONFIG_NOT_LOADED:
            agent_config = await asyncio.to_thread(_safe_load_agent_config, agent_name, user_id)
        configured_model = getattr(agent_config, "model", None)
        if configured_model:
            candidate = configured_model
    if candidate and app_config.get_model_config(candidate):
        return candidate
    return default


async def compact_thread_context(
    accessor: CheckpointStateAccessor,
    thread_id: str,
    *,
    keep: tuple[str, int | float] | None = None,
    force: bool = True,
    user_id: str | None = None,
    agent_name: str | None = None,
    model_name: str | None = None,
    app_config: AppConfig | None = None,
) -> ThreadCompactionResult:
    """Summarize old messages in a thread and write a compacted checkpoint."""
    resolved_app_config = app_config or get_app_config()
    read_config = {"configurable": {"thread_id": thread_id, "checkpoint_ns": ""}}
    snapshot = await accessor.aget(read_config)
    snapshot_config = snapshot.config or {}
    checkpoint_id = snapshot_config.get("configurable", {}).get("checkpoint_id")
    if not checkpoint_id:
        raise LookupError(f"Thread {thread_id} checkpoint not found")

    binding_known, checkpoint_agent_name = _checkpoint_agent_binding(getattr(snapshot, "metadata", None))
    # The body hint may still select a compatible summarization model for
    # legacy state, but it never authorizes or attributes a memory write.
    effective_agent_name = checkpoint_agent_name if binding_known else agent_name
    agent_config = await asyncio.to_thread(_safe_load_agent_config, effective_agent_name, user_id) if effective_agent_name else None
    run_model_name = await _aresolve_thread_model_name(
        model_name,
        effective_agent_name,
        user_id,
        resolved_app_config,
        agent_config=agent_config,
    )
    memory_enabled = binding_known and (checkpoint_agent_name is None or (agent_config is not None and getattr(agent_config, "memory_enabled", True) is not False))
    middleware = _create_compaction_middleware(
        app_config=resolved_app_config,
        keep=keep,
        run_model_name=run_model_name,
        skip_memory_flush=not memory_enabled,
    )

    channel_values = snapshot.values or {}
    messages = channel_values.get("messages")
    if not isinstance(messages, list) or not messages:
        return ThreadCompactionResult(thread_id=thread_id, compacted=False, reason="not_enough_messages")

    state = {
        "messages": list(messages),
        "summary_text": channel_values.get("summary_text"),
        "task_history": channel_values.get("task_history"),
    }

    runtime_context = {"thread_id": thread_id, "user_id": user_id}
    if effective_agent_name:
        runtime_context["agent_name"] = effective_agent_name
    runtime = SimpleNamespace(context=runtime_context)
    try:
        # ``raise_on_failure`` is independent of ``force``: a manual caller always wants
        # a generation failure surfaced (even a force=False call that met the threshold),
        # so it must not collapse into the force=False "nothing to compact" branch below.
        result = await middleware.acompact_state(state, runtime, force=force, raise_on_failure=True)  # type: ignore[arg-type]
    except SummaryGenerationError as exc:
        # A compressible thread whose summary LLM failed (after the run-model fallback)
        # is a real failure, distinct from "nothing to compact". Route it to the
        # already-consumed ContextCompactionFailed path (HTTP 500 -> frontend error
        # toast) instead of a compacted=False result that reads as "does not need
        # compaction".
        raise ContextCompactionFailed("summary generation failed") from exc
    if result is None:
        return ThreadCompactionResult(thread_id=thread_id, compacted=False, reason="not_enough_messages")

    update_config = dict(snapshot.config)
    if binding_known:
        update_config["metadata"] = {CHECKPOINT_AGENT_NAME_METADATA_KEY: (DEFAULT_AGENT_NAME_METADATA_VALUE if checkpoint_agent_name is None else checkpoint_agent_name)}
    updated_config = await accessor.aupdate(
        update_config,
        {
            "messages": Overwrite(list(result.preserved_messages)),
            "summary_text": result.summary_text,
            **({"task_history": result.task_history} if getattr(result, "task_history", None) is not None else {}),
        },
        as_node="manual_compaction",
    )
    new_checkpoint_id = updated_config.get("configurable", {}).get("checkpoint_id")

    return ThreadCompactionResult(
        thread_id=thread_id,
        compacted=True,
        removed_message_count=len(result.messages_to_summarize),
        preserved_message_count=len(result.preserved_messages),
        summary_updated=True,
        checkpoint_id=new_checkpoint_id,
        total_tokens=result.total_tokens,
    )